I have a system recently installed using third party Lithium battery with BMS accepted by CAN connection on Cerbo GX. The systetm is configured on ESS.
It turns out that system send an alarm from the BMS instance with high voltage alarm (the limit is 57V) but the solar charger shows only 55.6V.
However on MPPT detailed history shows on battery a max value of 59.82V. We have three batteries of 104Ah 51.2V in parallel, two Multiplus 5kW and 100A 150V MPPT solar charger. The alarm comes from battery BMS. Absorption and float charge parameters in solar charger are 58.4V suggested by manufacturer.
This alarm only appears when batteries are 100% SOC. We don’t know why batteries get a max value of 59.82V if solar charger paramteres are lower than this value.
The MPPTs are still functioning after the battery is fully charged, in order to supply power to inverters.
Now, with variable load conditions, the MPPTs are a little slower to adapt and there are cases when the solar production can overshoot.
This translates with a slight increase of the DC voltage. 1.4V overshoot is not much versus 58.4V set voltage. It’s just 2% more.
BUT…
58.4V is way to much for charging voltage. It’s 3.65V / per cell, absolute maximum allowed for LiFePO4 chemistry.
Set instead absorption and float charge parameters to 56.8V (3.55V / cell).
Even better 56V (3.5V / cell).
Thank yoy for your reply @alexpescaru. I have set a lower charge voltage and the system doesn’t shut down althought VRM still shows the alarm. Even with a BMS tool connecting batteries it doesn’t show any alarm but VRM does. However, I don’t mind if the sytem still runs in ESS mode.
It happens every day as soon as battery reaches 100%.
As @guystewart explained in the topic below, cause is incompatibility of chineese BMS with Victorn specifications. Instead of lowering CVL, BMS sets CCL to zero when battery is full. I tried to contact Basen Green (my battery brand) with questions about Victron compatibility (which they declare), but was silently ignored. Thus have to live with it.
@dgmar_ni
have a look on battery safety controller.
It’s a free software ond free hardware that is plugged in between the Cerbo and the BMS and has several optons to manipulate BMS data. Though <ou can change CVL according SOC.