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Troubleshooting for SLA battery charger

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I have built this battery charger according to this site


I manage to charge the battery but it very slow.

Can i know what charging voltage should i use. What i mean is what is the output voltage from LM317 should i make? It seems like even i increase the output voltage from LM317, the output voltage at the diode (anode) also same...looks like it depends on the battery.

And how do i know whether it is fully charge or not? Is i t possible to modified the circuit so i can know the battery is fully charge without probing the current or voltage?


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Hi Harry,
VR1 sets the max voltage, and VR2 sets the current of that project.
IC2 is made to be a constant current source so its output voltage equals the battery's voltage.
You would need to ask the battery's maunufacturer about the battery's fully-charged voltage. Some older lead-acid batteries are 13.8V, some newer ones are 14.4V. The battery's fully charged voltage is also affected by its temperature. ;D

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Is it the LM317 used to set the charging voltage? When i chg the output of LM317, the charging voltage (at anode or cathode of diode consider as charging voltage?) also chg.

If as u mention, if IC2 made to be constant current source and because of this, the output voltage equals the battery voltage, then how will it charge? I thought it only will charge if the output voltage higher than battery voltage?

The charging voltage i have to adjust before or after the battery is inserted?

Is it when the charging current drop to a low constant current source, it indicates fully charged?

Thanks audioguru

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You have to set it up as follows:

(1) Make the knob for current control into the minimum (full of left).
(2) Make the knob for voltage control into the minimum (full of left).
(3) Short-circuit the output of a charger.
(4) Turn the knob for current control to the right until the charging current is set to    about 300mA.
I think that a problem does not have even a 500mA setup.
I am making it little current, in order to charge a battery for a long time.
(5) Connect a charger to a battery.

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