pls explain battery in series & parallel

[apurvmj]

Hi all,
I have some query about battery connection for power use.
say we have two 9 V batteries in parallel for load of 9 ohms, it will draw 1 Amp current. So both the batteries will contribute (aprox.) half the current i.e. 0.5 Amp.
When we have them in series, voltage will be 18 V & for 9 Ohm load current drawn will be 2 Amp. My query is does both batteries contribute 2 Amp or is it 1 Amp each?
Thanks.

 

[KeepItSimpleStupid]

Don't do parallel battery connections. Bad things can happen especially if one battery is partially discharged.

You actually have to model a battery as an ideal voltage source and a series resistor. The series resistor in the model limits the short circuit current.

Current is the same EVERYWHERE in a series circuit. In your parallel example and if and only if the batteries are the same and have the same internal resistance then each will supply 1/2 the current. If they aren't then one battery may be trying to charge the other or the current will current divide between the two batteries, In other words, one battery might get too hot leak and do other nasty things.
Kircoff's current law states that I1+I2= 1 Amp Basically, only in the movies will the batteries deliver equal currents. In practice, they will not.

A 9 ohm load will need I = 18/9 or 2 Amps like you said. Each battery will supply 9 V at 2 A. Kirkoffs law states that 9 9V+9V = 2 Amps*R

 

[panic mode]

2amp each. in series circuit same current flows through each part of the loop. but that is a calculation only using given assumptions. 9V batteries I know will not do 2A (at least not while maintaining voltage).

 

[apurvmj]

thanks all

 

[audioguru]

A 9V alkaline battery quickly drops its voltage as it runs down with a high current load.
Haven't you looked at the datasheet on a battery manufacturer's website?
With a 400mA load the voltage drops to 7V in about 8.5 minutes and is dead at only 6V in about 40 minutes.