How to remove Protection circuit from Trustfire batteries


If you are having trouble with your trustfire batteries cutting out, you can do this.



You planning to use the new security things for these batteries?


yep. :) I already put some together. :)

but you make a good point. I forgot to mention that in the video.

So everyone remember, you need to use the poly fuse with the otherwise unprotected batteries.



That makes me wonder if there is any data on battery temp while in the water? I bet they stay cooler.


Hey Darcy,

Thanks for the video on how to remove the protection circuit from the Trustfire batteries. Can you post a pointer to poly fuse instructions? I assume I'm supposed to use that while charging the batteries?


Hi All:

While it's tempting to break off the protection circuitry from the Trustfire batteries and insert your own polyfuse, I would discourage folks from doing so.

The polyfuse that we are shipping with current kits, and that we offer in the store, is sized for the LiFePO4 batteries that are currently using. If you go to a site like, and compare the current ratings for LiFePO4 cells vs. LiMnNi cells, you'll see that the LiFePO4 cells are rated for significantly higher currents. So if you use the polyfuses sized for LiFePO4 cells with the Trustfire cells, are they really protecting you from anything? I don't know. Will anything really bad happen to the Trustfire cells if you pull too much current with the protection circuit removed? I don't know. Just be aware that if you're trying this at home, you're running in a configuration that we have never tested here at OpenROV HQ, so you're kind of on your own.

If you're suffering from battery dropouts with Trustfire batteries and are thinking of cutting off the protection circuit, first make sure that you've installed this patch in your software. It cuts down the number of nuisance trips significantly, and may be a simpler and safer solution to the problems you're having with your ROV.