How to SAFELY bring up the voltage on a totally discharged APX battery!
Hi Folks! Have you ever been stuck with an APX battery that went to zero volts? So called "smart" chargers don't recognize a zero volt battery, ditto my CADEX battery analyzers. I refused to concede defeat and throw out a small mountain of grossly overpriced discharged batteries, so I finally worked out a rejuvenation scheme: if you can get the battery back up to over 2 or 3 Volts, then both the "smart" chargers and CADEX recognize it as a bona fide battery. So, how do you do this safely? You need to limit the current, or run the risk of a spectacular thermal runaway. Although that might be a candidate for a viral video, it sure isn't safe or wise! What would be a reasonable current? I reasoned that if I limit it to around the maximum current of an APX on high power transmit, that should be safe. Some batteries (like BK/RELM DPX Lithium batteries) are simple to bring up: You connect a (current limited!!!) power supply and slowly raise the voltage. At some point, it will start drawing current. You raise the voltage a bit more, and when you get around 10 Volts or so, the battery should be ready for a "smart" charger or a battery analyzer. The APX batteries have to be finessed: They typically don't do anything until you get up to around 12 Volts, then you'll see a sudden current draw. My method is to drop the voltage a bit, flash the battery again, and keep on dropping the voltage until I get to a point where the battery starts drawing steady current. About 30 seconds of charge at that point should work. The video goes a bit long (you get two batteries zapped for the price of one!), but you can see the kabuki dance needed to successfully revive the batteries. My record with this process is about 19 out of every 20 batteries can be woken up. Whether the batteries test well is another story: Ones that are otherwise good are still good, but it won't help adding capacity to an already worn out battery. This simply allows you to recharge the batteries, or get them to the point where you can test them. Thanks for watching! -Tom

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