Just need to make sure I'm figuring this out correctly - advice or suggestions are appreciated.

Capacitors ARE capable of storing their charge even when not connected to their charging circuit, right? If so, for how long can they maintain this charge with the following example?

I have a rather low-output rechargeable power device (averages 0.7v output) which is supposed to be powering another device with higher optimal energy requirements (between 2.0v-3.0v). If I string up a capacitor(s) in a circuit with the charging device, dump as much power as possible into the capacitor and thus deplete the recharger, could I then disconnect the rechargeable power device in order to recycle it so that it will no longer be depleted and will be ready to put more power into the circuit? As long as I close the circuit before disconnecting the rechargeable power device, will the capacitor remain charged? And if so, will stringing several capacitors together in series provide enough output to get the other device operating within its nominal range?

I've been trying this with batteries so far, but my 1000mAh NiMH batteries simply can't be recharged since the output voltage from the recharger is so low. These batteries been used in circuits where the rechargeable device outputs about 1.6v, and the battery then outputs about 0.7v once fully charged. I had thought at first that this might be a potential match, but I can't get the damn batteries to recharge in this new circuit.

7/27/2007 5:36:50 PM

You are describing a dc/dc charge pump topology. It is used in very low "boost" power environments (think mA's for LEDs). It basically consists of charging capacitors off of a known reference and then stacking them on top of each other; which is exactly what you described just not done by hand, lol . There is no reason you cant do it by hand. An ideal capacitor would not self discharge but in reality, as you assumed, they will.

There are much better ways to boost a voltage. 0.7V is a really low starting point.

7/27/2007 5:50:46 PM

Perhaps you should PM [user]DrEmmettBrown[/user]

[Edited on July 27, 2007 at 5:51 PM. Reason : .]

7/27/2007 5:50:52 PM

^^ Weight and size are definite considerations. I had humorously thought of using something like a stepping transformer, but it's not practical with this application. I only need for this circuit to run at nominal output for about 30 seconds, tops. What other suggestions might you recommend?

7/27/2007 6:05:58 PM

You need to find out your power requirements first.

7/27/2007 7:00:48 PM

The requirements for the device I need to power (small motor) are 3.0v nominally. It'll run with only 0.7v, but it doesn't run worth a damn.

7/27/2007 7:05:52 PM

^ youve got the weirdest fucking website ive ever seen.

7/27/2007 8:01:08 PM

btw quinn is being modest, he is the power supply designer for a major company...

he knows his shite

7/27/2007 8:59:40 PM

V=L di/dt goes a long ways when youre sub 4mhz, hahahaha

7/27/2007 9:48:37 PM

^^^ LOL. I haven't owned that domain in about 2 years now. Guess I forgot the link to it was still here.

The major problem is impedance of the motor. It needs much higher power than the rechargeable source puts out. I can't swap either device, unfortunately.

I'm pretty certain that this is the motor. Unfortunately, it has no markings whatsoever other than the name of the manufacturer.

http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=re_140ra

7/27/2007 10:42:26 PM