I created a device which is powered with 6 NiMH AA rechargeable batteries. The device uses between 10-100mA current. It is nothing special about it, there are some foil and electrolyte capacitors from + to - to stabilize the power of some chips and there is a microcontroller.

As I understand, the NiMH rechargeable batteries are sensitive for short-circuits. So I wonder if over time an element fails this could lead to a short-circuit.

It there any protection for the rechargeable batteries necessary for a such setup to protect the batteries? Or more precise: Is it usual to add some protection for the rechargeable batteries in battery powered devices?

  • \$\begingroup\$ Linguistic note: In many European languages the word accumulator simply stands for rechargeable battery. \$\endgroup\$ – Nick Alexeev Nov 8 '14 at 20:27
  • \$\begingroup\$ @NickAlexeev You mean I should replace the word accumulator with rechargeable battery for better understanding? \$\endgroup\$ – Flovdis Nov 8 '14 at 20:28
  • \$\begingroup\$ As an American, without the context of "NiMH AA", I'd have no idea what an "accumulator" was. \$\endgroup\$ – DoxyLover Nov 8 '14 at 22:37
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    \$\begingroup\$ @DoxyLover Thank you for this comment, I edited my question to solve this problem. \$\endgroup\$ – Flovdis Nov 8 '14 at 22:41

Luckily, the NiMH batteries are relatively tolerant to abuse, compared to other battery chemistries.

Fuse in series with the battery. If could be a non-resettable fuse, or it could be a resettable PTC fuse. If the load (i.e. circuit powered by the battery) develops a short, it will draw excessive current from the battery, which in turn will cause the fuse to open and break the short circuit.

The type and rating of the fuse would depend on the design and operation of your circuit that consumes the battery power.

Check the peak current consumption of your device. Electric motors, for example, can draw a large current for short time when they start-up under nominal conditions. This is normal, and it shouldn't trip fuses. But if there is a short through the motor, that has to trip the fuse. One way to address this is to use a slow fuse, which opens only after a high current has been sustained for some time.

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  • \$\begingroup\$ You mean in the case of a short-circuit, the NiMH batteries would probably be damaged, but there would not be any harm from overheating? \$\endgroup\$ – Flovdis Nov 8 '14 at 21:00
  • \$\begingroup\$ @Flovdis I meant that if a NiMH AA battery is shorted (or it's being over-charged), it's not likely to set itself on fire (compared to a Li-ion cell), or to release a lot of hydrogen (not enough to be an explosion hazard). \$\endgroup\$ – Nick Alexeev Nov 8 '14 at 21:23

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