question

dfraizer avatar image

75/15 MPPT direct to Victron Lithium 2X200 amp @12.8v

Can I shutdown my house and starter disconnects while my boat sits on a mooring and have my solar wired directly to my lithium batteries to keep them charged while I am not on the boat? I am told my BMS CL 100 will continue to draw off the start battery

battery charging
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Stefanie avatar image
Stefanie answered ·

Hi @DFraizer,

absolutely not recommend to charge your expensive lithiums without BMS because the BMS will be the device that disconnects your MPPT if something gets wrong (over voltage, under voltage, temperature).

I suggest charging the batteries to lets say 50-80% SOC and then disconnect everything from the batteries. The self discharge rate is so low that your batteries will survive for months.

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I should have been a little clearer with my question. My BMS CL100 will still be powered by the start battery and managing my Lithium battery bank even though the battery switches will be off. The BMS will be linked and powered directly to my start battery. I am told the BMS will only draw 5ma while the boat sits idle on the mooring. I will also program my MPPT 75/15 to shutdown on high or low charge input.

Ok, misunderstood your question then.

Don't see a problem leaving it the way you're describing. But be aware that due to the low discharge (from the BMS) PV will keep your batteries more or less always at 100%. Maybe it makes sense to tweak battery charge settings in the MPPT for lower absorption and float voltages.