Replacing reversed polarity battery

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Re: Replacing reversed polarity battery

Unread post by Megabeccatron » Wed Oct 18, 2017 6:57 am

If this crazy scenario happened. Would the damaged battery have a lower output? And then, let's say the alternator and connections are all correct... If I put on a new battery and the output/voltage/amps are higher could I potentially surge the system and do damage?

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Re: Replacing reversed polarity battery

Unread post by bbodie52 » Wed Oct 18, 2017 7:34 am

A new battery will not harm your system, as long as the same polarity that you have now is maintained. That is why you need to test your current battery polarity with a DC multimeter to confirm the POSITIVE (+) and NEGATIVE (-) labeling on the battery.

If your battery labeling on your old battery is correct (and not internally reversed) there is no reason to expect its operational life will be shortened. If it turns out that the battery had been completely discharged and reverse charged (as in the previous explanation) then the operational life might be shortened, because the internal plate composition would not match the reversed polarity.

If the battery polarity checks out as normal and matches the labeling, and your Corvair actually has a positive ground system and a positive ground alternator you may not want to rush into a conversion back to negative ground. Obtaining a normal negative ground alternator that mounts properly would also require obtaining the correct oil filter adapter to mount the alternator, plus a new gasket and support bracket, and possibly a new external voltage regulator (unless you buy an alternator that has an internal regulator). The alternator should be configured as a reverse rotation Corvair alternator with the correct cooling fan, and your Corvair wiring would need to be modified to match the new alternator and negative ground configuration. All of this adds up to several hundred dollars for parts, plus the work required to fix everything.


A new battery with a greater amperage capacity would not harm your car, as long as the correct polarity is maintained and matches your current configuration.
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Re: Replacing reversed polarity battery

Unread post by Trip » Wed Oct 18, 2017 6:17 pm

Wow, this is a strange one indeed!
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Re: Replacing reversed polarity battery

Unread post by Jim in Wis. » Thu Oct 19, 2017 5:57 pm

I've worked on a lot of '30's and 40's Fords - 6 volt positive ground - and have seen quite a few times where someone put the battery leads on wrong, made it negative ground. The car will run - the charging system sort of works but the amp meter will read "backwards". The starter works fine because it's a series wound motor. Sometimes no harm is done and all it needs is to put the cables on right. If it doesn't charge the voltage regulator might be fried.
Your car has an alternator which might be wrecked, but I bet not. Unless the alternator is marked positive ground - which is real doubtful - I have a feeling all you need to do is put the cables on right. Measure the battery voltage after charging it with the correct polarity - if you have 12 volts or better you might not need a new battery.
I spent 35 years working on electric lift trucks and I saw a lot of goofy stuff happen, but I never saw a battery get charged "backwards". If the charger was hooked up wrong it would get really hot and blow a fuse or explode the battery (that makes for an exciting day).
Jim S.

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