[SOC] Batteries in Parallel

[Fred Jensen]

Tom McCulloch wrote:
> Hi,
> Definitely an SOC question here:
> 
> 1)  If I put two of those little 3 volt disc batteries (both the same 
> type and number) in parallel will I get the equivalent of a 3 volt 
> battery that lasts twice as long (more or less)?

Sort of but usually a little less.
> 
> 2)  Would these 2 batteries be in parallel if I connected the two 
> positive ends together and the two negative ends together.  Should I 
> then run one wire from the positive ends and one from the negative for 
> use in the circuit?

Yes.

The problem comes with the fact that no two batteries will have exactly 
the same discharge curve, and eventually one will have a slightly lower 
terminal voltage than the other which will then tend to discharge the 
higher one continuously.  Battery chemistries with very flat discharge 
curves work better in this configuration.  I wouldn't try it with 
Li-<anything> batteries.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2008 Cal QSO Party  4-5 Oct 08
- www.cqp.org