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

[PacificGreen]

Not many people make big large energy home based storage systems on 12v for a reason. Why would you on a boat?

[autumnbreeze27]

My counter is BMV-600S, settings per Victron for Lifepo4. My alternator is controlled with a mc-614. My BMV seems to be pretty accurate, within a few % I'm sure, since when it gets up to 100% I can see the amps drop to 0.

Even when the solar gets the battery up to 100%, it stops charging. If the boat systems are drawing 10-15A, the net is 0 to the battery per the BMV. It seems to work that way whether the charging source is shore, alternator, or solar.

I figure if I get 50%, + or - a few % won't make your break me, since I could take it to 20%.

I don't have a way to check individual cell voltages. The engineer that I met at balqon that sold me the battery, when I asked him about needing to monitor the cells individually, said it wasn't necessary, and they mostly were building electric trucks for commercial purposes. Don't want to argue that here, because I know you guys like to monitor everything, I'm just debating if I need to add a switch to disable the alternator if it's at 100%. I prefer to come in to an anchorage at 100% power if I can. Depending on the weather and time of year, I can go a week or so without starting the engine.

I guess I just don't get the theory that I need to disconnect the alternator if it's not pushing any juice to the battery. My voltage for 100% SOC on the bmv is 13.7V, which I figure isn't actually 100%. So if all my charging sources are 13.7 is 100% SOC, I'm really stopping the charge in the high 90% range.

I monitor my battery manually, and when it gets above 90% I usually turn on the water heater, or make something in the toaster oven, and bring it up to 100% slowly.

Typically when the bmv shows the battery is above 85-90% it's only pushing 10-20 amps into the battery, after running the house loads. That's with the solar and alternator doing their normal thing.

So I guess the question is, if my alternator is pushing 10 amps to the house to run navigation and refrigeration, and 0 is going to the battery, I should still consider disconnecting it?

[PacificGreen]

Originally Posted by autumnbreeze27

My counter is BMV-600S, settings per Victron for Lifepo4. My alternator is controlled with a mc-614. My BMV seems to be pretty accurate, within a few % I'm sure, since when it gets up to 100% I can see the amps drop to 0.

Apparently these are very good systems. I had a chance last night to review the documentation some on the alternator but don't really have any experience charging batteries with alternators other than automotive.

Originally Posted by autumnbreeze27

Even when the solar gets the battery up to 100%, it stops charging. If the boat systems are drawing 10-15A, the net is 0 to the battery per the BMV. It seems to work that way whether the charging source is shore, alternator, or solar.

Ah the residual boat drain. Yes and that is exactly how the solar should function to mostly offset the electrical cost of the boat systems. So your solar controller is working great and your BMV is recording properly.

Originally Posted by autumnbreeze27

I figure if I get 50%, + or - a few % won't make your break me, since I could take it to 20%.

That all depends on your situation I guess. Going lower on the bank and using all the energy has its merits and then counts as a full cycle in my opinion. The data really is up in the air as to what is a full cycle and what is not. You like me hope that by not total discharge perhaps we can buck the system so to speak. Others would say use all the energy. In a marine environment no play it safe when possible especially if you use the bank for propulsion.

Originally Posted by autumnbreeze27

I don't have a way to check individual cell voltages. The engineer that I met at balqon that sold me the battery, when I asked him about needing to monitor the cells individually, said it wasn't necessary, and they mostly were building electric trucks for commercial purposes. Don't want to argue that here, because I know you guys like to monitor everything, I'm just debating if I need to add a switch to disable the alternator if it's at 100%. I prefer to come in to an anchorage at 100% power if I can. Depending on the weather and time of year, I can go a week or so without starting the engine.

What size are your cells and how many if you don't mind me asking? You have the miniBMS clone produced by Balqon then. You still can put your voltmeter across the cells and get readings from them manually as I must when I'm curious. For the most part it is not necessary but it should still be a rudimentary skill and procedure you practice in case you ever need to shunt off current or add current to quickly equalize a cell to avert disaster. That is fine about being 100% at destination but just make sure your not holding them there dumping current into them for longer than needed. Nice about the time to start the engine.

