Auto Battery Charger

579

08:13:11

Okay the main features are activation at 12.6V and deactivation at 11.3V. It says no solution when it has to reactivate again, but it should work. The green LED means charging, the red LED means ready to discharge. The 1ohm resistor limits the current to 7A. Since a car battery will never be at 0V, but somewhere around 11V when discharged , the voltage drop from the 2ohm resistor in the beginning will be 3V, at 7A, meaning that it should be rated at 20W. Since the resistor is charging a battery and not handling a constant resistive load, there is no need for current limiting circuitry, because the resistor will not drop any voltage when the battery is almost charged. 

published 10 years ago

pajaka

10 years ago

I think you should limit the charging current, the rule of thumb is current of 10% of the baterry capacity

thebugger

10 years ago

I'm just showing the control circuit. Anyone is free to build the supply circuit itself. Some may prefer filtering for instance, others may want current limiting, and such.

nikisalli

10 years ago

ok but where is treesholds regulation?

nikisalli

10 years ago

i made this circuit also but i prefer the varible treesholds one i made because you can change limits of charging and discharging with reference voltages

crazypz_pl

10 years ago

I tried to fix no solution errors, but I failed... I think cooperation of op amp and relay is the reason.

thebugger

10 years ago

Yes i tried i few times and gave up. Niki, the thresholds can be varied by the 3 most left resistors. The main voltage divider (10k,55k) controls the upper threshold and the 72k resistor controls the lower threshold.

nikisalli

10 years ago

it's the led part that makes it doesn't work

nikisalli

10 years ago

i tried now on breadboard but the limits are totally different from the Simulation

thebugger

10 years ago

It depends on the op amp. I recommend you use a JFET op amp because the inputs will have infinite (sorta) resistance to DC, and won't cause the thresholds to shift.

hurz

10 years ago

No need for a jfet opamp. Input impedance doesn't matter here. The external network resistance is about 7.6kOhm so even good old 741 wont cause a change of thresholds. For niki there must be something else wrong. E.g. niki take care of the output config 0V and 12V and supply is 15V. 0,12V is for a rail2rail opamp by 12V supply.

thebugger

10 years ago

Good old 741. As old as it is, it's just as awesome. I juat finished a wien bridge oscillator, and it has a bandwidth of 500Hz to 50Khz. One thing i don't like about the 741. It's slew rate is quite limited and the bandwidth is not very broad. I had to readjust the negative feedback for higher frequencies. At 50Khz it gets quite figgly to adjust, and there is some distortion, but that's probably because at 50Khz the resistor in my positive feedback is 33ohm. Still remarkable

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.