I just left our boat in the yard, for the Caribbean hurricane season, and I’m seeing a strange SoC curve on the Lynx BMS. Loads are a pretty steady 50W, but the SoC starts suddenly changes rate, a couple of days into storage.
FWIW, Solar charging is currently disabled, to let the batteries drift down in charge a bit. There is some sporadic wind charging, but it’s minimal, and visible in the battery current.
The battery bank ran completely flat (to the point of low cell alarms) with the BMS still reporting 45% charge. I’ve never had it that flat before, but we’ve been below 20%, under normal use.
If I integrate the battery current (at 1 minute resolution) I get 927 consumed Ah, which is almost exactly the bank capacity (5×200Ah 24V). Integrating power is even closer, 24.1kWh.
So, clearly the BMS was accurately observing the discharge, but incorrectly tracking consumed charge, discharged energy, and state of charge.
There is an inflection point in the rate of discharge on the 18th that does not correlate to any charge in current on the battery.
Aside: Not quite sure why this got tagged as DIY, it’s really a bug report. This was a professional install, but the installers aren’t going to be able to help me at this point…
Which BMS firmware are you on. There was an update to V1.13 in Feb of this year and the change log states the following, including, fix issue with Cumulative Ah Counter. Clearly it worked for the first few days of being in storage and then stopped counting down. I wondered about the current being below the threshold, but at 2A it should be OK and is registering.
v1.13 – 17 February 2025
These are the SmartLithium (non-NG) batteries, so we’re on version v1.11. 1.13 has only been released for the NG BMS.
Totally misread that then. I have no explanation for your issue, it is rather unusual.
