Charger charging lead acid 12v battery?

[Superbasher]

Hi guys,
I've been looking at an Ansmann xBase charger, and it says on the product description that I can use it to charge a 1-6cell PB (lead) battery, so would I be able to charge a 12 lead acid leisure battery to run the charger when I am at a bash or out for a few hours?
Thanks
Matt

[BrianG]

Most chargers specify the pb battery as 2v/cell. Since that charger will do 6 cells, that is 12v. So, it should work just fine.

[Superbasher]

Awesome, might have to keep an eye on it just to make sure (if i end up getting the battery)

[BrianG]

Of course, the battery you use to power the charger will have to have more Ah capacity than whatever battery you are charging, depending on the pack voltage too.

You can use a cheap modded PC power supply if AC is available, or use your car battery as long as you're not charging packs all day.

[Superbasher]

I forgot about that MAH thing! As the ansmann has a 5amp charge limit. I may end up not bothering, as most bashes I got to there is a power supply there.

[BrianG]

lol, that darn mAh thing! To make sure you have a 12v battery large enough, multiply your max pack voltage (4.2v/cell for lipos or ~1.4v/cell for NiMH) by the Ah rating, multiply that by 1.2 (for charger efficiency), then devide that by 12v to get the minimum Ah rating of the 12v battery. So, if charging a 4s 8Ah pack, you need a 12v battery Ah rating that is at least 12Ah.

[Superbasher]

So for my IB3800's it's
(~7.2 x 3.8) x 1.2 / 12 = 2.736ah - Sounds kinda low? Unless my math is wrong, which it could be.

[BrianG]

No, it's fine, sorta. I use 1.4v/cell for NiMHs since that is what they generally peak to, but the math itself looks good.

8.4v x 3.8A x 120% / 12v = 3.2Ah.

Let's say you were charging 6s lipos at 10A, you'd need:
25.2v x 10A x 120% / 12v = 25.2Ah

[Superbasher]

Now that a lot of power! Thankfully I am not thinking about going LiPo any time soon