I have recently made a charging circuit for my 2.5Ah Lead Acid battery using LM317 IC. Please check the circuit diagram at:
http://electronics-diy.com/schematics/893/battery-charger.jpg

My current circuit doesn't have the transistor Q1. In this case, the charging is too slow. However, I want to charge my battery to 80% within 3-4 hours. After this time, the power goes off again and the battery needs to be charged during this time so that my router keeps on running during the power outage time.
I'm an engineer but not electronics engineer and that's why I need help. Would this circuit charge my battery in the specified time ? If yes, I would add the transistor Q1. Any help in this regard will be appreciated

 

Do you have any connection at all in place of Q1?
If so where and what is connected

 

What is the A-hr rating of the battery?

That device can only put out about one Amp max.

 

What is the A-hr rating of the battery?

That device can only put out about one Amp max.

haseebhm stated it's 2.5AH, so a 1A charge is on the high side. AFAIK lead acid prefers a charge rate of AH/20, or here 2.5 / 20 = .125A

 

I have recently made a charging circuit for my 2.5Ah Lead Acid battery using LM317 IC. Please check the circuit diagram at:
http://electronics-diy.com/schematics/893/battery-charger.jpg

My current circuit doesn't have the transistor Q1.

Then it won't work as designed.Q1 is how it regulates the charging current. You might post a schematic of what you actually built up.

You don't say what the source is driving the circuit. An LM317 can drive something like 0.5 - 1.5A depending on input-output voltage differential.

FYI: that circuit need some output capacitance, bigger the better. 0.22uF is not nearly enough.

 

Then it won't work as designed.Q1 is how it regulates the charging current. ou might post a schematic of what you actually built up.

You don't say what the source is driving the circuit. An LM317 can drive something like 0.5 - 1.5A depending on input-output voltage differential.

FYI: that circuit need some output capacitance, bigger the better. 0.22uF is not nearly enough.

That's what I was trying to get out of him, but he hasn't been back..

 

I'm sorry for getting back so late, i was stuck. I have modified my circuit already and placed the Q1 transistor. Now my actual circuit is according to this diagram, except that I have used a 1uF capacitor on the output instead of 0.22uF. What I want to ask is:
1. Whether this circuit will charge my battery in 4 hours ?
2. Would it overcharge the battery if connected for longer duration?
3. Further Details: I have connected the battery through a diode to avoid back-flow of current when power is not available. And at the output, I have placed a 12v zener diode regulator with 1ohm resistor in series for my router. This will be the 12v output for my wireless router. So if the power goes off, my router will still be running through the battery and the battery. Am I doing it right ? Its working the way I want it to, I just have to put a heatsink on LM317 now.

 

That's what I was trying to get out of him, but he hasn't been back..

Actually, I have used a 1uF capacitor at the output. Is it enough ?
At the input, I have 24V through transformer and full-wave rectifier and two 1000uF capacitors for filtering. Do I need to change that too ?

 

I'm sorry for getting back so late, i was stuck. I have modified my circuit already and placed the Q1 transistor. Now my actual circuit is according to this diagram, except that I have used a 1uF capacitor on the output instead of 0.22uF. What I want to ask is:
1. Whether this circuit will charge my battery in 4 hours ?

As I said before:

"You don't say what the source is driving the circuit. An LM317 can drive something like 0.5 - 1.5A depending on input-output voltage differential."

The charge time depends on the charging current. What is driving the circuit? How much current can it put out?

 

Actually, I have used a 1uF capacitor at the output. Is it enough ?

No, I would recommend at least 22 uF.

At the input, I have 24V through transformer and full-wave rectifier and two 1000uF capacitors for filtering. Do I need to change that too ?

What is the current rating of the transformer?

 

3. Further Details: I have connected the battery through a diode to avoid back-flow of current when power is not available. And at the output, I have placed a 12v zener diode regulator with 1ohm resistor in series for my router. This will be the 12v output for my wireless router. So if the power goes off, my router will still be running through the battery and the battery. Am I doing it right ? Its working the way I want it to, I just have to put a heatsink on LM317 now.

The R2/R3/R5 resistors set the final full charge voltage. If you put a diode from there to the battery, the voltage at the battery will be too low.

 

No, I would recommend at least 22 uF.

What is the current rating of the transformer?

Current rating of transformer is 1500mA.

 

The R2/R3/R5 resistors set the final full charge voltage. If you put a diode from there to the battery, the voltage at the battery will be too low.

Yes but I have adjusted the R5 potentiometer accordingly.

 

As I said before:

"You don't say what the source is driving the circuit. An LM317 can drive something like 0.5 - 1.5A depending on input-output voltage differential."

The charge time depends on the charging current. What is driving the circuit? How much current can it put out?

As I mentioned earlier, the circuit is driven by 24v rectified DV input. And at the output is the battery and a router which is connected with a zener diode for regulation. Router takes a current of 500mA.

 

I suppose this is a constant current charging circuit and hence the charging time can be known. Am I right ?

 

No, I would recommend at least 22 uF.

What is the current rating of the transformer?

The transformer current rating is mA