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Old 06-09-2013, 04:17   #241
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Re: Lithium Batteries (for the rest of us)

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We use a Sterling Pro-Charge Ultra and a "custom" setting. This charger allows you to build a custom program. With this charger I have it set to charge to 13.8V then drop to 13.4 which essentially turns it off unless a load kicks on. We very rarely use our battery charger though. Once the bank attains 13.8V it gets to a point where very little current will flow into the bank at that voltage. While it is not technically full, as in upper knee full, it simply gets to a point where 13.8V can no longer push any more current into the bank... It tapers to this level, in fairly short order, once the current starts to drop...
Mainesail, does the sterling use current to monitor the switch from 13.8 to 13.4 or do you do it manually , what happens if there is a shore power connection and the charger is running the systems loads.

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Old 06-09-2013, 04:51   #242
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Re: Lithium Batteries (for the rest of us)

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Originally Posted by goboatingnow View Post
Why are you talking about bulk, absorption and float in the context of Li, its has no meaning.

I understand you leave the alternator at 13.8 and left the current taper off and you do this manually. now I see what you are doing.

Dave
The reason for bulk, absorption & float is only in relation to what we have available for alternator charging regulators.

My alt will not come up to target voltage for quite a while so that is bulk charging.. When it hits 13.8V it is now in the regs absorption mode where it remains until current tapers to 5A +/-. I use float as my charge termination but also have the ability to do it manually via an alt cut switch...
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Old 06-09-2013, 05:14   #243
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Re: Lithium Batteries (for the rest of us)

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Mainesail, does the sterling use current to monitor the switch from 13.8 to 13.4 or do you do it manually , what happens if there is a shore power connection and the charger is running the systems loads.

dave
Yes in a sense it has an internal current sensor but it has no idea what the system current is so it is like most any charger, pretty dumb. It does do a good job of dropping to float and staying there even if their are loads on the system. It will do this so long as they don't exceed the chargers capacity and bump it back into a cycle. This is one reason I only charge to 13.8V because the bank never really gets "full" and I am leaving some capacity on the table, about 7-10Ah's.... At 13.8V it is pretty hard to do any damage to these batteries as they eventually get to a point where no more current will flow in at that voltage. If I were to bump it to 14.2V I can get that extra 10Ah's in but not at 13.8V...

As you know in order to have a truly "smart" charger that worked based on current and voltage there would need to be multiple shunts so the charger could tell the difference between accepted battery current and system loads and charger output.. As of now I don't know of any that do this well.. Most chargers use an algorithm and I find the Sterling to be a decent one. Again, this is why I prefer my switch mode DC power supply as my "shore charger" and I manually manage it....

These are just choices I have made for this bank. Time will tell if it works well. Thus far the cell balance and cycle testing shows it works quite well and limits risk of over charging. While the taper at 13.8V is slightly slower it is still LIGHTNING fast compared to any LA technology and I can certainly live with it....

I generally don't leave any charge source unattended with Li including solar.. I charge then shut off. The only time I leave solar on is when I am running loads that match or exceed solar output or I am charging back from a deep discharge and know it will take multiple days before getting close to full. If I know I am done for the day, with the boat, I will stop charging at about 70-80% capacity as I don't want to leave them always sitting at 100%... Yesterday I left her at 92% SOC with the fridge running but no solar... I am trying to get to 200 cycle before we haul her in November... Accelerated cycle testing is NOT easy to do and getting 200 cycles in less than a year has proven quite challenging......

I have only twice seen my solar regulator actually get to 13.8V because the accepted bank current usually exceeds my solar capacity in current. The bank really has to be at about 99% for a 13.8V charge voltage before our solar current catches up...
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Old 06-09-2013, 05:50   #244
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Re: Lithium Batteries (for the rest of us)

Maine Sail's approach sounds very sensible to me.

I think a lot of people are still using lead acid thinking where a 100% SOC is very good for the batteries. With lithium it is better to avoid 100% where possible, particuarly at high temperatures and when the batteries are kept at 100% SOC for long periods.

