I'm wondering if it is okay to put a lithium ion battery directly next to a strong permanent magnet. Would this affect the functioning of the battery? Can it lead to early failure? In the worst case, can it lead to an internal short circuit?

In my setup, a small lithium ion battery (100-200mAh, similar to this link ) is used in the same device as a couple of neodymium magnets (N52 cubes, the strongest kind). The magnetic field at the surface of the magnets is up to 0.6-0.7 Tesla, which is really, really strong. Due to the mechanical design, the battery has to touch one or more magnets - there isn't any other good place to put it.

I can't think of a specific reason that wouldn't be okay, except that is a strong enough field that it could affect not just ferro- but also paramagnetic materials, and possibly affect chemical reactions so it might mess up the chemistry at the battery electrodes. Also it is a strong enough field that there isn't any everyday experience with it, hence I have no intuition about what to expect. The battery certainly doesn't come with a spec for "max allowed magnetic field".

  • \$\begingroup\$ I can't think of any reason the magnetic field would cause problems. Obviously the cell must be mechanically protected. Just out of curiosity, are there any hall-effect devices in the battery protection circuit (or BMS)? \$\endgroup\$ – mkeith Sep 18 '19 at 18:50
  • \$\begingroup\$ @mkeith the battery protection uses a Seiko IC (S8261) and a pair of mosfets (8205), that's all. It's amazingly simple for what it does :) \$\endgroup\$ – Alex I Sep 18 '19 at 19:08
  • \$\begingroup\$ I think that uses shunt-based current sensing. So no hall effect device. So that is good. \$\endgroup\$ – mkeith Sep 19 '19 at 17:29

It should not have an affect on the battery, the magnetic field my deviate the path of ions and electrons slightly but not have any effects on the battery itself.

If the magnets 'slam' into the battery this could puncture it so be wary of this also as very strong magnets can accelerate objects with metal in them.

  • 3
    \$\begingroup\$ If the battery has an unusually sophisticated protection circuit that uses hall-effect current sensing, there may be problems with that, but not with the cell itself. \$\endgroup\$ – Hearth Sep 18 '19 at 19:16

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