Battery/Voltage-Regulator Selection

[Omega Glory]

Hi all,

I've been working on a filter/amplifier project for a guitar, and I'm trying to figure out how to best power it, while primarily optimizing for operating time, and size/weight of the solution.

The circuit can operate on a voltage range from 5.5V to 1.8V (though the performance is better if the floor is around 2V instead of 1.8V). At 4.5 voltes, the circuit draws between 1 and 2 mA, (so a power consumption of about 9mW in the worst case).

I am aiming to have this circuit operate off of battery power for at least 100 hours, and am attempting to find a battery/voltage regulator solution which optimizes the operation time, and the size/weight of the design.

Currently, I am powering the circuit off of 3AA batteries, in series, but I'm wondering if anyone has thoughts/opinions on using a boost converter with 2AA batteries, or a buck converter with a 9V battery, to meet the 100 hour requirement at a reduced weight/volume, and if so, if there are any recommendations for good parts (optimizing for low part count and low ripple).

If there are any more details that would be helpful to this conversation, please let me know. I don't have permission right now to share the schematic of the device being worked on, but I can certainly share more particular details.

Thanks for your thoughts/opinions/help,

- Omega Glory

[Peabody]

I think using any kind of switching regulator would only add noise to the circuit.  So it seems just powering directly from the batteries, with no regulator, might be the best option.

Lithium is going to give you the most power in the smallest package.  And a flat lithium polymer cell might give you the smallest device overall.  Something like this one:

https://www.amazon.com/2600mah-505573-Lithium-Polymer-Replacement/dp/B091YMWC72/

would give you about the same battery life as three AAs.  Then you would need a charger module, such as a TP4056 module without battery protection (the LIPO already has protection built in).  And you would need an On/Off switch for the circuit somewhere downstream from the battery - so you can still charge it when the amp/filter is turned off.

LIPO would give you the additional advantage that you don't have to open up the box to  change batteries.  You just plug in a USB power source to recharge.

[avandalen]

You have to use modern op amps and such that operate on a low supply voltage. They use virtually no electricity and you can use a single battery cell.

[Omega Glory]

Looks like I don't have a problem after all. I found these nice discharge curves for various batteries: https://lygte-info.dk/info/BatteriesLowCurrentDischarge%20UK.html and discovered that if you draw 5mAs from a AA battery, it will take about 23.5 days (564 hours) for it to drop to 1V. This suggests to me that I can just put two in series to achieve the >= 2V supply @ 100 hours.