Can a bad solar panel or connection cause an overcharge in the charge controller?

[CVRider]

I have a 200W BougeRV solar panel and 30a BougeRv charge controller. I used this with 2x80ah marine batteries to run a 12v fridge (55w when cooling). I have a cheapo voltage current meter attached to the negative battery terminal and all negative wires (the charge controller and the fridge) attached to the other end of the voltage meter. Everything worked fine and the batteries were fully charged each night and only down to 12.5v in the morning.

I recently bought a 100a lifepo4 battery from DC House via ebay. I hooked this up to the same solar panel/ charge controller/ voltage current meter and changed the controller settings to Lifepo4. I came out mid day to check on things- the solar panel was in full sun and both the charge controller and the voltage current meter read 17v. I immediately disconnected the solar panels. I checked all my connections and tried again the next day and had the same problem. I then swapped out the BougeRV 30a controller for a generic 30a controller. I came out mid day again and both the controller and the voltage current meter read over 15v. I disconnected the solar input. As I checked the connections, I found that the positive MC4 connector was not snapped all the way in. I double checked that both charge controllers were set to charge lifepo4 at max of 14.6 volts.

Now I'm trying to figure out where my problem is. Is it two bad charge controllers? Is it a bad Lifepo4 battery? Is it a bad solar panel? A bad solar panel connection or connector?

Any help appreciated!

 

[sunshine_eggo]

I have a 200W BougeRV solar panel and 30a BougeRv charge controller. I used this with 2x80ah marine batteries to run a 12v fridge (55w when cooling). I have a cheapo voltage current meter attached to the negative battery terminal and all negative wires (the charge controller and the fridge) attached to the other end of the voltage meter. Everything worked fine and the batteries were fully charged each night and only down to 12.5v in the morning.

Everything sounded fine...

R recently bought a 100a lifepo4 battery from DC House via ebay.

And then this! Welcome to learning that your prior battery knowledge is nearly worthless.

I hooked this up to the same solar panel/ charge controller/ voltage current meter and changed the controller settings to Lifepo4. I came out mid day to check on things- the solar panel was in full sun and both the charge controller and the voltage current meter read 17v. I immediately disconnected the solar panels. I checked all my connections and tried again the next day and had the same problem. I then swapped out the BougeRV 30a controller for a generic 30a controller. I came out mid day again and both the controller and the voltage current meter read over 15v. I disconnected the solar input. As I checked the connections, I found that the positive MC4 connector was not snapped all the way in. I double checked that both charge controllers were set to charge lifepo4 at max of 14.6 volts.

Now I'm trying to figure out where my problem is. Is it two bad charge controllers? Is it a bad Lifepo4 battery? Is it a bad solar panel? A bad solar panel connection or connector?

Any help appreciated!

Your battery has imbalanced cells, one is hitting max voltage, and the BMS is cutting the battery out of the charge circuit.

This is incredibly common across all brands.

PWM controllers operate by shorting the panels to the battery. You're basically measuring panel voltage.

It's possible both charge controllers are damaged as they don't react well to the battery being removed when the PV is attached.

Recommend you set absorption to 13.8V, float to 13.6V and absorption time to 2-4 hours. If you can't make these settings, you should probably put the LFP on its on 12V AC charger for a few days.

 

[CVRider]

Thanks Sunshine. I made sure to disconnect the solar panels before disconnecting the batteries. If I put the Lifepo4 battery on a 12v ac charger, will that balance the cells?

 

[sunshine_eggo]

Thanks Sunshine. I made sure to disconnect the solar panels before disconnecting the batteries.

Hopefully, that's fine, but the problem is the battery removed itself from the charge controller via BMS protection. It's literally like you took the cable while it was charging and disconnected it.

If I put the Lifepo4 battery on a 12v ac charger, will that balance the cells?

Hopefully, yes. Ideally, you'd want to hold the battery at 13.8-14.4V for several hours.

 

[CVRider]

I put the battery on a charger for a couple days and all seems to be working correctly now. Fortunately the charge controller don't seem to be damaged. Thanks for the help Sunshine!