RC car battery question. Rebuilding battery pack.

NightHawkRMX

Illustrious
Hello. I don't know a lot about batteries or RC cars, so bear with me.

I have a WL tech 12428 RC car: https://www.amazon.com/WLtoys-12428-Scale-Crawler-Vehicle/dp/B06X3TH4K6

It is 3 ish years old. Bought from Gearbest.

Works great, however, it has developed an unusual problem lately. If I pull the trigger to max acceleration, it will accelerate fine (very fast, but maybe a little slower than normal, idk) for about 2 seconds, then it will stop. It won't move again until I disconnect the battery and reconnect it. This happens with a fully charged battery and cold motor, or with the exact opposite.

My theory is that the battery is aging poorly and no longer can provide the required power for the car under load. Given the unbranded Chinese cells, I found when I opened the pack, I'm not surprised. The fully charged battery pack only reads 6.5v, 1v less than expected.

The battery packs label says "BY 18650 2S1P 7.4V 1500mAh 17K13"

I opened the pack and it is 2 3.7V 18650 cells without any brand. I believe they are wired in series to get the 7.4v advertised.

Each cell says "3.7V 5.55Wh", Which I doubt given how much I have heard about fake 18650 cells.

I also noticed some damage to a cell:https://ibb.co/NWc0RHz

Questions:
  1. How did this damage occur? How to prevent it?
  2. Can I simply connect 4 batteries so that there are 2 pairs in series, and both pairs are in parallel? This should get me the same voltage but more runtime. Will this cause any issues?
  3. Can I use the same charger if I add capacity?
Was thinking of these:
https://www.ebay.com/itm/4Pcs-Panasonic-NCR18650B-High-Drain-Flat-Top-Battery-3400mAh-Rechargeable-USA/383242349568?hash=item593b062c00:m:mMRJ5_IDoTjhfFp2NT2fB_A
 

MeisterENOX

Reputable
Dec 8, 2016
10
0
4,510
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  1. Battery damage, particularly rechargeable battery damage can be caused mainly by erratic charging or heating issues, perhaps leaving the toy to charge longer than necessary. However, rechargeable batteries degrade over time no matter what the circumstances and it is an unavoidable process. I would suggest not draining the battery every time and maybe not leaving the toy to charge over night to prevent overheating.
  2. In theory, given that the output voltage is the same, a bigger battery will just result in a loner run time, however make sure not to mix and match different battery brands and do not exceed the stated voltage on the existing batteries as you risk frying the intricate hardware inside the car. I trust that you have sufficient knowledge of batteries to know what you are doing.
  3. I am tempted to say that you can still use the same charger because the only thing that is being changed is the battery capacity, however take that with a grain of salt and research more before taking any action. The last thing you would want is for a battery to blow up and cause a fire.

Please have a look at all the links and make your final verdict:


Sources:
https://www.batterystuff.com/kb/articles/battery-articles/proper-care-and-feeding-of-a-nimh-battery.html
https://www.rccaraction.com/everything-need-know-rc-batteries/

http://rccarcrazy.blogspot.com/2013/05/how-to-make-your-rc-car-faster-pt2.html
https://www.allaboutcircuits.com/textbook/direct-current/chpt-11/practical-considerations-batteries/
 
Nov 20, 2019
62
4
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Thanks. I found some chinese cells lying around and made a working pack using a ton of solder as i lack the proper equipment.

I may add some more cells soon.
If you're looking for new cells, here is a vendor that is highly reputable.. I have only bought from them, and have always been satisfied.

Also highly reputable..

There are others, but these are the 2 that come to mind. I hope you can get your RC car back in action!

As a vaper, finding legitimate batteries is of the utmost importance and crucial for safety, as it is also true in all other uses. There are so many fakes out there, and I highly advise against buying li-ion 18650 batteries from amazon or ebay.
 

AllanGH

Reputable
As a vaper, finding legitimate batteries is of the utmost importance and crucial for safety, as it is also true in all other uses. There are so many fakes out there, and I highly advise against buying li-ion 18650 batteries from amazon or ebay.
Having been a vaper since about 2008, I can agree with the sentiment, outside of the supply chain platform exclusion.

Find a reputable brand and stick with it. Find a known good vendor and follow that vendor wherever they go.

I've bought MXJOs from a single source, for the past few years, and purchase from his store front on Amazon, or on Ebay, and I get the same high quality product.

Being an informed consumer, in the new age, requires technical knowledge of the product being sought, and plenty of research, otherwise you are going to be suckered by somebody.
 
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