Changing the battery of a 10-year old e-bike/e-scooter

[JussiPussi]

TLDR: Need suggestions/tips/advice on changing a lead acid battery to a lithium ion one, and figuring out the connector that needs to be used. And also what stuff to look out for. Thanks in advance!
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Good day everyone. New ebike owner here so please excuse my ignorance and limited knowledge about the matter.

My uncle just gave me a very old e-bike, around 10-12 years old at least. It's a Foton ebike with a really large and heavy battery, which I assume is lead-acid (as shown in the pictures below). The thing weighs a lot and doesn't seem to hold a charge anymore even after charging it for 24 hours. The charger also smells like burnt plastic early on but that went away after a few hours thankfully.

When I install it on the bike, it turns on, with the brake, headlight, and signal lights all working perfectly. The charge indicator also says it is full. However, the wheels won't turn by itself even if I turn the throttle at full. It will start turning very slowly after I engage the pedals but other than that, it's too weak to even assist the pedaling. I also hear some metallic "slipping/grinding" noise inside the rear wheel hub, where I assume the motor is located.

This is the actual bike/scooter but I don't think the manufacturer has a dealer or service center in Canada.

Someone from reddit suggested replacing the lead battery with the a lithium ion one. Based on the charger, the battery is a 48v one but I'm not sure about the amperage. I looked around Amazon for Li-on batteries of that capacity and my other concern is the connector. The li-on batteries doesn't seem to use the "3-prong" connector used by the charger and the bike.

 

[amberwolf]

It is very likely from the symptoms that the battery has failed from age, but that the rest of the system is working. Without a good battery to verify, can't say for sure, but it's a good starting point.

The battery pack might be repairable, but if it is original from 10 years ago it is likely to require all the cells to be replaced to do this. Depending on the kind of battery, it's probably going to be easier/cheaper to just replace the whole battery (and it's charger).

The charger indicates it's only for lead-acid, so it's highly likley there are just four series SLA in there, and it'd be pretty easy to replace them, but for the cost they won't last as long (or perform as well over their lifetime) as a good new lithium battery would.

Are you willing to open the battery case to see what's in there first? If so, post some good clear pictures of the battery casing from all sides, at high resolution, preferably taken in direct sunlight (cameras generally focus better in such light than even with their flash).



FWIW, the connector they chose to use for the DC (output) side of the charger is a regular IEC AC cord type. It's a really bad idea for multiple reasons to do this, not least of which is because you can accidentally plug a battery directly into the wall instead of a charger if just an AC cord is used instead of the charger, but it's unfortunately a very common mis-design.

If you just repair the battery and the rest of the system works, there's no requirement to change the connectors out, but if you change the battery to a different one you'd probably be changing the charger and getting a different charge connector in the bargain anyway.

 

[JussiPussi]

I appreciate the detailed response sir. Is it okay for a newbie like me to just screw the battery open? Are there any safety precautions I should know about?

And yeah, I'm more inclined to change the battery altogether. At the same time, I'm hoping that a identical capacity li-on battery is lighter. Thanks in advance.

 

[amberwolf]

I appreciate the detailed response sir. Is it okay for a newbie like me to just screw the battery open? Are there any safety precautions I should know about?

Since it is probably not holding a charge, there's likley nothing to worry about in there, especially after a few days of sitting there unused.

But as I noted, if you post pictures first, we'll be able to see more of how the case is made and how you might be able to safely open it, etc.

And yeah, I'm more inclined to change the battery altogether. At the same time, I'm hoping that a identical capacity li-on battery is lighter. .

An identical capacity one will be lighter and probably smaller. It would probably fit inside the casing you have there (but you'd have to measure its' internal dimensions to ensure you find a pack that will fit in it).

If you can get a higher capacity pack that will still fit in it, I'd recommend that--then you have more capability than original, even as the pack ages.

Lithium vs lead specifications are not quite direct comparisons, so picking a new pack might be a little more complicated than just finding one with the same Ah capacity and voltage.

It also has to be able to deliver enough current (A), and the cheaper packs often don't do that part very well.

 

[999zip999]

Do you have a multimeter or voltmeter you can get a cheap one for under $10 that way you can put it on a higher setting than the battery you have a 48 volt battery put it on 100 volts that way you won't blow up the multimeter or voltmeter he always put them at a higher voltage than the article your checking. Now check the voltage and you'll see how much charge there is in your battery before you take it apart. How are your soldering skills ?