280 AH lifepo4 cells lost balance

[aness]

Hello, recently went on a trip to Glacier NP, which was great, but my power system was letting me down.
I checked the voltage of the cells on my 2 280 AH batteries. The one was perfectly balanced as it was when I built the batteries, the other had these voltages on the cells:
Cell 1 3.22
Cell 2 3.45
Cell 3 3.45
Cell 4 3.34

When the battery was built a few years back they were balanced. They have been hooked to a Daly BMS whenever they are in use. I am wondering if I just need to rebalance these cells or do I have bigger problems?

I also have been having discharging issues with these batteries since I first got them. The Daly BMS are rated for 150 amp discharge each. Sometimes I pull anywhere from 70 to 130 amps through a 3000 watt inverter. When this is done for over 5 minutes, the alarm starts to go on the inverter for low voltage and the voltage does drop to around 13.0 or sometimes lower. I feel with the battery size, my system should be able to handle that load, but it seems to struggle with time.

 

[aness]

Here is the BMS used on both. The length of wire to each battery is equal.

 

[Alkaline]

4s active balancer the 5A one should fix the issue.

 

[aness]

4s active balancer the 5A one should fix the issue.

Would I be better off picking up a table top power supply and doing a top balance?

 

[Alkaline]

No you would just be spending time for worse results, just get something like this and be done:

https://www.amazon.com/Cywhrvzsf-Equalizer-Balancer-Equalization-Capacitor/dp/B09G74WDN5/

 

[aness]

No you would just be spending time for worse results, just get something like this and be done:

https://www.amazon.com/Cywhrvzsf-Equalizer-Balancer-Equalization-Capacitor/dp/B09G74WDN5/

Alright, then just leave it on that battery and don't worry about the other battery that is staying balanced for now?

 

[Alkaline]

I used the 8s version on my 2 grade B packs and they kept in balance, just charge to full every now and then and you will be fine, it balances better when cells are near full.

you can put a on/off switch on it, but I didn't bother just left it connected and forgot about it, stayed balanced for 2 years.

Daly Balancing is not the best so this should help.

 

[aness]

I used the 8s version on my 2 grade B packs and they kept in balance, just charge to full every now and then and you will be fine, it balances better when cells are near full.

you can put a on/off switch on it, but I didn't bother just left it connected and forgot about it, stayed balanced for 2 years.

Daly Balancing is not the best so this should help.

Appreciate the help, thanks. Any ideas on if I should be able to pull the 150 amps between the 2 batteries? I will see if the battery being balanced properly will hopefully get that working better also.

 

[Alkaline]

balancer should not have any affect on what amps you are pulling.

 

[DIYrich]

I would float at 14.4v for 8 hours, and see what the bms can do. If it improves, then float some more.

 

[Ampster]

I bought a 2 Amp active balancer for my 3P16S pack of LF280s. I love my Orion BMS for all the other features but the balancing current was not enough for these big cells.. The cells are also Grade B and were purchased over 15 months from three different vendors so they were never matched well. I did ininitally take a week to parallel top balance them but within a couple of months they began to drift at the top. I turned off the balancing on the BMS and the active balancer keeps the pack balanced at the top of the charge curve. I also only charge to 3.45 volts per cell.

 

[aness]

I bought a 2 Amp active balancer for my 3P16S pack of LF280s. I love my Orion BMS for all the other features but the balancing current was not enough for these big cells.. The cells are also Grade B and were purchased over 15 months from three different vendors so they were never matched well. I did ininitally take a week to parallel top balance them but within a couple of months they began to drift at the top. I turned off the balancing on the BMS and the active balancer keeps the pack balanced at the top of the charge curve. I also only charge to 3.45 volts per cell.

I don't think I am able to turn off balancing with my Daly BMS, will this be an issue?

 

[Ampster]

I don't think I am able to turn off balancing with my Daly BMS, will this be an issue?

Can you adjust the voltage when balancing starts? Setting it high would essentially disable it if it is high enough. if you can not turn it off I think two different types of balancers could create some conflicts, espectially since active balancers take energy from high cells and distribut it to low cells, whereas the Daly and other shunt based balances just put some resistance on the cell to bleed off voltage and that might affect the readings of the active balancer.

 

[aness]

Can you adjust the voltage when balancing starts? Setting it high would essentially disable it if it is high enough. if you can not turn it off I think two different types of balancers could create some conflicts, espectially since active balancers take energy from high cells and distribut it to low cells, whereas the Daly and other shunt based balances just put some resistance on the cell to bleed off voltage and that might affect the readings of the active balancer.

I don't have a way to connect to the BMS, no bluetooth or wifi connection. I am not completely sure the daly BMS even has active balancing.

 

[Ampster]

I am not completely sure the daly BMS even has active balancing.

