Homemade "power runner" battery pack for camera mp3 player cordless drill??

I'd love any info on making a homemade device like the one here
http://www.hotmp3gear.com/powerrunner.htm


Power Runner Universal Battery pack

How about this...
10 NimH AAs to make a 12 volt pack Charged by a Multi-Current
Universal Smart Charger found here
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1215

I need the charger to be compatable with 110-240 volts for overseas
travel.

But how do I regulate the output voltage going to my different devices
which need different voltages?
I was thinking of hooking the pack up to a cigarrett lighter and use a
multivoltage cigarette lighter adapter like the one found here
http://www.jr.com/JRProductPage.process?Product=693573

Would this be inefficient?? Or is there a simpler way..like an inline
switch that changes the voltage?

When you have a 12 volt battery pack and power devices that run below 6
volts are you sacrificing efficiency?


Thanks
Jay

 

good idea

Cordless drills usually use sub-c cells, I'd go with those - or a ready
made 12v drill pack.

voltage regulator.

cars run ITRO 14.4v with engine on. I forget what V NiCds need to
charge, but it might be higher than this.

yep.

There is a better way, which is to run your 6v devices off half of the
batteries, then off the other half. The (trivial) downside is you need
to charge them as 2 packs of 6v, ie your charger to battery connection
will have 3 wires not 2. This way you'll get twice as long run times on
6v loads, and ditto with <6v.

If you just need 6v and 12v out, no regulator is then required. For 9v
run it off 12v via 3x diodes in series, for 5v off 6v via one diode.


NT

 

They need a constant current source not a constant voltage. There might not
be enough headroom to make a decent constant current source if you only have
14.4V

 

Doesnt necessarily have to be constant, as long as its limited. Of
course they cant be charged from a V source like lead acids.

If the NiCds needed 13v minimum, one could probably work with that,
using eg a low dropout current limiting regulator. But I dont know what
V is needed.

There is one workaround if theres not enough headroom: charge the pack
as 2x 6v packs. This means breaking the connection halfway along the
battery chain - eg with a piece of card - and current limiting the
charge for each 6v section.


NT

 

Yes that would be the best way to go. You can buy chargers for that really
cheap.