Need Help - New Batteries Only Charge Halfway

General Discussion about large electric scooters and motorcycles and other things with no pedals.
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David in Canada   1 µW

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Need Help - New Batteries Only Charge Halfway

Post by David in Canada » Mar 15 2018 5:48pm

Hi all, I am in desperate need of help with a scooter battery issue.

I recently got six new 12V 20ah batteries for my 72V e-scooter, as the old ones were toast. I installed them and charged them up, and they show as fully charged (the momentary startup display shows around 80V, which is about right for new batteries in my scooter, from my experience). Then I start to drive and the battery display on the scooter immediately drops down to 3 bars, from 6 (fully charged). It happens almost right away.

I thought the batteries were defective/old stock, so I went back to the scooter store and got 6 fresh ones. Installed them, and same thing occurs. So it's something wrong on my end.

The old batteries would display six bars when fully charged, so I don't think it's the charger (which worked fine before the battery swap). Obviously those old batteries would start to die quite quickly, as they had 3500+km on them, but I would still have to drive several km before the bars would drop down to 5, then 4, and so on. The brand new ones are at only three bars right away on a full charge. I didn't do anything different other than replace the batteries.

I was going to bring it in to the store to get it looked at, but wanted to see if anyone on here had experience with this issue, and could give me some guidance. Thanks so much in advance for any help.

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x.l.r.8   100 W

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Re: Need Help - New Batteries Only Charge Halfway

Post by x.l.r.8 » Mar 15 2018 11:03pm

80v is an actual reading or just indicated by the bars? you need to see what you are drawing by using a cheap meter

https://www.aliexpress.com/item/Battery ... 0.0.m7wCsB

https://www.aliexpress.com/item/300V-10 ... 0.0.m7wCsB

this will give you the information you desire to see what is actually happening
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amberwolf   100 GW

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Re: Need Help - New Batteries Only Charge Halfway

Post by amberwolf » Mar 17 2018 2:46am

Could be that they have a bad lot of batteries (or they've sat around so long they're junked).

Could be that some of the batteries they've got are already fully charged, and some aren't. This is "unbalanced" and means when the charger thinks it's done, some of the batteries are overcharged and some aren't fully charged, and the overcharge goes away really fast (or immediately) when any load is applied.

Could be they're not meant for high current (there's different types) and they might be sagging in voltage badly because of that.

Could be a bad connection between batteries or from batteries to controller. Broken wires, bad crimps, spread contacts, etc.

mettleramiel   10 W

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Re: Need Help - New Batteries Only Charge Halfway

Post by mettleramiel » Mar 18 2018 12:54am

Coming from someone who sold batteries for scooters for years, I'm willing to bet it is the batteries, but they might still be ok.

What you should do is first charge them each individually or in parrallel to balance them. Next, lead acid batteries like to be cycled a few times, especially when they have sat for months. Take them out for a spin and once they're about half way drained, charge them again (overnight, preferrably). You should notice a capacity increase over the first 4-6 cycles.

If the results are still the same after this, take advantage of the warranty and replace them.

David in Canada   1 µW

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Re: Need Help - New Batteries Only Charge Halfway

Post by David in Canada » Mar 18 2018 9:55am

Thanks so far to everyone for the replies - very much appreciated.

To the last poster - I thought it was the batteries the first time I changed them up, so I replaced them. When the exact same thing happened the second time, I ruled out the batteries, as the second batch was a different brand and supplier. I realize it's still possible, but it would be a little more unlikely at this point.

Interesting that you mention cycling through them a few times. I've heard of that before. So far I have not gone for a long ride; the longest being about 13km (to the scooter store and back to test the charger), and the others were maybe 3 rides between 2-6km. I would love it if they started showing more charge after a few more rides but I feel like it's wishful thinking.

What I might do is put the old batteries in and see how they behave - that would answer a lot of questions. If they show a full charge like before (but drain quickly), then the new batteries are absolutely the issue. If they behave the same as the new batteries, I did something that is causing the issue when I changed the batteries. I'll likely do this today, and post a report. Thanks again for all the help - you guys are all giving me some good advice.

David in Canada   1 µW

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Re: Need Help - New Batteries Only Charge Halfway

Post by David in Canada » Mar 18 2018 10:03am

To amberwolf:

If the batteries are unbalanced, I don't think I have the equipment to charge the batteries individually, unless it's possible to take the terminals off all the batteries except one and run the charger, then repeat the process five more times with the other batteries. Is this safe and/or a procedure that would work? I don't have a voltage meter to test each battery, but perhaps I should invest in one if they are not too expensive.

Thanks again.

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amberwolf   100 GW

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Re: Need Help - New Batteries Only Charge Halfway

Post by amberwolf » Mar 18 2018 12:34pm

If you have a Harbor Freight in your area, and get junkmail flyers, they often have "free with any purchase" coupons for their cheap DMM, which is good enough for most troubleshooting. (as long as it actually works in the first place; some don't). So you can buy some <$1 item and get the meter free with it. ;)

Unfortunatley you can't safely use the charger on just one battery, as it likely isn't designed for that kind of voltage range.

But you could parallel connect all the batteries together, + to + and - to -, and then they will all equalize their charges. Keep in mind if there is a large imbalance there can be a large current flow and wires can get warm or even hot. (but if there is that much imbalance, the lower-voltage battery is probably damaged anyway, as it means it's sat for a long time at a low voltage, so it's sulfated inside).

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Re: Need Help - New Batteries Only Charge Halfway

Post by John in CR » Mar 18 2018 9:29pm

After this set don't waste more time and money on the short-lived, toxic, low capacity, lead anchors that are killing your scooter's range and performance. Lithium batteries can be had on even frugal budgets. The time and effort to learn about and build your own pack is well worth it, and once you have good batts you'll wonder how you lived with the lead for so long.

David in Canada   1 µW

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Re: Need Help - New Batteries Only Charge Halfway

Post by David in Canada » Mar 20 2018 12:04am

amberwolf -

I am going to try parallel connecting the batteries together as per your suggestion, but I have a question that might sound stupid, being that I've never done this before: do I turn on the charger after parallel connecting the batteries, of do I just simply connect them and let them sit for a while?

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Re: Need Help - New Batteries Only Charge Halfway

Post by amberwolf » Mar 20 2018 12:07am

Charger does not get connected at all.

Neither does anything except the batteries, not the vehicle, etc.

Only the batteries get connected, all positives connected to each ohter, but not to anything else.

All negatives connected to each other but not to anything else.

Do not connect any positive to any negative.

If you had a multimeter (voltmeter) you could simply measure each battery to see if they are all the same or not, and avoid the other work if they are.

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