Damaged batteries and reduced solar input?

[ckelly3415]

Hey all!

I am worried my Lifepo4 battery bank has been damaged from the cold but unsure how to tell for certain. I have 3 206ah SOK batteries in parallel for a 618ah battery bank. My system has been dying a lot as the weather turns colder and the sun is not so high in the sky.

I charged my system to full the other day with a smart charger, and drained the system to empty to see what I am working with. At about 390ah of consumed energy, my battery bank voltage dropped to 10.5V, and the system died. They are not the heated models and I tried to charge them using a smart charger last winter in cold temps because I’m an idiot.

I have 600 watts of solar, and I am also now noticing that even when parked in full sun, the bank is only charging up at ~230 watts. Would this be expected from November sun output or could damaged batteries also be reducing the amount and speed that they are able to charge? Is there a way to confirm that the batteries are damaged or not? I’m missing over 200ah of energy seemingly so that leads me to believe that they are….
Thanks!

 

[n2aws]

Honestly, I think we'll need some more details.

You mentioned the AH per battery, but not the voltage, how many cells in series, etc.

Is it possible that your cells are imbalanced?
If you connect to the BMS on the batteries, are then any alarms/notices?
What temperatures are the batteries experiencing? And did you try charging or discharging them during the cold extremes?

 

[Ampster]

Assuming they are 48 Volts and original capacity was 618 and you now have 390 Ahrs, that is a loss of 11.5 kWhs of capacity. As the previous poster suggested there is more information needed.

 

[Q-Dog]

Assuming they are 48 Volts and original capacity was 618 and you now have 390 Ahrs, that is a loss of 11.5 kWhs of capacity.

Why do you assume 48 volts? Look at the graphs they posted.

I suspect some imbalance. I would disconnect all the batteries and try charging them up to full individually.

 

[Ampster]

Why do you assume 48 volts?

I did not look at pictures because I am on my phone and traveling. That would then mean his original capacity was about 7.5 kWhs. I agree he should verify capacity to make sure imbalance is not reducing that.

 

[740GLE]

I’m on my phone sitting on my couch and clearly see the pictures is a 12v system.


Either way, don’t all SOK have low temp charging protection? So I would rule out damage due to charging under freezing temps.

I’m guessing this is a 3p set up, do you have pictures of how the 3 batteries are connected? Using proper wiring techniques right? If the wiring is incorrect, you’ll never get fully charged.

Tell us more about this smart charger, unless voltage was 13.8-14.4v for 4-6 hours it tough to say they are fully full.

OP, when you thought your batteries were healthy, what was the max PV you saw at the peak of the summer. I’m guessing you never saw more than 500w peak, and 400-450 was more common. I’m guessing you’re seeing winter production issues that is resulting in 230w.

 

[Benjamin Yang]

Voltage Recovery:
Allow the batteries to warm up to room temperature and observe if the voltage recovers. If the low voltage was primarily due to cold temperatures, the voltage may increase as the batteries warm up.
Battery Management System (BMS) Data:
Check if your LiFePO4 batteries have a built-in Battery Management System (BMS). The BMS should provide information about individual cell voltages, temperature, and overall battery health. Monitor this data to identify any abnormalities or imbalances.
Capacity Testing:
Perform a capacity test on the batteries in more moderate temperatures. Discharge the batteries and measure the total capacity they deliver. Compare this with the specified capacity from the manufacturer.
Solar Panel Output:
While reduced solar output in November is expected due to lower sun angles, you should still be able to generate a reasonable amount of power with 600 watts of solar. Confirm that there are no shading issues or other factors affecting the solar panels' performance.
Check for Parasitic Loads:
Ensure that there are no parasitic loads draining the battery bank when it's not in use. Even small loads over time can significantly impact the state of charge.