battery driven stuff

[The Peasant]

Hello Martin and everyone.
>
> From time to time one needs battery supply, e.g. if you want to play
> your little synth at the beach... (WASP), or if you need a little mic
> preamp for outdoor recording etc..  Usually severall NiCd or other
> elements are cascaded to get a reasonable voltage.

I have been using sealed lead-acid batteries for things like this for years.
See my website below for more info.

> Therefore I'd suggest the following:
>
> Instead of serial cascade, just use the elements in a parallel way.
> The output voltage of NiCd is stable over discharge, so I hope there
> will be no large currents as the elemets will fight against each other.

This seems to me to be a lot of trouble to go through, added complications.
With the batteries I use you can easily put them in series for higher
voltages or run an invertor from them.

> I don't know much about batteries and such, but I'm getting
> better. Could this
> parallelism be a problem for element lifetime or performance?

Not normally a problem for discharge, but you would have to separate them to
charge them properly. The charge current to each cell must be controlled.

> If an element gets weak in serial connection, there will be also
> currents through the element chain (if the circuit still works).
> This will also stress the weak element further.
>
If all of the elements are purchased new together, the chances of one being
significantly weaker than the others is doubtful, so this should not be a
problem.
>
> Ok, if this works we have a rather stable 1.2V supply that should work
> until the last element has lost it's charge. In order to get to
> some usefull
> voltage I would suggest a step-up switcher. Yes I know, noise and
> problems.
>
> Do you think that a 1.2V to 5V or even 1.2V to 20V ratio is possible
> with good performance?

Yes, but it is an expensive solution if you need very much current
capability.

Hope this helps,

Doug

______________________
The Electronic Peasant

www.electronicpeasant.com