Lithium Smart Batteries lose all charge in a month while disconnected?

DIY
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1

My Victron batteries went dead in a few weeks with nothing taking any consumption ??

I’ve got two 12v 200ah smart lithium Victron batteries in parallel in a full victron system with Lynx Smart BMS 500. The van was put into storage for a month so we turned off the Lynx Smart BMS (via external contactor switch) thereby completely disconnecting the batteries from the system. The batteries were at 80% SOC when they were disconnected.

Around 4 weeks later we turned the system back on (expecting around 80% SOC still in the batteries) only to find they were both seriously depleated… below 6v at the terminals.

I performed a recovery after low voltage event (6. Troubleshooting & support) and both batteries appear to be totally healthy again; though now I’m not sure how much I can trust them.

Has anyone else seen behavior like this with Victron Smart batteries? I don’t know how this is possible as the BMS should disconnect the batteries if they ever get as low as 10%. Any thoughts what I could investigate to determine if these batteries are still viable? What would cause a Smart battery to lose all it’s charge in a month (80% → 0) when disconnected?

2

You have to check the wiring maybe there is something connected directly to the battery?

3

That was my first thought and verified the batteries have only the cable going directly into the Lynx Smart BMS.

I found someone else here in the community who had the exact same issue. I’m thinking I should run a couple tests to determine ghost draw from the BMS.