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-   -   LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks (https://www.cruisersforum.com/forums/f166/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html)

CharlieJ 14-10-2014 15:23

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Buff the terminals with a ScotchBrite pad, apply NoOx, torque the fastener, spray the exposed inter-connects with Boeshield T9.

Jd1 14-10-2014 15:49

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by CharlieJ (Post 1653816)
Buff the terminals with a ScotchBrite pad, apply NoOx, torque the fastener, spray the exposed inter-connects with Boeshield T9.

Thanks Charlie! What kind of store carries NoOx - would Home Depot / Rona have that or is it something only the electrical wholesale places have ?

ColdEH 16-10-2014 07:10

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1653803)
It has likely been mentioned but searching this thread is a monumental task .... so forgive me for asking this again:
What do you use for corrosion protection on the cell inter connecting strips? The Balqon strips are 4 layers of pure copper with no tinning and I would rather keep that shiny and not with a funky green patina on the interconnections.

I actually bought a set of these .

EV Works Braided Cell Interconnector 55-12 55mm nominal pitch, 12mm holes

They are tinned and don't stress the terminals if there is any expansion or shifting. Got them from Australia and didn't take long at all.

Regards

hellosailor 16-10-2014 08:07

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
In the States we call those "tinned ground straps". They are sold in auto stores, typically in longer lengths, and the material itself can also be bought by the roll. It is sometimes flat ribbon, sometimes actually tubular so it can be used as an RFI shield as well. Crimping on end terminals, or fashioning them, is left to the buyer when you buy it by the roll.

The advantage is that they easily adjust to any length between two posts, and with "known" spacing on battery terminals they're probably just a needless expense compared to copper slugs, for most people.

Jd1 26-10-2014 10:26

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I am gradually making progress with my lithium install. The batteries are in the boat and set up for initial testing. I have set up the House Power BMS and the little cell boards. Yesterday I finished a top balancing. When I left, all four cells were in shunting mode indicating they were above 3.65V but below 3.8V. This morning I was expecting to see all batteries around 3.65 or so volts.
Instead, I have the following result:
3.596V
3.576V
3.599V
and
3.383V !!!!!
The first three cells are in the range I was expecting but what is going on with cell #4?
This is not the first time that cell #4 behaved odd - it was doing a similar thing while I was in the process of balancing but I wanted to verify this behaviour after balancing - which I now have.
I am unable to do a full load test at this time as I am still waiting for my order of battery cables to come in.
Another bit of trivia - the cell that is acting up has marks on the case left by allthread rod as if it was previously installed. I was assured by Balqon that the cells are all new but that some cells out of every batch are tested and the marks might be from that. IMHO the marks are wayy too deep for that unless the have some gorilla of a guy strapping them into the test setup ... but that is only my opinion.
Question: Is the behaviour I am seeing an indication of battery age or previous use or should I ignore this issue until I have my cabling set up for a full capacity test ?
Has anyone else run into this kind of issue ?
I will be doing a full capacity test one way or another but I am getting concerned and wanted to see if other people have run into this kind of behaviour.

Thanks

Maine Sail 26-10-2014 11:30

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1663434)
I am gradually making progress with my lithium install. The batteries are in the boat and set up for initial testing. I have set up the House Power BMS and the little cell boards. Yesterday I finished a top balancing. When I left, all four cells were in shunting mode indicating they were above 3.65V but below 3.8V. This morning I was expecting to see all batteries around 3.65 or so volts.
Instead, I have the following result:
3.596V
3.576V
3.599V
and
3.383V !!!!!
The first three cells are in the range I was expecting but what is going on with cell #4?
This is not the first time that cell #4 behaved odd - it was doing a similar thing while I was in the process of balancing but I wanted to verify this behaviour after balancing - which I now have.
I am unable to do a full load test at this time as I am still waiting for my order of battery cables to come in.
Another bit of trivia - the cell that is acting up has marks on the case left by allthread rod as if it was previously installed. I was assured by Balqon that the cells are all new but that some cells out of every batch are tested and the marks might be from that. IMHO the marks are wayy too deep for that unless the have some gorilla of a guy strapping them into the test setup ... but that is only my opinion.
Question: Is the behaviour I am seeing an indication of battery age or previous use or should I ignore this issue until I have my cabling set up for a full capacity test ?
Has anyone else run into this kind of issue ?
I will be doing a full capacity test one way or another but I am getting concerned and wanted to see if other people have run into this kind of behaviour.

Thanks

You left these unattended and on charge at 3.65V per cell while actively shunting.......?

How exactly did you top balance?

Were the individual cells charged to 3.XV+ and X.x tail current before wiring in parallel?

If so what were these parameters?

Did you parallel top balance?

What voltage did you push the parallel cells to?

What was the tail current you stopped at during top balance?

What was the max parallel top balance voltage?

How long were cells wired in parallel before pushing the top balance voltage to 3.75 - 3.8V?

