I am planning to use a 18650 battery and a casing like below to run a raspberry pi zero W outside on my watch, but I hear bad stories about lithium ion batteries, like 18650, exploding on a regular use.
ex: https://www.youtube.com/results?search_query=lithium+ion+explosion

I see 18650 batteries with protection circuit installed, but people talk about bad/fake circuits, and I don't know what to rely on.

I don't have enough knowledge to be confident on this kind of power supplies. I would like to ask people with knowledges what I should look for more safe battery power supplies.

For an instance, if I get a case like below which seems to have some protection circuit in it, does it mean I don't need a 18650 with protection circuit?

Or, if the circuit in this battery case isn't really for protection, how can one tell what is protection circuit, and how safe the circuit it is?

battery case

enter image description here

4 Answers 4


A lithium-ion 18650 cell is, I believe, 3.7 volts. You'll need a switching boost regulator to bring the voltage up to no more than 5.25v.

You can either handle all the power regulation yourself, or you can have the Raspberry Pi do this, but to do that, you need to make a USB power cable. This has higher thickness wire than normal, but no data wires.

I've used lithium-ion and LiPo and LiFeSo batteries for years. A few months ago my cell phone battery expanded and pushed off the case. I normally power robots with these batteries and they take a lot of abuse. I realize this paragraph is purely anecdotal, so take it with a grain of salt. But I do know that a lot of other robot hackers use lithium rechargeable batteries.

Probably a safer alternative is to get a USB power pack meant for charging cell phones and tables. There is usually one port with a 2.1 amp capacity. These are fairly sturdy. I would not go for the budget ones. The power is cleaner in the better ones.


18650 batteries are in everything, laptops, cars, those portable usb phone chargers, tools, e-cigs, just to name few. They are unsafe in the same way gas is unsafe. Great tool / energy source but use it in way it wasn't designed and you will get unintended consequences.


Battery 18650 is used in some applications. why you scared? 1. if you use powerbank case. It's perfectly safe. but you need a fast charging ability or min 2,1A. for better performance. 2. You better find battery module / UPS module for 5,1 V that can discharge up to 3A. 3. Raspberry is safe without any battery module. Raspi have built in battery indicator. And then, you need a micro usb module. (very cheap design)

Protection circuit is just to protect your electric circuit, like fuse (electrical safety device) to protect against overloading, short. You do not need to know what electronic components are used in circuit.

what you need to know is : The circuit discharge is must 5V. or max 5.5V (dangerous if you are not expert). You need a parallel baterry if you want raspi to live longer.


Bad quality batteries exist, I would really recommend if you buy them from Aliexpress get the expensive ones (at least not the cheapest); same goes for the BMS and boost circuits (try and research the brands previously on the internet forums like this one). It is not normal for batteries just to explode.

Also please note that doing engineering is just that, experimenting with different materials that may not always fit your use case, so be ready for some level of failure. Remember you want to attach some random electronics to your body and that may not be as straightforward as it seems.

  • I would add that you should not buy 18650's with a stated capacity larger than 3500mAh as they are likely fake (and usually still expensive). Also, buy from reputable battery brands like Samsung, LG, EVE, Sony. Always use a protection circuit (or BMS) and an actual LiIon charging circuit. There are many BMS boards sold as BMS/chargers, but they are not chargers.
    – StarCat
    Mar 22 at 7:29

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