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

[pulper11]

Hello - I'm using trophy batteries 120AH 48V. I purchased two of them.

Since purchasing these, they have needed to be replaced.

The first one would had a cell that continually went below 2.8V, which I believe was the cutoff where the battery would go into alarm mode. It would actually go below that value. That would trigger the battery to turn off. I would have to open up the battery and charge that cell to at least 2.8V before reconnecting to my inverter. That battery was replaced.

The second one had the same issue. However, in addition to the above, it also dropped to 80% SOH. Also, when it would shutoff, it would go down to 0% SOC. It's not that the screen just showed 0% SOC - it would actually, when recharging, start from 0. That one was also replaced.

The first replacement has the same issue and is also at 80% SOH now. The second replacement has the same issue (cell voltage going too low and shutting off).

This seems very odd to me that this would happen 4 times. However, Trophy CS hasn't identified any issue with my setup.

I'm wondering if anyone here can look at my setup and see if anything might be wrong and leading to this issue.

I've attached a diagram here. The only differences between my current setup and the diagram are that the PV disconnect and the ground fault device are switched in location. Also, I have only 6 panels up, in a 3s2p setup.

All positive cables are the same length and type, as are the negative cables.

Thanks.

 

[sunshine_eggo]

Your use case is more likely at issue than your configuration. Let's explore that first.

1. What are the other 15 cell voltages when one hits 2.8V?
2. Are you regularly charging your batteries to > 3.40V/cell where you confirm all 16 cells are 3.40V or higher? IIRC, Dan likes to keep them to 54.7V (3.42V/cell), but I think the charger limit value is 56.3V (3.52V/cell).

99% of new batteries are not top balanced upon receipt. If they are not top balanced, or are not charged regularly into the balancing voltage range regularly, balance can continue to degrade until capacity is greatly diminished.

Over the course of 3 years where the batteries were NEVER fully charged, even Battleborns lost nearly 50% of their capacity. It took the owner holding the batteries at elevated voltage for about a week before it recovered to about 90Ah capacity.

 

[pulper11]

Thanks so much for the reply!

I forgot to mention that these issues all have occurred within 1.5 years. The most recent replacement (the last one mentioned above - battery 4 below) was installed in my system in the end of September, 2023 (less than a month ago). The previous replacement (battery 3 below) was installed July, 2023.

That may have been pertinent information! LOL.

Regarding your questions about configuration and cells:
For the first battery replaced, I listed all the cells for Dan in an email. Here they are:
1 3301
2 3290
3 3257
4 3328
5 3290
6 2501
7 3331
8 3295
9 3332
10 3297
11 3293
12 3291
13 3291
14 3288
15 3280
16 3284

For the second battery, I took screenshot of the cell voltages from the program that he uses:



Here's the third battery (from today):




And the forth battery (from today):

 

[pulper11]

On my LV6548, bulk charging voltage (#26) is 56.4 V.
The floating charging voltage (#27) is 56V.
Low DC cutoff voltage (#29) is 48V.

 

[kts78]

I had a similar problem with this (2 trophy 220ah) in the first 2 months my soc was dropping, the solution for me was to raise the float voltage so it would hit the equalization mode (kinda what Eggo was saying). Not sure if I was not draining them enough but the inverter usually just stayed in float mode and would not charge enough to equalize. Pretty sure I changed the float voltage to 56.8 and now 1 year later batteries are 99-100soc. Watch the battery monitor when they are charging, you will see when it starts to correct low cells.

 

[pulper11]

I had a similar problem with this (2 trophy 220ah) in the first 2 months my soc was dropping, the solution for me was to raise the float voltage so it would hit the equalization mode (kinda what Eggo was saying). Not sure if I was not draining them enough but the inverter usually just stayed in float mode and would not charge enough to equalize. Pretty sure I changed the float voltage to 56.8 and now 1 year later batteries are 99-100soc. Watch the battery monitor when they are charging, you will see when it starts to correct low cells.

