Voltage division of a 5v regulator output?

[jack476]

So here's my problem. I have a pair of noise-cancelling in-ear headphones, and they require a AAA battery. Batteries are expensive so I only use rechargeable ones, but those have a lower capacity (700 maH) and don't last long. I want to make it last longer by putting several of them together into a battery pack. However, that would need to be regulated down to the voltage of a single AAA battery, 1.5v, but I only have 5v regulators.

What I'm thinking of doing is putting a resistive voltage divider on the output of the 5v regulator that would take the voltage down to the 1.5v that the headphones are rated for. Would that work?

 

[cpscdave]

Could you not just put the batteries in parallel instead of series?

batteries in series increase the voltage,
batteries in parallel increase the effective capacity

Or so is my understanding :D

 

[jack476]

Could you not just put the batteries in parallel instead of series?

batteries in series increase the voltage,
batteries in parallel increase the effective capacity

Or so is my understanding :D

That actually makes a lot more sense. But wouldn't it risk putting more current through the headphones than they're designed to take?

 

[rootone]

Nope, the current drawn is determined by the resistance (aka 'load') of the headphone circuit.
It will be the same regardless of how many batteries you have in parallel.
The total current supplied will be shared by the batteries, so that means the individual batteries will last longer before needing recharging.

 

[berkeman]

What I'm thinking of doing is putting a resistive voltage divider on the output of the 5v regulator that would take the voltage down to the 1.5v that the headphones are rated for. Would that work?

The parallel battery idea is a good one. Just make sure the batteries are matched well (charged the same, same age, etc.) before you parallel-connect them.

BTW, on your idea of doing a resistive voltage divider down from 5V, that will not extend the battery life. What you gain with the higher voltage is lost in wasted head in the resistor voltage divider. Instead, you would use a "Buck" DC-DC converter to convert the higher voltage down to 1.5V. Buck DC-DC converters can be around 90% efficient in many cases.

 

[CWatters]

Why put several cells in parallel when one larger cell will do?

>3600mAh NiMh cells are available.

 

[jack476]

Why put several cells in parallel when one larger cell will do?

It's just all I've got on hand at the moment. I also just bought my textbooks and I don't want to spend any more money than I have to for a little while.