Working Air Battery

[Mk1]

@all

Guys have a look a this fire from a potato.

One potato emptied in the middle filed with salt and toothpaste , 2 wire they seem the same material , so i don't thing galvanic here , 5 minute and voila enough current to start a fire , its probably a trick but if real really worth looking into .

http://wickedhowtos.com/index.php/2009/05/28/how-to-make-fire-with-a-potato-potato-battery-cotton-ball-fire/

[jeanna]

I have been using and loving my air batteries.
I am letting them dry out and I squirt them before each use.
They will last a very long time.

But, I think I have found 2 interesting things to add to out reservoir of knowledge.

1- These seem to INCREASE in output when I put them to use.
I have noticed this since the beginning.
If I use a 1 ohm resistor to measure the mA available to my ckt, I will watch the number go up!
This is opposite to the usual.

2- I should probably put this next one on the joule thief thread, because it has to do with how the joule thief works, I think.
In the case of adding one of these air batteries which shows around 30mA available, I cannot get a jtc to turn on more than a minimum of leds.
I checked this out using my scope, on a few high power circuits I have and the highest I could get was 28v where it was over 450 with a AAA.
So, something is becoming more clear. hmm.

thank you,

jeanna

[stephenafreter]

@jeanna
Yes it is strange that the Joule Thief output power is very low with those batteries ...
Is there a recharging effect with normal AA batteries, or is it a problem with the meters while spikes are going back to the batteries ??

I tried silver wire with magnesium ribbon and it's great.
Silver leaf version is faster to build, but silver coated wire makes it easy to put an outside layer around the magnesium ribbon, increasing power output.

I need to go for big size battery to get decent output power, enough to light a room ... I'll work on that 

PS: My first silver leaf magnesium battery is still running after almost one week. Now I have the Epson salts and my batteries should last even longer, as you demonstrated in comparing with table salt.
Thanks for sharing !

[DrZoidberg]

I think I found a substance that can make those batteries powerfull even when dry.
"Solid gel electrodes".
These electrodes are used in medicine. They seem to be dry but they are very well conducting. I haven't found out yet what material they are made of. But that "solid gel" seems to contain a lot of moisture which it doesn't loose even when exposed to dry air for a long time. I think it's a great material for a dry air battery. The battery would perform nearly as well as a wet battery without having to add any water to it.

[conradelektro]

@ jeanna and stephenafreter - Joule Thiefe power consumption

I measured many times the power consumption of Joule Thief circuits with a digital storage oscilloscope (measurement over a 1 Ohm resistor, 1 mV corresponds to 1 mA, see the attached picture).

One can see that a JT consumes power in a saw teeth like fashion in sync with its frequency of oscillation.

If the power consumption of a JT is measured with a digital multimeter one gets the "average power consumption".

This "average power consumption" is a useful number but one has to take into consideration that the battery must be able to supply about the double amount of the "average power consumption", not continuously but intermittently.

If for example a JT consumes on average 30 mA, the battery must have the power to supply about 60 mA. And in case the battery delivers only 30 mA maximum the JT will have a poorer output because the pulses on the coil will be truncated (in comparison with a battery that can deliver 60 mA).

Greetings, Conrad