My reading of the limited evidence is that 90 to 40% is healthier than 100 to 50%. The former range also gives much more leeway against an inadvertent high voltage event.
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Old 06-09-2013, 06:38   #245
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Re: Lithium Batteries (for the rest of us)

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Maine Sail's approach sounds very sensible to me.

I think a lot of people are still using lead acid thinking where a 100% SOC is very good for the batteries. With lithium it is better to avoid 100% where possible, particuarly at high temperatures and when the batteries are kept at 100% SOC for long periods.

My reading of the limited evidence is that 90 to 40% is healthier than 100 to 50%. The former range also gives much more leeway against an inadvertent high voltage event.
I am not making any claims that it should be done this way, it is only how I have chosen to do it after doing hundreds of hours of testing. If it does not work well I will be the first to try and figure out why and will let you know. I am not in this for a "my-way or the highway" thing just to try and figure out a safe way to charge/discharge LiFePO4 on a boat, not ruin cells and to get long life. To me right now giving up a few Ah's on the top end seems a very reasonable way to go about this. It may not be for everyone, but works very well for me...

I went into this as an experiment and to get better educated on this technology. It has meant hundreds of hours of charging and discharging and playing with voltages, measuring temps etc. etc. but I want 600+ cycles before I would even consider deeming it a success.

Over the winter I will be doing a lot more cycling as it is easier in the shop and I can get two 80% DOD cycles into one day.

Once you get the hang of it it is as easy as flooded batts to manage. It is getting it set up and dialed in that takes some experimentation. I plan to top balance once per year at this point but as of now we don't need any and our BMS has never been pushed to shunting/balancing levels...

Perhaps pushing to higher voltages actually necessitates the need for cell balancing, but I can't really say? All I can say is that we have charged to well below the upper knee, cycled to 80% DOD regularly, and the cells are 100% spot on...

One thing this whole process has taught me is that series flooded batts, as in 6V batts, may also need balancing if the voltage never gets pushed high enough. Place un-equally charged 6V into a series situation and they seem as if they can get themselves out of balance too?

Can't say for sure because I have not had a chance to get my Midtronics or Argus analyzers on the ones I have found out of balance as an as-new baseline.. I have far too many customers who refuse to push the voltage higher than 14.4V with flooded batts. I now wire 6V batts in parallel before placing them into service and charge to a "wake-up" voltage of 7.5V or an equalization voltage until the current drops to below 0.3% of "C". We'll see how this works in the future. I have always done "wake-up" charges but not with 6V or 2V in parallel...

I am now physically measuring 6V batts and finding out of balance batteries in quite a few installations. With these situations a simple push to 15.5V often fixes it..

We still have a lot to learn with LiFePO4 on boats at fractional "C" levels for charge & discharge.. There is a lot to be learned from the EV world but they use the batts totally differently than we do so I take it with a grain of salt until we have more data for the way we use the batteries on boats..

So far I am EXTREMELY happy with this technology. It is simply amazing to watch my voltage rarely if ever fall below 13.2V. Even at 80% DOD the engine starts like it is connected to 20 AGM batteries and the voltage barely budges...

it's cool stuff, but I think we still have a lot to learn and that will take time...... If I could even get 1000 cycles out of this bank, at 80% DOD's, that would be AMAZING..... I see many LA batts die before they even hit 150 cycles to 50% DOD......

My average customer (the ones with mostly stock systems power or sail) goes in the water in mid June and comes out in mid September. They will use the boat/cycle the batts for an average of about 6 days per month for three months.

Even if we bumped that to 10 days per month and figured they cycled to 50% DOD every day, which they don't, that means the batteries get cycled approx 30 times per year. 30 cycles X 5 years would be 150 cycles. With these systems I usually see batteries last about 3 years or 90 cycles (on average)! This is often due to sulfation and undercharging. LiFePO4 does not suffer from this.. One problem solved..!

Adding solar and tweaking the charging system, and convincing them to equalize, I can push these same customers to 6-10 years but still that means under 300 cycles in a best case scenario for most of my customers... I am already at 164 cycles but to 80% DOD for about 75% of them....
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Old 06-09-2013, 09:24   #246
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Re: Lithium Batteries (for the rest of us)

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Originally Posted by Maine Sail View Post
The reason for bulk, absorption & float is only in relation to what we have available for alternator charging regulators.