Was any baseline capacity done at all before the installation?

Does cell number four also tap out early on LV?

Jd1 26-10-2014 12:18

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Maine Sail (Post 1663458)
You left these unattended and on charge at 3.65V per cell while actively shunting.......?

No, I charged under supervision until all cells were shunting and then disconnected the charger
Quote:

How exactly did you top balance?
A combination of single cell charging, some cell draining and some multi cell charging to get them all into the same ballpark for cell voltages. Let them sit for a day to rest, charge the pack and top off individual cells as needed to get all cells into shunting territory. Let sit to finish shunting plus an overnight rest. Top up the next day to get all cells to eventually shunt. Most of this happened at 20A charge current. I did a final topping off at about two amp for about half an hour. Disconnected charger and let the batteries finish shunting and rest.
I have not yet moved the cell level board to another cell to verify that it isn't an issue with that circuit (which I doubt).
Quote:

Were the individual cells charged to 3.XV+ and X.x tail current before wiring in parallel?
I did not do a tail current charge. The cells are 700 AHr and I figured 20A was insignificant so virtually all charging was based on voltage with shunting and resting. There was a minor bit of reduced rate charge but again that was probably insignificant in the overall picture.
No significant charging was done while the cells were in a parallel configuration.
Quote:

If so what were these parameters?
The cells were mostly just brought up to the 3.65 to 3.8V range and the shunting took them down to just below 3.65 and resting might have dropped them a bit further here and there hence the multiple charges to shunting and subsequent rests.
Quote:

Did you parallel top balance?
Initially the cells were set up in parallel for 3 or 4 days but no significant charging was done in that configuration. They were mostly allowed just to equalize their voltages.
Quote:

What voltage did you push the parallel cells to?
didn't
Quote:

What was the tail current you stopped at during top balance?
Let's call it 2 amps but it wasn't a proper tail current.
Quote:

What was the max parallel top balance voltage?
N/A
Quote:

How long were cells wired in parallel before pushing the top balance voltage to 3.75 - 3.8V?
3 to 4 days
Quote:

Was any baseline capacity done at all before the installation?
No, I was unable to do that as I had no SOC monitor nor BMS (to automatically turn the load off) nor proper cabling.
Quote:

Does cell number four also tap out early on LV?
Don't know this until I can do a capacity test when cabling gets here, probably Thursday.

Thanks for your input!

T1 Terry 27-10-2014 03:06

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1663434)
I am gradually making progress with my lithium install. The batteries are in the boat and set up for initial testing. I have set up the House Power BMS and the little cell boards. Yesterday I finished a top balancing. When I left, all four cells were in shunting mode indicating they were above 3.65V but below 3.8V. This morning I was expecting to see all batteries around 3.65 or so volts.
Instead, I have the following result:
3.596V
3.576V
3.599V
and
3.383V !!!!!
The first three cells are in the range I was expecting but what is going on with cell #4?
This is not the first time that cell #4 behaved odd - it was doing a similar thing while I was in the process of balancing but I wanted to verify this behaviour after balancing - which I now have.
I am unable to do a full load test at this time as I am still waiting for my order of battery cables to come in.
Another bit of trivia - the cell that is acting up has marks on the case left by allthread rod as if it was previously installed. I was assured by Balqon that the cells are all new but that some cells out of every batch are tested and the marks might be from that. IMHO the marks are wayy too deep for that unless the have some gorilla of a guy strapping them into the test setup ... but that is only my opinion.
Question: Is the behaviour I am seeing an indication of battery age or previous use or should I ignore this issue until I have my cabling set up for a full capacity test ?
Has anyone else run into this kind of issue ?
I will be doing a full capacity test one way or another but I am getting concerned and wanted to see if other people have run into this kind of behaviour.

Thanks

If you are charging each cell separately, does #4 cell always drop low when left sitting over night? Have you tried removing the shunt board from #4 cell, recharging to 3.6v and letting it sit over night to see if it still drops down as low?
The symptoms you are describing are all too common when using these shunting boards, no matter who makes them, this has lead to quite number of people removing all their shunting boards and simply controlled voltage charging and many have discovered their problems simply went away. Others had already had cells dragged to 0V resulting in cell damage, but the cells still came good once the shunt boards were removed, just down on capacity.

T1 Terry

Jd1 27-10-2014 07:31

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 1663892)
If you are charging each cell separately, does #4 cell always drop low when left sitting over night? Have you tried removing the shunt board from #4 cell, recharging to 3.6v and letting it sit over night to see if it still drops down as low?
The symptoms you are describing are all too common when using these shunting boards, no matter who makes them, this has lead to quite number of people removing all their shunting boards and simply controlled voltage charging and many have discovered their problems simply went away. Others had already had cells dragged to 0V resulting in cell damage, but the cells still came good once the shunt boards were removed, just down on capacity.

