For a particular battery type, the maximum voltage is fixed by the
chemical reaction. The maximum current (amps) before the voltage starts
to drop depends on how big a surface the electrodes have, how well
mixed the liquid stays, etc. The power is the product of the current
and the voltage. Capacitors don't supply and power and don't help
increase the power you can get from a battery. A store-bought power
supply works nicely if you plug it into the wall and pay your electric
bill. Then you can skip the lemons altogether.
How long would you say maybe a mason jar of acid would work...? Or
is there a magic there in the lemons make up balancing the water and
acid perfectly in its makeup?
A good-sized mason jar would work a lot longer than a lemon, if you
have a nice way of holding the zinc and copper electrodes in place. The
electrodes might get used up before the zinc concentration in the
solution got high enough to require replacing the acid.
There's no special magic in the lemons, although I think acid
solutions should work better than alkaline ones for getting the zinc
electrode to dissolve.
The fluid in a car battery DOES carry current, and is not anything
like distilled water. I think it's largely sulfuric acid. (and it has a
lot of lead in it- nasty stuff) When it starts to dry out, you add
distilled water because it's the water that's evaporated, more than the
other components. Various crud in tap water (calcium salts) would just
In my experience you couldn't power anything like a useful light
with a lemon battery. Hooking lots of lemon batteries up in parallel
will help get you more current at the same voltage. Maybe you could get
some very low-power electronic device to work for a while. Under the
right circumstances, a GPS device could be important for survival.
(published on 10/22/2007)