Can it be Used for Charging Lead Acid 12v Battery?

If the 12v battery is charged to less than about 9 volts, the 9.4v charger might bring it up to about 9 volts, but certainly not to 12v. The 9v is probably too weak a charge to be useful. Operating a 12v battery at such a low charge may weaken it. Thus you need a better approach.

Hi

Thanks for reply. Can the 9.4V/10Amp charger would be good to use as source to some "circuit" which will output 12v or more than 12V, and then this 12V or more would be used to charge lead acid 12v bettery ? What kind of circuit should be that ?

Optimum finished charge on a 12 volt lead acid battery is 15 volts. Most chargers charge them to at max 14.5 volts to prevent over charging. I don't know if your 9.4 volts is name plate voltage. If it is then it was designed for some other battery other then lead acid. As they are 2 volts per cell. It may be for lithium batteries which are 1.5 volts per cell. I doubt that the finish output is close to 12 volts. The charger itself has curcuitry that limits the current output as the voltage increases.

Nominal voltage is just that. A name, a value at rated current. Measure the actual unloaded output voltage. If this is not a switching supply, the actual voltage is quite higher and it just might do. Can you give us a measurement? S.M.

hi

Unloaded output measurement is 9.4 V.

I think I should open the case and see inside to check whether all is well as it should be: Trasformer leads, Diodes, Filter Capacitor ?

What you suggest ?

Well in that case I don't think it's worth the trouble since you must get into modifications territory which can be dangerous if you don't know exactly what you're doing. But anyway if it's a classic single winding transformer with 4 diodes in bridge or has winding with a middle tab as (-) with 2 diodes it's easy to get double the voltage with some added components. If it's a switching supply it might be modifiable but I wouldn't suggest it. In all cases you could also go for a step-up DC/DC conversion but cost rises significantly so no gain there. S.M.

I have opened the box and found two diode bridge rectifier circuit inside with center tap transformer. I measured the full secondery voltage to be 18.8 V and half secondary voltage (between center tap and either diode) to be 9.4. I saw no filter capacitor inside. So to give a try I have placed the 1000uf/35v capacitor as shown in figure. Test the voltage again and bingo now it is 14.5V. I think now I can charge 12V bettery with it. Interesting part for me is that the filtering capacitor somehow increase the voltage about 4V, for which I am searching the reason on internet. If someone have any idea why filtering increase the voltage, please comment.

have fun.

Hi

Next question is how the overcharge make battery life short. As I mentioned in previous post that 15V are available after adding capcitor, so to avoid overcharge what should be done ?