Hello,
My BMS is only charging a few amps for a few minutes, then the charging pencentage drops slowly to 0%. I have a multiplus compact, a fridge and other loads connected that are powered when the engine is running, without drawing energy from the lithium battery.
The multiplus compact charges well. I have this setup for a while and never managed to make it work…
Here are some pics:
The voltage drop seems too big for me. The BMS is measuring 13.8V but the BMV 13.3V, so you are loosing 0.5V while only 5.4A are flowing. At 100A charge current that would be ok, but not at 5A. Check all your connections, cables, crimps, fuses, for high contact resistance or looseness, on positive and negative
Also keep in mind that the smartBMS can only limit the charge current, and thus limit the charge voltage. It can not raise the voltage. If the incoming voltage from the alternator is already low, then its going to be even lower on the battery connector due to the internal circuitry. If the incoming alternator voltage is at 14V then theres no way the BMS could charge to 14.2V
Thank you for yout help.
I never noticed the voltage was to low… The connections all seem fine, I have 4meters of 70mm2 between the starter batterry and the BMS, I have an Orion 12/12-18A home, I could put it before the starter battery side off the BMS and see if that helps? It would deliver a good voltage and at least give 18A to the BMS?
As explained above, your alternator voltage looks too low. Covered in this FAQ. Check your connections with a multimeter for voltage drop, vehicles and boats suffer vibration and connection corrosion at times. This includes the negative return path.