that's a great explanation!

but i wanted to know how you do it with a circuit.
do you compare the voltage levels using comparator??
It is necessary to have a voltage regulator for battery operated circuits right?

Thanks!

That could be done to squeeze the fullest amount possible from a battery, but doing so requires a different chemistry than lead acid. One that isn't so damaging to the cell structure after complete discharge, like, Ni-cad; NiMh; molten salt types(industrial), and even the old alkaline NiFe.

If you use a lead acid battery, you will want to keep discharge within a small defined window. 99.9% of circuits are just fine with this range as the supply.

If you want to have operation during 'recharge' then adding a regulator would be good. The voltage boost during recharge might be to much for some circuits.





Do only what you must do to make a circuit work well, and work safely. Needless complexity leads to failure(by various definitions) in most cases.

 

suppose i have a circuit & it needs 200mA of current then will the battery provide only 200mA or the full capacity(delivering without much effort).no matter how much i try to understand i cannot get this part.

 

Only the amount of current that the resistance allows will flow.

Decrease resistance and more current flows.

With no change in resistance, a change in voltage will cause more or less current to flow.

I = E/R

Increase R and I decreases
Decrease R and I increases

Increase E and I increases
Decrease E and I decreases.


It's all there in that one little equation called Ohm's Law.

 

i have already looked into this equation to understand.lets say a circuit needs 12v & has an impedance of say 80 ohm then the circuit needs (12/80) 0.15A.but my battery can provide me suppose 200mA then my circuit takes 0.15A from battery & the remaining (200-150) 50mA is free which can be used by other circuit(if connected) right? I am sorry if i am making this very foolish question but i have no other resource :-(.thanks!

 

The voltage from a battery drops as it is discharged by a load. Then the current in most loads decreases.

I don't know of a 12V battery that supplies 200mA. The tiny one used in a garage door remote cannot supply as much as 200mA and a car battery can supply hundreds of Amps.

The capacity of a battery is not a current, it is a current for a certain amount of time and is rated in MAh or Ah.

 

hello guys i have a small doubt my battery says it can supply 220Ah.Now suppose if i have a circuit which consumes 180mA.Now i have like 1.2Ah.

Again if i have other circuit which takes lets say 100mA then i have 785mAh left right?

please help me?

220amps/hour... but it's not going to give that runtime in the real world as people pointed out once it hits around 70% discharge it declines pretty quickly from that point on..

But if you're going to work it out 180ma (0.180amps/220 = runtime ) would give roughly 122 hours if it really is a 220ah battery... is it a Deep Cycle or Car (Lead acid?) battery?

 

The capacity of a battery is not a current, it is a current for a certain amount of time and is rated in MAh or Ah.

i guess i understand how it works now!