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FrozenGate by Avery

Backpack Portable CO2 Build

Meatball said:
14.8V * 2 = 29.6V

Are you still going to use a voltage converter to get the extra 2.4V you need?
Click to expand...

I don't "need" to use it if I use the batteries. However I'd think it would be better if I did use it. The minimum is 28V in
 
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I think you will be fine without it. At 28v that is 3.5v per cell. Full charge the voltage will be 33.6v. So once the voltage is too low the batteries will be pretty much dead anyways.
 
Well, I don't want to have these drivers I bought just sitting round. Though they are rated for 12V IN so they will be useful for other projects. Hmm...

Now how would I charge these cells? There any special way? Could I just apply 14.8V and let them go? Or do I need a special charger?
 
You need a constant current source to charge them. A charger from the hobby store made for Li-po's should be fine.
 
I have a lambda 20V 6A PSU with constant current that in charge all of my Lithium batteries on. So I'll just use that. I just wasn't sure if it needed some sort of special power supply.
 
Since its a multi cell pack you need a balancing charger!

Cheapest 4 cell one I saw on hobbyking was $9.
 
A balance charger charges each cell separately to a pre set voltage, then stops. Since no two cell are exactly electrical identical when they are put on the charger, each one needs individual attention. This is mostly only done on Li-po's.
 
Yeah, it can be dangerous not to use one. A bench psu would essentially just charge until the pack is at 16.8v. If some of the cells have different voltages (because of slightly different capacity) then some can be under charged and others over charged. For example, three of the cells could be at 4.1v and the fourth at 4.5v. It still equals 16.8 so as far as a bench psu knows its fine but really it would be damaged from over charging. Then the next time it would be even worse. Possibly even catch fire.
 
Okay. I thought so. Because this pack is sealed I had assumed that each cell was already balanced. However upon looking at the cells it looks like that ribbon cable is just for that. I do understand about balancing cells. Its one of the reasons why I'm straying away from super caps if I can. Charging them individually is a PITA. I'm still going to do tests with them. However before I go playing with these drivers I want to put them on a scope and see how they perform under load. This way I can be 100% sure nothing bad will happen should I decide to use 12v battery alternatives ect. I have to wait until I can get to mariomasters house to do that since I do not own a scope nor do I know how to properly read/use one.
 
Yeah, 12v SLA are definitely a viable option. 10AH 12v SLAs arent huge (definitely backpackable) and shouldn't be very expensive. Plus less finicky than lipo, but they are heavier.
 
While other batteries may be more forgiving, all LiPo/LiIon batteries need to be charged with special smart chargers so they don't overheat and/or explode. Don't go cheap on that part of the battery equation.
 
This build sounds like great fun !!

I can't wait to see what creative uses you'll have for a portable CO2 laser!!
Please post your pics!
:beer:
Dr_Evil.jpg
 
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^ Everyone at work always asks me about the flux capacitor. Nobody ever uses the Dr.Evil reference :(
 
in the mean time, you may be able to charge the individual cells with the balance leads. It will take 4x longer though.

Wish it was easier to turn a laptop battery pack into a balance charger...
 
Please tell me your going to fit this on a Shark? Make sure the Shark has the proper Laser Goggles for your wavelenth!
 
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