I again had a low voltage cutoff on my way home last evening. This is getting very frustrating. I had ridden into work that morning and it was a very satisfying, high-speed, no problems trip in. I let the BFP (Bosch Fat Packs) cool off a bit (they weren't even warm) but I thought it would be wise.
I charged the whole pack and let it complete on its own. I then double checked by putting each pack on the charger to make sure they were full. I reconfigured the packs again into the 72V configuration I use for my ride home and let the pack sit for about 4 hours at my desk. When I got down to my bike and connected the packs to my DrainBrain meter, the pack only showed 75.7V when they should show 83.8V! I knew I was in for a short ride but took the bike anyway. I made it about 1 mile from work when it died. I checked each group of 3 72V packs and found that they were all down to LVC of approximately 63V. I took the bus home and then checked each pack. 2 of the 6 batteries were drained down to almost nothing <5V but I was able to charge them back to their usual 41.8V float charge setting.
I'm thinking that my current configuration of 3 72V 2S packs is not optimum for my situation. I am going to rewire the packs for 2 groups of 3 BFPs in parallel and then series the 2-3 cell packs for the 72V configuration. This should help spread the load from 3 groups of 72V packs to one 72V pack. I'll be very careful to wire each pack with the same lead lengths so as to not cause any balance problems and to double check the configuration before loading it on my bike.
This is a great learning experience!
More later,
Ambrose
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