T1 Terry

Yes, the cell has behaved like this earlier.
My next test will be to exchange the cell boards of another cell with cell #4's board to test out exactly that scenario. The cell board does not appear to have an elevated temperature (indicating failure) but one never knows for sure until this is verified.

Maine Sail 27-10-2014 07:51

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
What T1 said in paragraph #1 plus...

It does not sound like you actually balanced the pack.. Without a tail current for each cell at 3.XX V it is tough to say where that cell is. If parallel balancing they need to be charged in parallel, above resting V, not just left to sit in parallel. The best time to let them sit is after pushing them to the 3.8V top balance point..

Once all cells have been brought to the same point, for Winston I use 3.75V and the same tail for each cell, then wire them in parallel and push to 3.8V and allow the current to taper. Remember this is now a 2800Ah pack so even the difference between 3.75 and 3.8V will take considerably time.. Watch cell temps while doing so..

This is why getting each cell as close to identical as you can before wiring in parallel and pushing to 3.8V is pretty critical. Letting them sit in parallel brings voltage parody but mA level currents are still moving and with a 700Ah pack this can take time due to the voltage....

I highly doubt this is a cell board issue and shunt balancing that wide of a spread, 0.216V, is a loooooong tedious process best left to manual then parallel top balancing. Shunt balancing is intended for minor variances. You have large variances...

It sounds to me like the top balance simply was not adequate for the size bank. It could be a bad cell but you need to charge each cell to a top point, which is exactly the same, then let them all sit, and measure voltage of each cell individually.

My Winston cells shipped to me out of balance and it was as simple as doing a corrective top balance. 500+ cycle later they still in near perfect balance..

Jd1 27-10-2014 08:20

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Ok, I will first exchange cell boards and give that a try and once that has been verified I will bring all cells to the same voltage, hook them up in parallel and do another (parallel) balance. I will then gradually reduce current over a 5 hour time period (the longest I have patience for while watching the entire setup), let them sit overnight to rest while still paralleled, separate the cells and let them rest overnight and finally measure cell voltages again.

Maine Sail 27-10-2014 08:49

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1664059)
Ok, I will first exchange cell boards and give that a try and once that has been verified I will bring all cells to the same voltage, hook them up in parallel and do another (parallel) balance. I will then gradually reduce current over a 5 hour time period (the longest I have patience for while watching the entire setup), let them sit overnight to rest while still paralleled, separate the cells and let them rest overnight and finally measure cell voltages again.

The batteries will reduce the current automatically at X volts and X SOC.......... You don't need to stand there are watch it the entire time just set a timer to check every 30 minutes or so and hit them with a temp gun.

Do not use your power supply to determine cell voltage use your DVM at the battery terminals as the determination....

evm1024 27-10-2014 09:08

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Just for a FYI. With he "same" 700 AH cells that were top balanced per Maine Sails advice my cells read 3.339 each with one cell dropping down to 3.338 every now and then. These cells are about 70 AH below a charge to 13.9 v @ 20 amps (3.475 per cell). Very nicely balanced.

I only have a few cycles to 60% SOC on them.

I've not done a full capacity test on them yet. Something I need to do. I would love to have the voltage curve at the lower knee for these cells of mine. (both at a 100 A rate and at a 20 A rate - time....)

nimblemotors 27-10-2014 09:34

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
It isn't complicated, remove the bms junk, put them in parallel, and charge them all with a constant 3.6v power supply until the current drops to zero.
Now they are top balanced. Disconnect them from the charge and each other and let each cell sit for at least a couple days or even a week or two.
Check the voltages, if they have dropped too much, they are not good.

Then discharge each one down to 2.5 volts, and check their capacity, they should be pretty close to rated capacity. Now they are bottom balanced.

Now you know what you have, if they are good and their capacity.

T1 Terry 27-10-2014 16:21

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by nimblemotors (Post 1664119)
It isn't complicated, remove the bms junk, put them in parallel, and charge them all with a constant 3.6v power supply until the current drops to zero.
Now they are top balanced. Disconnect them from the charge and each other and let each cell sit for at least a couple days or even a week or two.
Check the voltages, if they have dropped too much, they are not good.

Then discharge each one down to 2.5 volts, and check their capacity, they should be pretty close to rated capacity. Now they are bottom balanced.

Now you know what you have, if they are good and their capacity.