Thanks kts78!
Dan advised me to move it to 56V a while ago. I believe it was lower than that as default. Obviously that didn't do the trick.
A couple of questions:
Do you think 56.8V will make a difference from 56V? If not, any other suggestions?
Can anything be done about the 80% SOH battery?
Thanks.

 

[sunshine_eggo]

Your cells look pretty messy.

Thanks kts78!
Dan advised me to move it to 56V a while ago. I believe it was lower than that as default. Obviously that didn't do the trick.
A couple of questions:
Do you think 56.8V will make a difference from 56V? If not, any other suggestions?
Can anything be done about the 80% SOH battery?
Thanks.

You didn't answer:

2. Are you regularly charging your batteries to > 3.40V/cell where you confirm all 16 cells are 3.40V or higher? IIRC, Dan likes to keep them to 54.7V (3.42V/cell), but I think the charger limit value is 56.3V (3.52V/cell).

Regardless of setting, are you actually hitting those peak voltages and are you doing so nearly every day for a couple hours a day?

Now it's time to go the other direction... what are the 16 cell voltages when the battery is at peak voltage?

If you're consistently failing to attain absorption voltage, cell imbalance will eat away at usable capacity.

 

[pulper11]

I agree that the cells are very messy.
I've looked through some of my solar assistant screen shots from the past.
One of the batteries would get above an average of 3.4V while charging, while the other would be an average of 3.33V. Both would be at 100% SOC according to SA.





These screenshots are from August, prior to getting one of the replacement batteries.
The replacement battery that has gone down to 80% SOH. That's in under a month. During that time, with the rain and weather, it would have been hard to consistently get over 3.4V on that battery for hours out of the day before it dropped to 80%.

 

[WindWizard]

One of the batteries would get above an average of 3.4V while charging, while the other would be an average of 3.33V. Both would be at 100% SOC according to SA

As @sunshine_eggo was mentioning, all 16 cells need to be above 3.4 Volts to maintain a healthy pack, not just a few of them.

​

 

[pulper11]

That's good to know. I did not realize these packs were as sensitive that a few months of averaging 3.33V or so, and not hitting 3.4V, could cause them to break down. It sounds like this is industry wide and not specific just to Trophy Batteries.

How do you guys handle the winter months where the amount of sunlight throughout the day (up north like me) is limited greatly for about 3 months or so? I can't see myself getting 3.4V for a couple hours nearly every day unless (and even then it's questionable) I do not use the batteries at all. So I either use the batteries and have them break down in a few months (going from 100% to 80% SOH and then perhaps lower) or I pack them up and wait for the longer days.

Perhaps I over-purchased on the batteries and don't have enough solar output so that I can use more than one? I have six 315V solar panels facing south.

 

[sunshine_eggo]

Can you plot the min/max cell voltage over the course of a day?

That's good to know. I did not realize these packs were as sensitive that a few months of averaging 3.33V or so, and not hitting 3.4V, could cause them to break down.

"Break down" is strong wording. Each cell loses charge at a different rate than its pack mates. Failure to provide enough balancing time causes them to continuously deviate in state of charge.

It sounds like this is industry wide and not specific just to Trophy Batteries.

Nope. Every single one of them. When you pay a premium for TRUE matched cells from an authorized distributor (2-3X typical cost), this issue decreases, but it will still impact capacity if allowed to continue.

Lead acid requires similar treatment for multiple reasons - both cell imbalance, and self-destruction when regularly not fully charged.

Your batteries aren't actually deteriorating on a cell basis, they're just losing usable capacity because some cells are hitting 0% when others are 20-30%. On the top end, you're likely seeing the high ones hit 100% while the low ones are 70-80%

How do you guys handle the winter months where the amount of sunlight throughout the day (up north like me) is limited greatly for about 3 months or so? I can't see myself getting 3.4V for a couple hours nearly every day unless (and even then it's questionable) I do not use the batteries at all. So I either use the batteries and have them break down in a few months (going from 100% to 80% SOH and then perhaps lower) or I pack them up and wait for the longer days.

