traingang

Prefacing this story with the fact that i am a dumb guy, an idiot, not an electrician, not a bike mechanic, and my experiences may not reflect others'.

i bought a used ebike on craigslist for $200 back in February; think it only had like 70 miles on it. a "Ride1up Roadster V2". It's a stealth ebike (looks like a normal bike, battery in downtube, motor in rear wheel). i charged it once as proof that i could, then i only rode it sparingly all spring and summer.

Pictured: not mine, but same model

jump to july, the bike is powering my partner up a steep hill and it starts cutting power. battery is nearly dead; we're a mile from home, whatever.

get home, plug the bike in to charge - charger shows "green" light only, indicating it isn't charging. give it a while, only ever shows green.

hmm, that's bad.

After checking voltage on the charger (outputting 42v), i test the voltage on the battery (SPOILER: last time i did this is what caused the whole problem).

the charger & charge port look like laptop ports (see example pic, obviously not of a bike)

when i got the bike, i wanted to test the battery health by checking voltage with a multimeter at the port. this is dumb, don't do this. when i tried, i arced from the positive and negative (it's impossible to get the leads in there without crossing them), popping a secret fuse, and disabling the bike from taking future charges; something i wouldn't figure out until august. i figured i melted something in the charge port so i bought a 5 pack of replacement charge ports for $8. before i cut the wire to splice in the new charge port, i called my dad, because i always call my dad before cutting wires. he recommended checking for connectivity on the port, and it showed it was good.

to test the battery this time, i actually removed it from the bike and tested it at the connector ports. in this pic, the charge port is the circular part that i arced, the yellow connector is the proper place to check voltage (aka charge port connector)

?gave me the confidence to do what i did next. i tested the battery voltage at the controller port, which measured 34.4v. at the charger connector, the battery showed 0.0v - confirming the battery has voltage but not on that wire. This video also showed that i COULD trickle charge the battery through the controller port; essentially a backdoor into the battery. i was able to get the battery up to 34.5v this way; i didn't want to push it.

i call the manufacturer and explain the situation. they sound intrigued by the "battery backdoor" method, but say they can't comment on any of that stuff. they can't confirm if there is a fuse in the battery when i ask. they tell me to contact a battery repair business, or to spend $215+shipping on a new battery.

I get the confidence to remove 2 screws from the battery cover and look in the battery. there's a big obvious 5amp automotive (full size not mini) fuse that popped. i run over to the auto parts store, overpay for some fuses, and replace the burned fuse with a new one. close everything up, attach it to the charger, and VOILA, the battery is taking a charge. been charging about 25 minutes and it is up to 36.3v.

fixing shit feels good.

yes, i know be careful with ebike batteries. these are samsung cells, at least. it'll be funny when this thread shows up on SEO for someone trying to solve this problem with their own bike. welcome to hexbear, nerd