Battery Too Good To Be True?

Heat84 · 2025-02-08T21:39:48+00:00

I wanted to put this in the electronics section here, but that doesn’t exist here. I have an electric bicycle and the current battery is 24V and 24Ah. I rode it for at least 5 more miles than I should’ve a week ago and discharged the battery too much and it won’t recharge anymore. I get enough of a charge to go about a quarter Mile😭. I found a new one. But it seems too good to be true. Its 30Ah and it costs about half of what I paid for the 24Ah battery that I have now and it’s physically smaller than the one I have now. Does it make sense that the newest electric bicycle batteries would have more Ah capacity but are physically smaller and cheaper than the previous ones? Another question I have is about the heat from extra Ah causing the metal part of wire nuts and wire couplers to brittle-ize. The stock battery was 8Ah. There’s nothing wrong with the wire itself. I’m not having this problem any more since I replaced 2 stock wire couplers on the controller wiring with crimp on connectors and replaced 4 wire nuts(2 by the controller and the 2 for connecting the battery). Why would more battery capacity create more heat? It’s not like it’s more volts. Doesn’t more voltage create more heat? As for the brand name, Duracell and Energizer or the car battery brands don’t make electric bicycle batteries, so you have to go with the weird unknown brands. But this is the weirdest brand name I’ve ever seen. It’s not even a name. It’s more like an acronym. It’s sold by Amazon(and only Amazon apparently). That has to be a good sign right?

Heat84

real_aurgathor weight – should be roughly the same – can be heavier, but a significantly lighter pack should be a red flag

The one I started this thread to replace weighs 6 pounds. The one I need to return weighs 2 or 3 pounds. I really hope these newer batteries weigh alot less just because they’re using newer technology that has a better weight to capacity ratio. Those batteries I linked to on EBay weigh 2-2.5 pounds.

real_aurgathor

Heat84 I really hope these newer batteries weigh alot less just because they’re using newer technology that has a better weight to capacity ratio.

While some newer technologies have a better weight to capacity ratio, those batteries won’t be cheap, and they are not very likely to show up in electric bikes.

Heat84 Those batteries I linked to on EBay weigh 2-2.5 pounds.

I don’t think I would buy that – but I’m not you. 😉
At the very least check the dimensions of battery pack to see if it’s roughly the same size.

px_eliezer_

I don’t know what region you are in, but have you considered a battery store such as Batteries Plus ??

https://www.batteriesplus.com/

Somewhat-Reticent

px_eliezer_ have you considered a battery store

If you do, consider making them take your unfit battery pack for recycling.

Heat84

px_eliezer_ I don’t know what region you are in, but have you considered a battery store such as Batteries Plus ??

https://www.batteriesplus.com/

There’s one a mile from me.

Heat84

Somewhat-Reticent If you do, consider making them take your unfit battery pack for recycling.

I already do that. I bring light bulbs there too. I brought fluorescent tubes there once and they charged me. I believe because they were bigger than a certain size.

Heat84

real_aurgathor I don’t think I would buy that – but I’m not you. 😉

I don’t have alot of choices. Even if I wanted to stick with stock, the manufacturer doesn’t sell them(Or the bike itself) anymore. Although I did find the stock battery somewhere else. But 8Ah isn’t enough for me. Not to mention it’s a rip off since it’s the same price(or more) as the higher Ah batteries.

At the very least check the dimensions of battery pack to see if it’s roughly the same size.

I have to check them anyway to make sure the battery will fit in the compartment.

Sparkchaser

Heat84 I can’t use this because it appears to read voltage telemetry from the controller and not voltage directly from the battery(judging by the tiny size of the wires).

It can read the battery voltage anywhere as long as it is just connected to the battery. The wire size doesn’t come in to play since the current to read the battery is very low.

Heat84

Sparkchaser It can read the battery voltage anywhere as long as it is just connected to the battery. The wire size doesn’t come in to play since the current to read the battery is very low.

Wouldn’t I connect it in series? The 24 volts won’t fry the tiny wires?

Sparkchaser

Heat84 Wouldn’t I connect it in series? The 24 volts won’t fry the tiny wires?

You measure across the battery terminals for voltage. The current used by the meter is very low. This is a simple diagram of the 2 measurements.

Somewhat-Reticent

Heat84 Here they imply they charge if you’re not buying replacements.

Heat84

Sparkchaser

You’re right. It worked.😀 But something weird happened. The indicator has 6 leds and the middle 4 were on. They battery is defective. It won’t hold a charge. Maybe the 4 middle leds on means defective battery. But when I test the battery with a multimeter, it reads 23.7. I thought Lithium batteries didn’t get memory charges. But it looks like that’s what’s happening.😕

real_aurgathor

Heat84

Heat84 It won’t hold a charge.

