Will it hurt the battery? If I left it overnight would I run the risk of "exploding" the battery?
I have a 7Ah SLA battery that I need to charge, but I don't have a charger and I don't want rake out $50 for a charger. Even if I did I need to charge it by the weekend, so I probably couldn't even get it in time.
If I use a 1Amp wall wart it should take 7 hours to charge the battery. Would it be bad for me to plug the battery in for 7 hours and then unplug it when the voltage is about 13.5-14volts or so?
Best Answer
It's unlikely that your 1A wall-wart will handle the battery load, as regulation tends to be quite poor on many lower-quality models. Don't expect constant-current charging - most likely the voltage will sag as the load increases. I wouldn't assume it to be able to maintain 1A over the whole cycle. Also, some wall-warts don't like being connected to a source (like a battery) without isolation.
Technically, charging a SLA at 2.35 to 2.4V per cell is OK (14.1 to 14.4V), but it's risky to leave the apparatus overnight, especially since the wall-wart doesn't have the ability to change modes (or shut off) to charge the battery properly without damaging it.
I suggest reconsidering the idea. If you can find a lab supply with an adjustable current limit, you could charge the battery in a much safer manner. A proper SLA charger is your best bet.