Hi, I am powering my radio with a 12v rechargeable battery but as soon as the battery starts to lose charge, the radio starts acting funny. I was thinking of builidng a circuit that could somehow switch to an external
Adaptor12v+ --->|-------[ ]-----Load Diode Bat+
Cannot be more complicated.
Have fun
Stanislaw Slack user from Ulladulla
Most people would use the external voltage to prevent the battery running down.
How do you charge the battery now? If you have the right kind of charger, you can just leave the charger on it. I just bought a charger for a 12V sealed lead-acid battery yesterday that does a nice job of charging the battery fairly quickly, and then going into a safe float-charge mode that will not damage the battery if left on it for long periods. Such chargers are a bit pricey but may be worth it for hassle-free operation. If you want to build your own, I can recommend the TI UC3909 chip as a basis; it does a very good job of switching to float mode if you set it up properly. There is good data in the data sheet and I believe there's a good ap note on it too, on the TI site. With that, it becomes following a "cook book" recipe, though it takes some familiarity with electronics (or extreme luck) to get it right.
Cheers, Tom
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