As far as I know there is no active balancing in the Daly. It is shunt based, which means it uses resistors to shunt the current around a cell that is high. Same process as putting a resistor or light bulb across one cell.

 

[aness]

As far as I know there is no active balancing in the Daly. It is shunt based, which means it uses resistors to shunt the current around a cell that is high. Same process as putting a resistor or light bulb across one cell.

So is this type of balancing not a problem with the active balancer you recommended? I purchased it already and am just waiting for delivery.

 

[Ampster]

So is this type of balancing not a problem with the active balancer you recommended?

It is hard to predict. Personally, from what I have read about the Daly, I would buy another BMS. There are some with one or two Amp active balancers. I like more control over my BMS and balancer than the Daly appears to give.

 

[aness]

It is hard to predict. Personally, from what I have read about the Daly, I would buy another BMS. There are some with one or two Amp active balancers. I like more control over my BMS and balancer than the Daly appears to give.

Don't really plan to buy a new BMS. Would I be smart to disconnect the BMS when I put the active balancer on the cells?

 

[Ampster]

Would I be smart to disconnect the BMS when I put the active balancer on the cells?

You would lose all the other advantages of having the BMS which is a risk that I would not take.

 

[Berseker]

Here is the BMS used on both. The length of wire to each battery is equal.
View attachment 162383

it appears you bought a non smart daly bms. fortunately now, daily has a 1amp smart active balancer, you can buy that , set it up properly and hook on the pack. it shud get and keep them balanced within a couple of days.

jk has a 2amp balancer, while the mighty NEEY has a 4amp to 15amps balancer. choose the best for your needs, based on cost.

the initial error was buying the wrong type of bms. a non smart bms


edit: these are lazy ways of getting it to balance within a week or 2, if you get a good balancer, however the standard way of resolving this issue..is to dismantle the pack and top balance again to 3.65v. and then reassemble again. however cells will naturally creep apart after some time, so the final lasting solution is to slap on a smart active balancer.set it to come on at 3.37v to 3.4v and when delta is up to 0.02a

 

[SeaGal]

... The one was perfectly balanced as it was when I built the batteries, the other had these voltages on the cells:
Cell 1 3.22
Cell 2 3.45
Cell 3 3.45
Cell 4 3.34

Over a few years, not surprising there is an imbalance, but I'd check connections on cell #1 in particular and cell #4 to a lesser extent. 3.34V is not that low when charge is removed from the cell. 3.22V however is very low compared to the other 3.

There has been a lot of talk of balancers on here so far - but I'd use a bench top PSU to bump up cell #1 to 3.45 and then do same with cell #4.

Then check connections and float with BMS / balancer attached and see how it goes.

 

[aness]

Over a few years, not surprising there is an imbalance, but I'd check connections on cell #1 in particular and cell #4 to a lesser extent. 3.34V is not that low when charge is removed from the cell. 3.22V however is very low compared to the other 3.

There has been a lot of talk of balancers on here so far - but I'd use a bench top PSU to bump up cell #1 to 3.45 and then do same with cell #4.

Then check connections and float with BMS / balancer attached and see how it goes.

I got the 5 amp balancer off of Amazon that was recommended. It brought the cells to 3.33 for all but the one that was low it got it to 3.30 before I hooked it back up to my solar. I have the active balancer connected now and the charger looks to be floating and the cells are as follows. Cell 1 was one that was very low before the balancer.

Cell 1 3.31
Cell 2 3.60
Cell 3 3.36
Cell 4 3.36

Is 2 trying to help along Cell 1? My feeling is Cell 1 may be starting to fail? How does one know if a Cell is toast?

The system is sitting at 14.5 V right now and drops to about 13.4 if I use it to charge my ebike battery. Seems to function normally there, but I don't feel like I have the full capacity of 560 AH from the 2 12v 280 AH batteries.

Thanks for your help.

 

[Substrate]

Something I've noticed - for some reason some BMS makers think that a balance-trigger-voltage of 3.40v is acceptable. It is NOT, as much as urban mythology tries to make it. Along with "always balancing". How to fry those rice-grain resistors.

So just checking - if your adjustable bms has the balance trigger at 3.4v, that is at the bottom of the upper discharge knee. Change that to 3.5v trigger - even if that means many cycles of rebalancing afterwards to get it truly right.

 

[Berseker]

Something I've noticed - for some reason some BMS makers think that a balance-trigger-voltage of 3.40v is acceptable. It is NOT, as much as urban mythology tries to make it. Along with "always balancing". How to fry those rice-grain resistors.

So just checking - if your adjustable bms has the balance trigger at 3.4v, that is at the bottom of the upper discharge knee. Change that to 3.5v trigger - even if that means many cycles of rebalancing afterwards to get it truly right.

but some people only charge to 3.45v. am not sure 3.5v balance trigger is a good idea for unbalanced pack