I have two 12V 4.5Ah sealed Lead Acid batteries from an old electric scooter. The scooter is a decade old, and packed up a few months after purchase. The batteries were literally left as is for almost ten years, and I am unsure if they were connected to the circuit or not during that time.
Okay, so the one measures 1.1V, and the other -0.6V! The negative voltage is very odd as the batteries were in series and I can't think how that could be physically possible through (dis)charge..
I do not have any desulphation equipment or similar, all I have is an alarm "UPS box", which slowly charges SLA batteries, although it never gets them above 13.4V as that is what it outputs when no battery is connected, also it's all linear - nothing fancy.
Is there anything I can do to resurrect these batteries with the equipment I have, or should I just have them recycled? I have a fair amount of knowledge in electronics if there's anything I could do. Also, are there any dangers hooking it up to my charger or hooking up one with a voltage too low in general?