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peterbc asked

Quattro with 3rd Party Lithium over winter when on shore power

I am planning new DIY LIFEPO4 batteries for my boat, with Quattro 5000/24 in France (and MPPT).
I have Electrodacus SBMS0 BMS which can remote on/off the quattro (8 yrs old), and switch off its AC sources at high voltage via SSRs. Also have remote control cable for Smart Solar MPPT 100/50. SBMS0 also has temp monitor for disabling charge at high or low temps (5deg default minimum).

What I'm concerned about is winter time when no one on board. I'd like to run some small AC loads for monitoring, and trickle charging the Engine Battery (24v) and Generator (12v) lead acids via Victron Blue Smart chargers.

Q1. Should / can I disconnect the LiFEPO4 batteries from the Quattro for winter ? and will the quattro still allow shore AC power to my minor loads ?

Q2. Alternatively can/should I leave connected and set a charging profile to maintain just a low SoC ? (eg all at bulk/absorb/float at 26.2V which is 3.275 v/cell, and approx 60% SoC) ?

Q3. What charging profile should I use during season when I want to let the SBMS0 control charging and loads ? I understand slightly higher than the default cutoff of the SBMS0 which is any cell reaching 3.55V , then back allowed once 3.40v reached). So if I choose 28.8 V for bulk/absorb/float (3.6V/cell), it should never reach those Volts, as SMBS0 will cut it off once one cell reaches 3.55V. ? SBMS will cut off Quattro and all DC loads (via a Battery Protect) once any cell hits 2.8V, and only re-allow when V get back to 3.2V.

Thanks for reading this far ! .. Peter

MPPT ControllersMultiPlus Quattro Inverter ChargerLithium Battery
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1 Answer
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peterbc answered ·

To anwser my own question:

Q1 . I will disconncet the batteries (including BMS and Active balancer), after discharging to approx 80% SOC

Q2. Its not really possible to control SOC safely via pack bulk/absorb/float voltages. Its also very hard to charge a pack to a specific SOC. You set the high volt disconnect. Anything much below 3.5 volt could give variable results. So essentially its charged to 100% SOC every time. For this reason I am disconnecting as I dont want my pack at 100% all off season. This is not as severe a problem with LFP vrs NMC chemistry however.

Q3. I'm setting Absorb/Float as 29V. The SBMS0 is in full controll, dont overthink it and try to control with the pack level settings as well.


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