Crashed! Please help me find a way to troubleshoot and get it back up.
Iíve had a 700 ah 12 volt lifepo4
system in my boat
running without issues for about 4 years. The Battery
Management System has decided to shut down and I canít get it back running. The cells each have a healthy and balanced charge and sit at about 13.5 volts collectively. I think I saw 3.4, 3.4, 3.4, 3.3 individually. No temperature change so not hot.
We were motoring along for a few hours when I noticed my two lead acid batteries
(bow thruster and starter - on same alternator
as lithium, but connected via isolators) were charging
too high at about 15v. I then checked the lithiums and saw they were at about 14v at terminals, but 17v at the alternator
side of fuse. So I shut down the engine
When I shut down the engine
, the lithium (ie house bank) also shut down. I pushed a reset button on them, they populated for about 70 seconds, then shut down again. I tried this repeatedly with the same result until the reset button no longer activated the system at all.
Some additional info:
- prior to the trip, I swapped out the two original lead acid starter type batteries
for a couple of newer deep cycle lead acids. My originals were getting old, and these healthier batteries were available. I like having lead acids in case the lithium suddenly was to shut down during full alternator charging
, the extra power would be spilled into the lead acids - which is what I think happened here - saving my alternator. I swapped them out without any changes to the configuration and no contact with the the lithium cells. So nothing else changed.
I have now swapped back to my original lead acid batteries for the starter and bow thruster. Reverting to the original configuration brought no change. (Iím now using those newer deep cycles as my house bank in place of the lithiums as a temporary solution until I solve the issue. All these batteries are behaving normally.
- one of the mini BMS circuit boards which monitors the individual cells was brittle at the ring connection on the cell post (and had been since the original installation). Now that Iíve been touching everything toward solving the issue, it broke off completely. I soldered it to a wire lead as a repair.
- the company I purchased from is no longer in business. Companies with similar BMSs will only sell replacement parts
if you bought the whole battery system from them.
I donít know where the failure is,
- an individual cell monitor
- The BMS controller
- The fuse or shunt
- The reset button
I donít want to spend $2,000for a new monitoring system. Ideally I would like to rule
out any small part failures or obvious issues. Iím hoping someone can put me onto a good solution. I am just an end user, not an electronics
DIYer by any means.
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