question

REC ABMS I assume, has various settings for charge control.

CHAR stops the charging (3.650V)

CHIS is the voltage hysteresis, where charging is reenabled (0.250V)

With this settings crarge would be reenabled at 3.650V - 0.250V at 3.400V

If you have reduced CHAR to something stupid low to extend battery life - like 3.4V and did not touch CHIS, your BMS will wait until 3.150V to re-enable charging (20% SOC).

Another frequently messed up parameter is SOCH (SOC hysteresis), set to 0.05 or 5%, means even if voltage drops to 3.4V in the above example, charger will stay disabled until SOC is below 95% to prevent pumping all the time. Some people enter there values they don't understand (like 0.5), causing charger to stay off until 50% discharge, some even try to set the parameter to 95% like 0.95, what translates of 95%DOD or 5% SOC. I think REC has adapted the FW to prevent such out of the world settings in the meantime.

This are the regular parameters for charge control, on topp there are the CV CC limits for the CAN BUS protocol (synonyms for absorption, float, rebulk), I cannot comment on them as I don't use the DVCC / CAN for good reason (DVCC works only with some Victron gear, I have other charge sources that are not monitored, I don't want to rely on a single point of failure (Cerbo, CAN) for charging, so I use independently configured chargers and the BMS oversees and cuts them off only if they misbehave by hardware signals (optocouplers for graceful shut down of chargers and non essential loads - Quattro 2 wire bms control - and relays as last line of defense to punish reluctant hardware for high / low voltage protection).

Did you solve your issue?

You may contact Tine at REC for an updated firmware if your config is correct and the issue persists.

Hi Johanndo, Yes this solved my issue. By some account the setting hysteresis was set to 1. After correcting this the BMS behaves like intended.

Now the battery charging profile looks like this.

It remains 100% due to solar power, discharges during the night and recharges during the day. Is this OK with regards to battery life-time? Of should I have it discharge further before charging again? I'm I correct to assume the SOCH setting is intended for this purpose?

Again thank you for solving this issue!

Depends on your usageIf you generally don't use the battery, so it stays full all the time, you could reduce the absorbtion voltage and stop earlier. But usually the battery is happy when cycled not too deep. We usually cycle between 50% and 90%, but not on purpose, we just use that much energy, that the solar can't keep up with full charging, we may reach absorbtion 2 times per month.