What you are about to read happened to me yesterday. My [house power] generator has a 12v lead-acid battery, much like a small car battery, used to turn the starter. The battery had gone bad and so I went to Advance Auto and bought a replacement. They said it was fully charged. So I got home, connected it to the generator and attached the trickle charger. The trickle charger, oddly, did not show a green light as it should. So I tried the charger in another outdoor wall socket. Still no green light. I then measured the voltage on the battery. It was MINUS 12.2 volts! Not POSITIVE 12.2 volts as it should have been. I took the battery back to Advance Auto and they measured the voltage. It was indeed backwards. Presumably the factory had somehow manufactured it backwards. Meanwhile, that backwards voltage killed the trickle charger and it may have damaged the alternator circuit (charger) in the generator. The local Advance Auto manager has filed a Customer Complaint now that he has confirmed the defect and I await a call from Customer Service. It could end up costing them $2000, or perhaps just my charger and a replacement battery. We’ll see. Quite annoying to say the least. To clarify, imagine you have a battery with a “plus” sign molded into the case next to one terminal and at the other end a “minus” sign molded into the case next to the other terminal. But imagine then that the voltage from the “plus” side is actually “minus” and vice versa. That’s what I have. The battery is made in China.
Clarification – did not happen to me, but to a fellow I know
Interesting. Never heard of that before. Never know about stuff made over there though. I just got a new shaver battery made in china. Maybe I’d better put a meter on it first.
I’ve seen 12V car batteries have reversed polarity, always from someone running it completely dead and then hooking up the charger backwards. I assume that’s what happened here, the battery was manufactured but then charged backwards.
I don’t see how that could have damaged the battery charger at home though. A charger without circuitry to protect itself wasn’t worth much anyway.