Battery power for projects - inexpensively

mrburnette

Senior Member
Continued from: AXE133Y-Evolution-with-20X2-for-Display-12-hour-Clock-amp-Temperature

Batteries ... the mention gives me shutters from all of the aggravation they have created in the past. Once, when I was young, the choice was only carbon-zinc and C or D was the only cells with any "Oomp"... so, the old molded, spring-loaded battery holders were nearly the only choice unless one decided to solder the batteries into place! Later in my teens, NiCads became available in C and AA sizes and were a godsend for electronic powering. Just carry the AC line into the box, use a resistor (some of my friends preferred a small flashlight bulb) and a silicon diode and you could trickle-charge the NiCads until they were ready to use.

Wow, have things changed. We still see AA batteries in holders used for projects, but they are of the alkaline variety, usually because they provide a good value/Watt and often because finding anything else is just a pain.

With the proliferation of so many smart portable consumer devices, LiON battery packs and loose LiON batteries are everywhere. But there are several chemistries used and to properly manage the safety of charging LiON, one must not only know the battery chemistry, but use an algorithm specific to the chemistry assuming the intent is to be safe and to ensure that the maximum life of the LiON batteries are secured.

For my last couple of home projects, I have had complete success using LiON both safely and cheaply. Yes, cheaply. Yes, conveniently. I thought I would share this little secret just in case someone has not yet discovered it yet.

THE SECRET:
Small, consumer 5V battery packs designed to deliver "emergency" power to consumer electronic devices. And also, consumer power-packs that contain the 5V buck-charger for the 5V pack. For the former, one can purchase a variety of portable emergency battery packs intended for the briefcase or purse that can fully charge a dead phone! The output of the device is 5V and the charge input is 5V... use with those AC wall warts that deliver 5V via a USB-style connector. Here are two that I have chosen that I am particularly familiar with:

1) Mobile phone clone 5V USB charger: Cellphone 5V

2) Consumer portable battery: Wii 5V LiON

In the case of #2, I found a local surplus house that had the Wii 5V packs with USB cable for $6 each and I bought 4... great since mine were not glued and by removing the screws, I was able to make the small pack even smaller. Also, this pack included a inductor-buck charger and IC which allows the charging USB to always be connected... if the AC goes off, there is essentially no cross-over time to battery as the battery is always used for output.

So, for your next project, hunt around for products that may have been overproduced or were self-contained for a declining consumer popular device. You may be able to find some seriously cheap Watt-hours in a self-contained package.

- Ray
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Flyer007

New Member
Great idea!!!

Is the Wii one outputting a solid 5.0V? There is a closeup of the Amazon one that seems like it outputs a little higher.
 

mrburnette

Senior Member
Weebit higher (like 5.4V) with the wallwart delivering a charge... I stuck a 1A silicon diode in series to drop about 0.6V and the PICAXE seemed happy... Actually, the PICAXE never seemed to care, but the 1-sec quartz clock chip did and would not oscillate with the higher voltage even though is has a 4.7K inline resistor and 3 forward-biased diodes across the old clock chip.

Anyway, you (may) need a inline series diode to drop just under 5V.

- Ray
 

beb101

Senior Member
Hi Ray,

I just bought one of these batteries from your 2nd link (Amazon) and the label says:

Input --> 5v DC , 0.5A
Output --> 6V DC, 0.1A
Capacity --> 2800 mAh

I measured the output voltage after USB charging and it is exactly 6V. Any suggestions on how to drop this down to 3.3V.

Baxter
 
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