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

 

[gnuuser]

did you go to the website and search the spec sheet on it?
they should have that info for you

heres aa link that you can download the manual and specs from.
http://www.nodevice.com/manual/newmans/hitachi/uc14yfa_service_manualpdf/get32331.html

 

[Wire]

did you go to the website and search the spec sheet on it?
they should have that info for you

heres aa link that you can download the manual and specs from.

You can view the manual for for free here:

http://www.ereplacementparts.com/images/hitachi/UC14YFA.pdf

I have read through it but still cannot understand how to get 14.4v from the charger, could you take a look and see if you can understand how it would be possible?

Still really need help!

 

[gnuuser]

if ive read the manual correctly the discriminating resistor in the battery between t and - is what determines the voltage the battery receives and the thermistor controls the output based on the battery's temp.
reading a voltage without a discriminating resistor will give you full output from the positive and negative terminals

 

[grantr37]

you can get a benchtop power supply from the internet or maplins(like radio shack/tandy that closed down in the UK back in 1999)or use a secondhand PC computer power supply which you can take out of an old computer or buy from ebay......the drill charger is not suitable at all....

 

[AndyOz]

What is the application you want to use the power supply.<br><br>A battery charger is an unregulated power supply and gives a very poor output wave. It is fine to charge a battery but little else. As grantr37 says a bench or dedicated supply will be a far better option.&nbsp;<br><br>First look at the application and match the power supply to that. I understand you want to utilise what you already have, but without major modification it will not be fit for purpose.

 

[Marvo]

A Ni-Cd / Ni-MH battery charger isn't going to give you a constant output. It will have intelligence that monitors the internal resistance and possibly the temperature of a battery when one is being charged and it will adjust the charging voltage and current accordingly to ensure optimum charging conditions. Also the charging current it supplies isn't pure DC, it's modulated DC consisting of the AC output from a small inverter which is then imposed on to a DC carrier.

Bottom line is trying to use a battery charger for anything other than charging batteries isn't going to work unless you're willing to reconfigure the internal circuitry at component level. If you need a regulated 14.4 V supply rather buy one.

 

[telectrix]

said it all.^^^^^^

 

[DPG]

Question asked, good answer given in the first reply. Not very often that happens! Daz
PS, can I ask are you a Electrical Trainee, and is your earth rod longer than 2 feet

 

[Wire]

A Ni-Cd / Ni-MH battery charger isn't going to give you a constant output. It will have intelligence that monitors the internal resistance and possibly the temperature of a battery when one is being charged and it will adjust the charging voltage and current accordingly to ensure optimum charging conditions. Also the charging current it supplies isn't pure DC, it's modulated DC consisting of the AC output from a small inverter which is then imposed on to a DC carrier.

Bottom line is trying to use a battery charger for anything other than charging batteries isn't going to work unless you're willing to reconfigure the internal circuitry at component level. If you need a regulated 14.4 V supply rather buy one.

Thanks a lot for the help, but I am trying to use the charger to charge a car battery!

 

[Wire]

What is the application you want to use the power supply.<br><br>A battery charger is an unregulated power supply and gives a very poor output wave. It is fine to charge a battery but little else. As grantr37 says a bench or dedicated supply will be a far better option.&nbsp;<br><br>First look at the application and match the power supply to that. I understand you want to utilise what you already have, but without major modification it will not be fit for purpose.

I need it to charge a car battery!

 

[Amp David]

Why not get a car battery charger then?

Would you use a car battery charger to charge your Hitachi cordless?

 

[DPG]

Don't do it. Get a charger intended for lead-acid batteries. Different battery chemistrys need different charging techniques. Daz

 

[Earthstore]

12V CAR / VAN / MOTORBIKE BATTERY CHARGER 4AMP / NEW | eBay

There you go £12.75 on Ebay, including free delivery:wink_smile:

 

[DPG]

Bargain! Get one bought.