Backpack Portable CO2 Build

[benmwv]

I say use two of these ($24):
Turnigy 5000mAh 4S1P 14.8v 20C hardcase pack (USA Warehouse)

Should give you around 30 minutes runtime. These are rated for 20C, and tested up to 30C. You will only be drawing 2C so no need to worry about the discharge rate.

Fiddy, that's awesome. What are the circuit boards going between the caps for?

 

[Cyparagon]

^Balancing the voltage and/or ensuring charge doesn't get too high.

 

[jeffreythe00]

Right. So just a small update.

I'm going to at the very least try these boost caps as a power supply. I know they are not ideal but they are just sitting here collecting dust anyway. I've already ordered two boost drives rated at 150W each. So hopefully those will regulate the voltage just a bit.

I'm probably gonna order that lipo pack BLORD posted as its well within my budget. Perhaps I'll order two.

Anyway. That's where I stand with this project. If work does not suck today. I will do some testing with my caps (no driver) and just see what this beast can do. I'll make a video and post it.

 

[phenol]

I'd use a Pb-Acid 12V battery and a step-up converter to boost the voltage to 29-30V. You could make your own with handy parts like TL494 and a pair of low Rds_on mosfets in a push-pull arrangement. It could be free-running; in this case the output voltage will drop proportionally to the battery voltage.Or it could have a feedback regulating the output voltage within the usable charge of the battery. Moreover, since this design implies the use of a HF transformer, you have the option of making the output isolated from the input /battery pack/.
A pair of 3milliohm Mosfets is sufficient for 350W of power with modest heatsinking. For one project i had to make a 12V->400VDC booster (400W) and using a similar topology, the heatsink from a 350W PC power supply that i used to accommodate the 2x2 mosfets was comfortably cool to the touch at full power. And it wasnt incredibly efficient (90%)because i had to use snubbers to tame the wild voltage excursions around the secondary rectifier. A 2.5 boost ratio will definitely lend itself to better control and efficiency.
in addition to that, you could add soft start, under voltage lockout to protect the batt from deep discharge, overcurrent protection....
if you choose to go this way, you are sure to have lots of fun (and possibly a handfull of toasted fets until you get it right)

 

[jeffreythe00]

^ :thinking:

As much as I would love to do awesome stuff like that... I'm still very new to the world of electronics. As you can see I still struggle with simple things. However this is very good information for someone who is electrically inclined.

 

[phenol]

audiophiles use such kind of boosters to power their amplifiers off 12V vehicle sources. the basic design is not as complicated as it may seem, there may even be kits out there for the less electrically inclined. it seems like a viable solution, as lead-acid packs are relatively cheap, albeit heavy...

 

[joeyss]

Why not use Nicads? They have more energy than a lead acid and can be disharged at 30-50C. They tolerate being ran totally dead and will last more cycles than a NimH. Either way I'm not a huge fan of Lead Acid for anything portable.

 

[Meatball]

I still vote for Li-Po. If you save up a bit, they are worth it. They pack in the highest energy density, the circuitry for proper charging cycles can be found everywhere, and they have already been proven to work well with the only other porta-CO2 out there.

 

[jeffreythe00]

^ I agree 100%. Right now I'm limited to what I have though. My power supplies can't provide a sufficient amount of voltage or current to even charge my capacitor bank let alone a LiPo bank. I guess you can call this what it is. The "Testing phase". I plan to ditch the backpack idea all together tbh. Once I get these boost drives. I can use any DC source I want at whatever voltage as long as it can handle the current. I don't even know if this laser powers on yet. AFAIK the last time it was run was late 2008. So it might not even run.

I'm probably going to go with dual lifepo4 cells in a prepacked package. This way all I need to do is add a charger.

 

[jeffreythe00]

Quick update. The laser works!

I hooked up the laser to 30V from my boost caps and gave the interlock 5V and the tube was glowing a nice orange color! I will defiantly have to showcase that when I get this build going.

Now, I ran the laser for a total of about 1 min. That minute drained 1V. So I'd say with these caps that I will have around 10-15 mins with a boost drive. I'd like to increase this as it takes me hours to charge those boost caps from my 7.5V 30A PSU. So I'll be on the lookout for some Lithium cells or NiMh cells.

Now, for the test I needed a beam stop. Looking round I decided that I would use my HID's aluminum case. Since it is textured. it would help scatter the beam. I put my safety glasses on and turned it on. Success!

The laser worked so well that it melted my case which I'm still not sure if it is aluminum or plastic.

http://i278.photobucket.com/albums/kk98/jeffreythe00/IMG_20130115_191427.jpg

Also bad news on the boost drives I ordered TWO from a seller on ebay. However I guess he only had one even though the listing said "more than 10". Well Instead of contacting me and asking if 1 was okay. He sent me a refund for the price of a single unit and shipped the other... SO now I'm stuck waiting for another boost drive.

 

[Cyparagon]

My power supplies can't provide a sufficient amount of voltage or current to even charge my capacitor bank let alone a LiPo bank.

Are you talking about wall warts or something? Because virtually any bench power supply can charge virtually any battery or any low-voltage cap.

For the caps, charge two in series to cut the charge time in half.

 

[jeffreythe00]

Are you talking about wall warts or something? Because virtually any bench power supply can charge virtually any battery or any low-voltage cap.

For the caps, charge two in series to cut the charge time in half.

Well, Not a wall wart. Both of my PSU's are more capable. It's just not "ideal". I do not have any balancing circuits for my boostcaps so charging any more than two at a time is not a great idea.

What I meant was. "I do not have a plug and play setup for charging supercaps"

My PSU's are 0-20V/0-6A and 0-7.5V/0-30A

I also have a 0-130VAC 7.5A Variac, 50A full wave bridge rectifiers and a rewound MOT. So I can charge at just about any voltage. Though the MOT Overheats quickly and will saturate. So not ideal as well.

Plus I probably have 5 or so old laptop power packs and ATX psu's, neon xformers, flybacks ect.

So I have plenty of power.

 

[Meatball]

If your voltage decreases on the order of ~1V/min I would be concerned about the stability of the boost supplies, especially if they're both operating at the same time. It would depend solely on the quality of the drivers and their circuit design etc. Maybe its no big concern eh Cyparagon?

Anyways, an amber plasma color is a sign of a desirable gas mix in the tube. Your tube appears to be very healthy!

Btw, if your mot is saturating, you could try increasing the air gap in the core, or just try adding one if it has none.

You know, H'mike used a bunch of high quality 18650s in series to get ~32VDC. Not a bad idea eh?

 

[Hemlock_Mike]

I'm now using 26650's. You can find them (6000 mAHr) for about $14/2 on Fleabay.
That's about $60 for 8 of them.
HMike

 

[jeffreythe00]

So I'm probably gonna buy two of these.Turnigy 5000mAh 4S1P 14.8v 20C hardcase pack (USA Warehouse)

Any opinions?

 

[Meatball]

14.8V * 2 = 29.6V

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