This sounds like an electric vehicle battery balancing regime, of no value if you don't intend to completely drain you cells each time you use them. Electric vehicle users often drag their cells down to the last bit of capacity, house battery owners do not, or at least should not. The capacity test will only match the manufacturers figures if tested by the same method as the manufacturer used, 0.5C current draw until the cell measures 2.5v under the 0.5 load. For a 700Ah cell that would require a 350 amp load that could maintain that load for 14 hrs, not likely to be something you have on hand is it.
Even at 3.6v you will damage the cells if you hold them at that voltage for very long so don't do it if you want long battery life. If you are using a 20 amp charger that equals a 0.02C load, paralleled as 4 x 700Ah cells equals 2800Ah, charge that pack with a 20 amp rate charger and you will be charging at a 0.007 charge rate, trickle charging to 3.6v kills lithium cells faster than shooting them, don't do it, if you really want to use this method, restrict the top end voltage to 3.5v and charge till the current flow drops, then a short charge to 3.6v on each individual cell and stop as soon as it reaches 3.6v. If the cells all stay above 3.5v for 12 hrs, the cells are fine.
Most definitely remove the shunt modules to do this balance charging or you won't know if it's the cells still accepting charge or the balance modules consuming the charge. Also, you will not know if the cell is not holding charge or if the shunt module is consuming the cell capacity.
As far as cell balance in a 4 cell in series string, you won't see an imbalance until the cells are full, anything above 3.45v, no balance board made can shunt 20 amps so they will be as much use as an ass pocket in a singlet in trying to top balance a battery pack while charging, so why add complication to a system with something that isn't capable of doing the job you think you fitted it for in the first place. 12v Li batteries stay within 100mA of each other all the way till the last bit of charging when the cell goes over 3.45v, with or without balance boards, you don't need to balance within a range this tight anyway, so why try to fix something that isn't broke by using something that can't do the job intended anyway?

T1 Terry

Jd1 27-10-2014 16:42

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 1664414)
If the cells all stay above 3.5v for 12 hrs, the cells are fine.
T1 Terry

Added about 7 Ah to the cell that is showing strange results which got me to 3.8V. I disconnected the cell board and watched the voltage fall rather rapidly - I will check again tomorrow but I think I was well into the 3.5V territory within half an hour of stopping the charge current. I will verify things tomorrow but it definitely looks like the cell is dropping it's charge. The remaining cells are all above 3.5V which I am quite happy about.
I also disconnected the Cellog 8 just to be certain that there is no possible way that electrons could sneak from one end of the cell to the other end :)

T1 Terry 27-10-2014 17:59

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1664427)
Added about 7 Ah to the cell that is showing strange results which got me to 3.8V. I disconnected the cell board and watched the voltage fall rather rapidly - I will check again tomorrow but I think I was well into the 3.5V territory within half an hour of stopping the charge current. I will verify things tomorrow but it definitely looks like the cell is dropping it's charge. The remaining cells are all above 3.5V which I am quite happy about.
I also disconnected the Cellog 8 just to be certain that there is no possible way that electrons could sneak from one end of the cell to the other end :)

Do the recharge a second time if it falls below 3.5v after a few hrs, I suspect that cell has higher internal resistance so the voltage climbs much faster as it reaches the end of charge. If this cell continues to do the same thing once in use, without the balance boards attached I'd looking for a claim

T1 Terry

nimblemotors 27-10-2014 18:16

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

This sounds like an electric vehicle battery balancing regime, of no value if you don't intend to completely drain you cells each time you use them.
No value to know if the cell is bad, or its capacity, uh huh,
And the 3.6v will damage the cells. :rolleyes:

T1 Terry 28-10-2014 02:36

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by nimblemotors (Post 1664499)
No value to know if the cell is bad, or its capacity, uh huh,
And the 3.6v will damage the cells. :rolleyes:

This is a quoted post from an admin member of the Australian Electric Vehicle Association forum. These guys eat and sleep this stuff and the combined qualifications of these guys would make your head spin

you can read more from where it came from here Upgrade to Lithiums? - The Australian Electric Vehicle Asn - Page 2
Quote:

I once used a 0.35A LED constant current power supply to balance out a set of 16 90Ah cells, all with BMS modules on them that shunted at 3.65v
I left it on over a weekend

after the weekend, all cells were 3.65v, all bulged, all lost capacity, all had higher internal resistance.
please don't float them

you already have a single cell charger - just leave it attached to the lowest cell until it is full, then move to the next one

what current is the single cell charger?
A short burst to 3.6v will not harm the cells, holding them at 3.6v or higher will wreck them :banghead:

T1 Terry

bill good 28-10-2014 06:22

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Terry, I am replacing my house batteries with LIFEPO4S. What is a "short burst" @ 3.6V? I note all the CV portions of the charge is approx 2hrs no matter on the capacity/brand & was going to use the overall voltage of 14.6V for manual top equilizing when/if needed. The 2 hr max charging time would always be active both with normal daily 14v max & the periodic 14.6V. Solar system max 30Amp 300 AmpHr CALB cells. Cell shunts from EV-POWER. Aim to operate 14-12.6V range. Any problem seen with this setup??

Regards Bill

ColdEH 28-10-2014 07:06

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hi Maine Sail.

Just a quick thought , this top balancing process takes a long time, around one day for each 300 ah Sinolpoly cell , and I have 8 of them .
Is it ok to leave these things sitting at 3.75 v while I do the other ones ?


I will go back and top them all off quickly before I put them all in parallel.

