Getting 14.4v from a 7.2v - 14.4v Charger

[Wire]

Hello, I need a 14.4v voltage source and had a drill battery charger lying around that apparently charges at this voltage. Here is a photo of the unit:



When plugged into a wall socket I used a multimeter to test the voltage output, when connected to the positive and negative ports (labelled left and right of the hole in the photo) I get 38v.

Inside the hole there are two more ports at the top and the bottom labelled 'T' and 'S', when i connect the positive pin of the multimeter to the 'T' output of the charger, and the negative pin to the 'S' output of the charger I get 2v.

When I connect the positive multimeter pin to the + output of the charger and the negative to the 'T' output of the charger I get 33v.

When I connect the positive multimeter pin to the + output of the charger and the negative to the 'S' output of the charger I get 35v.

When I connect the positive multimeter pin to the 'T' output of the charger and the negative to the '-' output of the charger I get 5v.

When I connect the positive multimeter pin to the 'S' output of the charger and the negative to the '-' output of the charger I get 3v.

What I would like to know is how do I get 14.4v out of this supposedly 14.4v charger! :S

Any help at all would be greatly appreciated!

Many thanks

 

[Marvo]

As DPG say, a lead acid charger and an 'intelligent' Ni-Cd / Ni-MH charger are two completely different animals, you can't use one to do the job of the other or at least not without serious modifications. A basic lead acid battery charger is available as a cheap supermarket item, these cost the equivalent of about ten UK Pounds where I am and they are fine for occasional charging but your battery will last a lot longer if you use a better charger with built-in monitoring.

 

[Marvo]

Two identical threads merged.

 

[grantr37]

If you try to charge a car battery with that charger you might cause a fire,it will not charge a car battery, you can get a secondhand car battery smart charger from ebay for a few pounds...maybe you could borrow a charger as well?

 

[tazz]

Battery chemistry, makes different charging methods....Nicad, or NiMH are current related and actually the voltage is not inportant. Their own chemistry sets it voltage....so a 6v nicad can be very easily charged from 7-20v, but here the current limiting is important. So you can charge a Nicad via a diode and a 2k2 resistor in series with any voltage, and it will sit the happly charging for years (EG and bell box battery). Sealed lead acid SLA, is the opposite, it needs a regulated voltage, so for 12v it needs exactly 13.8v to keep it charged, but its chemistry will limited the current internally, so here votage is important, so a 12v lead acid battery charging at 13.8v will again sit there happy charging for years ( eg Alarm panel).