My alt will not come up to target voltage for quite a while so that is bulk charging.. When it hits 13.8V it is now in the regs absorption mode where it remains until current tapers to 5A +/-. I use float as my charge termination but also have the ability to do it manually via an alt cut switch...
never seen an standard alt, with a float cycle , interesting

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Old 06-09-2013, 11:16   #247
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Re: Lithium Batteries (for the rest of us)

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never seen an standard alt, with a float cycle , interesting

dave
Me neither but I don't have a standard alternator or regulator.. Of course many of the Hitachi alts mimic this once they get warm because they temp compensate by reducing voltage. It often looks like float but the alt is just protecting itself...

IMHO anyone using a "standard alt" for LiFePO4 is going to have trouble eventually. Probably sooner than later. I am using a dual fan custom built HO alternator specifically wound for good low RPM performance and am driving it with a Balmar MC-614 external regulator that allows control of just about every parameter one could ask for. She can pump out 100A at engine idle....

Even with this HO alt I have had to limit its output, via the regulator, to about 110A - 120A when hot... Without reducing its output via the Balmar regulator she would quickly climb well past 225F and enter temp limiting. The temp limiting feature drops the field by 50%.

Once cool it would pop back to full output and repeat the process all over. This really cut into my initial charging performance. I tried cooling ducts etc. but this battery still demanded full current for so long the alt still beat itself up.

Rather than use the Balmar temp limiting feature I used a feature called "belt manager" which reduces the field permanently. It is designed to protect belts from burning up. With LiFePO4 it comes in handy to prevent alternators from burning up.... I am driving it with a serpentine belt so no worries there but the heat was astounding at 140+ amps....

The belt manager feature helps me avoid alternator temp limiting which digs into performance worse than limiting to 110A +/- amps when hot. After all the tweaking and adjustments it can now run at 110-120A all day long and not exceed 225F.... You really need a much bigger alternator than 110A-120A if you plan to run at 110A-120A all day long.


I am currently on the boat and taking some more cell balance measurements with the meter I have been using as my control meter. It is a NIST calibrated Fluke 179.

I am not real happy with the Cell Log for accurate data and the Fluke is the meter I have been basing everything off since the beginning.. The Cell Log is a good tool but not what I want to use for accurate measurements.

Here's what I just measured:

Unloaded resting @ 77% SOC - Cell temps 72F:

Cell #1 = 3.361V
Cell #2 = 3.362V
Cell #3 = 3.361V
Cell #4 = 3.361V

Loaded @ a -15.5A average load @ 75% SOC - Cell temps 72F

Cell #1 = 3.314V
Cell #2 = 3.315V
Cell #3 = 3.315V
Cell #4 = 3.314V


Charging @ 116A 13.72V - 13.73V - Cell temps 72F

Cell #1 = 3.430V
Cell #2 = 3.431V
Cell #3 = 3.430V
Cell #4 = 3.429V

Charging @ 32A - 34A (current dropping quickly) 13.81V (regulator voltage limiting) - Cell temps 72F

Cell #1 = 3.451V
Cell #2 = 3.452V
Cell #3 = 3.452V
Cell #4 = 3.451V

Not half bad for 164 cycles, approx 75% of them to 80% DOD, and no cell balancing since the initial top balance....
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Old 06-09-2013, 11:24   #248
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Re: Lithium Batteries (for the rest of us)

Hey Folks
I wonder if I might get some help. Im enamored with the idea of the Lithiun Ion batteries. Not because of any one factor, but I want a system that is dependable, safe, and doesnt need a lot of care and feeding. I'm considering the Lithionic or the Smart battery. Yes, I know, huge expense, but I'm a big fan of plug and play. My time to R and D things is at a premium. So I suppose my question is; are these types of LI batteries good, reliable purchases?
Thanks
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Old 06-09-2013, 13:49   #249
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Hey Folks
I wonder if I might get some help. Im enamored with the idea of the Lithiun Ion batteries. Not because of any one factor, but I want a system that is dependable, safe, and doesnt need a lot of care and feeding. I'm considering the Lithionic or the Smart battery. Yes, I know, huge expense, but I'm a big fan of plug and play. My time to R and D things is at a premium. So I suppose my question is; are these types of LI batteries good, reliable purchases?
Thanks
Ed
Maybe someone will chime in, but none of the usual suspects here I'm aware of have any experience with those. There may be some limited experience with Genasun or Mastervolt, two other makers of packaged systems.

