Charging battery with transformer

[Tim M]

Will a 12v transformer charge a battery? If yes, how beefy does it need to be?

[Nos4r2]

Originally Posted by Tim M

Will a 12v transformer charge a battery? If yes, how beefy does it need to be?

No, not unless you've got a rectifier,and it needs a higher output than 12v too-around 14v is about right IIRC.

Buy a battery charger!

[Tim M]

Originally Posted by Nos4r2

Buy a battery charger!

Thought someone would say that

[Tim M]

http://cgi.ebay.co.uk/12-VOLT-BATTER...1%7C240%3A1318

This looks just like a transformer with a pair of croc clips

[jwalker]

No it doesn't. It's a small regulated power supply.

[JABS]

Tim,

This is a motor cycle trickle charger. Designed for maybe a 10 or 20 amp hour battery.

You probably have 100 mamp hour batteries. It will barely mask the self discharge of your boat batteries.

You need a decent man sized charger since your batteries are probably at the top end of car battery requirements.

[Tim M]

Hi Tony.

It's only a little battery I'm trying to charge (can't remember the capacity off hand). I think I'll just fire the outboard up tomorrow and let it charge off that for a while!

[JABS]

What size battery are we tralking about? Amp hour capaCITY IS IMPORTANT. yOU NEED TO BE ABLE TO HANDLE THE CAOPACITYT IN A MAXIMUM OF TWENTY HOURS.

Are the speakers OK??

[jyasaki]

Originally Posted by Tim M

Will a 12v transformer charge a battery? If yes, how beefy does it need to be?

Transformer by itself, no. It outputs AC at 12V RMS (which should give you the required peak voltage once you rectify the sinewave.)

Begging for problems, though: Battery chargers are usually current limited (in case of a completely drained battery or somesuch) whereas the jury rigged transformer wouldn't be.

Small smart chargers aren't all that expensive. Larger automotive types (not smart - stupid, perhaps?) are even less.

jky

[Matt]

I used to use one of the little chargers on my old boat, which IIRC had 60ah batteries, 1 on each battery. Kept them adequately charged for months when I wasn't using it.