[timd157]

Please can you advise me what I need to solve this problem:
I have a Racal Dust filter mask I use in my woodturning. It is a simple motor in a mask that blows a stream of fresh air through a filter. The product is no longer made but is still very serviceable but the rechargeable battery pack needs replacing.
The only information I have is as follows:
Racal product. Charger Input 240v 50 Hz Output 4.2v 230mA .96VA
The battery pack contains 3 X 5/4 Nicad rechargeable batteries of a size no longer obtainable ( my local branch Maplin's has searched for me) and it ran for 4 hrs.

There was an 8 hour offboard rechargeable battery pack available once, which had 3X 1/2D Nicad cells.

I want to make an 8 hour rechargeable battery pack connected by a lead to the mask which contains the motor. The connections are not a problem, I can change them as needed. Can I use the same charger?

Hope you can help. My local Maplins said they thought they could but were too busy when I went there.

[tkrussell]

The critical issue with a battery or pack is what the ampere-hour is rated. First, the voltage rating of a charger needs to be approximately 10% high than the voltage rating of the battery. Any charger of the proper voltage will charge a battery, however, the amp output of the charger , if too small, will take a longer time to charge the battery.

I found that the cell you have produces 2600 milli-Ampere-hour, and using a charger with 230 mA output it will take over 13 hours to charge the battery. If you can get a 500 mA charger, for example, the battery will charge in 6 hours.

So, the charger you have will charge the battery pack, but at the sacrifice of time.

[timd157]

Please can you advise me what I need to solve this problem:
I have a Racal Dust filter mask I use in my woodturning. It is a simple motor in a mask that blows a stream of fresh air through a filter. The product is no longer made but is still very serviceable but the rechargeable battery pack needs replacing.
The only information I have is as follows:
Racal product. Charger Input 240v 50 Hz Output 4.2v 230mA .96VA
The battery pack contains 3 X 5/4 Nicad rechargeable batteries of a size no longer obtainable ( my local branch Maplin's has searched for me) and it ran for 4 hrs.

There was an 8 hour offboard rechargeable battery pack available once, which had 3X 1/2D Nicad cells.

I want to make an 8 hour rechargeable battery pack connected by a lead to the mask which contains the motor. The connections are not a problem, I can change them as needed. Can I use the same charger?

Hope you can help. My local Maplins said they thought they could but were too busy when I went there.

Thanks TKrussel for that
But what do I need to make an 8 hour rechargeable battery pack?
What sort of batteries and how many? Do I join them in series or parallel?
TimD

[tkrussell]

What voltage and amperage do you need?

[labman]

''which had 3X 1/2D Nicad cells.'' Bet if you can find the specs for 1/2 D cells they are electrically close to a C cell. Should be easy enough to find 3 of them and connect them up in series. Your charger should take twice as long to charge an 8 hour pack as a 4 hour one.

[Stratmando]

Any amount of batteries, so long as it is 3.6 volts, or 3 cells. 1.2 volt per cell X 3.
You can do series and parallell, to increase capacity.

Would something like this work:
Sharp CL250 3.6 Volt NiCad Cordless Phone Battery at Lowcostbatteries.com
Like above, make sure charger can handle increased capacity.
What are physical dimensions of batteries?