My Canon EOS M wont turn on - Polarity Accidentally Reversed.

So, i built a 7.2v 4ah lithium battery pack for my Canon Eos M to make it last 4x longer. I made a dummy battery to power the camera off the external battery. I believe i may have wired the connections backwards. i was wondering, does anyone know if the Canon Eos M has reverse polarity protection, or a surface mount fuse i could replace. right now the camera doesnt show any signs of life. even with the oem batteries.

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With the battery removed use an Ohmmeter to connect across the +ve and -ve battery terminals in the camera and see if there is a reading at all. (start with lowest range first, then work up range if no reading displayed). Do the test both ways, i.e. swap the leads over. If you get either a s/c or o/c the power input circuit is gone. A reading in one direction only may offer some hope of less damage.

I would suspect that there is no reverse voltage protection, as in most cameras, (do not know yours specifically) the battery can only go in one way and work and even if it could be charged in camera the charging cord also goes in one way only. Therefore most probably it would be considered not necessary and an extra expense for the maker.

Of course this is only conjecture on my part, but reverse voltage protection is exactly that. It protects against reverse voltages. If it has got reverse voltage protection then it might depend on what method was used as to whether it can auto reset when correct polarity is applied (not in your case it seems) or whether there is a sacrificial component that has done its' job and protected the rest of the electronics, that has to be replaced. It won't solely be a fuse, (if there is one). They guard against excess current flow not reverse current flow. It might blow after other components have failed and the current flow exceeds its' rating perhaps.

Here is a link to a teardown of your camera. Hopefully it may be of some help in finding your problem.

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