Serially wired Nicads

[j.m@talk]

I'm changing the cells in my drill powerpack ....... (New powerpacks are silly money) :rolleyes:

So we have 9.6v 1900 mAH
8 cells serially wired 8X1.2v=9.6v

So do I get 8 237mAH batts
OR
8 1900 mAH batts ?

I thought the physical size would clue me in ...... But I can get either config in either size :(

Yeah I know I'm supposed to know this stuff :-@

:t

[Billforce]

I really don't know the difference. When I changed mine, I used 1600's.

[zybch]

Originally posted by j.m@talk


Yeah I know I'm supposed to know this stuff :-@

:t

Tell me about it. I've got several bits of paper giving me electronics certifications but I still get stuffed up with things like your battery prop :(

[MJCfromCT]

Well, if they are in serial, then current is the same over the batteries:

1900 ---1900---1900---1900 --> if these four are in series, then you will end up with a 1900 mA current over the entire circuit.

Current is not added in this way in parallel.

You add voltages when power supplies (batteries) are in series. So you are right about the 1.2x8.

[j.m@talk]

Lucky somone knows what theyre doing :D ........ You stand here & watch this .............. I'm going in to the next room to switch it on ;)











(One born every minute):p

[Bovon]

Originally posted by MJCfromCT
Current is not added in this way in parallel.With cells in parallel, voltage stays the same, current adds.

With cells in series voltage adds, current remains the same.

i.e., 3ea. 1.5 volt cells that have a capacity of 1000 mah connected in series will be 4,5 volts at 1000 mah. Connect the 3 cells in parallel, and the voltage will be 1.5 volts, but the current increases to 3000 mah.

Use 6 ea. 1,5 volt cells and connect 3 ea. "banks" of 2 cells in parallel, then connect these (3 banks) in series. Now you have 4.5 volts at 2000 mah (using the same voltage and ampere hour cells as above)

This is known as series-parallel connecting.

Theoretically there is no limit to series/parallel connecting.

Using a WAG figure, say 5000 flashlight batteries are used to make up one bank..all connected in parallel. Make 8 banks and connect all banks in series. You now have 12 volts and lotsa amperes...start your truck on a very cold day!

[MJCfromCT]

I probably could have been a bit clearer instead of saying "Current is not added in this way in parallel".

If you have a circuit with a number of components in series, they will have the same current throughout them (Kirchhoff's Current Law).

For a circuit with components in parallel, the voltage drop across each component will be the same (Kirchhoff's Voltage Law), but the current across each will be diferent.

http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/DC-Current/SeriesParCompare.html

[j.m@talk]

Well I'm trying to upgrade my drill a lil while I'm at it...... It has a smart charger so all should be hunky dorey....... Its those rapid charge cycles that stuff the batts up :(

[ukulele]

The charger is rated for the current, so you risk damage to the charger if you use batteries with a significantly higher capacity. Ideally what you want to do is to match the voltage to the drill and if the capacity is a lot higher then the old batteries, then slow down the rate of charge with resistance. I have done it with a 12v light bulb and a potentiometer in series with miliamp meter. You just adjust the current to match the rated output of the charger and wait a little longer or get a bigger transformer to charge it with.

[j.m@talk]

I thought smart transformers were smart enough to do that them selves ?

Isn't that the whole point ? (Obviously I'm not going up to 4 Ah or anyfing) :t

[ukulele]

Originally posted by j.m@talk
I thought smart transformers were smart enough to do that them selves ?

Isn't that the whole point ? (Obviously I'm not going up to 4 Ah or anyfing) :t

Perhaps, I usually make my own. I have too many spare parts and too far to drive to buy expensive smart parts. Smart part are for smarty pants. ;)

[j.m@talk]

I dunno we are only talkin a Bosch Drill here......
http://www.rucni-naradi.cz/Foto/PSR96VE-2.JPG

[j.m@talk]

New Battery Pack £45 I need at least 2

Or a complete new drill wiv 2 batts £80 :rolleyes:

Umm Take the Batt pack to bits & see whats what ;)

[ukulele]

Don't buy battery operated tools unless you use them every day or two. The batteries die from boredom.

[j.m@talk]

Fink thats whats happened :(

[herosrest]

Just duct tape the trigger down for an hour a day.