# Want to switch two batteries from parallell to series power (how?)

Discussion in 'Electronic Basics' started by NA, Feb 24, 2004.

1. ### NAGuest

I need to know of a simple way of wiring up two batteries so that with one
switch, they can provide power in parallell giving me longer battery life,
or series, giving me double the voltage. It's been a while since I've been
out of electronics and this seems like such a simple problem to solve.

Can any kind person reply? Thanks!

2. ### the WizGuest

You need a double-pole, double-throw switch that can handle the current load.

Label the batteries B1 and B2.

Wire B1 minus as the negative lead of the battery pack and B2 plus as the

Switch contacts

B2 + B1 -
O O

B1 + B2 -
O O moving contacts

O-----------O

When the center contacts connect to the bottom contacts, the batteries are in
series; in the other position they are in parallel.

Be sure that the batteries are the same type and voltage and, if rechargeable,
that they are at the same charge level.

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3. ### CFoley1064Guest

Subject: Want to switch two batteries from parallell to series power (how?)
Putting two batteries in parallel usually isn't a good idea, because of small
differences between batteries in age, load life, &c. You will usually get a
lot less than twice the life out of the two batteries in parallel than you
would with a single battery. With major differences, you may find that the
weaker battery actually acts like a load on the stronger, leading to premature
end of life (total life can actually be less than one battery alone).

If you do this, though, make sure you replace both of the batteries at the same
time, preferrably with fresh ones, and ideally from the same package.

Good luck
Chris