Regarding the need of a Smartshunt

[haraldhh]

I read the FAQ and it stated that You don't need a Smartshunt as well. This is probably fine if You're using an inverter or anything else that causes a permament load of over ~0.4 A.

I am building a 4S battery for my boat (EVE 280Ah), and the testrig I have right now (MPPT, JK-BMS, raspberry, smartshunt) draws around 5 watts all the time while idling as measured by the Smartshunt. The BMS says 0 A and Idle. It turns out that the JK BMS is unable to measure currents under 0.4 A or thereabout.

If you have a scenario with a small constant DC-load and you set the BMS as the battery monitor in a Victron GX device you will have issues with determining the correct SOC. Actually, You will believe You have a high SOC but you can be at 10% or less.

I feel that the Smartshunt calculates it correctly, after two weeks I have ~59% reported by the smartshunt and 82% by the BMS. I have manually drawn around 20 % from the battery after charging to avoid having it at high voltage, and the BMS hasn't moved a bit in two weeks despite a constant 5 W load.

TL;DR the battery with monitoring will empty itself in 30 days just by monitoring it. If you want to have a LiFePO₄ battery and not using it I recommend setting the sleep function on in the BMS and shutting if off.

(5 watts is ridiculous in itself, my ~65 liter fridge uses around 0.55 A in average during the day so the battery in itself with solar charger and monitoring draws almost as much as keeping a lot of beer cold)

/rant