Just a thought

Regards

nimblemotors 28-10-2014 09:19

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

A short burst to 3.6v will not harm the cells, holding them at 3.6v or higher will wreck them
If they cells ARE BAD, then charging them will show them to be bad.
I recently finished testing over 300 cells, I must have wrecked all 300 of them at 3.85v...NOT. Some puffed up, indeed, BECAUSE THEY ARE BAD CELLS.
When you buy new cells, should you find out if they are bad so you can return them under warranty? I would. Bad cells still work, just relatively poorly.

In general Lithium should not be float charged.
Charging them at all does 'wreck' them, so if you want the battery to last, never charge one. :rolleyes:

T1 Terry 28-10-2014 17:47

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by nimblemotors (Post 1664936)
If they cells ARE BAD, then charging them will show them to be bad.
I recently finished testing over 300 cells, I must have wrecked all 300 of them at 3.85v...NOT. Some puffed up, indeed, BECAUSE THEY ARE BAD CELLS.
When you buy new cells, should you find out if they are bad so you can return them under warranty? I would. Bad cells still work, just relatively poorly.

In general Lithium should not be float charged.
Charging them at all does 'wreck' them, so if you want the battery to last, never charge one. :rolleyes:

No matter what I say, you have already decided you are right and I'(and many others) are wrong. so you just go ahead and do it your way, but please don't guide others to follow your path until you have at least 1,000 cycles on your cells to prove you really do know better :peace:

T1 Terry

SV THIRD DAY 28-10-2014 17:53

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
The beauty of the different opinions on a chat room forum is that you start to get a good feeling of who's approach and in a way world view you want to follow. So even the bad advice can actually help in the learning process. The trick is that casual users of the forum have a hard time figuring out who knows what they are talking about vs just talking.

T1 Terry 28-10-2014 17:54

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by bill good (Post 1664759)
Terry, I am replacing my house batteries with LIFEPO4S. What is a "short burst" @ 3.6V? I note all the CV portions of the charge is approx 2hrs no matter on the capacity/brand & was going to use the overall voltage of 14.6V for manual top equilizing when/if needed. The 2 hr max charging time would always be active both with normal daily 14v max & the periodic 14.6V. Solar system max 30Amp 300 AmpHr CALB cells. Cell shunts from EV-POWER. Aim to operate 14-12.6V range. Any problem seen with this setup??

Regards Bill

A short burst means stop charging when the cell reaches 3.6v until the cell voltage drops below 3.4v, then resume charging and repeat the cycle as often as required to reach the 14v or 14.2v for faster charging max battery voltage. Once a mth manual equalising if you must to reset the 100%SOC, but stay under the 3.62v mark as your max. individual cell voltage, cell cycle life depends on it. If you want to gamble that I don't know what I'm talking about after over 1,000 cycles of house battery experience it's up to you, they are your $$ not mine.

T1 Terry

roetter 28-10-2014 18:46

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Problems with my 12V/1400Ah

Last december I installed 8x Balqon 700Ah cells in my boat as 2P4S.

I top balanced the cells with a bench top power supply to 3.8V until the current droped to less than 3A. I let them sit 24 hours and then pushed them to 3.8V again for one hour.

After the install I used them while living on the boat until end of March. My daily energy consumption is around 350Ah.

In March we stored the boat and I drained the cells to about 50%SOC. Left them completely disconnected. In July we returned to the boat for 2 weeks and all seemed well.

For storage in July I again drained the batteries to about 50% SOC.

The storage procedure is that the LiFePO batteries are completely disconnected by removing all cables. The starter batteries are connected to the house bank and maintained by 1800W solar reduced to max output of 20A at 14.5V/13.4V .

Upon return two days ago the two cells forming the second set were down to 2.6V while the other cells were at about 3.2V.

After changing the solar to charge the LFP's again, the lagging cells quickly caught up. Now, after just over 2 days, all cell-bundles are sitting at
C1-3.330V
C2-3.287V
C3-3.327V
C4-3.330V

I assume since this is pretty much on the flat slope, that could mean a 30%+ difference in SOC.

I have not run the battery above 13.4V yet, as we have run the water maker for 10 hours. Also, the fridges have been working hard as we filled them with groceries and drinks.

Tomorrow, I plan to take them to 13.8V and see what the diffrence in voltages is. If I have time I will take them higher, until the first set of cells reaches 3.5V.

I guess I will have a long time of top balancing the cells with the good old "short" cable.

What is a good way to easily check which of the cells is bad? I guess I would have to rearrange the cells into two 12V sets with the two questionable cells in one battery. Then top balance and run them down to see if one has reduces capacity. Hopefully that one would also be the one with the slow self discharge.

I "hope" I will be able to get the bad cell replaced by Balqon. Timing is a big thing as we will be in Ft. Lauderdale only for a few days in about 2 weeks. Right now we are in George Town, Exuma and will go to the Abacos after Ft. Lauderdale.

