No didn't remove battery but did test at the battery not under the hood.

The fancy electronic tester had a dead battery so he used the old school "hair dryer" style tester that pulls a real load. The battery acted like NiCd battery with memory. Where it would charge to full, supply decent current but only have 10% of normal capacity.

Haha, yes that might explain it! I have seen something similar a few times before. A bit of corrosion at the battery connections forms an electronic junction similar to a diode or part of a transistor and can do some strange things. There can also be some strange internal things go on in a battery but with a real load test and maybe a hydrometer, more than 99% of battery issues can be weeded out.

They use a Desulfator to remove the sulfate on the plate. The desulfator work by pulsing current to the battery.

Cheap desulfator can be bought on Amazon. I use one for my motorcycle battery over the winter as well as for the boat battery when I had a boat.

https://www.amazon.com/BatteryMINDer...ds=desulfating

I could have possibly bright my old battery back to life but I was happy with upgrading to AGM at a fair price of $170

Just got the AGM too. My battery was testing at 11.7 volts after a full overnight charge, & was giving me tons of problems in general. Luckily saved the receipt from Autozone, & 4 years later have upgraded from the Gold to the AGM for $18 at AutoZone :rofl::rofl::rofl:

We only get 1 year warranty out here and that goes for no name brands as well as brand names...pretty annoying as I would have invested in an agm too but the warranty for a varta agm versus cheaper lead acid were the same

That's a GR8 deal. You basically got 88% of your $$$ back to be applied.
I was thinking the pro-ration on yr 4/5 was much much less.