Chinese e-bike

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pengyou
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Chinese e-bike

Post by pengyou » Dec 09, 2017 10:46 am

I just "splurged" and bought a Chinese e-bike - I am back in China. It was only about US$250, so I don't expect high quality, cutting edge stuff, but I do have a couple of questions that will help me become more knowledgeable about ebikes. I charged the battery last Wednesday but didn't use the bike until the following Sunday. When I did, I found that the battery was dead. The battery is (supposed to be) a lithium ion battery, 48v, 12 amp pack. It is a light pack - I would guess 10 pounds-ish. It is easy to carry up the 3 flights of stairs to my apartment.

My question: why would the battery pack discharge so quickly? The people in the shop told me that "that's the way it is" but that does not coincide with my meager knowledge of this kind of battery. It is mostly academic at this point, unless the problem indicates that there might be a short or improper grounding. Any thoughts?

markz
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Re: Chinese e-bike

Post by markz » Dec 09, 2017 8:39 pm

Could be the cheap BMS used on the battery. Whatever the case fully charging the battery and leaving it for a few days is not ideal to begin with, but it should never fully discharge the battery. Your battery could very well be completely dead, like reading zero volts. Does your charger work on it?

pengyou
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Re: Chinese e-bike

Post by pengyou » Dec 11, 2017 8:20 am

Yes, it charges back up and works fine. I thought lithium batteries would hold a charge even if placed on the shelf for a while.

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fechter
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Re: Chinese e-bike

Post by fechter » Dec 11, 2017 9:12 am

Any of my packs will hold a charge for over a year if left sitting. Something is draining the pack. Some of the new controllers have features like "anti-thief" that could drain things if left connected to the bike. If the pack drains by itself without being connected, something is wrong.
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amberwolf
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Re: Chinese e-bike

Post by amberwolf » Dec 12, 2017 1:31 am

Does it have a USB power converter in teh battery? Maybe they did like another I've seen and wired it around the BMS to the actual battery terminals, and/or it's defective and causing a drain.

Or if it has a battery meter in the battery, and it's always lit up...

Maybe teh bike when "off" isn't really off and leaves controller/display/etc connected, and it's draining the pack.

Also, if it's like the last one I opened up, at least two of the crimps on internal connectors were so bad that the wires just basically fell out of htem. So under any load, it would appear to be dead, due to the high resistance.

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dogman dan
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Re: Chinese e-bike

Post by dogman dan » Dec 13, 2017 8:17 am

Sounds like the bike is never really off, or something is draining it.

try charging and then unplugging overnight, see if that helps. If it does, then something on the bike is draining the battery.

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