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# Multi-Voltage Battery Pack

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Could rapidly switching batteries between parallel and series connections (?100Hz~2MHz) provide two distinct voltages?

I'm building a handheld device, about the size of a digital multimeter, and it needs two voltages. They are 2.4V and between 5.5-8V. My original solution was to use two rechargeable NiMH AA's in series for 2.4V and a rechargeable NiMH 9V (funny thing - those 9V NiMH's are actually 7.3V = 6*1.2V).
It'd be really cool if I could build a 6xAAA battery pack that supplies [email protected] (3|2*1.2V, 3*900mAh) and [email protected] (6*1.2V, 1*900mAh)

Does anyone know if it's plausible?
The power draw from all 6 batteries should be nearly equal (the switching circuit would drain one battery marginally faster).

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Hi Amplificar,
Welcome to our forum. ;D
You don't need to switch batteries, just stepup the voltage of two or three cells to any voltage you want, like the circuit does in an LED flashlight.

In Google, enter Silicon Chip Never Buy Another 9V Battery. Google will give you a link to Silicon Chip magazine's project that steps up the voltage of two AA cells to 9V or many other voltages.
Unfortunately you need to pay to see the entire article.

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Thanks for the reply. I also found an article by searching google for Circuit Voltage Booster.

I knew about dc-dc converters, but I haven't had any luck working with them. The step-ups I've seen generated a lot of HF noise, couldn't supply a lot of current, got less efficient and greater ripple as more current was drawn, and required inductors & booster ICs.

I ruled them out for this project because of the problems I had.

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Why does part of your circuit need a lower supply voltage than the other part?
Most electronic circuits work fine with a higher supply voltage.

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• 1 month later...

I'd just run the batteries in series to get the higher voltage, then tap off at the 2.4V point for the lower voltage stuff. Simple.

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