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K5HRA Tech

Rechargeable Battery Tricks

So I’m cleaning up the office again, and I come across my old set of Cobra FRS radios, model 3850’s.  A while back the rechargeable batteries that came with them stopped taking a charge, so I bought a set of Amazon brand AAA batteries, and it should have all been good.  Nope, wouldn’t take a charge through the radios.  If I put them in another charger, no problem.  So that’s what I’ve been doing.  I wasn’t going to mess around if it worked that way.

This time I’m like, “nope, this is going to work the right way now.”  So a quick Google search later, and I discover that there’s a little contact in the battery bay that must contact the negative post/battery casing for the radio to charge the batteries.  Apparently the factory ones have this consideration built into them, where the ones I bought do not.  A quick X-Acto knife surgery on just that battery to remove the plastic covering, and voila.  The red-charging light of success appeared.

I’ve called out the little contact switch and the surgically modified area of the battery in the attached image.

Just an FYI to anyone who ran across this.  Shame that Cobra makes it seem that you have to buy their batteries just to make this work.  I haven’t priced them, but I bet they’re significantly more expensive.

DO NOT try this with regular old Alkaline batteries.  You’ll make a nasty hazardous mess of battery acid and probably ruin your radios.  Also be careful cutting.