drill batterys

[docfunk]

I have a bosch 24v drill that has 2ah batterys, I was at work today and "found" 2 12v 6ah re-chargeable lead acid alarm batterys so if i link said alarm batterys together then connect them remotely to the drill via a long cable so we can get it into tight places, will I A,get 24v and B, get 6ah which is 3 times the "power?" or would I get 12ah? and do you guys think it will work?

 

[Les W]

If you connect them in series you will get  24V @ 6Ah
If you connect them in parallel you will get 12V @ 12Ah

 

[pete h]

A lot of use this system allready but make sure the plugs on the leads can only be connected one way to maintain the correct polarity to the drill.

 

[SamT]

I think we knackered one of our bosch GBH's this way. we got hold of two 12v lead acid motor bike batteries and connected them in series to make a 24v battery housed in a small darren drum.

Problem was if the drill 'grabbed' there is a huge demand for power as the windings come to a standstill, which - having a 6aH battery is readily available. This first of all burnt the contacts out in the switch,  (this sorted via a sneaky bypass wire) we then proceded to burn the motor out a bit. (it still kind of worked - but was never quite the same).

Im no electrical whizz - so cant back up my post with hard science - but Im sure someone like Nick Williams will have an opinion.

There was a great moment in the pub when i first got em that they where shorted by accident. It was a cross between a firework and an arc welder (and for only 24v, it was quite impressive). Much mirth and ammusement from the locals - untill the fire alarm went off. 

 

[shotlighter]

Not the best battery for the job by any means but they're cheap (especially when free) & do the job for a while at least.
Used 'em on & off for about 15yrs with GBHs & not yet wrecked a drill as a consequence - worn three out mind!

 

[biffa]

I've got a couple of 7Ah lead acid cells in an (imitation) Pelicase and they have worked well with an old Black and Decker 24v SDS drill.  Did manage to destroy one set of switch contacts in a way similar to that described by Sam T, but replaced the switch and drill has been happy for the last three years.

I think that NiCad cells have a greater series resistance than lead acids hence can't provide such a large short circuit current. 

 

[nickwilliams]

I think that NiCad cells have a greater series resistance than lead acids hence can't provide such a large short circuit current. 

Wrong way round - the internal resistance of 7Ah Nicad cells will be lower than a 7Ah Lead Acid battery, but in fact in either case it's low enough that it won't be the limiting factor on how much oomph you get at the drill.

Nick.

 

[JonJ]

We have been uisng the system you describe for years, its works fine and is cheap. You just need to protect the batteries from physical abuse when dragging them though the cave, 10 mm of neoprene works fine.

 

[AndyF]

You can put a fuse in series, to protect against the stalled drill situation, make it generously rated due to start up current though...