First "real" BMS disconnect - all is good.

[wholybee]

After more than 2 years, I have my first BMS disconnect event. Everything worked as designed, with no damage or issues.

I had a work trip to the East Coast as California was inundated with storm after storm for about 2 weeks. Solar is my only regular charging method. 2 weeks of rain and it couldn't keep up, and with my absence I couldn't do anything about it. I got back and found the battery dead and BMS disconnected. The bilge was dry, and my fridge cold. The BMS logged 34 LVC events. Between which solar was apparently able to keep my bilge dry and fridge cold. The Victron MPPT showed that voltage had hit 0V for the previous 5 days, but not prior to that. The BVM showed 330Ah used, from my 300Ah battery. That is close to what I measured when the battery was new 2 years ago.

Anyway, while I don't have any shore charger, I do have a 75A power supply that I have used to quickly charge in the past. I hooked it up and over a few hours brought the battery to 14.1V. As it reached 14.1V, the cells were still balanced to 0.01V. Balancing is configured to start at 0.015V and never triggered. I don't expect any loss in capacity or cycle life from this event.

My battery is a 300Ah battery built from 12 Calb 100Ah cells in a 3p4s configuration, with an overkill solar BMS. A lot of people don't like FET BMS's and IMHO over engineer the protection systems. I am happy with it, and it has proven effective.

Watching it *very* closely as it charged, I was surprised at how much energy really was between 3.4Vpc and 3.5Vpc. I thought you were very near 100% after 3.4Vpc, but from there to 3.5Vpc was about 10% of the capacity. Charge rate had dropped to 30A by that time, so about .1C, and it took an hour to get from 3.4 to 3.5.

[Jammer]

Originally Posted by wholybee

. A lot of people don't like FET BMS's and IMHO over engineer the protection systems.

I agree with this. I've seen quite a number of over-engineered systems that try protect against nonexistent problems and statistically improbable failures. Having proper fusing is one thing but trying to protect the bank from failing due to overdischarge in a 1:10,000 scenario usually ends up making for a system that is less reliable and harder to troubleshoot.

[wholybee]

Originally Posted by Jammer

I agree with this. I've seen quite a number of over-engineered systems that try protect against nonexistent problems and statistically improbable failures. Having proper fusing is one thing but trying to protect the bank from failing due to overdischarge in a 1:10,000 scenario usually ends up making for a system that is less reliable and harder to troubleshoot.

In all fairness, California getting 14 days of rain is statistically a 1:10,000 scenario. But I didn't need thousands of dollars of fancy BMS, CANBUS controlled, anything I can possibly connect to the BMS I should, to protect my pack. A basic $150 BMS with nothing fancy did just fine.

I don't really have anything against those systems, but I feel much of it is unnecessary.

[smac999]

when the solar came on each day was it able to reset the bms and put any power into the battery? or did the bms stay shut down the whole time, and the solar power was simply going direct to the loads?