Alkaline Battery for Boost converter for 1000ma current requirement?

Question

I am working on a very small scale project that needs 300-600ma bursts at 5v for 10-20 seconds (a bank of LEDs) followed by a period of low power consumption (around 10ma for around an hour or so for the timers).

The idea is to have a battery connected to a boost converter (I chose this one https://www.adafruit.com/products/2030,PowerBoost 1000 Basic - 5V USB Boost @ 1000mA from 1.8V+) to power all the components.

I have looked into different battery sizes and have so far disregarded: -coin type batteries due to high current requirement.

1- Am I correct in assuming that even 5 coin cell batteries (in parallel) would not be able to provide 600mA of current for any reasonable amount of time without overheating?

This website claims that an AA CAN provide 1 amp, but not for very long. http://rightbattery.com/118-1-5v-aa-duracell-alkaline-battery-tests/

If their calculations are right, i should be able to draw 1 amp from an AA battery with an estimated capacity of 509mah. If only I could use one AA it would be perfect for my project, but at 300ma one AA would just about power on the components but would probably not be able to provide enough current for the converter to output 5V and 600ma.

In which case, is it feasible to power something like this using 2 or 3AA or aaa batteries? or do i need to count my losses and get a small 500mah lithium ion battery instead?

Would be great if someone could comment on just how sturdy alkaline batteries are to power something like this.

Thanks

Answer 1

Your boost converter requires at least 1.8V, so at a minimum you need two 1.5V cells. 600mA x 5V = 3W. Assuming 90% boost efficiency the battery needs to deliver 3.3W, which is 1.7A at 2V (1V per cell).

A typical AA Alkaline will only deliver 200~300mAh at this current. However a 1.7A burst for 20 seconds per hour is an average of only 9mA, while the idle current will probably be around 25mA. That adds up to ~34mA total, so you should get close to full battery capacity provided that the battery contacts, wiring and power switch are also able to handle 1.7A bursts without excessive voltage drop (don't use a battery holder with coil springs!).

AA Alkalines have a capacity of 1800~2000mA at low current, so you should get at least 1800/34 = 53 hours or a bit more than 2 days of continuous run time. Will this be enough? For a device which is only used for a few hours per day it might be, but the user probably won't like having to replace the batteries too often. However one advantage of AA is that the user has the option of using rechargeable cells instead. Good NIMH cells such as Sanyo/Panasonic Eneloop can handle 2A without losing capacity, and 2 cell NiMH chargers are cheap and readily available.

Answer 2

That Adafruit converter requires a minimum input voltage of 1.8 volts. As a fresh Alkaline AA cell is 1.5 volts, you'll need at least two AA cells in series to power it.

The module's rated 1 Amp (1000 mA) at 5 volts output is 5 Watts. The unit claims 90% efficiency, so the input power will be about 5.6 Watts, or 1.9 Amps at 3 volts from fresh batteries. The battery voltage will drop with use, and with high current draw, increasing the required current.

For your 600 mA load, the current from a 3 volt battery pack will be over 1.1 Amps, which I think is a bit much for AA cells. You may want to consider C cells.