Battery power solution ideas for 400maH 12v pedal?

[Jopn]

Sigh...

Ok, so I'm playing with a trio and we're looking to do some busking.  I've got my suitcase drumset built up and ready to go, our bassist is playing upright, and our guitarist is playing acoustic and running his vocals through a battery powered vox.  BUT... I can't manage to pry his TC Helicon VoiceLive out of his hands.  Granted, it IS a really nice sounding pedal for voice with many great effects that he's mastered.  So I'm stuck trying to figure out how to battery power this damn thing.

The advertised current draw is 400maH, which is a considerable draw.  That has me leaning away from an 8 AA rechargeable battery pack. 

An idea that crossed my mind while working in the garage was my 18v Dewalt cordless drill.  Would I be able to hack something up for those batteries?  I'd need to step it down to 12v then probably do my due diligence in researching power supply filtering.  But the availability of these already being on hand, with the ability to have a few spares charged up is pretty appealing.

Thoughts?  Any other obvious solutions I'm missing?

[italianguy63]

Gel motorcyle battery.

[petey twofinger]

i would try a lm7812 , http://www.fairchildsemi.com/pf/LM/LM7812.html and fuse it

or 8 d cells

or a sealed lead acid battery

check the lounge for pics of our outdoor rig ...

[GibsonGM]

Gel motorcyle battery.

+1    You have an awful lot of current draw there!  I don't see any other practical way...

[italianguy63]

It's relatively small-- self contained, and easy to charge.  There are 12V gel cells they use for alarm systems that could work too..

[Jopn]

Cool!  Never heard of gel batteries before now, so I'll start doing some research.

Hopefully I can find some good spec sheets to figure out how long they maintain 12v before they dip.  I think that's going to be the trick, since a lot of these batteries are designed for applications where consistent delivery over their charge isn't critical.  That's one of the advantages that I saw going the 18v cordless drill battery route, since I could regulate that down to 12v and have 6v of swing before I had to worry (provided I remembered to heat sink!)

[italianguy63]

You should be able to find one pretty inexpensively.  I also recommend you buy a "float" trickle charger from Harbor Freight.  I think they are about $6 bucks.  It is a slow charger, and you can keep it hooked up ALL THE TIME when you aren't using the battery.  That way the battery won't go flat from lack of use.  I used to only get about a year and a half life on my motorcyle (bat), and my last one has been on my bike about 4 years.  MC