Jd1 28-10-2014 19:57

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by roetter (Post 1665306)

What is a good way to easily check which of the cells is bad? I guess I would have to rearrange the cells into two 12V sets with the two questionable cells in one battery. Then top balance and run them down to see if one has reduces capacity. Hopefully that one would also be the one with the slow self discharge.

I bought a cheap 3kw inverter from Canadian Tire the other day ($219.99, how could I go wrong at that sale price). I will use that to power my boats electrical heater and should be able to put a nice load on the batteries to test them. I will have the SOC meter hooked up and the BMS system will disconnect the load when a single cell hits 2.5V (I think). I will have to watch things as I get to the lower voltages with the one questionable cell I have but my SOC meter will tell me exactly how much power the lowest performing cell has just before everything shuts down.

Quote:

I "hope" I will be able to get the bad cell replaced by Balqon. Timing is a big thing as we will be in Ft. Lauderdale only for a few days in about 2 weeks. Right now we are in George Town, Exuma and will go to the Abacos after Ft. Lauderdale.
You are missing all the gorgeous rainy and windy weather we are having out here in Victoria :)

T1 Terry 28-10-2014 22:55

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by roetter (Post 1665306)
Problems with my 12V/1400Ah

Last december I installed 8x Balqon 700Ah cells in my boat as 2P4S.

I top balanced the cells with a bench top power supply to 3.8V until the current droped to less than 3A. I let them sit 24 hours and then pushed them to 3.8V again for one hour.

After the install I used them while living on the boat until end of March. My daily energy consumption is around 350Ah.

In March we stored the boat and I drained the cells to about 50%SOC. Left them completely disconnected. In July we returned to the boat for 2 weeks and all seemed well.

For storage in July I again drained the batteries to about 50% SOC.

The storage procedure is that the LiFePO batteries are completely disconnected by removing all cables. The starter batteries are connected to the house bank and maintained by 1800W solar reduced to max output of 20A at 14.5V/13.4V .

Upon return two days ago the two cells forming the second set were down to 2.6V while the other cells were at about 3.2V.

After changing the solar to charge the LFP's again, the lagging cells quickly caught up. Now, after just over 2 days, all cell-bundles are sitting at
C1-3.330V
C2-3.287V
C3-3.327V
C4-3.330V

I assume since this is pretty much on the flat slope, that could mean a 30%+ difference in SOC.

I have not run the battery above 13.4V yet, as we have run the water maker for 10 hours. Also, the fridges have been working hard as we filled them with groceries and drinks.

Tomorrow, I plan to take them to 13.8V and see what the diffrence in voltages is. If I have time I will take them higher, until the first set of cells reaches 3.5V.

I guess I will have a long time of top balancing the cells with the good old "short" cable.

What is a good way to easily check which of the cells is bad? I guess I would have to rearrange the cells into two 12V sets with the two questionable cells in one battery. Then top balance and run them down to see if one has reduces capacity. Hopefully that one would also be the one with the slow self discharge.

I "hope" I will be able to get the bad cell replaced by Balqon. Timing is a big thing as we will be in Ft. Lauderdale only for a few days in about 2 weeks. Right now we are in George Town, Exuma and will go to the Abacos after Ft. Lauderdale.

Do you still have the bench top power supply available? If so you could separate the 2 suspect cells from the pack and charge each to 3.6v, then let them sit, the crook cell will drop lower than the good cell by a large margin over 12hrs or so.

T1 Terry

ebaugh 29-10-2014 15:13

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hi everyone,

I've not been following the thread the last 12 mos or so. I hope everyone is well and having great success with their LFP installs. We have been marina bound, my wife and I essentially working full time to replenish the cruising kitty. But the boat has left the dock once in about 12 months.

Our LFP install is now a little over 2 years old. About a year ago we pulled 4 of 48 cells and ran a capacity test at about C/3. Just reran that exact same test a week or so ago. Year 1 the batteries were actively cruising. Year 2, the same 4 cells sat on a shelf waiting for me to reinstall them, but I never did. Not stored at 50%, as they should have been, probably more like 95%.

We don't have a baseline from the install, but assuming they met specification when new, we are seeing a capacity loss of 10-15% per year. The 100Ah cells are sitting at about 71-72Ah today. The loss appears to be more time dependent than number of cycles. These are GBS cells.

The 30A rate is roughly C/3 on new cells, but is approaching C/2, so that would tend to start skewing the results.

This difference while substantial, would not be readily apparent on the boat since I rarely went below 50% in normal operations.

Similar tests, one 12 months ago on new out of the box 100Ah cells and another this week, after one year of storage at 50% SOC showed a 5% reduction in capacity. These were Forzatec (Google is your friend) cells. Much better! But perhaps still significant.

The testing is with 4 cells in series after a fresh top balance. Outside of capacity, the cells behaved just like any other LFP cell. The 4 cells as samples in each group exhibiting almost identical capacity change.

