suggestions for building a battery pack (NIMH)

[bp_968]

I need to build a pack to power my Lowell ID-Light (used for still and video photography). I am looking at using these:

http://www.batteryjunction.com/tpeh-td12000.html

But they don't have solder tabs. Is there a off the shelf 10 cell plastic battery "pack/holder" (like radioshack used to carry for AA) that will handle a 50watt draw? I want to use 10 cells to produce 12v (well, 14 or so at full charge).

If there isn't an off the shelf solution does anyone have suggestions for a DIY pack build?

Here is the light:
http://www.bhphotovideo.com/c/product/185677-REG/Lowel_ID_01_ID_Light_Focus_Flood_Light_.html

Mines running a 50w bulb though. (if pack could handle the 100w that would be nice too.).

Thanks!

 

[hopkins]

Hi bp
Guess your application is that you need to be mobile (on foot)
carrying all the gear, ready to illuminate something for
picture taking at a moments notice.

50watt light @ 4amps will melt those little radioshack holders.

Suggest 12volt sealed lead acid batteries carried in a hip pack.

Cable would come out and go up to the light.

Buy 2 (two) 12volt 4amp/hour batteries. (or 2amp/hr - half the weight but also half the time of operation)

Buy a hip pack at a camping gear store. Cut some foam
(from a backpacking sleeping pad... etc.)
to make little nests for the batteries in the pack
so they don't bang together.

connect cables in parallel for 12volt 8amp/hours . You're in business.

Could be much cheaper with less connections.

http://www.frys.com/product/2855784

 

[bp_968]

I already wired up a 12v 7ah battery for it. I was hoping to find something lighter and with more run time, thus the NIMH setup. I have 24 A123 cells for a RC heli setup but 16 cells is $$$ (4x4 for 14v/9.2ah) plus I'd have to wire a voltage cut or something into setup so I didn't drain them dry and burst into flames.

I don't think I can solder on those button cells without tearing them up (the NIMH)

You'd be amazed what they try to sell those battery packs for to video and photo people on B&H and other places (the shop who sold me the light had a simple LA 12v battery in a bag from some famous maker for like 150-200$!).

I do like the idea for the camping foam though!

bp

 

[hopkins]

You're right about the insane cost of those battery packs for Vid lights.

If you can make carrying the SLA battery more comfortable thus
reducing the irritation factor, you'll save a lot of $$$.

Some of the cordless drills now have lithium batteries packs.
Not sure what kind of charge scheme they use or the capacity.
Might be something to check.

Long series connections of NiCd cells never seem to last long in cordless power tools.

 

[Mr Happy]

If you're careful, you can solder to NiMH cells, especially bigger ones like D cells. The RC people seem to do it all the time. Undoubtedly the cells can be damaged, but if you use a good hot iron and are quick so the heat doesn't have a chance to soak in beyond the solder point it will work. Practice on some disposable heavy duty cells until you get the technique right. I destroyed an AAA cell when I got it wrong, but after learning from the failed attempt I soldered up an AAA pack from button cells that is working fine.

 

[hopkins]

Yes the big iron has its uses.

Looking at the spot weld connection technique
on cordless drill battery packs has me wondering
about a DIY rig to spot weld a pack
Fear of electrocution though is my main phobia.

 

[bp_968]

You're right about the insane cost of those battery packs for Vid lights.

If you can make carrying the SLA battery more comfortable thus
reducing the irritation factor, you'll save a lot of $$$.

Some of the cordless drills now have lithium batteries packs.
Not sure what kind of charge scheme they use or the capacity.
Might be something to check.

Long series connections of NiCd cells never seem to last long in cordless power tools.

I've ripped open those drill lithium packs for use in RC Helicopters. You need to charge the batteries with a special charger designed for them (I have a great universal charger that charges them all) and they are 3.6v 2300mah per cell. They are super light but at 10$ a cell you really need an application that requires either the lightest pack possible (thus, heli/plane) or very very high discharge rates (heli). Since I want at least a 1hr pack, preferably 1.5hr then I only need cells that can handle a 1C discharge rate, not 20-40C or more like those can. My heli lasted 5-8 mins so it was peaking at 15-20C at least.

Here is a great link about them:

http://www.rcgroups.com/forums/showthread.php?t=599316

 

[HarryN]

Unless you are really into soldering up your own packs, it might not be worth fooling with that approach. There are a number of reasonable places to get a pack made up by people with all of the right equipment and lots of experience.

I have some r/c packs by cheapbatterypacks.com - sub C 5000 ma - lots of cell layout and termination options available.

IIRC - it was about $ 100 total for 2 each 7.2 volt 5000 AH packs with premium connections, etc.

A nice looking enclosure box and you are good to go.

 

[hopkins]

thanks bp 968
Good that someone has opened up one of those
new lithium power tool battery packs
and lived to tell.:twothumbs -without fire and poison smoke.

The weight savings vs cost makes airborne applications
seem like the best way to go. Although a long running
high drain headlamp could also be an option where weight
is a factor.