Originally Posted by autumnbreeze27

I guess I just don't get the theory that I need to disconnect the alternator if it's not pushing any juice to the battery. My voltage for 100% SOC on the bmv is 13.7V, which I figure isn't actually 100%. So if all my charging sources are 13.7 is 100% SOC, I'm really stopping the charge in the high 90% range.

If it says your not charging then your not charging. I don't think you need to add a switch if you believe your gear but frankly compare and contrast the price of a switch compared to your cells? What if anything ever failed with the regulator? Add the switch and be done with it. Nice now I have your 100% full voltage so lets see if I can relate. I have to convert everything to 48v first. 13.7x4 = 54.8v for me with my Balqon cells. That would be full and if I did not have to hold my bank there long I wouldn't. The very second you take the charge away from them anyhow they will naturally want to come back down to 53.3 = 13.325 anyhow. I very seldom rode my bank higher than 54v = 13.5. The effect is slower at 48v for me but at 12v nominal you must see the 13.5v, 13.6v, 13.7 volt ranges happen pretty darn quick. What is the amp charge rate of the mc-614? Once the energy is in the bank its in the bank especially if you know your coloumbs have been counted correctly.

Originally Posted by autumnbreeze27

I monitor my battery manually, and when it gets above 90% I usually turn on the water heater, or make something in the toaster oven, and bring it up to 100% slowly.

I don't find any fault with this and is actually good practice. For me it is all about +/- amps in and that is how I generally manage my bank as well. Although I'm sure your mc-614 does the current tapering for you.

Originally Posted by autumnbreeze27

Typically when the bmv shows the battery is above 85-90% it's only pushing 10-20 amps into the battery, after running the house loads. That's with the solar and alternator doing their normal thing.

Yeah but I feel your are right at your activation point of your chemical at 13.7 full nice and safe but I would simply call 13.5v full and stay way out of that range unless you really feel you need it. If your not using your bank for propulsion then there really is not any need. 13.5v for me is 54v and generally I would never be above 54v in normal use ever and when I was I knew the bank was in a steady state of fullness which I could sense and derive by the amount of time a charger was plugged in and how quickly and easily it would jump up above 54v. That was always a good indication to start using energy like you say.

Originally Posted by autumnbreeze27

So I guess the question is, if my alternator is pushing 10 amps to the house to run navigation and refrigeration, and 0 is going to the battery, I should still consider disconnecting it?

Ah that is the crux of it isn't it? I would say if your riding your voltage above 13.5v disconnect it. So far as I'm concerned your buffering to hard. Now if your batteries were sitting at 13.4v then I would say your safe to buffer with no problem. I can only relate how my 48v system works and I have a better voltage spread to have made these observations with. After 54.4=13.6 these cells are full and climbing hard really hard and they want that upper knee bad.

[john61ct]

Originally Posted by autumnbreeze27

So I guess the question is, if my alternator is pushing 10 amps to the house to run navigation and refrigeration, and 0 is going to the battery, I should still consider disconnecting it?

If you are sure that your manual system is keeping charge from flowing after the "best to consider this" 100% point, then you're right, no switch needed.

But personally I would want an alt field disconnect switch anyway.

There are many scenarios where your charging is taking lots of HP which you would want made 100% available for propulsion power for a critical period.

Or you may need to isolate the bank quickly while you need to keep the engine running.

I thought they were pretty standard, nothing to do with LFP longevity.

[john61ct]

Originally Posted by PacificGreen

Now if your batteries were sitting at 13.4v then I would say your safe to buffer with no problem.
...
After 13.6 these cells are full and climbing hard really hard and they want that upper knee bad.

I am a little confused, so staying with 12V.

