# Supplying 1A to a load for 5ms using battery

Discussion in 'General Electronics Chat' started by FND, Aug 8, 2009.

1. ### FND Thread Starter Member

Apr 2, 2009
16
0
Anyone,

I really need help / suggestion on how I can make a power supply 1A of current to a load for at least 5ms using a battery. I've been on this for quite sometime already. My load resistance is quite high which i have yet to determine the exact figure.

2. ### bearing01 Member

Jul 29, 2009
14
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Load resistance is high and you want 1 Amp?

12 Ohm load will need a 12*1A = 12V battery.

If you have a 100 Ohm load then you will need a 100 Volt battery.

Remember, current is something that is drawn by the load. You can get 1A out of a 1V battery if you have only 1 ohm load. You can get 1A out of a 2V battery if you have 2 Ohms. Current isn't drawn only when you create a current source. Even then, if the current source tries to push current into too big a load then the source will saturate and not supply the expected current.

3. ### FND Thread Starter Member

Apr 2, 2009
16
0

Is there anyway i can use a supercapacitor or anything like that? How does a supercapacitor work anyway?

Jul 7, 2009
1,585
141
If you give more details and a schematic, you're likely to get better help. 1 A for 5 ms is 5 mC. If you calculate the capacitance needed to store such a charge for different voltages, you can figure out if you can use a low-ESR capacitor to supply the needed current (C = Q/V). For example, at 5 V, you need a capacitor of 1 mF; at 12 V, 417 μF. These are pretty easily found values, so a capacitor may be all you need.

Clearly, the internal resistance of the battery will play a factor in the design here -- you may or may not need the capacitor.

You can get more information about batteries here. One way to measure the internal resistance of a battery is discussed here (page 8 and also look at the Energizer PDF referenced at the end of the document).

5. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Supercapacitors are typically rated for low voltages.

It would be very helpful if you could tell us what your load resistance is, and if your load is purely resistive, or if it has reactive components (inductance, capacitance) to it.

6. ### russ_hensel Distinguished Member

Jan 11, 2009
820
47
Supercapacitors work basically like capacitors with high capacitance. If you understand capacitors then you might want to ask how supercapacitors differ. Is that what you need?

7. ### FND Thread Starter Member

Apr 2, 2009
16
0
Thank you very much to all of you.

Here's the thing, the load is almost purely resistive (i've yet to calculate its resistance coz multimeter wouldn't do). I don't know exactly what it is but what i can tell u is that it is something like gun powder. It needs about 0.8A for only appxmtly 5 to 8ms thru it then it will burn. I tested with a car batt 12v it can burn, so what i want to do is to produce that amount of current in that short period of time but in a smaller size.

Sorry that im not able to provide more info coz basicly that's all i have, but that little bit about capacitor that one of u had mentioned helped to give me an alternative.

Appreciate for all your kind help.

8. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Why not use a constant current source connected to a timer? What is your power supply source?

9. ### t06afre AAC Fanatic!

May 11, 2009
5,939
1,222
From your description it look like you want a short energy burst, in order to ignite some gunpowder by heating up a resistance wire of some sort. One of my upcoming project is a desulfator for car batteries. I found it here. http://home.comcast.net/~ddenhardt201263/desulfator/lowpower.htm If you modify this circuit. It may deliver the energy spike you need. I think it may work muck like a flash lamp circuit. Perhaps you just can pick one out from a disposable camera

Last edited: Aug 10, 2009
10. ### FND Thread Starter Member

Apr 2, 2009
16
0
Hi Guys!

Here goes, I managed to ignite the gun powder (sort of) yesterday using a 6V, 22Ah battery (eveready). So, from that I managed to determine the load resistance.

What i did was, I used that battery with a known resistor (2.2k ohm) in series to get a known current (2.7mA). When i triggered the switch I observed the voltage drop at the load which I got 1.63v. From there, I calculated the load resistance (603.7037 ohm).

Then I tried to use 2 energizer 9v batteries in parellel but it did not work.

Then, I got confused what is actually the current requirement to ignite that.

SgtWookie - the load resistance is 603.7037 ohms.
t06afre - yes, a short energy burst is what i need, & thx for the link.
Bill Marsden - my power source is a battery, I'm trying to make it portable and as
small size as possible.
Someonesdad - I am thinking of using a capacitor as the power source.

11. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
9v "transistor" batteries have very low current output.
Try using eight alkaline or NiMH "AA" cells in series. Eight cells will give you 12v. Since you say that you can get it to work with a 12v auto battery, the eight AA batteries should work for a brief amount of time.

12. ### t06afre AAC Fanatic!

May 11, 2009
5,939
1,222
Well I did such experiments then I was young. And perhaps you should experiment with several materials. Like Edison did then he developed the Lightbulb. Try some experiment with steel wool, but not the type with soap. You can ignite loosely packed steel wool with a small battery. Do not pack the gun powder to hard. It will ignite more easy if it is not to dense packed. At least the part you want to ignite first