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# how to charge a 12V, 44Ah car battery with trickle charger ?

#### flabbergasted

Oct 3, 2011
11
Hi, I want to charge a 12V, 44Ah car battery to keep as a spare battery in the trunk of my car. I used it to start my car twice but it doesn't have enough juice to turn over the engine anymore. I am trying to charge it with a 12V trickle charger, on the charger it says 12V, 1500mA, it's been connected to the battery for 2 hours so far and the green light that signals the battery is charged has not come on yet.

Will this charger (12V, 1500mA) charge the battery (12V, 44Ah, 18VA max) ?

thanks,
r

#### BobK

Jan 5, 2010
7,682
Hi, I want to charge a 12V, 44Ah car battery to keep as a spare battery in the trunk of my car. I used it to start my car twice but it doesn't have enough juice to turn over the engine anymore. I am trying to charge it with a 12V trickle charger, on the charger it says 12V, 1500mA, it's been connected to the battery for 2 hours so far and the green light that signals the battery is charged has not come on yet.

Will this charger (12V, 1500mA) charge the battery (12V, 44Ah, 18VA max) ?

thanks,
r
It would take 44 / 1.5 = 29 hours to fully charge an empty battery if it were 100% efficient. I believe charging is somewhere around 60% efficient, so, about 29 / .6 = 48 hours. 2 hoiurs ain't gonna do it.

Good luck.

Bob

#### duke37

Jan 9, 2011
5,364
VA is a term used for AC circuits, how does this apply to a battery?

If the charger is charging at 1A and the battery is discharged, the battery therefore needs 44Ah, you need to charge for 44 hours minimum.

Having a loose lead/acid battery in a car gives me the collywobles. Have you thought about what would happen in an accident. A shorted battery could start a fire and if split would spray sulphuric acid over the car causing corrosion if you are lucky and over you if you are unlucky.

A battery self discharges and needs to be topped up at least once a month to stop sulphation and loss of capacity.

Why not get the car electrics mended?

#### flabbergasted

Oct 3, 2011
11
VA is a term used for AC circuits, how does this apply to a battery?

Oh sorry that is from the charger.

Thanks for the info duke37 and BobK, the battery charged in 8 hours, i guess it wasn't totally flat.
duke37 you have a very good point about keeping a spare battery in the trunk, i will think about that and maybe just buy a new battery.

r

Last edited:

#### davenn

Moderator
Sep 5, 2009
14,142
failing all that, why not just do the obvious....
Charge it off the existing car charging system thereby having a fully charged battery available ALL the time ?
batteries rolling around in trunks ... naaa not a prob. there are many ways to secure them!! its something us ham radio
operators do often for additional power when up on hilltops doing comms stuff

Dave

#### Resqueline

Jul 31, 2009
2,848
If it reached "full charge" in 8 hours with a 1.5A charger then the battery presently holds no more than 12Ah. It is probably seriously sulphated and needs more charging.
I recently drained my own starting battery completely (by leaving lights on) and while it seemed to be recharged within 24 hours it needed a week to regain full acid density.

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