If I charge AT 13.8V, in other words, climb the CC curve TO that setpoint, then hold CV there for say 30 minutes and STOP.

Let the bank just sit and rest for a few hours, and it's SITTING at 13.6V

I choose to define that as my "safe 100%" charge, don't think any reason to go past that in routine usage.

Now, is that cycle described as "charging to 13.8V" or "charging to 13.6V" ?

[PacificGreen]

Originally Posted by john61ct

I am a little confused, so staying with 12V.

You know john61ct so am I. You seem to be contributing lots to these forums in many different threads. How about you answer a few questions about yourself that I have asked previously.

Originally Posted by john61ct

If I charge AT 13.8V, in other words, climb the CC curve TO that setpoint, then hold CV there for say 30 minutes and STOP.

It's not "AT" its to 13.8V. If you want but do you even have batteries?

Originally Posted by john61ct

Let the bank just sit and rest for a few hours, and it's SITTING at 13.6V

If you say so.

Originally Posted by john61ct

I choose to define that as my "safe 100%" charge, don't think any reason to go past that in routine usage.

Okay suit yourself.

Originally Posted by john61ct

Now, is that cycle described as "charging to 13.8V" or "charging to 13.6V" ?

Honestly why do you ask? Are you a Bot? I can't make heads or tails out of your regurgitated responses half the time.

[exMaggieDrum]

Originally Posted by john61ct

If you think about it, they must be positioned between the cell "inside" and the external connections. The easier and more expensive Integrated Systems you can buy, that per cell monitoring and control is a routine part of what you're paying the extra money for.

I'm not speaking to LFP batteries, composed of multiple LFP cells at a nominal 2.7v with a built in BMS in the battery. I'm speaking to multiple, individual cells that I have to put together with external bus bars to connect to make a nominal 12v battery.

[exMaggieDrum]

Originally Posted by Maine Sail

Joe,

The thing you need to focus on most is losing the lead acid mind set.

IDEAL LFP USE= Charge>Shut off All Charge Sources>Use Stored Energy>Charge>Shut off All Charge Sources>Use Stored Energy>Charge>Shut off All Charge Sources>Use Stored Energy>Repeat>Repeat

Getting over the lead acid mind set is the absolute hardest thing for most LFP converts. Floating or keeping LFP at high states of charge will lead to loss of capacity.

These batteries like to be used, they do not like to be floated or kept at high SOC's. Unlike lead, keeping these batteries full actually causes harm and capacity loss.

If you are on-board the easiest solutions, beyond your BMS protections, which won't protect the bank from you keeping the bank at high SOC's continually, is to wire manual shut offs for:

Alternator = Switch at helm to shut down regulator or cut field
Solar = Switch wired per controller manufacturers instructions to isolate PV
Battery Charger = Already has a switch
etc..

When at the dock isolate the LFP, discharge it to 50% SOC, and let it sit there. Use a lead acid reserve bank for dock side buffering.

MaineSail,
You read something in to my post that I did not say or mean. I am sorry if it was confusing. My design and plan is to do exactly as you put in bold in your post.

I am putting in two switches to be able to turn off the power to my two Balmar alternator regulators, one for the engine alternator and one for the DC generator, although I would just shut down the generator in practice. I can turn off my inverter/charger if on shore power, especially whenever I am leaving the boat, even for a short while. I have a remote for my Outback solar charger and will only have it on when I am cruising and will turn it off whenever the cells are even close to "full".

I have not installed my system yet but I will in a a couple months (after vacation and finishing up a bath remodel I got sucked in to). The cells I have I top balanced (per my previous posts last year) to 3.65v and then took them down to 2.9v where they still are. When I use the boat the plan is to charge them up to "full" and then make sure something is discharging them. I will turn something on to manually discharge them before I leave the boat.

I will turn off all charging sources whenever, in every case, after I go through the charge regimen that you and others have recommended. I intend to be VERY conservative but will still have the HousePower BMS in the system along with high and low battery cutout switches, including for AC to the I/C.

