Charging car battery with Inverter.

[VR457]

I have a 240v to 12v inverter powering my sons car stereo system at home (including 2x10 subs!).

Anyway, i have a car battery at 11.9v at present and no trickle charger. Could i use the inverter to do the job by connecting the battery to it? It has a variable 12-14v setting or a fixed 13.8v switch.

[lathiat]

Wouldn't do that as it wouldn't be current limited in any way - not a good idea!

Closest bet would be to connect it to a running car by jumper cables if you have any.

[lathiat]

Also basic car chargers are pretty stupidly cheap here from a hardware store in Australia

[VR457]

I have been charging it from a running car but it is taking forever. I stop the car every 20 mins, leave the battery for 20 mins and repeat again. Lots of petrol later i have moved from 11.6 to 11.9v, measured after leaving it overnight.

Any links to cheap trickle chargers?

[Nick Mann]

http://www.ebay.co.uk/itm/AutoCare-4...ht_1101wt_1037

There are cheaper ones, but they don't look so good.

[VR457]

Thank you. I thought i needed 12-18A versions so this is good news.

[Davezj]

why don't you power it from a 12V power supply, rather than a battery.

what sort of current are you driving into the stereo.

[Nick Mann]

The one in the link is similar to mine, but as mine is approx 15 years old I'd guess the technology in it is slightly more advanced!

It works fine, although it can take a day or even two to fully charge a very dead battery.

[VR457]

why don't you power it from a 12V power supply, rather than a battery.

what sort of current are you driving into the stereo.

The power supply gives out 25 - 30A and when he cranks the stereo up the needle will briefly show overload.

Anyhow, i went to Hfrds and bought this charger for £30. After 7 hours of charging the battery it is at 12.3v (from 11.9v) but currently charging at 14.9v and making faint bubbling noises. It's not got hot so i am monitoring it as i go along and seeing what happens.

The info i looked up shows an AGM battery at 100% SOC should show 12.9v. I have a long way to go.

[SEAN-NZ]

make sure the battery is in a ventilated room, can apparently possibly give off flammable gas while being charged, forgot what the gas was though.

[wintertidenz]

Hydrogen gas. It's pretty bad for you, and yeah a match lit round that wouldn't be a good thing.

I use a 6A charger - it takes a day or two to charge, but it's a 3 stage charger and only cost me $60. A good charger shouldn't really be causing the acid to bubble though? What kind of charger is it?

[SEAN-NZ]

a day or 2? i borrowed a charger that has a display that would peak at about 4 amps that would charge overnight, unless your batterys massive, i was trying to charge a 560cca battery

[Davezj]

The power supply gives out 25 - 30A and when he cranks the stereo up the needle will briefly show overload.

Anyhow, i went to Hfrds and bought this charger for £30. After 7 hours of charging the battery it is at 12.3v (from 11.9v) but currently charging at 14.9v and making faint bubbling noises. It's not got hot so i am monitoring it as i go along and seeing what happens.

The info i looked up shows an AGM battery at 100% SOC should show 12.9v. I have a long way to go.

Jamil,
whatever you do, don't charge the battery in the house.

any spark could cause the hydrogen gas to explode in fire ball and spray battery acid everywhere.
unplug charger before disconnecting it from battery, as battery disconnect with the chanrger still plugged in will cause a spark and is the most common reason for battery explosions.

anything in the vasinity of a continually charging battery will get covered in acid vapour and start to corrode over time.


Car Batteries are not something to have in the house.

[VR457]

That sounds dangerous. I'm hoping an AGM battery will not do that but i will relocate the whole lot to the garage now.

I got rid of the £30 charger and got this: http://www.amazon.co.uk/Ring-Automot...sim_sbs_auto_3

Turns out an AGM battery is a very fussy customer and requires a three stage charger to coax it back to life. Plus, it does not like being charged above 14.4v and the charger i was using was doing 14.9v.

[wintertidenz]

That should do the job. Another really good charger is the CTEK one - I think they are designed for AGMs from memory.

Sean - when the battery reads 9v because your car alarm decides to drain it really fast, it takes a while to bring the charge back up.

[SEAN-NZ]

ahh, still cant remember mine taking days, even from less than 8, as my gauge wouldnt read below 8