Hello from France (excuse my poor English, and also the long story).
In my RV (a camper van), a Victron system was installed in January 2019 by the van fitter, a pro, with the advice of a Victron technician.
The system is composed of :
a smart Lithium 12 volts battery 200 Ah
a BMS 12 200
a smart BMV 712
a MPPT smart 100/30 with 2 x 150 Wc solar panels
a Buck Boost 50 amps
a Multiplus 35 A 800 W
a Battery Protect 50 A.
During 3 years, everything was OK.
In May 2022, I reconnected the battery to the devices (each winter I disconnect it during several months) and I started the engine :
I observed no increase in the SOC ! Victron Connect told me ‘charge deactivated’.
So, after a few minutes, restart of the engine (I dit it several times) and Victron connect showed me that cell #4 had an increase of its voltage above 3,80 volts, sometimes above 3,9 (the current received from the buck boost was around 40 amps) when the 3 other cells stay at their initial value.
I then plugged the system into the 220 volts mains; same thing happened although the voltage of cell #4 was «only» around 3,77 volts (amps received were between 25 and 30).
When I let the system on the mains, a cycle of deactivation – activation begins and after several hours, the Multiplus was able to charge the battery, it has a 100% SOC.
When only under the sun, everything works fine, the current received from the MPPT is lower (around 15 A or less) and the battery can take the charge.
So I went on a trip with my camper van for several weeks : there was no improvement. I just noticed that the cells were very often unbalanced.
When at home (July 2022), I asked the installer to start a balance process, thinking that, maybe, it would have an effect on cell 4; they did it, with the help of a Victron technician, and finally after several days of low current charge, the cells were balanced.
But, in fact, no change, when starting the engine, the load is deactivated after few seconds.
I went again on a trip during the summer, relying on the sun, but I had to go every 2 or 3 days to a place with electricity. A pity as I am a fan of off-grid in the nature.
Remark : one day, after the engine start, it was OK, cell #4 and cell #3 had both a voltage increase but less than 3,75 (3,73 and 3,69) while the 2 other didn't move → no deactivation ! I was happy.
This phenomenon continued one day more but unfortunately not after.
The only event I can remember is that the evening before, I was off road (a poor track during some meters), there was a big hole and bump on my way and I had to manage it together with the gradient, so not very slow.... maybe the battery was shaken a bit.
I would like to know if it is possible to easily disassemble the battery, have a look on cell #4 and its connection, and perhaps, at the end, to replace it by a new cell from Victron.
Appreciate any help from the community, as the installer says : will have to replace the battery.
Thanks
