RVD
1 kW
Hi everyone, it's been a long time since I've been back here. Quick summary...I was active in here way back in the day when I was building electric bikes, playing with various battery technology (lipos, etc.), etc. A few years ago I moved overseas to Korea and brought some of my bikes with me. I got rid of all of my lipos and harnesses and chargers, etc. when I moved and only kept the 18650 packs, etc. I was messing with building my own packs back in the day but never actually got into it and sold off all of my naked cells and gave away my spot welder, etc.
Anyway, on one of the bikes (BBS02 mid drive), I changed out the battery (small capacity 52v 8ah 18650 pack purchased from luna) to a larger capacity 52v 12ah chinese made aliexpress hard pack 18650 2+ years ago. I connected everything and it worked fine and had a few nice rides with it, etc. The ad (and pricing iirc) reflected samsung cells so I thought they were high quality, etc. i.e., I didn't cheap out.
But this weekend I decided to take the bike out so last night I charged up the battery for the first time in about a year. Battery was dead but after plugging it into the charger for awhile, it seemed to come back to life and charge. There are small led indicators that show charge and it slowly went up.
This morning it was fully charged. Battery felt slightly warm to the touch but I think that's relatively normal...it wasn't super hot or anything. I unplugged the battery charger and went to work.
About an hour or so after I left I get a frantic call from my wife saying that the battery is on fire! Being in Korea, we live in an apartment in a high rise so obviously that's not good. She tried to pour water on it but obviously smoke everywhere, water won't help much, fire department called, etc. I think they took care of it but I don't know how much damage there is in the apartment right now.
So where did I screw up? Or did I? Battery was unplugged so I guess there was thermal runaway? I didn't take the battery apart but I'm pretty sure it had a BMS in it, etc. My only guess is that the cells were pretty dead after about a year or sitting there?
Anyway, on one of the bikes (BBS02 mid drive), I changed out the battery (small capacity 52v 8ah 18650 pack purchased from luna) to a larger capacity 52v 12ah chinese made aliexpress hard pack 18650 2+ years ago. I connected everything and it worked fine and had a few nice rides with it, etc. The ad (and pricing iirc) reflected samsung cells so I thought they were high quality, etc. i.e., I didn't cheap out.
But this weekend I decided to take the bike out so last night I charged up the battery for the first time in about a year. Battery was dead but after plugging it into the charger for awhile, it seemed to come back to life and charge. There are small led indicators that show charge and it slowly went up.
This morning it was fully charged. Battery felt slightly warm to the touch but I think that's relatively normal...it wasn't super hot or anything. I unplugged the battery charger and went to work.
About an hour or so after I left I get a frantic call from my wife saying that the battery is on fire! Being in Korea, we live in an apartment in a high rise so obviously that's not good. She tried to pour water on it but obviously smoke everywhere, water won't help much, fire department called, etc. I think they took care of it but I don't know how much damage there is in the apartment right now.
So where did I screw up? Or did I? Battery was unplugged so I guess there was thermal runaway? I didn't take the battery apart but I'm pretty sure it had a BMS in it, etc. My only guess is that the cells were pretty dead after about a year or sitting there?