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Using an ev as back-up solar battery

Hi, first post here.

We have an off grid pre built board Victron system with 3kw peak solar, wind turbine, 10kva Quattro inverter & 4 puny 48 volt lead acid batteries.

It works fine when its sunny, but after 4 hours of full sun the batteries are 100% SOC and the MTTP shuts down charging, wasting a ton of electrical generation. However feeding 2 static caravans with a total of 300 watts over night means the autostart genny kicks in in the early hours. Rather than buy more single batteries I have bought a complete scrap Renault Zoe with a 40 kwh battery. My plan is transform the 400v traction battery voltage through an inverter to 240v ac and feed that in to the board as if it were an autostart generator 240 v input. I can already regulate this by setting the SOC or voltage that the genny supply kicks in at.

In the daytime, when my 48v LA batteries are full, I would switch the previously wasted pv voltage through the existing Victron inverter, to charge the ev via a standard 240v wall charger.

The ev is complete and has its own battery management system. Over a week, in the summer I could charge the Zoe with 6kwh a day. I know this because I charge my BMW IX with this by plugging it in to the existing 240 volt board and using a mechanical timer, charge it for an hour every 2 hours in full sun without draining the lead acid batteries.

As a second step, if I can get the above working, I could maybe fast dc charge the IX by plugging it directly into the Zoe 400v traction battery?


It may not be super efficient, but can it be this simple?


battery charging
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Mike Dorsett avatar image Mike Dorsett commented ·
I think that you might be better off dismantling the Renault battery (carefully) and rebuilding it as a 48v battery to use directly in your system. You can then use an off the shelf BMS that will interface whit your system. Messing around with the DC fast charge is problematic, as this relies on CAN bus messaging to control the charge rate and to engage the battery.
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