the battery off my old Massy210-4 and switch it to the B7500.
WAIT FOR IT! THE DAMN THING WORKED LIKE IT WAS SUPPOSED TO! No amount of reasoning for a good battery going dead, would result in that battery reversing polarity! The upscale Schumacher charger, connected in the correct way, should have charged the battery in the correct polarity. RIGHT? WRONG! ! ! Explain that if possible.
Batteries in general can have the appearance of being "good" yet not be!!!!!!!
My wife' s CR-V would start fine if somewhat "warm" - outside temps in the 40's. But once it dipped into the 20's - it would just clicky-clicky.
I said hell, I will fix this right up!!! Cleaned the terminals and charged the battery and it started right up..... well that was fixed!!! O hell no it was not!!!!!!
I ordered on of those battery testers - the kind that places a load on it and tests the internal resistance and all those good things......... CAME UP in big bold letters ......... REPLACE!!! the life was at 32% the charging ability was 12% or something like that ........ but it still showed 12.5 volts with a meter.
Moral of the story - you can have 12 volts across a human hair wire - but it will never deliver the amp amount to turn the starter - and in my case the volts were there BUT the ability to deliver amps was not.
AND for what it is worth - many a "dead battery" cannot be helped via a high amp charger.
I replaced her battery with a new one at wally-world and bullya - starts right up.