How did you determine that?

Heat84 . I thought Lithium batteries didn’t get memory charges. But it looks like that’s what’s happening.

That’s “memory effect” and Li-ion batteries don’t have it. However, Li-ion batteries have a number of other failure modes. But in your case I think it was insufficient capacity to begin with, based on their different sizes.

Sparkchaser

Heat84 You’re right. It worked.😀 But something weird happened. The indicator has 6 leds and the middle 4 were on. They battery is defective. It won’t hold a charge. Maybe the 4 middle leds on means defective battery. But when I test the battery with a multimeter, it reads 23.7. I thought Lithium batteries didn’t get memory charges. But it looks like that’s what’s happening.😕

So, I spent 5 bucks and bought that battery gage. Here’s what it looks like on the inside. Pretty much what I expected.

The one LED on the left means it’s about 16V. After it gets above 17V the end light goes out and the next turns on. As the voltage is increased the others start to turn on. If it’s about 23V the middle 4 will be on. Once it gets to full voltage the right 5 LEDs are on, the left one stays off.

The voltages are approximate but for $5 not bad.

Heat84

real_aurgathor How did you determine that?

I already explained it earlier in the thread:

Heat84 On a fully charged battery, the battery died after 4 miles of riding. I’m in Florida so no hills or mountains. Then a couple days later, with a fully charged battery, I rode the bike 2 miles with no problem and didn’t charge it over night. The next day, I went to use the bike and the battery was dead. But the battery should’ve been 80% full.

Heat84

Speaking of the defective battery, the seller gave me a 50% refund and I didn’t need to ship it back to them(Which I was hoping for). I’m not happy about not getting a full refund but I’ll live with it. I’m probably lucky to get what I got.

I found a proper new battery: https://www.ebay.com/itm/335807393871. Its $151, 20Ah, and weighs 4.85 pounds. That’s more like what you would expect the weight and price to be. It comes with a connector, but I’m not gonna cut it this time. I’m gonna get a male XT60 connector and put a short red and black wire on it so I can use a battery with an XT60 connector or no connector. Most of the batteries I’m finding now have a connector, so maybe I won’t use the short piece that would enable me to go connectorless.

I found a couple other batteries on EBay, but they’re too big to fit in the compartment.

real_aurgathor

Heat84 I already explained it earlier in the thread

“Won’t hold charge” normally used with batteries that have a high discharge rate. In your case, the most likely cause is that the capacity of your battery is much smaller than claimed.

Heat84 I tested the indicator with a 1.3v rechargeable AAA battery and I held the wires on the battery with my bare fingers. And I got shocked!🤯 How did that happen?🤯 I didn’t know it was possible to get shocked by 1.3v.

If the indicator has a sufficiently big inductor somewhere, connecting it to DC builds up a magnetic field, and when you disconnect the battery the field collapses and that generates some voltage of opposite polarity, normally much larger than the DC voltage initially applied to build up that field.

Another possibility that the source (static electricity) came from elsewhere and you just grounded yourself at that moment through the indicator while playing with that AAA cell.

Heat84

I tested the indicator with a 1.3v rechargeable AAA battery and I held the wires on the battery with my bare fingers. And I got shocked!🤯 How did that happen?🤯 I didn’t know it was possible to get shocked by 1.3v.

What would happen if I had the polarity reversed with the indicator? I know with a multimeter, the needle trys to move the wrong direction with an analog, and you just have to ignore the — in front of the number with a digital. It it as harmless with the indicator? It won’t fry the indicator?

Somewhat-Reticent

Low skin resistance moment. Gives more perspective on defibrillator.
( I’ll defer to more knowledgeable for indicator effect query. )

Heat84

Sparkchaser So, I spent 5 bucks and bought that battery gage. Here’s what it looks like on the inside. Pretty much what I expected.
![](https://i.broadbandbulletin.com/2025-05-17/1747488417-807149-batt1.jpg)

The one LED on the left means it’s about 16V. After it gets above 17V the end light goes out and the next turns on. As the voltage is increased the others start to turn on. If it’s about 23V the middle 4 will be on. Once it gets to full voltage the right 5 LEDs are on, the left one stays off.

The voltages are approximate but for $5 not bad

The product info says it was designed for 24 volts. I thought that meant that each light is 4 volts.

Heat84

Sparkchaser
I have it installed and working now. I meant to ask you, why was it designed the way it was instead of logically(Each LED = 4 volts and the LEDs going off from right to left as the battery voltage gets lower)? That’s the way it’s labeled(The right to left part at least).

Sparkchaser

One more thing, when the one left LED just turns on, it’s draws about 500uA.
When the right 5 LEDs are on it draws about 2.7 mA.

Heat84

Sparkchaser

What does uA mean?

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