Problems with Batteries Low Cell Voltage - happened to four different batteries.

[400bird]

What is your over voltage release setting? That's when it will reconnect to allow charging again.

Also, your trying to turn the higher voltage in that one cell into heat. The BMS can probably only do this at 40mA or something tiny. If you can get inside the battery, you can do this manually at higher current.

 

[pulper11]

Here are my BMS settings on the first battery:





Here are my cell readings before charging the battery:



Here they are after charging and hitting max cell voltage protection:



When I re-connected the charger to this battery to charge it, it would not charge. Even though the battery cell levels were within safe regions now (third photo), I had to reboot the battery before it would charge. When I connect the charger to other batteries, when I flip the breaker switch, it charges right away (so long as it's not in protection mode).

Hope these settings help. Let me know if you need anything else here.

Appreciate your time.

 

[sunshine_eggo]

The lack of charging is normal. The drop in the high is a combination of 1) voltage naturally settling and 2) the BMS burning off charge.

Based on the high and low, that battery needs to be replaced if it's under warranty. It essentially has a small fraction of its usable capacity. I would estimate about 40-50% of rated.

 

[400bird]

Based on the high and low, that battery needs to be replaced if it's under warranty. It essentially has a small fraction of its usable capacity. I would estimate about 40-50% of rated.

Just looks crazy out of balance to me. I normally want to see cell voltages through the entire SOC range before calling it.

Here are my BMS settings on the first battery:

Too bad, it doesn't show when the over voltage fault clears.
Is this the same "first battery" from post #3?
If so, it shows the same data to me #6 is low and #7 is high.

When I re-connected the charger to this battery to charge it, it would not charge. Even though the battery cell levels were within safe regions now (third photo), I had to reboot the battery before it would charge. When I connect the charger to other batteries, when I flip the breaker switch, it charges right away (so long as it's not in protection mode).

Hope these settings help. Let me know if you need anything else here.

Appreciate your time.

I'd open up the battery and discharge cell 7 manually. The BMS internal balancing is going to take forever to correct that imbalance.
It might take a few cycles and #6 may need to charge up some to catch up to the other 15.

 

[sunshine_eggo]

Just looks crazy out of balance to me.

Yep.

I normally want to see cell voltages through the entire SOC range before calling it.

That evidence has been presented in this thread.

#6 is the cell that drops out at empty and is at < 40% charge when cell #7 goes over-volt with most of the others at a likely high-ish state of charge (70% and up).

Too bad, it doesn't show when the over voltage fault clears.
Is this the same "first battery" from post #3?
If so, it shows the same data to me #6 is low and #7 is high.

Yep.

I'd open up the battery and discharge cell 7 manually. The BMS internal balancing is going to take forever to correct that imbalance.
It might take a few cycles and #6 may need to charge up some to catch up to the other 15.

Nope. This is an absolute headache and will require hours of effort and monitoring.

How could a "few cycles" make up for ~50Ah of capacity imbalance?

While I accept that as much as 10% imbalance could be present in a new battery, there is no excuse for this. Trophy needs to resolve it.

A user shouldn't have to deal with a ~50% imbalance in cell SoC. This is not acceptable.

 

[400bird]

While I accept that as much as 10% imbalance could be present in a new battery, there is no excuse for this. Trophy needs to resolve it.

A user shouldn't have to deal with a ~50% imbalance in cell SoC. This is not acceptable.

I forget that not everyone has the tools, equipment, time, etc that I have. You're right, this is an off the shelf, assembled battery. A consumer shouldn't need to do this.

I still would ?‍

Request warranty, treat the replacement differently.

 

[sunshine_eggo]

I forget that not everyone has the tools, equipment, time, etc that I have. You're right, this is an off the shelf, assembled battery. A consumer shouldn't need to do this.

I still would ?‍

Request warranty, treat the replacement differently.

I'm not saying I wouldn't either. I have an uncanny ability to invest tremendous effort into things that aren't worth my time where the only reward is the satisfaction of having done it. I'm pretty sure it's a diagnosable condition.

 

[400bird]

I'm not saying I wouldn't either. I have an uncanny ability to invest tremendous effort into things that aren't worth my time where the only reward is the satisfaction of having done it. I'm pretty sure it's a diagnosable condition.

The less rewarding version is spending hours and hours only to find it more broken than expected and trashing it anyways. And yes, I'm pretty sure our condition is in the apa handbook.

 

[pulper11]

Thanks for the help! I will at this point work on the batteries that are connected to the solar panels.

This battery above is the first battery from the first post and post #3. This battery was replaced. However, when I attempted to return it, Dan said don't bother now. Same with the other replaced battery. I apologize for any confusion here...it's hard to explain the whole situation and I sincerely hope I haven't lead anyone astray here trying to help me. I wasn't originally planning on working on this battery when I posted. However, after reading the posts here, I was hoping that with setting changes and my monitoring it would get it back to function properly seeing as was mentioned I screwed up originally. Obviously I was wrong in that it is beyond repair for my capabilities. I will stop working on it.