Again, "break down" is not the right phrase or concept.

You need to ensure the batteries are spending several hours per week at elevated voltage that permits balancing. If you go for long periods of time falling short of absorption voltage, then you need to compensate for it during good periods.

Perhaps I over-purchased on the batteries and don't have enough solar output so that I can use more than one? I have six 315V solar panels facing south.

Nope. You have insufficient PV for your loads. You could have half the battery capacity you have, and you'd still be having the same issue.

PV/solar conditions determine how much you can replenish per day.
Battery capacity determines how long you can go between charges.

You have likely never top balanced the batteries to ensure that you can use their full capacity. It says a lot about Dan/Trophy that he's been willing to replace batteries when they're not being used properly.

You would be destroying lead acids left and right.

Recommend 57.6V bulk/absorption - you need to drive them as high as you can as quickly as you can.
Recommend 55.2V float - until you can confirm all cells are 3.45V at this level

Once balanced, drop to 55.2V bulk/absorption and 54V float.

 

[pulper11]

The battery was at about 75% SOC 30 minutes ago. Now I just checked it and it is at 0% SOC. During that time, I only had two led lights on. This is as it happened previously.

Obviously the Low Cell Voltage was triggered to stop the battery. However, to bring it down to 0% SOC doesn't make sense to me. Nor did it to Dan with the previous batteries. And as mentioned previously, this is not just showing 0% and then when it recharges it starts back at 70%. It unfortunately IS at 0% and will now have to charge all the way up.

Can someone explain why this would happens?

 

[sunshine_eggo]

The battery was at about 75% SOC 30 minutes ago. Now I just checked it and it is at 0% SOC. During that time, I only had two led lights on. This is as it happened previously.
View attachment 172824
Obviously the Low Cell Voltage was triggered to stop the battery. However, to bring it down to 0% SOC doesn't make sense to me. Nor did it to Dan with the previous batteries. And as mentioned previously, this is not just showing 0% and then when it recharges it starts back at 70%. It unfortunately IS at 0% and will now have to charge all the way up.

Can someone explain why this would happens?

I'm really not following you.

If a single cell is at 2.50V, the battery has absolutely no usable capacity left. Why wouldn't it make sense to be 0%? There's 0Ah in it. Why shouldn't it be 0%? Perfectly logical to me.

2.5V = 0%
3.131V = 14%
3.215V = 16%

That's an empty battery. It needs to be charged "all the way up."

The above disparity is either due to imbalanced or deteriorated cells. Until the battery is top balanced, and you can test capacity, you can't say which.

If the SoC is jumping around, it's because the BMS has no clue what's going on because it has completely lost track of Ah in and out and is guessing at SoC based on voltage, which is notoriously unreliable.

This is a completely simple situation where you're using more energy daily than you can replace with PV. You have two choices (pick one or both):

1) use less energy
2) produce more energy (generator)

I'm guessing you're doing this habitually, and it's a chronic problem.

Simple solution. Consume less energy and/or run your generator. Charge your batteries. You're just abusing them senselessly. If these were lead acid, and they were at 42V, you'd simply say, "Hmm... batteries are dead. Time to fire up the generator."

 

[pulper11]

You're right...you aren't following me. You seem to be dead set on comparing my use to lead acid, which I am not using. "If these were lead acid..." and "you would be destroying lead acid left and right". How can what I'm doing be "habitual" when I've owned a battery for less than a month? How can a BMS that is claimed to have greater than 5% accuracy "have no clue", "completely lost track", and be "guessing" in under one month and it's due to abusing it "chronically"?

@kts78 indicated he had the same problem as I have with the same company until he switched settings. Glad it's not just me who has been "abusing them senselessly".

 

[400bird]

While blunt, everything sunshine Eggo said in post #13 is accurate.

