phatty mo wrote:

Too_Many_Tools wrote:

Reading the thread on the Voltaic pile in sci.chem.electrochem.battery,
I started considering what would one have to do to build a "Robinson
Crusoe" battery to power equipment in an emergency.

Assuming a battery of 12v and respectable current to power
communications equipment, how would you do it?

What materials would you use?

How would you charge it?

I look forward to your contributions.

TMT


I've been wondering along similar lines..
I've been wondering how I could make a reasonable ~12V battery,cheaply
and easily.

Maybe some sal****er cells,built up in Tupperware containers?
Assuming maybe 0.5V per cell,and (if they're large enough) perhaps 10AH?
24 containers in series,it would be fairly large!
If we can find some good electrode materials,the cell voltage may go
up,so we would need less cells/containers

Salt and water are both readily available,and pretty cheap,so the
electrolyte could be replenished easily enough...(any ideas for
something better,that's easy to get,and fairly cheap?)
But,I'm not sure what would be best to use as "plates",keeping the
cheap,and easy concept in mind.(They will eventually corrode away,right?)
Perhaps some kind of setup with pipes-inside-of-pipes.
Pehaps you could then build the cells up inside of some lengths of PVC?
4 inch diameter PVC,maybe 3-4 feet long,with a copper pipe inside of a
steel pipe,inside of the PVC pipe?
Keep a bag of salt next to it,and when the power goes out,dump some salt
and water in the cells,and turn on a (LED) light or something for a
while.. could be handy.

I recall seeing an "emergency battery" that used sea/salt water for an
electrolyte..apparently it went through electrodes quickly..
But it had a decent capacity,and was fairly small,maybe half the size of
a car battery?
But I've no idea what exactly they used for electrodes.
It could be useful to have a "backup" battery with an infinite shelf
life,untill you fill it.
Perhaps then you could just rinse it out,and store the electrolyte (or
not,sal****er is fairly non-toxic,shouldn't be an issue to dispose
of/dump.) and store it untill you need it again?

I'd actually like to build something like this,but at this point it's
just a half-thought bouncing around my brain.
If you have any ideas,I'd like to hear them!
What about the water activated lights in lifejackets? Quite small,
aceptable current, but once wetted they can't be shut down; the cell
continues to degrade if disconnected.