Bad battery charger

[StephenGiles]

I've been trying to charge up a couple of motorbike 12 v batteries without much success, I use these sometimes for breadboard power. The current draw seems to be 39 microamps - can I assume that the charger is buggered (not by me I would add!)?
Stephen

[StephenGiles]

My father used to charge a second battery in the boot of his car for use in his caravan. As he is dead I can't ask him about this, but is this as simple as connecting a second battery in parallel with the normal car battery?
Stephen

[petemoore]

I've saved alot of time and money by haveing the spare charged battery in the trunk. Also helps get traction in snow/Ice.
 Instead of calling a tow truck, or getting the jumpers out, I just stick the freshly charged battery in where the dead one was, and I'm down the road [for about 45 minutes to 2 hours with a bad charging system and the lights off]...a good [you can get a medium sized battery with alot of cranking amps that'll fit in most cars battery holders] top/side post battery will probably be needed/used eventually if you drive a car.
 Just top off the charge once in a while and the mostly unused/[stored with charge] battery is like new...and ready to be installed when the old one dies....good to GO.
 See I got stuck with dead car a couple times in winter wasteland...I figured I could always use a good battery or sell it. turns out to be totally worth it. Also for jumping other cars...you don't risk burning up your alternator and can get access to cars parked where a battery installed in your car...the jumpers won't reach.  
 1 tow charge exceeds the price of the battery.
 1 battery can eliminate the need for MANY tow charges.
 I hate to wait...

[StephenGiles]

Thanks Pete that's great.
Stephen