You're right...you aren't following me. You seem to be dead set on comparing my use to lead acid, which I am not using. "If these were lead acid..." and "you would be destroying lead acid left and right". How can what I'm doing be "habitual" when I've owned a battery for less than a month?

Because you've killed 4 in what sounds like the exact same manner.

How can a BMS that is claimed to have greater than 5% accuracy "have no clue", "completely lost track", and be "guessing" in under one month and it's due to abusing it "chronically"?

Because you've never taught it how big the battery is or gotten/kept the battery in good health.

@kts78 indicated he had the same problem as I have with the same company until he switched settings. Glad it's not just me who has been "abusing them senselessly".

Settings include how full you charge the battery. So, without knowing what settings were changed, it's probable the settings that user changed were to get hr battery full and allow balancing.

 

[TomC4306]

Because the BMS only has one, accurate truth point...
It resets/calibrates at 100%.
But keep in mind SOC is a derived value, not a direct measurement.
If you run your generator to charge these batteries to full, the BMS will read 100%, but ignore that and let the charge continue.
Set your charger to 3.5 volts per cell and let it run until current drops to near zero.
NOW your battery is full.
NOW 100% on the BMS means 100%.

 

[Partimewages]

@pulper11
I don't see your settings posted anywhere?
When the battery was new did you charge it with a charger? Not just solar charger. If you have only charged with solar and a load applied its likely never seen 100% SOC and doesn't know where it's at.

 

[pulper11]

Thank you guys for the responses. I appreciate them. I'll hook up my batteries to my panel and charge that way and limit usage until that.
I've just recently been very frustrated with what's been going on "in life" and this was just piling on. My frustration came out in my last post.

If someone could answer the question I posed above though, that would be appreciated. If these cells need to get to 3.4 for a couple hours almost every day or else they're being abused, how do people in the north deal with winters?

Thanks

 

[pulper11]

One more thing...Instead of a panel connection, could someone recommend a charger for this? If they're not too expensive, then I'd possibly go that route. I have only charged with solar and per Dan in the past, made sure it stays at 100% even though 100% doesn't mean 100%. I'm sure now based on this that I did not go far enough. Again, I apologize for the tone in my previous response.

 

[sunshine_eggo]

Thank you guys for the responses. I appreciate them. I'll hook up my batteries to my panel and charge that way and limit usage until that.
I've just recently been very frustrated with what's been going on "in life" and this was just piling on. My frustration came out in my last post.

If someone could answer the question I posed above though, that would be appreciated. If these cells need to get to 3.4 for a couple hours almost every day or else they're being abused, how do people in the north deal with winters?

Generators or grid backup. I'm helping another forum member in Maine. He's able to meet 20-25% of his needs at this point with PV due to cloud cover. He falls back to grid to charge the battery to ~95% pretty much daily.

One more thing...Instead of a panel connection, could someone recommend a charger for this? If they're not too expensive, then I'd possibly go that route. I have only charged with solar and per Dan in the past, made sure it stays at 100% even though 100% doesn't mean 100%. I'm sure now based on this that I did not go far enough. Again, I apologize for the tone in my previous response.

https://www.amazon.com/Adjustable-Switching-Regulated-Adjustments-Jesverty/dp/B0B8S5W8PZ

This would allow you to set an exact voltage. 5A isn't much, but it would charge one of these batteries in a day from empty to whatever voltage you like, AND it would hold it there and taper current while allowing balancing.

Too little emphasis is placed on these batteries being fully charged and top balanced before deployment. Most vendors just rely on the likelihood that regular full charging and cycling will bring them into balance over a couple dozen cycles. In a situation where production lags consumption regularly, they'll never get top balanced, and they'll get worse with time.

Why don't they come balanced? Because on-shelf storage, customer deployment lag (orders and lets them sit for a few weeks) and hazmat shipping requirements mean any efforts by the builders to balance them when they go out the door is wasted expense.