I intend to be very conservative with my LFP's, and not do anything old school lead-acid. I am not sure what I said that made you think I am still thinking with a lead-acid mindset. I do appreciate your admonition in general as it is applicable to all of us who have or will have LFPs.

I have a CellLog monitor for the four parallel cell groups. I am not sure how the monitor can monitor individual 2.7v voltages without disconnecting them from each other in series with the other three groups to make 12v. I know the BMS does that as well. I don't see how I can do that with a handheld meter to get individual 2.7v cells readings rather than the average of the whole set at 12v or the 2.7v parallel groups without taking off the bus bars between the other groups in series. Even the BMS will only have four monitor boards for the cells in parallel.

But that is where I am lacking in knowing the physics and electronics of how that is done, not how to manage the battery charging and discharging.

P.S. I have my AC switches setup so I can isolate the I/C from shorepower and still provide it to my AC panel to run heaters, lights or anything else AC while at the dock. Since it is my only AC battery source it will not be able to "wake up" and try to charge the batteries while I am gone. I do need to design in how to still keep the DC bilge pump on when I leave. I may just put it on my start battery.

I would appreciate more on how the start battery would buffer the house bank and why when at the dock and all charging sources are off.

[PacificGreen]

Originally Posted by exMaggieDrum

MaineSail,
You read something in to my post that I did not say or mean. I am sorry if it was confusing. My design and plan is to do exactly as you put in bold in your post.

Maine Sail was addressing Joe in his text and so I guess that is you as well but he could have been addressing the other joe. And doing exactly as MainSail suggests is great for lithium. Not doing it or missing something like I may have leaving 53.2 volts in my resting bank for 10 months may have cost me cycles.

Originally Posted by exMaggieDrum

I am putting in two switches to be able to turn off the power to my two Balmar alternator regulators, one for the engine alternator and one for the DC generator, although I would just shut down the generator in practice. I can turn off my inverter/charger if on shore power, especially whenever I am leaving the boat, even for a short while. I have a remote for my Outback solar charger and will only have it on when I am cruising and will turn it off whenever the cells are even close to "full".

You seem to have all your bases covered there.

Originally Posted by exMaggieDrum

I have not installed my system yet but I will in a a couple months (after vacation and finishing up a bath remodel I got sucked in to). The cells I have I top balanced (per my previous posts last year) to 3.65v and then took them down to 2.9v where they still are. When I use the boat the plan is to charge them up to "full" and then make sure something is discharging them. I will turn something on to manually discharge them before I leave the boat.

Lord knows why you went with one idividual power supply in the first place to top balance all 16 of your cells. See the video above of that poor guy with his daytona electric car. What a nightmare for him to even consider top balancing small cells - a literal nightmare.

I started with a learning bank of 16 cells like you have and quickly discovered the only way to reasonably top balance and or maintain when needed was to have one of the RC type chargers hooked up to four at a time and left on auto charge to complete the top balance. And to top it off I soon realized that these small cells get post loaded and wiggle loose especially the way I was using them. The revolutrix rc charger is great and that is what some others use. I recommend HiTec as I mention in my one post about an active BMS above.

Originally Posted by exMaggieDrum

I will turn off all charging sources whenever, in every case, after I go through the charge regimen that you and others have recommended. I intend to be VERY conservative but will still have the HousePower BMS in the system along with high and low battery cutout switches, including for AC to the I/C.

Yes the infamous and rock solid zero data HousePower BMS. I'm starting to think it looks very similar to the Elite BMS which at least gives individual cell voltages and may be worth upgrading.

Originally Posted by exMaggieDrum

I intend to be very conservative with my LFP's, and not do anything old school lead-acid. I am not sure what I said that made you think I am still thinking with a lead-acid mindset. I do appreciate your admonition in general as it is applicable to all of us who have or will have LFPs.

