Sounds like the regulator inside of your alternator went south.....ideally the alternator should be charging between 13.8 and 14.2 volts and no more. Any more and costly solid state things like radios and cell phones have a short lifespan.... as you sadly experienced firsthand. The amperage load should have nothing to do with you voltage output, it should still always be between 13.8 and 14.2...Thanks Randy
