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Step up 6 volts to 9 volts? Halp!

I have a GB Instruments dmm i got at a Hamfest (Ham Radio Fest) in Peoria, IL a few years back for like $6. It's great, and its more accurate than my father's Craftsman from Sears that he paid $40 for about a year ago. I have replaced the 9 volt battery twice in it. 9 volt batteries are horrible for capacity, and I use this DMM so much it's almost a high drain on the 9v. I know that a standard 9v holds 500-700mAh. I have a whole box of old AAA batteries that have about 1.4+ volts still in them from a stupid car toy that drained an AAA .1v-.2v and called it dead. A standard AAA alkaline battery (E92 or equivalent) holds 1,200 mAh or 1.2Ah@1.5v. 4 alkaline AAA batteries holds 4,800 mAh@6v. I can fit 4 AAA batteries in the 9 volt holder in my DMM snugly with a piece of foam for anti-rattle. That's only 6 volts. The DMM will power on very dimly at 6v, so is there any circuit to make up for the lost 3 volts without adding a bulky power pack? There is a LOT of room in the DMM for mods n stuff. Thanks for any help Is there any way to step up

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Hardly. A PP3 can manage about 550 mAh a decent AA cell NiMh, probably 2800Ah. Even allowing for the step up, you're still well ahead of the game. Sure, a switcher is likely to ripple a bit at the O/P, but add a low ESR cap, shunted with 100n ceramic and you're good to go.
Yea, but he's not using nimh, he's using used alkalines.
He's still got nearly 3 x more in his bank than a PP3 !
Re-design7 years ago
Figure a way to add another 9v and run it in parellel. Those used AA or AAA batteries aren't going to give you much run time if any if you boost them up to 9v with a converter. Your DMM might not even work right with the different power source. BAtteries are pure dc and that converter is going to have some ripple in it.
josh10017 years ago
if your good with circuits this can work, replace the 12V zener diode with a 9 V one

http://www.aaroncake.net/Circuits/6-12conv.asp
lemonie7 years ago
I'd just find a way to use 6 instead, or get a plug-in (to mains) 9V supply? L
seandogue7 years ago
Sure. add a stepup regulator circuit. Not sure what your max load current is, but yes, it can be done. There are a variety of ICs that can be selected to describe a solution if the intended load current is known. Circuits range from single part solutions to an IC, a couple caps and resistors, perhaps a small inductor...
Try one of Dimension Controllers boost power regulators - all you need in one little, prebuilt package.

http://www.dimensionengineering.com/AnyVoltMicro.htm

Steve