# Help with designing a custom battery pack



## Batarray (Mar 6, 2012)

Hey folks, New member here. Ive been a longtime browser of the forum, and have been a flashlight enthusiast for as long i can remember . I remember when i was a kid, stocking up on the white led flashlights right when leds first hit the market, because they were cheaper to buy then ordering the diodes separately. My latest project is putting 6 cree XM-L's into the dome lights of my truck. They light up the parking lot pretty well at night:naughty:

LOL Anyways, my fascination of tinkering with electronics has gotten me into a few fun projects at work, and i thought who better to ask for help then the folks to tinker as well. Working on a personal project, and working on a commercial project are very similar however safety mainly applies to only one of them for most of use lol.

Ive taken the reigns on a custom battery pack project we have been tinkering with at work, and lately its taken a complete 180, and were back to where we started with almost. Here’s the scoop. We got involved in making a custom battery pack for a really large customer of ours. The ideal behind it is that it is used to power a led lighting panel to provide a up lighting for a item in a display unit that is in the middle of the store where no power would be avalable. it would be a rechargeable li-po pack that the store employee could pop out of its base and dock it in the charger overnight. Ive decided that it needed to be no less then 8500mAh, and output no less then 12v. With it being a li-po unit, typical package would be outputting 14.4v. I have a 12v PWM regulator that’s part of the led panel, plus it gives us about another 30min of runtime. Ok so i started off the project by looking at premade packs to help keep the costs down; mainly laptop packs. But they ran short of capacity and voltage output that we needed for this project. In the end we ended up getting a prototype pack made overseas for us to test out. 8800mah, 14.4v. Perfect size to fit into our base (around 6" x 5.5" x 1" tall). It worked great. It gave us the 10h of runtime we needed. But hers the problem, it needed a custom charger for it, then a custom plastic case for it to fit into, then UL certification, then theres still the chance that it would catch fire during the night as it was charging.. Not too good. Plus the pack would of ended costing about 750$ to us, for the low production qty we needed 100-200 units.. Totally out of wack, espically when a premade safe laptop battery pack is around 40-50$.

So i bring my question to you folks, do you know of any alternatives to my problem. Later on this week im going to start sourcing out camcorder batteries to see if theres a way i can put them in series to give us the voltage we need. They are the perfect package for us, chargers are a dime a dozen, they are compact, and already certified. But lack the capacity and voltage we need in a single pack.

Any other ideals for off the shelf parts that we can use. (preferably within that size restriction, but we can go about 3" tall on the height.

Thanks :thumbsup:


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## Kestrel (Mar 6, 2012)

Hello Batarray, welcome to CPF.

A difficult question here, if you don't get enough assistance in this rather out-of-the-way subforum, I would be able to move your thread to */Batteries-Electronics/*, */Fixed Lighting/*, */Special Application Lighting/* perhaps :thinking: - this thread is a difficult one. Please check out the other subforums and PM me if you'd like this thread moved to somewhere else that you think might be a decent fit depending on what you come across.

Try using the 'Google Search' function at the top left of each CPF page for 'custom battery pack' threads that deal with other applications besides flashlights and note where they are. Hopefully this will help; good luck,


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## Batarray (Mar 6, 2012)

Hi Kestrel,

I was not able to PM you. Probably because of the low post count. It would be greatly appreciated if you could move it into the "Battteries, special lighting". That would be awesome.

I also hope you dont mind me posting a thread regarding work related stuff. It was actualy the bosses ideal. I tell him bits and pieces here and there about all the other forums i use for getting other projects off the ground (mainly mechanical related stuff).

Figuring out how the power a pack is simple, figuring out how it wont burn a store down is different

Thanks


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## Kestrel (Mar 6, 2012)

I have moved your thread to */Special Application Lighting/* for now. Hope this helps,


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## Batarray (Mar 6, 2012)

Thanks!


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## AnAppleSnail (Mar 6, 2012)

To get UL-certified batteries and chargers mostly means buying a pre-made system. The liabilities involved mean your customer really does want UL gear, and I don't know how to go about getting hobby-made stuff UL certified. I can suggest either:

1. 12v lead-acid battery. Not sexy, light, or compact, but rather safe.
2. Drill battery. Get one on sale with its charger at Lowe's and you'll have what you want.
3. Other battery pack that is okay to charge/use indoors.

Clamping 18650s together really can be a liability issue if it's done wrong, and the insurance company won't hear of it. Good luck!


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## arek98 (Mar 6, 2012)

Have you considered SLA battery? It would be probably cheapest option.
This one for example has 12V, 10Ah. Dimensions 5.95”x4.48”x2.8” and should fit from what you wrote.
http://www.batteryspace.com/sealedleadacidbattery12v10ah120whs.aspx


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## Batarray (Mar 6, 2012)

AnAppleSnail said:


> To get UL-certified batteries and chargers mostly means buying a pre-made system. The liabilities involved mean your customer really does want UL gear, and I don't know how to go about getting hobby-made stuff UL certified. I can suggest either:
> 
> 1. 12v lead-acid battery. Not sexy, light, or compact, but rather safe.
> 2. Drill battery. Get one on sale with its charger at Lowe's and you'll have what you want.
> 3. Other battery pack that is okay to charge/use indoors.



I think i will try and push the SLA battery again. They initialy ruled it out because it caused us to have to change the original design of the base for them. But seeing that alternatives are dying quickly, they might have to change the design a bit

Heres a pic of the original pack we had (it has a nice alumium cover on both sides), it worked perfectly but didnt have the capacity we needed, and for them to re-create a higher capacity one, it would of ended up costing double what our recent design would of been.:huh: I will also look further down the path of the camcorder battery.


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