Nicad battery pack

[welldweller]

I am repairing an electronic torque wrench which has a defunct rechargeable battery pack. The battery pack is 4AA size, two on top of each other and side by side, if that makes any sense (L022 or L2x2 configuration??). THe battery pack says 4.8v 500MaH and is made by Panasonic (P50/L2X2L). Obviuosly I need another 4.8v battery, but do I need to keep to the 500MaH or can I go higher than this? I think the battery pack I want is obsolete.
Thanks

 

[davenn]

you can use higher current capacity if you wish, it would mean the pack lasts longer between charges
I have done this in the past for handheld tranceiver radios

Dave

 

[welldweller]

Thanks Dave. THought as much. Just wanted to make sure I wasn't harming the circuitry.

 

[shrtrnd]

I'm with davenn.
You should be able to get replacement batteries with three times the capacity of your old 500MaH now.
Watch out if your batteries are NiCad (Nickel Cadmium), or NiMH (Nickel Metal Hydride), ... it'll make a difference to your recharger. The recharging circuits are different for the two different types.
Like davenn mentioned, the current output for the old and new batteries would be equivalent. It's just that the amp-hour rating for the higher capacity batteries, means that they will operate at that current output for a longer period of time.

 

[davenn]

I'm with davenn.
Watch out if your batteries are NiCad (Nickel Cadmium), or NiMH (Nickel Metal Hydride), ... it'll make a difference to your recharger. The recharging circuits are different for the two different types.

and further to that important info from shrtrnd, make sure you DONT mix battery types
but Im sure you knew that already

D

 

[welldweller]

Thanks for all the info guys. Will give it a go.

 

[welldweller]

Battery

Well chaps, I have bought the closest thing I could find. It is a Varta 4/VH2700 battery. Trouble is, it is Ni-MH and not Ni-Cad. Also it has four wires coming from it and not just the black and red of the original. There are two white wires, one black, and one red. And idea how I connect these up to get the 4.8v? The hardware I'm putting the battery into has a small circuit board, which I presume is the charging circuit. Has a small SM transistor and diode, and not much else as I remember.
Any ideas please?
Can I just connect a 4.5v power supply to the input jack?
Andy

 

[Resqueline]

Ignore the white wires, they're presumably only connected to a thermistor inside. Just connect the black & red as per the original (if it was connected when you got it).
An appropriate charging device must likely be used but apart from that, being told zilch about the item(s) in question no-one can tell you anything but zilch..

 

[welldweller]

Ignore the white wires, they're presumably only connected to a thermistor inside. Just connect the black & red as per the original (if it was connected when you got it).
An appropriate charging device must likely be used but apart from that, being told zilch about the item(s) in question no-one can tell you anything but zilch..

Thanks Resqueline. The item in question is a digital torque wrench. I have powered it up by connecting a 4.5v DC power supply to the battery wiring. Seems to be working ok. The only gubbins in the end of the torque wrench body is a jack plug socket, and what looks like an LED (to show its charging/charged, presumably). When taking out the battery pack the wires separated from the small circuit board inside the unit. There aren't many components on the board. I think if I can replace the battery it should be OK.
Don't know how to charge it. I have a power supply which is a multi-voltage type with lots of different connectors on the end of the supply wire, and two knobs to select voltage and polarity. Would that do it?

 

[(*steve*)]

To charge NiMH batteries you require a dedicated charger. Most of those available require that they charge individual cells.

I just went looking for information on a unit I have that can charge packs of batteries, but didn't find in on the site of the company I bought it from :-(

Mine is a "Pro-cell Performance Multi-function charger" but I can't find anything on the web about it any more (I think it was originally designed to charge large mobile phone batteries -- in the days when they were removable to put on chargers.

My charger is switchable for 4.8, 6, or 7.2 V packs (4, 5, or 6 nicads or NiMH). You'll probably have the easiest time finding something like this in places that sell stuff for the radio controlled model market. You may have some trouble finding chargers for less than 7.2V though :-(

I'm not completely sure. Did you buy a complete new battery pack, or just replacement cells to put in the old pack? It doesn't make a lot of difference either way in terms of charging.

 

[welldweller]

I bought a new battery pack. It is in a shrink film and comes as a complete package.

 

[(*steve*)]

And presumably they fit inside a plastic case that may or may not removable from the tool to fit on a charger?

I would contemplate fitting a power socket on the battery case so that I could attach the batteries to an appropriate charger.

Using the correct charger will extend the life of the batteries considerably as well as (possibly) charging them faster.

You might consider an external charger like the ones listed on this page (I endorse them as nothing more than the first hit on a Google search for "4.8V NiMH Charger")

 

[Resqueline]

So; you don't have the original charger, can't provide us with any brand, model #'s or pictures, and missed where the wires went.. It won't be easy for us to help you then..

You can't use the power supply you have there for charging since it's a constant voltage supply, & there's no charging circuit in the wrench, only a charging indicator circuit.

If the original charger was 50mA it would have been in the 0.02 C category and so quite useless (& not recommended) anyway (75-87 hours charging time).

Devices having a 3.5mm (audio) jack for charging & a red LED usually had a dumb constant current (1/10 C) charger.
Remember the audio jacks gets shorted briefly when inserted.

The data sheet for your cells says; Charge Conditions at:
Standard Charge: 270 mA/ 14-16 h
Accelerated Charge: 540 mA/ 7-8 h
Fast Charge: 2700 mA (dT/dt,-dV)
Trickle Charge (0.03-0.05 C) no