Current only resistance?

[T805]

Is there such thing as a NO Voltage drop resistor? I have two 1.2v 2100ma batteries wired in parrallel. So my total power source would be 1.2v 4200ma.

I need to limit the output of the battery to use 200-300ma per hour at the same 1.2v. How do i go about doing this?

Thanks!

 

[dean_winchester]

you can go for current limiting circuit.

 

[chuckey]

1. you should not wire batteries directly in parallel, a difference of a mV in their voltages will cause the higher voltage battery to discharge first, while the lower voltage one will charge first. It will lead to a short battery life.
2. Why do you want to limit the discharge of the batteries? What happens if the load needs more current at 1.2V?
Frank

 

[T805]

@Chuckey - Would it make a difference if the battery were charged by a solar cell everyday? The reason i need to limit the current is because I need the batteries to last 14 - 20 hours a day. This is an outdoor solar project/prototype.

@Dean - Thanks for the suggestion. I looked into a couple shcematics, but with the directions that I saw, there was a resistor or transistor that was unexplained.

So I looked back at resistors. And according to an online resistor calculator, connecting a 0.62 resistor to my 1.2v battery would give me an output current of 322mah @ 1v. Does this solve my problem?

 

[chuckey]

Going back to what I said. If your load is 200 mA @1.2V, then in 24 hours it will consume 4.8 Ah. So when it has consumed 4.2 Ah, will you want to disconnect it? if you can disconnect it randomly after some indeterminate time, what is the load?, Why switch it on at all?
So now your load only needs 1V? Does it solve your problem, I don't know. There are ways of monitoring the current without any appreciable voltage drop, by monitoring the magnetic field due to the current and with a relay contacts you can get away without having any voltage drop until you switch the current off. You will need another power supply to run this kit, a minimum of 6V.
Frank

 

[siongboon]

Technically speaking, you will not be able to control the current and expect your circuit to work. What you can do is to design efficient circuits that uses as little current/energy as possible to achieve what you want to achieve.

It is like trying to control the fuel feed to the engine and expect the car to move as usual. You should design a efficient engine to improve the efficiency. Less fuel, more mileage.

@Chuckey - Would it make a difference if the battery were charged by a solar cell everyday? The reason i need to limit the current is because I need the batteries to last 14 - 20 hours a day. This is an outdoor solar project/prototype.

@Dean - Thanks for the suggestion. I looked into a couple shcematics, but with the directions that I saw, there was a resistor or transistor that was unexplained.

So I looked back at resistors. And according to an online resistor calculator, connecting a 0.62 resistor to my 1.2v battery would give me an output current of 322mah @ 1v. Does this solve my problem?