Now, for the batteries connected to the solar panels. If these have the same BMS settings as I posted above, should I make any changes to these settings? Kindly read post #40 on page 2 of this thread to see what's happening with these, although I have not invested as much time into them as the first battery. I'll be able to post settings etc in the morning.

Thanks again.
Paul

 

[400bird]

beyond repair for my capabilities. I will stop working on it.

Where are you located? I'll bet someone here would help balance that free/junk battery or at least take it off your hands.

Now, for the batteries connected to the solar panels. If these have the same BMS settings as I posted above, should I make any changes to these settings? Kindly read post #40 on page 2 of this thread to see what's happening with these, although I have not invested as much time into them as the first battery. I'll be able to post settings etc in the morning.

Thanks again.
Paul

Get the cells balanced in one of two ways: the extremely slow way, with your solar fully charging each pack once per day or the slightly less slow way with the bench power supply one pack at a time as described in posts 26-28.

 

[sunshine_eggo]

the battery in post #40 is only somewhat imbalanced.

The other battery attached to the solar is one of the 80% SOH batteries. It actually went up to 56.67V when the max cell was at 3739MV (smallest cell was at 3441MV). It dropped down to 53.46V and 3365MV (max)/3336MV (min) after the OV alarm kicked in.

3.441 min is still a high state of charge.

What are the other 14?

I think the BMS is not reporting SoC accurately for this battery as I would say it's at least 95% SoC based on 3.441V cell.

Regularly achieving > 3.45V/cell min (55.2V) for 2 hours should correct this over time and cycles.

 

[pulper11]

Here are the results today from charging using 55.2V/5A. This is for battery #4 in my first post. It is the most recent replacement battery (received in September 2023).

The first picture here is before charging using the DC charger:


The second picture is right when the maximum cell hit 3.75V.



I'll be doing this a few more times tomorrow.

Interesting is that it seems that the highest cell seems to be #7 and the lowest cell seems to be #6. Not always but on Battery #1 and #4 that's the case when you charge it. I don't know if that's of any interest to anyone who actually knows what they're doing though!

Regarding getting rid of battery #1, I can't get rid of it until I know if Dan wants me to ship it back to him or not.

 

[pulper11]

Unfortunately I haven't been able to spend as much time with this recently as I had been.
Here is my most recent attempt at maximum charging of the most recent battery received (battery #4 - same as in post #52).
Again, I've got the print screen when the maximum cell voltage hit 3.75V.



I also have exported the data of the time spent charging this battery. Even though I cleared the data before charging and the battery SOC was displayed at 100%, there still is a lot of data. Not sure if this is of use to anyone to try to help my situation, but I've posted it anyway.

One more thing - the starting point where balancing occurs for this battery is 3300MV. Let me know if I should change that now.

Do you think that this is still a viable battery based on the data? I see the cells going up since the most recent top balancing attempt. Hopefully that's a good sign and that (as mentioned previously) this will simply take a long time.

Thanks!

 

[pulper11]

Ok - This is for battery #4 (the most recent replacement battery that I've had for about two months now).

I was getting pretty frustrated in that a few of low voltage cells were not getting any higher on many subsequent charges. They were similar voltages when the battery would go OV to the voltages as shown in the links and pics above. It's been cell #7 that's running away with the voltage when charged and hitting 3.75V relatively quickly leaving many other cells in the dust.

I thought about using a resistor (and bought one) to bring cell #7's voltage down, but instead I've decided to charge each individual cell to 3.65V, starting with the lowest. This I imagine (maybe I'm wrong) will also help me determine if any of the cells are already well below capacity, something I thought might be the case since they were not getting much higher with each subsequent charge.

The lowest cell has been charged for about 24 hours now. Using the bench charger set to 3.65V and 5A, it took about 10 hours to get from 3.341V to 3.383V. Over the next 8 hours, it increased to 3.62V. However, it has stayed at 3.62V now for 5 hours now.

Here's the question (on top of requesting any additional advice on what I've stated above). Do I keep the charger at 3.65V and 5A until the cell makes it to 3.65V, no matter how long that takes? Do I switch to another cell now to get that up to around the same voltage (maybe 3.6V). Or do I increase the charging voltage (can't change the amps) to speed up the process and just keep an eye on the progress?

Thanks.

 

[400bird]

I thought about using a resistor (and bought one) to bring cell #7's voltage down, but instead I've decided to charge each individual cell to 3.65V, starting with the lowest.

Should work fine. It's probably more work (as you've got more cells to charge), but you should be able to get to the same place in the end

This I imagine (maybe I'm wrong) will also help me determine if any of the cells are already well below capacity, something I thought might be the case since they were not getting much higher with each subsequent charge.

I don't know that I see a way to extrapolate cell capacity from the imbalance that you are correcting.