I think the truth is they really don't fully address the "R&D" issue. While they can address the BMS issue, your charging sources: alternators, solar controllers, wind controllers and AC powered chargers all need to be set for LFP. This is not difficult for many of the more modern devices, but requires some attention from you, or a technician. But sometimes, other ancillary systems have to be modified or replaced.

LFP can be simple once installed and set up, but right now there just isn't a plug and play installation engineering solution. Part of the reason is what Maine alluded to, we don't have the optimum parameters all dialed in yet, but his are a great place to start.
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Old 06-09-2013, 13:51   #250
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Maine,

I really should remember...but I don't. What is the Ah capacity of your test bank? Thanks.
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Old 06-09-2013, 14:26   #251
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Re: Lithium Batteries (for the rest of us)

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Maine,

I really should remember...but I don't. What is the Ah capacity of your test bank? Thanks.
400Ah - Winston Cells
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Old 06-09-2013, 22:59   #252
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Re: Lithium Batteries (for the rest of us)

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The primary purpose of HVC monitoring is to prevent an individual cell getting out of balance in a series string and hence receiving greater that its allotted cell voltage. HVC on simply the charging voltage of the battery bank , really isnt doing anything at all,

What you are doing is more like charge termination. HVC is meant to be a fault protection

What I meant by the diode pack , is that if it blows out to a short circuit , your scheme looses its protection. I prefer HVC to cause a disconnection of the charting sources and I do not automatically reconnect on a HVC event terminating

HVC should be set about the charge termination voltage set point IMHO
Dave
Yes, my High Voltage Cutoff is my charge termination, cutting off all charging sources, or in the case of the alternator fooling it into thinking the battery voltage is 0.7V higher than it really is.
I guess what is confusing in my setup is that I use all the gear that I have unmodified (shore charger, alternator with simplistic internal regulator, unregulated solar of negligible power) and use my programmable voltmeter to ‘disable’ the charging source. Even if this should fail, all of the charge sources have their own regulation that will not lead to a sudden cell death. It may or may not be good for the cells if the situation goes on for months or years. No sweat, I or a friend will be at the boat at least once a week to check the Junsi CellLog data.

I still monitor each cell with a Junsi CellLog and can easily grab a very long piece of copper cable and ‘short’ the high cell(s). That is how I do the top balancing in the first place. All reports indicate that it is really unlikely to get imbalanced cells the way are using them. Anyway, you have to get into the upper or lowers knees to see any delta-V that is larger than 50mV (0.05V). The way my upper and lower voltage limits are set I am far away from them.

I have blown the split diodes twice with LA, but never to a short circuit, always to a broken connection. I am not sure they can even be blown to a short cicuit. Even if they would, there is no danger, as the alternator will still only go to 14.3 V, which is well within the safe range for long-term cell survival.

I don’t know what you want to say with ‘HVC should be set about the charge termination voltage set point IMHO’. I think that is exactly what I am doing. My HVC = my charge termination point.
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Old 06-09-2013, 23:37   #253
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Re: Lithium Batteries (for the rest of us)

Here are the first logs from the 360Ah installation on my boat.

The first graph shows the log of about 2 days for the 360Ah installation. On the left I am messing around with the programming of the voltmeter. It was initially set for 14.15V for some testing, then I dialled it back to 13.8 and left it alone for 2 days.
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The second graph shows one of those cycles annotated. I think it shows quite nicely that one can use a $35 programmable voltmeter to use the regular charge source on a standard boat to charge LiFePo batteries. I think it is a big turn-off to many people to replace the shore charger, convert the alternator to accept an external regulator, install and program the external regulator.