Considered cycling them a few times to see if the numbers changed, but don't really have the time now. The charge following the discharge shows the usual almost even one amp out equals one amp in to recharge, so if there was a change it would be very gradual.

I am looking forward to other reports, but it looks like 5-10% capacity loss per year might be unavoidable. If you can get your 2000-3000 cycles in 5 years there is a much stronger case than if it's going to take you 10 years or more to get there.

Best Bob


Sent from my iPad using Cruisers Sailing Forum

roetter 29-10-2014 15:14

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1665343)
...
You are missing all the gorgeous rainy and windy weather we are having out here in Victoria :)

We are glad we left on the first really bad day. Before that it would have felt strange to go to The Bahamas.

roetter 29-10-2014 15:17

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 1665395)
Do you still have the bench top power supply available? If so you could separate the 2 suspect cells from the pack and charge each to 3.6v, then let them sit, the crook cell will drop lower than the good cell by a large margin over 12hrs or so.

T1 Terry

No, the benchtop power supply is at home, 3000 miles away. I emaild Balqon 10 minutes ago. Let's see what happens.

goboatingnow 29-10-2014 15:29

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

We don't have a baseline from the install, but assuming they met specification when new, we are seeing a capacity loss of 10-15% per year. The 100Ah cells are sitting at about 71-72Ah today. The loss appears to be more time dependent than number of cycles. These are GBS cells.
Interesting , I wonder if the rate is linear over time.

Jd1 31-10-2014 20:45

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I finally was (sort of) able to do a capacity test today.
I tested down to 2.6V from about 3.5V per cell using an inverter and a heater. For most of the test I was pulling around 170A which of course dropped towards the end. I was also running into issues with low voltage for the inverter and had to substantially reduce power draw (down to 600W) at the end to keep the inverter from shutting down. I measured 630 Ahr capacity but I encountered an error in the beginning of the test that reset my A hr counter. I would guess that I am pretty close to 700 A hr total capacity but will not be able to verify this for at least another week or two until everything is hooked up. The charger that I am currently using can only do 20A and it will take forever to charge the batteries at that rate.
One nice little twist of irony - the cell that I was all worried about because it kept dropping from 3.6V to 3.4V while sitting actually had the highest voltage when the test stopped. I was very pleased to see that I was worried for nothing.

T1 Terry 01-11-2014 04:03

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1667457)
I finally was (sort of) able to do a capacity test today.
I tested down to 2.6V from about 3.5V per cell using an inverter and a heater. For most of the test I was pulling around 170A which of course dropped towards the end. I was also running into issues with low voltage for the inverter and had to substantially reduce power draw (down to 600W) at the end to keep the inverter from shutting down. I measured 630 Ahr capacity but I encountered an error in the beginning of the test that reset my A hr counter. I would guess that I am pretty close to 700 A hr total capacity but will not be able to verify this for at least another week or two until everything is hooked up. The charger that I am currently using can only do 20A and it will take forever to charge the batteries at that rate.
One nice little twist of irony - the cell that I was all worried about because it kept dropping from 3.6V to 3.4V while sitting actually had the highest voltage when the test stopped. I was very pleased to see that I was worried for nothing.

A good result, so the cell was still filling up, not actually loosing capacity, just distributing it throughout the cell. That first conditioning charge can be quite nerve-wracking the first time as you always expect the worst. This recharge cycle will get then full so be prepared for a bit of top balancing when you get that far.

T1 Terry

Maine Sail 01-11-2014 07:14

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1667457)
I finally was (sort of) able to do a capacity test today.
I tested down to 2.6V from about 3.5V per cell using an inverter and a heater. For most of the test I was pulling around 170A which of course dropped towards the end. I was also running into issues with low voltage for the inverter and had to substantially reduce power draw (down to 600W) at the end to keep the inverter from shutting down. I measured 630 Ahr capacity but I encountered an error in the beginning of the test that reset my A hr counter. I would guess that I am pretty close to 700 A hr total capacity but will not be able to verify this for at least another week or two until everything is hooked up. The charger that I am currently using can only do 20A and it will take forever to charge the batteries at that rate.
One nice little twist of irony - the cell that I was all worried about because it kept dropping from 3.6V to 3.4V while sitting actually had the highest voltage when the test stopped. I was very pleased to see that I was worried for nothing.

Why did you go to 2.6V? Was that just the lowest cell? Winston told me not to go below 2.8V even though the manual says 2.7V. For an accurate bottom balance 2.65V is okay in order to achieve a 2.75V resting voltage but this is carefully monitored and done with low "C" rate loads.

All my capacity tests have been cut off with the lowest cell reading 2.8V and no inverter shut down because this is 11.2V or better.....

Current should have actually gone up as the voltage dropped unless it was your inverters losing efficiency. I prefer to run the inverter at less than full bore so my current stays steady, though it will rise slightly as the voltage drops....

