Battery charging question.

[sappy2000]

Hi all,

I posted this question before but the solution provided didn't work. So let me try this again.

I have a black and decker 18v batt but the charger blown.

I have been trying to charge the batt with a computer psu. I know I need 21v to charge it.

The cheapo comp psu pumps out 22v (yeah supposed to be 24v from +12 and -12)

If I just directly connect the batt to it, it draws out 4 to 10 amps!!

A user suggest adding 6 diode, but didn't work, still drawing 4 amps

Then I added some resistors 26 ohms (5.5 v across ), current goes down to 300mA. But I have been charging it for 60 hours now and still the same. Current remains 300mA and the batt volt is still at only 16 v.

Please help, thanks!!

 

[tpetar]

What type is battery NiMh or NiCd ? From described starting current I supose it is NiCd.

Did you try to repair original charger ?

 

[edpalmer42]

What is the voltage measured across the battery when you're not charging it? It's possible that one or more of the battery's cells has shorted out. That would explain the high current draw when you try to charge it. When the original charger died, was it trying to charge the same battery? A defective battery could cause a charger to fail.

Ed

 

[sappy2000]

What is the voltage measured across the battery when you're not charging it? It's possible that one or more of the battery's cells has shorted out. That would explain the high current draw when you try to charge it. When the original charger died, was it trying to charge the same battery? A defective battery could cause a charger to fail.

Ed

Hi Ed, I only get 14v when the battery is open circuit. The charger was only used to charge this batt.

What type is battery NiMh or NiCd ? From described starting current I supose it is NiCd.

Did you try to repair original charger ?

hi tpetar, it's NiCd. https://www.blackanddecker.com/attachments/HPB18.aspx

I didn't try to repair the charger because the casing is not openable. I will need to cut it open.


What should I do now? :sad:

 

[tpetar]

hi tpetar, it's NiCd. https://www.blackanddecker.com/attachments/HPB18.aspx

I didn't try to repair the charger because the casing is not openable. I will need to cut it open.


What should I do now?

Cut and open case of charger, this status of charger is not good, from this point best you can do with that charger is to use guarantee or if there is no guarantee then try to fix a problem, if that is not possible then you should make new charger.

 

[edpalmer42]

Hi Ed, I only get 14v when the battery is open circuit. The charger was only used to charge this batt.




hi tpetar, it's NiCd. https://www.blackanddecker.com/attachments/HPB18.aspx

I didn't try to repair the charger because the casing is not openable. I will need to cut it open.


What should I do now? :sad:

It looks like 2 or 3 cells have shorted out and then killed the charger. Don't try to change the bad cells - new and old cells don't play nice together. You could look around for any cheap 18V nicd drill battery and take the cells out of the new one and put them into the original case. Watch for sales or discontinued models. Most of the battery packs use the same size cells.

As for the charger, tpetar is correct. If there's no warranty, open it up and see what's inside. The charger is likely very simple and might be easy to repair. If there is a wall wart for the charger, check it before you ***** anything open. Some of them have an internal fuse which may have blown. It's not that hard to repair or replace a unit like that.

Ed

 

[sappy2000]

Cut and open case of charger, this status of charger is not good, from this point best you can do with that charger is to use guarantee or if there is no guarantee then try to fix a problem, if that is not possible then you should make new charger.

Hi tpetar, how do I make a new charger? Can I buy a buck converter and convert my 24v to 21v and charge the battery?

 

[bobot]

hey try to learn the no a ampere hours needed for the battery from the manufacturer..and see whether the pc outputs required amphr.

 

[sappy2000]

hey try to learn the no a ampere hours needed for the battery from the manufacturer..and see whether the pc outputs required amphr.

What do you mean by that?

 

[tpetar]

Hi tpetar, how do I make a new charger? Can I buy a buck converter and convert my 24v to 21v and charge the battery?

This is not necessary, because 24V is ok voltage for your needs. No need for -12V 0 +12V.