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Reversed battery polarity. What did I fry?

I was working on an battery enclosure for my BlueROV2, and somehow got the polarity mixed up in the wiring harness. I applied 14 volts of reverse polarity to the entire system. I got a quick spark at the connector when I plugged it in, then nothing.

Now when I plug in the battery the correct way, I get nothing.

What components did I likely destroy?

Hi @StrikeLines,

Ouch, sorry to hear that, that has the potential to cause some serious damage. None of the components on the BlueROV2 have reverse polarity protection, so you’ll need to check just about everything.

The first set of components plugged directly into the power rails would be the first to check. This will include all the ESCs, PSM (power sense module), BEC (5 v converter), lights, and the ROV side Fathom-X board. Check those one by one if you can. After that, check the control components powered by the BEC, including the Raspberry Pi and Pixhawk, but perhaps just the BEC died and those are fine.

The thrusters should be undamaged.


I just got finished running through the system.

It looks like the power sense module was the only victim of my incompetence. It was passing voltage, but had more than a megaohm of resistance across its leads. Since positive power hits the power sense module before reaching the main bus, its failure acted like a circuit breaker, and likely saved the rest of the electronics.

I’m not sure if it was designed that way, but it sure is a nice feature for reverse polarity protection.

Looks like I got off easy. That part costs just $31. One of the lower incompetence taxes I’ve had to pay recently…

Thanks for the help!

Hi @StrikeLines,

Whew, glad to hear it, and happy to help! That is pretty much the best case scenario, with the PSM saving the rest of the system.

Whether or not it was designed that way, lets go with yes, totally an intended feature…