My capacity tests from 550 cycles forward will be done with a lab grade DC load device for better accuracy. I will establish a new baseline...

A full Winston cell will rest at about 3.38V - 3.40V. They won't stay at 3.6V for very long...

Jd1 01-11-2014 21:20

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Maine Sail (Post 1667693)
Why did you go to 2.6V? Was that just the lowest cell? Winston told me not to go below 2.8V even though the manual says 2.7V. For an accurate bottom balance 2.65V is okay in order to achieve a 2.75V resting voltage but this is carefully monitored and done with low "C" rate loads.

All my capacity tests have been cut off with the lowest cell reading 2.8V and no inverter shut down because this is 11.2V or better.....

Current should have actually gone up as the voltage dropped unless it was your inverters losing efficiency. I prefer to run the inverter at less than full bore so my current stays steady, though it will rise slightly as the voltage drops....

My capacity tests from 550 cycles forward will be done with a lab grade DC load device for better accuracy. I will establish a new baseline...

A full Winston cell will rest at about 3.38V - 3.40V. They won't stay at 3.6V for very long...

The figure of 2.6V was based on the Balqon documentation on their web site. The voltage quickly recovered (didn't watch the actual voltage though) when the load was taken off the batteries.
My inverter shuts down at about 10.8V or so and I had a fairly long cable going and was losing some voltage there. It was a 3 kW inverter but I was only pulling 2 kW.
I don't recall what the current was doing exactly but I do remember that I had to reduce the total load to avoid (or correct) the inverter shutdown due to low voltage.
I will probably run this test again once all the control electronics are installed which will be some time yet ... today I managed to get a whopping 30 AHr worth of capacity into the batteries so it will take another 20 boat days at that rate :)

SV THIRD DAY 01-11-2014 21:31

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Jd1 (Post 1667457)
I finally was (sort of) able to do a capacity test today.

I would guess that I am pretty close to 700 A hr total capacity but will not be able to verify this for at least another week or two until everything is hooked up. .

Just so I can wrap my head about your thinking, what's your rationale for the 2K draw tests down to 10.4v Bank/2.6v cell voltage? I guess this is the difference between data type testing for "data" compared to more real life testing where you don't see those huge types of loads. In a way is the BS of the batteries being rated at a 0.5C discharge rate because what real world cruising boat ever sees a 0.5C load? I know you want to verify that you got what you paid for...but what most cruisers want to know is how long these expensive LiFePO4 banks will last and hold up under real life cruising type loads.

Jd1 01-11-2014 21:53

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by SV THIRD DAY (Post 1668243)
Just so I can wrap my head about your thinking, what's your rationale for the 2K draw tests down to 10.4v Bank/2.6v cell voltage? I guess this is the difference between data type testing for "data" compared to more real life testing where you don't see those huge types of loads. In a way is the BS of the batteries being rated at a 0.5C discharge rate because what real world cruising boat ever sees a 0.5C load? I know you want to verify that you got what you paid for...but what most cruisers want to know is how long these expensive LiFePO4 banks will last and hold up under real life cruising type loads.

Pretty simple actually - 2 kW draw because that was the biggest load I had (1600W load plus the inverter took the rest apparently). The 2.6V was based on the Balqon documentation (the graph showing cell voltage vs capacity with a big red line at 2.6V meeting the various discharge curves.
https://www.balqon.com/wp-content/upl...ttery_2013.pdf on page 5 shows 2.6V intersecting with the 1C discharge curve with 0% charge remaining.
I used the biggest load I had because I had to be present and I wanted the time to be reasonable but at 175A or thereabouts it is nowhere near 1C anyway.
In case I didn't mention it, the A Hr count was generated by a Victron BMV700 SOC meter.
Oh yes, I wanted to verify that I got the capacity I paid for, especially with the one cell that was suspected of being a used cell.

SV THIRD DAY 01-11-2014 21:58

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Got it.
The question I have then is what data/info do we have showing the relationship between these large discharge rates and the more typical discharge rates seen on a real life boat? I'm just trying to figure out if this test is good for the real world...or just for testing. What AH capacity would you get at a 20A or 15A draw? More...less or do we know?

Jd1 01-11-2014 22:24

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by SV THIRD DAY (Post 1668251)
Got it.
The question I have then is what data/info do we have showing the relationship between these large discharge rates and the more typical discharge rates seen on a real life boat? I'm just trying to figure out if this test is good for the real world...or just for testing. What AH capacity would you get at a 20A or 15A draw? More...less or do we know?

Going back to the graph I referenced above, from Balqon, the rated capacity of the batteries is rated at a 1C load. There is a 0.5C curve showing that you get additional capacity with a lower draw. I do not know how much additional available capacity you might see if you went to a really low discharge rate (I suspect it will be yet a bit more).
As far as I am concerned this test is only good to establish a baseline and to make sure you got what you paid for.


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