New Battery Issues

[Gearboy801]

Hi folks, I’ve got my kids electric dirt bike and it came with a 36V 1000mAh battery which started to die out on us. I recently upgraded the battery to a brand new 36V and 1400mAh. I wired it all together, shows full power on the battery, sit on it and start to get it throttle and it begins to go but then suddenly and completely dies. Zero power, no lights on the throttle handle, nothing. Turn the key off/on and still nothing. However the second I plug in the charger to the battery then it will start back to full power (shows full bars on the battery power indicator). I go through the same thing over and over. I’ve fully charged the battery overnight, unhooking/rehooking back up the batter. If I lift the back of the bike and give it throttle it will be fine and I can twist it wide open with zero issues, however the minute I sit on it (or my kid), it dies after it starts to take off. What could be the issue?

 

[6zfshdb]

I'm not sure what you mean by a 1000 mAh motor. It should be Ah, not mAh.

It could be the battery is defective or the BMS isn't capable of providing enough current for your motor. Also, If the wire you used is under gauged, or you have a bad connection, the voltage will drop under load and cause the controller to cut out. Depending on the length, 10 or 12 gauge wire is usually required. A voltmeter can be used to diagnose the problem.

Welcome to the forum! If you provide more information, like the make & model of the bike and battery, you may get more replies

 

[Gearboy801]

Thank you for the reply. Attached are pics of the bikes & the specs.

It has adjustable power knob and if the knob is kept on the lowest setting then it will work but the bike is slow. While I am riding it I can slightly increase the power too much then it dies(say power range is 1-10, I can turn it up to about a level 3 but then it dies). I haven’t touched any of the wiring in the bike, only connected the new battery.

 

[harryS]

When that happens to me, it's because the battery couldn't supply enough current to run the motor. You get the voltage sagging and then it goes below the cutoff voltage of either the battery or bike, Lift the wheel. and if the bike hits full speed w/o any load, it's likely the battery,

The 1000mah and 1400mah batteries are only 1.0AH and 1.4AH respectively, Did you miss a zero when typing? Can't find them on Google. Please provide a link where you bought the second one. You may have bought a crappy battery.

When sellers offer crappy batteries, they list them in mAH to make the number seem bigger.

 

[Gearboy801]

That makes sense what you are saying. Attached is a pic of the battery I purchased.

 

[harryS]

I see your kid's bike can draw 10-35A. The battery probably can deliver only 10-12A, That's good enough for people with 250W Ancheer bikes, and those are the users giving it good reviews. In the bad reviews, two users said it only delivered half the advertised capacity.

To sum up, a mediocre battery and not powerful enough for 35A. You want a seller to tell you he's got a 36V battery capable of 30A discharge, That's going to require premium cells,

 

[m@Robertson]

As I read thru the thread, I was thinking to myself that the battery may be outclassed. Looking at the last posts... that seems to confirm it. And the pics let me find the battery. Here is the direct link:

https://amzn.to/4dqpgsH

Advertised as a 36v 14ah battery... for only $179. Everyone with experience in the marketplace knows exactly what the problem is now. Nothing worth a damn is so low priced. And when I read the ad, it says the battery has a "20a BMS" which is waaaay too low. Bearing in mind that they are no doubt advertising the peak value, and the continuous value is probably half that... Your pack is good for 10a continuous power almost certainly.

I bet you have to plug the battery in to get that little jump back to the motorbike, right? Thats what happens when the BMS pops. Battery shuts off until the pack is plugged into a charger to reset the BMS.

Sorry to say that you wasted your money. Even more importantly though, batteries that are safe enough to put into things that reside in your home cost a lot more money than this. You quite literally bought from almost the worst place possible (AliExpress would be worse) to get a quality product. And I'm not down on Amazon I buy stuff from them almost every day. But never a li-ion ebike battery.

 

[Gearboy801]

This all makes sense and really appreciate everyone taking the time to help me dig into this and understand what the underlying issues is. That said, where would you recommend I purchase a good battery for this e-bike? I’d like to have something that can go further allowing my kid to ride longer between charges. What are the pros/cons with going with something that maybe is a bit stronger? I don’t want to mess up the motor but would like something that will not drain as fast giving more of the thrills for longer periods of time.

 

[m@Robertson]

Well, whatever it is you buy is going to have to fit in the space available, and have the right plugs unless you take it upon yourself to cut the wires and change them so they match (I'd do that on the bike side not the battery side). What you need to do is twofold: Find a battery that physically fits, and find it from a reputable vendor.

Unfortunately... 36v is not the easiest thing to replicate, because almost everyone who DIYs (and thus wants to buy a DIY battery) is going to build with a 48v, 52v or even a 60-72v system. I can point you to reliable vendors for those higher voltages, but 36v? I don't know of any. If EM3EV sells 36v, thats where I'd go. They are in China but they have a hard earned good reputation. When you see the prices, you'll see why it was so obvious you got ripped off. You want a battery with a 30a BMS minimum. 40a would be better based on what you are sharing above, but 30 is a lot more common.

 

[indianajo]

No more voltage, the controller can sense that. More AH cannot be felt, except when you hit the throttle uphill the voltage is stiffer and will not sag below the minimum where the controller shuts off. I bought a 17.5 ah battery that will supply 50 A. I've used a controller that will supply 45 A to a 1000 w hub motor. Battery cost $630 in Jan 2018. Still running fine. Would not fit your scooter probably. Has 11 stacks of 14 cells. Luna is out of the 48 v business, 72 v only. Some people say california ebike sells good batteries.