hydro-don

I am wondering if someone would enlighten me about charging lead acid batteries? I use a 12V 9Amp battery, and usually charge it by plugging it in to my cigaratte lighter for about 30 minutes, and it seems to keep it charged OK. Lately I have experienced poor performance and longevity from my batteries. The last one lasted only 3 months. I also use a Tower 12V, .5mah charger to routinely charge after sitting a while. My question is how long can I keep this charger going, and to what voltage should be tops. I have seen 13.8 volts sometimes. Is this harming the battery or not? What isthe max time I should leave this charger on, and boil over the battery?

jooNorway

Chargers for lead-acid are voltage related. They push in more amperes as long as the battery voltage is low, and when the voltage raise the chargers usually nearly stop charging (if you use right kind of charger! ). This means you can connect a 500mA lead-acid charger to your 9Ah battery for 24 hours without damaging it.
An other behavior of lead-acid: they last longest if they are top charged the most of the time. They do not like to be left half-empty or lower, this really shorten lifetime.
There are differences in ideal top voltage depending on temperature, gel/liquid acid, and if it is for starting-current or low-current use. 13,8V is a safe voltage, some batteries like to be topped at 14,4 - 14,5 Volt...

backfire

Here's some basic info on sealed lead-acid batteries:

http://www.power-sonic.com/singlesheet.pdf