Again you can see that unless your name is Joe he was not addressing you.

Originally Posted by exMaggieDrum

I have a CellLog monitor for the four parallel cell groups. I am not sure how the monitor can monitor individual 2.7v voltages without disconnecting them from each other in series with the other three groups to make 12v. I know the BMS does that as well. I don't see how I can do that with a handheld meter to get individual 2.7v cells readings rather than the average of the whole set at 12v or the 2.7v parallel groups without taking off the bus bars between the other groups in series. Even the BMS will only have four monitor boards for the cells in parallel.

Now finally we get the the real questions. I only wish I could use a CellLog to monitor all 16 of my batteries but for some reason they still produce there units with an RC battery mentality and couldn't be bothered to make a unit that would measure 16 cells in series.

After some various back and forth regarding your obvious confusion about how to get individual cell voltages from your bank I dig some research from your previous posts here and in other topics here as well. I see know how you have configured your batteries 4S4P or 4P4S configuration and how you have arranged your CellLog and BMS to that affect.

I can see why you will never be able to get individual cell voltages from your system. I also think that this is an inherent design flaw in your set up. If you wanted a 400ah system why you just didn't purchase 4 400ah cells like main sail did and you would have been so happy as the starting point.

This guy did it correctly so far as I'm concerned with 12v nominal. LiFePO4 for House bank final designs - Page 6 - Cruisers & Sailing Forums

Originally Posted by exMaggieDrum

But that is where I am lacking in knowing the physics and electronics of how that is done, not how to manage the battery charging and discharging.

Yes well much of it has to do with a learning curve for sure and to some degree just making mistakes as I may have with leaving my batteries at 53.2 when you obviously even realize I should have left them at 2.9v per cell.

Now don't get me wrong on your setup. I'm sure other people have gone 12v in 4S4P like old school mentality but why?

Originally Posted by exMaggieDrum

P.S. I have my AC switches setup so I can isolate the I/C from shorepower and still provide it to my AC panel to run heaters, lights or anything else AC while at the dock. Since it is my only AC battery source it will not be able to "wake up" and try to charge the batteries while I am gone. I do need to design in how to still keep the DC bilge pump on when I leave. I may just put it on my start battery.

Inadvertently you have purchased your solution already. Split your bank into 4 100ah 12v banks. Power the bilge pumps with one. Make a 12v bank for the starting battery. Have one for a spare starting battery or then rig three at 4S for house loads that you can charge and discharge in a cycle.

Otherwise rig for 16S 48V and down convert to your 12v needs. You would just need a 48V alternator and charger.

Originally Posted by exMaggieDrum

I would appreciate more on how the start battery would buffer the house bank and why when at the dock and all charging sources are off.

I think he is suggesting getting an expendable bank of lead acid to abuse instead of burning cycles off the lithium.

[PacificGreen]

The more I sit here knowing my batteries on the boat are resting at 53.2 volts 3.32v per cell the more anxious I am about getting back to the boat. I believe a trip out the following week is in the works and that I can't afford to hold off until good weather.

I have calculated the HousePower BMS parasitic draw on the bank as follows:

At 5 miliamps it will draw down my batteries at a rate of 1 amp-hr for every 200 hours (8 days). A 100 amp-hr bank should be good for about 80 days at that rate.

So I have a 400ah 48v bank and should be good for close to a year.

The bank has been in this state for with this small load for 9 months now. When last checked in December the voltage was still at 53.2v. I know that I intentionally wanted to leave it at a higher than acceptable out of service voltage to account for this draw.

After sitting here rereading what MainSail provides for data with his test cells in the garage I'm wondering what I'm doing still sitting here. I by this time should at least see 50volts on the pack.

[senormechanico]

This is beginning to sound like,

"I bought a Ferrari to look at, and drive a Trabant to work every day."

[PacificGreen]

Originally Posted by senormechanico

This is beginning to sound like,

"I bought a Ferrari to look at, and drive a Trabant to work every day."

