I am making a learning toy which kids can play with and learn basics of programming. But i am tired of keep replacing the AA batteries as they run out in few days. So i am thinking of using rechargeable battery. But i am very worried to use it considering it is kids toy and people says lipo and li ion battery can explode. There are dangers or over charge and heat etc.

Is it safe to use them? Which one to use?

I am using Arduino pro mini 3.3v and some times 5v.

I was planning to use: XCSOURCE 5 pcs 1A 5V Micro USB TP4056 Lithium Battery Power Charger Board Module TE420

I think some users have misunderstood the question and have voted this question to be closed. This questions is very much to deal with programming also apologies if i have not made it clear.

  • We can get the battery level in the code, but is there any way in code we can some how turn off the charging when the battery has been fully charged.

  • I am under impression (might be wrong, you can correct me), normal
    battery single AA cell dies after some time on heavy use (using dc motor etc). But
    rechargeable batteries are bigger with multiple cells in it they will last longer. So if i am running some code in a loop for long time
    will the battery get over heated will it be a problem.

  • I am voting to close this because as the question stands, it is off topic since it's about batteries and the fact there is an Arduino involved is irrelevant. A question about how to reduce the power consumption of your Pro Mini would be on-topic. However, I would recommend that you search for previous questions as that is likely to have been asked already.
    – per1234
    Sep 13, 2017 at 9:42
  • If it's in a sturdy container and has protection circuitry there will be no issues. Sep 13, 2017 at 10:34
  • It depends how old the children are and if they are supervised sufficiently. Why not use a wall wart? Why not use rechargeable NiCad batteries? OK Cadmium gas can be released and that could cause blindness, disability, etc, but AA batteries can be made to explode. You need to risk assess your solution based on the users, no one here can tell you its safe. Sep 13, 2017 at 12:01
  • no common commercial batt will overheat from just running code w/o other hardware.
    – dandavis
    Sep 15, 2017 at 19:35

1 Answer 1


Probably the easiest/cheapest and safest option is to buy a original USB Power Bank and there you have it. Power banks for cellphones/tablets have overvoltage/overcharge/undercharge protection on them and they are also completely sealed, so it should be perfectly safe to handle one of those to your kids (Of couse not some cheap chinese crap).

They can then charge the power bank over USB on any PC or Wall charger and then use it for hours/days.

If I'm allowed to give you a tip, you could eventually pick one of these here, they are pretty good in my opinion. TP-Link Power Bank Of course there are a ton of others around, so you can just pick one which fit your needs.

On your case you just cut a USB cable and plug the ends on the Pro Mini. If a short is detected, Power banks often just shut off and only turn on when they are charged again (You might try this first). If you use a 3.3V Pro Mini, just put a voltage limiter between it. You might also write "3.3V" on the voltage limitor and "3.3V" on the 3.3V version of the Arduino and teach your kids that if the Arduino has "3.3V" written on it, they should put that "3.3V" voltage limitor before it (or just not use 3.3V variants for ease of use).

  • I don't think battery banks, even good ones, can be considered perfectly safe. In fact if you look at the safety guidelines for these things, they will specifically tell you to keep them away from children. Reason being, kids can poke things into the USB outlets, and cause them to short-circuit, and potentially explode. Feb 21, 2018 at 7:29
  • @user1751825 They shut down if kids poke things in and short the circuit. It's really hard for brand name battery packs to explode. I've had a lot of them and since today no single one failed, nor have I heard of one failing in such a way. And, let's be honest: It's a lot safer than someone building his own power bank (OP wanted to build his own and even handle to his kids - bad idea)
    – Fusseldieb
    Feb 21, 2018 at 10:22
  • Does the voltage output matter, when using one of these power banks, or will the Arduino just draw whatever current it needs for its power usage regardless of the voltage? Feb 23, 2018 at 13:38
  • @StevenHolt Those powerbanks are all 5V, only the A changes between them. The example above has 2 ports, 1 being 1A and the other 2A (for tablets that demand more current). The Arduino will draw what he needs and nothing more, probably about 0.02 A. It will run for ages with that battery.
    – Fusseldieb
    Feb 23, 2018 at 13:48

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