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I'm building a small device based on ESP32 and powered by a 5V power supply (looks like <1A even when speakers are playing). I want to power it on batteries and it seems that everyone does Li-Ion batteries today (at least those are almost all the tutorials I find), but I'm a bit concerned as I know that these are more prone to explosions, catching fire, etc... Since the toy won't be used during the night, and for convenient, I thought to charge the battery via a wireless charger, although I know they provide slightly less current (I can charge slowly, I have the whole night..).

  1. What type of battery would you use for a baby's toy? Are Li-Ion really dangerous or I'm looking at old posts?
  2. I saw the Li-Ion batteries are 3.7V. If I connect 2 of them I'm over 5V already.. How can I get to 5V with those? Do I need some voltage regulator?
  3. Is there a recommended (and reliable!) charging module? Ideally with all other components needed if any?

Thanks!

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  • Just use NiMH. Mind the lead solder.
    – DKNguyen
    Commented Sep 1, 2022 at 21:26
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    I would just get a good quality USB power bank with the ability to charge itself wirelessly. Output voltage is already regulated, charging is taken care of.
    – vir
    Commented Sep 1, 2022 at 21:42
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    Might be opinion based but I think neither NiMH nor Lithium batteries have no place in baby toys. Use primary batteries for safety. NiMH has many times higher short circuit current than primary batteries, it can melt wires.
    – Justme
    Commented Sep 1, 2022 at 21:47
  • Agree.. With the additional things to take care for, and the risk in missing something, I think I'll go for a small powerbank that already has everything.
    – Zach Moshe
    Commented Sep 2, 2022 at 9:11

1 Answer 1

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LiIon is dangerous ... if you:

  • overload it (U > 4.2V)
  • load it with an high current
  • the LiIon-cell gets hot (because of sun or an other heat source)
  1. Use LiIon-cells, but reduce the charging current to a low level.
  2. To get the +5V you have to use a StepUp-converter. (MT3608 set to 5V)
  3. To protect the cell, you simply add a TP4056-Module (with protection circuit "DW01") (cost 50 Cent) to protect the LiIon-cell. There is a resistor R3 (1.2kOhm = 1A charging current), you can change the resistor to 3kOhm, this will reduce the charging current to 400mA.

I develop devices for Bio-laboratorys and use LiIon in this devices too. The charging current is low and the charging voltage is only 4.0V, so that the electrodes can not degenerate so fast, so the capacity of the cell will be stable for a long time.

Do all necessary safety measurements. Add a fuse, make sure that the device is stable, so that the battery can not be damaged because of brutal baby force.

If the NiMH cells would fell out of the device and the child put it in his mouth, then other bad things could happened.

If you want to use a powerbank, then you should know that they have mostly an under-current shutdown, so that they go off if the current is to low. So it is possible that your device stops working after a while, if the power consumption was low for some minutes.

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