parallel 9V batteries

[euronymous0001]

would i wire 2 9v batteries like a normal 1 9v battery? or do i need to put 2 100R resistors on their + terminal then connect the 2 100R resistors into the + hole of the pcb?
thanks 

[CynicalMan]

Definitely the latter, and don't forget a 10uF or more capacitor from circuit power to ground.

Why do you want 9V batteries in parallel?

[defaced]

Why the two 100r resistors in series with the battery + terminals?

[CynicalMan]

If the battery voltages are at all different, current will flow from one battery to the other. Without the resistors, the current will only flow through a couple of ohms of resistance, which would cause the batteries to heat up and possibly fail.

[defaced]

Ok, that's what I figured.  Same thing with parallel windings on transformers. 

[euronymous0001]

Definitely the latter, and don't forget a 10uF or more capacitor from circuit power to ground.

Why do you want 9V batteries in parallel?

2 batteries in parallel would mean more hours of battery life (if i am correct ) i would put it in a box that would taped to my strap, so i prefer to not change the battery in a long time 


so the cap you're refering to is the cap that is usually parallel with the protection diode to ground?

[Gurner]

I think the 100Rs are excessive - they're presence creates pure heat waste (wrt feeding onwards to the rest of the circuit).

I doubt you'd have much more than a few hundred millivolts of difference between batteries at any one time (if you change the batteries out at the same time) - Let's say 300mV

300mV = 200R/I    therefore I = 1.5mA

I'd probably go with something like 20R

300mV = 40R/I    therefore I = 7.5mA (still far away from generating any overheating risk)