Nicad battery query

[Bernie9927]

I have a 24 volt DC NUTOOL drill but have no battery charging information. The charger reads - 28V DC --- 400mA. My question is :- Approx. how long should I charge the (Nicad)battery to bring it up to 24 volts. Any advice would be much appreciated.

 

[^woody^]

Most of these branded tools have a 3 or 5 hour charge time

 

[Bernie9927]

Many thanks Woody. I thought the charge time was about 3 hours but I wasn't sure and as you have more or less confirmed that, I'll take it as read.

 

[EightyTwo]

If it's a 1200mAHr (1.2AHr) battery, it will need 3 hours at 400mA (3x0.4=1.2), assuming that it really charges at this rate!

 

[Bernie9927]

Many thanks 82.. The information on the charger is:-

MNCD24-3KA-H
BHY48 - 28BS
28V DC (solid line above 3 dashes ) 400mA

Does any of that give you an indication of its AHr ?

 

[EightyTwo]

That's the information on the charger... What about the battery? Does it say how many amp-hours (or milliamp-hours) its capacity is? If so, simply multiply this figure by 0.4 and that should tell you the number of hours required to fill it. I'd be inclined to run it a bit longer, just to be sure - say 20%.

If it's a PDC24 drill, it could be an hour...
http://www.amazon.co.uk/Tool-24V-Cordless-Drill-PCD24/dp/B000FFJIGC

The solid and dashed line symbol means DC whilst a wavy line means AC.

 

[Bernie9927]

Once again thank you 82. The battery has 1.0 Ah on it, so according to your calcs this should charge the battery in less than one half hour ie 1 times 0.4. Does this sound right to you?

PS Sorry about the delay in getting back on this but I was away yesterday

 

[Mursal]

1Amp divided by 0.4 of an Amp = 2.5 (I think)

 

[Bernie9927]

Many thanks Mursal but unless I am mistaken, 82 said "multiply" the 1 Ah by 0.4. Needless to say, I am a bit confused and am wondering if you are able to confirm which of you is correct ie divide by or multiply

 

[Mursal]

Sorry for sticking my opinion into the middle of this thread.

I think 82 gave an example of a 1.2Ahr battery having a charge time of 3 hours. Now, your battery is only slightly smaller at 1Ahr so it will take almost as long, somewhere between 2 to 3 hours. 0.4 of an hour, or 15 minutes, just doesn't make sense for almost the same size battery.
So that's why I divided by 0.4

 

[Bernie9927]

That's ok Mursal. I'm only too glad you gave your opinion as it confirms that I should charge the battery for around 3 hours.

Thank you all for your help

 

[EightyTwo]

SO sorry to cause confusion - I should have said "DIVIDE the battery capacity by the charging current...".

Battery capacity is measured in "amp.hours". That is amps times hours. A 1AHr battery could (ideally) provide 1 amp for 1 hour or a tenth of an amp for ten hours.

Charging is the same sum - charge at one amp for one hour or a tenth of an amp for ten hours. In your case, two fifths of an amp for five halves of an hour i.e. 2.5 hours.

This is all an ideal rule of thumb. There are physical and technical reasons why actual values on specification sheets will not follow the sums exactly. For example, it isn't possible to get (or charge at) 100A for 0.01 Hours!!

I hope that's made it clear...

 

[Bernie9927]

Yes it has 82. Many thanks for your input