The lowest cell has been charged for about 24 hours now. Using the bench charger set to 3.65V and 5A, it took about 10 hours to get from 3.341V to 3.383V. Over the next 8 hours, it increased to 3.62V. However, it has stayed at 3.62V now for 5 hours now.

Here's the question (on top of requesting any additional advice on what I've stated above). Do I keep the charger at 3.65V and 5A until the cell makes it to 3.65V, no matter how long that takes? Do I switch to another cell now to get that up to around the same voltage (maybe 3.6V). Or do I increase the charging voltage (can't change the amps) to speed up the process and just keep an eye on the progress?

Thanks.

In my opinion, you don't need to make it perfect, just get close and let the integrated BMS do the finishing work. I'd be fine with 3.55 volts. There's barely any capacity between 3.5 and 3.65 volts.

As it's sitting at 3.62 volts, what is the current? It sounds like it dropped into CV mode and has been lowering the current to hold the voltage stable.

 

[sunshine_eggo]

I thought about using a resistor (and bought one) to bring cell #7's voltage down, but instead I've decided to charge each individual cell to 3.65V, starting with the lowest. This I imagine (maybe I'm wrong) will also help me determine if any of the cells are already well below capacity, something I thought might be the case since they were not getting much higher with each subsequent charge.

My preferred method as it's exact. Resistor method is very inexact and requires several iterations.

The lowest cell has been charged for about 24 hours now. Using the bench charger set to 3.65V and 5A, it took about 10 hours to get from 3.341V to 3.383V. Over the next 8 hours, it increased to 3.62V. However, it has stayed at 3.62V now for 5 hours now.

when you report a voltage, are you reporting what the charger reports or what a voltmeter on the cell reports?

Are you using high quality leads, or the alligator clips?

In my opinion, you don't need to make it perfect, just get close and let the integrated BMS do the finishing work. I'd be fine with 3.55 volts. There's barely any capacity between 3.5 and 3.65 volts.

Agree. 3.65 is the maximum, but it's arguably no better than 3.55.

As it's sitting at 3.62 volts, what is the current? It sounds like it dropped into CV mode and has been lowering the current to hold the voltage stable.

This.

 

[pulper11]

As it's sitting at 3.62 volts, what is the current? It sounds like it dropped into CV mode and has been lowering the current to hold the voltage stable.

Thanks so much for the reply! (and @sunshine_eggo too while I was typing).
The current is very very low. I just checked...0.02A.

I'm using a voltmeter to measure the voltage. The clips are what came with the charger. Not great (as discussed before) but what I have on hand.

So, based on the two posts here, I'll move to another cell.

One other quick question...does the breaker and/or battery have to be on while doing this? I've kept it off. As you obviously know by now I don't have a great deal of knowledge with this!

Thanks again.

 

[sunshine_eggo]

Those cells are full when they measure 3.65V at the terminals AND 5A is flowing into them, so it was fully charged awhile back. i suspect the 3.62 vs. 3.65 is simply measurement error between the power supply and your meter.

Yes. Next cell.

To simplify/shorten the process, terminate charge when the voltmeter reports 3.60V or higher, and the power supply reports 5A or lower. Note that if you're using the alligator clips, you may find that you can't maintain 5A before you get to 3.60V.

Breaker off is best. When you directly connect to the cell terminals, it doesn't matter because it's like the rest of the battery doesn't exist, but it's safer that way.

Once you go from lowest to highest, cycle back through them to top them off. Shouldn't take more than a minute or two per cell.

 

[pulper11]

Update!!

I've been able to get all cells up to approximately 3.62V individually. Then I went through and charged them again. That took approximately 15 to 30 minutes each.

I've connected this battery to my inverter today.

One of the cells was high to start with (i think about 3.5 something) and I don't have all the cell totals for comparison unfortunately. But from Solar Assistant, when the high cell hit 3.75, the average of the cells was 3.463 and the min was 3.353. I'm a little concerned with the 3.353 but am happy with the average cells. It wasn't anywhere near that before! I'll let this run now for a couple of days of sun (if we get some) and see if the balancing improves. Or perhaps it might take longer than that??

The other battery (battery #1) that was suggested to be replaced above was still open and since I've just been doing this for the newest battery, I decided to give it a shot (increasing voltages of the lowest cells to 3.62 or so). I wasn't expecting much but so far I've been able to get 4 cells out of 4 (the only ones I've tried so far) to 3.62, including the one cell that is consistently very low. Is that a good sign or does it basically mean nothing?

thanks!!

 

[sunshine_eggo]

The other battery (battery #1) that was suggested to be replaced above was still open and since I've just been doing this for the newest battery, I decided to give it a shot (increasing voltages of the lowest cells to 3.62 or so). I wasn't expecting much but so far I've been able to get 4 cells out of 4 (the only ones I've tried so far) to 3.62, including the one cell that is consistently very low. Is that a good sign or does it basically mean nothing?

If thats' the original cell that was very low, it is going to take a very long time to charge, and the voltage will take forever to increase.