Click image for larger version

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The last days here have been very tray, so not much solar. Anyway, a 100W solar panel does not even tickle those cells.
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Old 06-09-2013, 23:48   #254
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Re: Lithium Batteries (for the rest of us)

The graph below shows cells connected to 8S1P = 24V. I top balanced the cells twice to 3.7V with a 10 hour resting period in between.
I then discharged at a measly, but house-bank typical, 7A using 4 automotive lightbulbs in 2S2P to just above 2.9V. I got 185 Ah out of 160Ah cells. Going between 13.8 and 12V should still give 160+Ah. Not bad.

The graph uses a 60s recording interval.

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I am now assembling the cells to a 2P4S battery matching the weakest with the strongest cell, second-weakest with second-strongest, and so on. I am hoping to get a well balanced pack doing it this way.
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Old 07-09-2013, 06:51   #255
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Here are the first logs from the 360Ah installation on my boat.

I think it is a big turn-off to many people to replace the shore charger, convert the alternator to accept an external regulator, install and program the external regulator.
.
Great data! Thanks for posting.

I don't see any flaws in your design. We have enough data now from all user groups that any kind of routine frequent balancing just isn't mandatory on these cells. And control systems can work at the bank level for "good" cells. I do still worry a bit about this long term since eventually cells can and will fail. You will catch that with your review of CellLog data. If you were there, you would catch it just observing the system in normal operation. I also think it's a good idea to have some kind of temperature monitoring. And audible alarms for unexpected conditions.

The "legacy" stuff does get in the way. But I think it's more of a cost issue than ability. Someone who could duplicate your installation, with money could program and install replacement or add on equipment.

I have given lots of thought on how to install LFP as painlessly as possible. To that end, I have developed, and am now in the testing phase of a LFP battery monitor using off the shelf industrial automation hardware. The concept is you can buy any cell size and configuration you want, take them out of the box, install them and address many of the integration issues. It will:

1) Automate the initial balancing of the cells
2) Protect the bank for HVC/LVC events (like a BMS)
3) Function as a SOC battery monitor (Like a Victron 602)
4) Monitor bank and if needed alternator temperature
5) The user interface is a web page, either integrated into the boats network, or a standalone hotspot. Use a cellphone, tablet or PC.

The "cookbook" install could without addressing any external systems:

1) If you have all separate charge and discharge paths, disconnect the discharge only for LVC.
2) Otherwise it would work on 1 solenoid for both charge and discharge on the LFP
3) Use a sacrificial battery, could be a UPS or motorcycle battery.
4) Parallel the sacrificial battery on charge (so all the charging sources always see something)
5) Disconnect the LFP bank at full charge
6) Reconnect the LFP and remove the sacrificial battery for discharge
7) If needed, a temperature sensor can also disconnect the LFP based on Alternator temp, leaving just the sacrificial battery until the temperature lowered.
8) Provide audible alarms
9) Have an emergency bypass

It doesn't have to be configured this way, but the idea of this configuration is it would work for any boat, regardless of what "legacy" equipment is installed. Hopefully if there is a flaw here, someone will point it out....

The PLC computer is $150, the ADC $100, an instrument amplifier $40 (if you want the SOC battery monitor function), the 8 channel relay box about $40 (if you need more than the 2 on the CPU, and required if you want to automate the initial balance). Plus a couple solenoids, a shunt and a router if you don't have Ethernet onboard. So it's not a CellLog level solution at $350+ for the hardware. But if you compare that to adding alternator regulators, battery monitors, replacing a charger, it might become attractive. And you get a system based on industrial strength equipment. How well this will work in a marine environment remains to be seem, but it should be better than the RC equipment, and does everything at the cell level.

It works now on the bench, but I still have a bit of work to do getting the SOC monitor function tuned, and then I need to do some final full cycle integration testing and install on my boat (the primary purpose for the exercise).

But I will share the code when it's complete for a couple systems if someone wants to be a beta tester.

The hardware can be found here:

http://www.triplc.com/nano10.htm

http://www.wayjun.net/index.php?main...products_id=43

http://sigma-shop.com/product/103/rs...ler-12vdc.html
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