Author Options:

How do i go about charging a small lead acid battery (7Ah)? is this method ok? Answered

Regarding charging a sealed lead acid battery, can i just apply a 12v wall wart at an amperage around a tenth of the rated Ah? i.e. 12v 700mA for a 7Ah battery (for what, 10hours?)

in context i'm looking at making some computer speakers (2.1) portable with a battery such as: http://cgi.ebay.co.uk/YUASA-fire-intruder-alarm-battery-12v-7Ah-lead-acid_W0QQitemZ290422260055QQcmdZViewItemQQptZUK_AudioElectronicsVideo_Video_TelevisionSetTopBoxes?hash=item439e840157i know these may not be suitable for deep cycle charging/draining, does this use count? and will i be damaging it with 12V constant even if i take off charge once i have worked out the time to charge it for? (dividing the amp-hours by the amp rating of the wall charger gives the number of hours right?) any help possible would be great, i want to get this project rolling and of course ill post it up here!?


I have had some success with this, designed for 12V a Pb-acid battery, charger:

It calls itself a "float" charger, and that might be a clue to the charging strategy it is using.  The way you use it is to just leave it plugged in for indefinite amounts of time.  It says in the manual that it will work with 12V Pb-acid batteries with capacity from 5 to 125 Ampere*hours.   I cannot say how long this particular charger will it take to recharge your 7 A*h battery.  I'm guessing that overnight would do it (and that the average current flowing during this time would be roughly ~1 A).  Again, sort of the assumption with this type of charger is that you leave it plugged in for a sufficiently long time, and also you can leave it plugged in forever (well months, years...) without hurting the battery.


You just need a 0-15 2 A transformer, 4 pcs 1N4007 diode, 1green colour led ,2 pcs of 4.7k resistor and 1pcs of 2200uf capacitor, and using all make a rectifier then connect it to filter which is capacitor and the led to capacitor with a resistor. And then connect positive of capacitor to positive of battery and negative to negative of battery. You are done. This recharges the battery very fast. I'm also using it for my 12v 7.6 Ah sealed lead acid battery.