Charging voltage spikes on Renogy Rover 40amp

[NewGuy23]

I have 4x12v panels in parallel feeding a Renogy Rover 40amp charge controller. For five years, this has been charging a bank of 2 x Renogy 200ah gel batteries in parallel, wired to an AIMS 3,000 watt inverter. Everything is 12 volt. This is a dedicated system that ONLY runs my well pump, which pulls 10.5 amps when it's running. Sometimes, it runs 2 minutes a day. Sometimes, 6 hours a day. I've had zero problems.

Yesterday, I replaced the batteries with one LiTime 100ah Mini LiFePo4 battery, and switched the charging profile to lithium. Immediately, the voltage would spike as high 17, trip an alarm that disconnected the CC, then it reconnects, spikes, alarm is triggered, rinse and repeat. I only let this happen 3 times and disconnect the charge controller from the panels.

Can anyone shed some light on what happened here?

 

[sunshine_eggo]

Absurdly common.

Welcome to the world of new LFP batteries that are imbalanced - it's more surprising when this DOESN'T happen. The BMS is cutting the battery out of the charge circuit instantly because one or more cells are hitting high limit, and the MPPT can't clamp down fast enough to prevent a voltage spike.

Reduce boost to 13.8V, boost duration to 120 min and set float to 13.6.

It should reduce/eliminate the frequency and severity of the spikes.

After several days/weeks of regular charging, they should come into balance, and you can charge to higher voltages without spikes. Even at 13.8V, you can get to 98%+ charged.

 

[Dynoman]

I have 4x12v panels in parallel feeding a Renogy Rover 40amp charge controller. For five years, this has been charging a bank of 2 x Renogy 200ah gel batteries in parallel, wired to an AIMS 3,000 watt inverter. Everything is 12 volt. This is a dedicated system that ONLY runs my well pump, which pulls 10.5 amps when it's running. Sometimes, it runs 2 minutes a day. Sometimes, 6 hours a day. I've had zero problems.

Yesterday, I replaced the batteries with one LiTime 100ah Mini LiFePo4 battery, and switched the charging profile to lithium. Immediately, the voltage would spike as high 17, trip an alarm that disconnected the CC, then it reconnects, spikes, alarm is triggered, rinse and repeat. I only let this happen 3 times and disconnect the charge controller from the panels.

Can anyone shed some light on what happened here?

Agree with eggo that your BMS is going into over voltage causing the spikes. The lithium profile on the Renogy Rover cannot be used on Lifepo4 batteries as it is too aggressive. The USER profile needs to be used on the Rover 40 and programmed with proper settings.

With the USER setting you can Reduce boost to 13.8V, boost duration to 120 min and set float to 13.6 as suggested. Once that is stable in the weeks that follow try increasing boost voltage slowly and reduce the boost time.

Suggest reading this message about setting up the Renogy Rover 40 amp MPPT solar charge controller with USER settings.

Renogy 40a mppt Li settings​

After reading the message in the link read the entire thread as you may find it helpful.

 

[NewGuy23]

Absurdly common.

Welcome to the world of new LFP batteries that are imbalanced - it's more surprising when this DOESN'T happen. The BMS is cutting the battery out of the charge circuit instantly because one or more cells are hitting high limit, and the MPPT can't clamp down fast enough to prevent a voltage spike.

Reduce boost to 13.8V, boost duration to 120 min and set float to 13.6.

It should reduce/eliminate the frequency and severity of the spikes.

After several days/weeks of regular charging, they should come into balance, and you can charge to higher voltages without spikes. Even at 13.8V, you can get to 98%+ charged.

That worked perfectly, thank you!