Yeah I hear ya there except in my case I can't even look at the Ferrari from where I'm sitting. I have an appointment tommorrow and later in the week the tolling motor arrives. I am going to head out after that for a trip out to verify things myself.

[exMaggieDrum]

Originally Posted by PacificGreen

Maine Sail was addressing Joe in his text and so I guess that is you as well but he could have been addressing the other joe. And doing exactly as MainSail suggests is great for lithium. Not doing it or missing something like I may have leaving 53.2 volts in my resting bank for 10 months may have cost me cycles.



You seem to have all your bases covered there.



Lord knows why you went with one idividual power supply in the first place to top balance all 16 of your cells. See the video above of that poor guy with his daytona electric car. What a nightmare for him to even consider top balancing small cells - a literal nightmare.

I started with a learning bank of 16 cells like you have and quickly discovered the only way to reasonably top balance and or maintain when needed was to have one of the RC type chargers hooked up to four at a time and left on auto charge to complete the top balance. And to top it off I soon realized that these small cells get post loaded and wiggle loose especially the way I was using them. The revolutrix rc charger is great and that is what some others use. I recommend HiTec as I mention in my one post about an active BMS above.



Yes the infamous and rock solid zero data HousePower BMS. I'm starting to think it looks very similar to the Elite BMS which at least gives individual cell voltages and may be worth upgrading.



Again you can see that unless your name is Joe he was not addressing you.



Now finally we get the the real questions. I only wish I could use a CellLog to monitor all 16 of my batteries but for some reason they still produce there units with an RC battery mentality and couldn't be bothered to make a unit that would measure 16 cells in series.

After some various back and forth regarding your obvious confusion about how to get individual cell voltages from your bank I dig some research from your previous posts here and in other topics here as well. I see know how you have configured your batteries 4S4P or 4P4S configuration and how you have arranged your CellLog and BMS to that affect.

I can see why you will never be able to get individual cell voltages from your system. I also think that this is an inherent design flaw in your set up. If you wanted a 400ah system why you just didn't purchase 4 400ah cells like main sail did and you would have been so happy as the starting point.

This guy did it correctly so far as I'm concerned with 12v nominal. LiFePO4 for House bank final designs - Page 6 - Cruisers & Sailing Forums



Yes well much of it has to do with a learning curve for sure and to some degree just making mistakes as I may have with leaving my batteries at 53.2 when you obviously even realize I should have left them at 2.9v per cell.

Now don't get me wrong on your setup. I'm sure other people have gone 12v in 4S4P like old school mentality but why?



Inadvertently you have purchased your solution already. Split your bank into 4 100ah 12v banks. Power the bilge pumps with one. Make a 12v bank for the starting battery. Have one for a spare starting battery or then rig three at 4S for house loads that you can charge and discharge in a cycle.

Otherwise rig for 16S 48V and down convert to your 12v needs. You would just need a 48V alternator and charger.



I think he is suggesting getting an expendable bank of lead acid to abuse instead of burning cycles off the lithium.

Pacific Green,

My name is Joe, and I believe that MS knows that. I took the cue that he was speaking to me from him quoting the post I made. May be I was wrong.

I respect you trying to do what is right for you using the knowledge you are getting from different sources. That is what we all are doing. I do, respectfully, disagree with so much of what you have just said, and I am too tired to deal with it at the moment, I'm going to withhold anymore comments for now.

[Maine Sail]

Originally Posted by exMaggieDrum

Pacific Green,

My name is Joe, and I believe that MS knows that. I took the cue that he was speaking to me from him quoting the post I made.

Post 5511 was quoting Joe Parklane.....

[PacificGreen]

I just discovered that they make from 1S to 32S balance, charging and BMS boards for the electric bicycle market. These would be an incredible time saver for top balancing cells. Seems some may come with LED's, a few with LCD displays and others with none.