power drill batteries

sojudave · #1 (**permalink**) 10-31-2009, 12:16 PM

I was working with a drill the other day and checked the battery. It's an 18v/18A NiCd battery. I was wondering how this could be applied to a hub motor.... two in series would make it around a 36v/18A system so I think the wattage would be 648. Is my math bad? The other thing is that I don't think that the Amps aren't Amp Hours. I thought I saw a bike on here or somewhere powered with these drill batteries. Just thinking out loud.

jdcburg · #2 (**permalink**) 10-31-2009, 05:42 PM

Hi sojudave - There are people using power tool batteries for ebikes - nicad, nimh and lithium. The holder is kind of clunky and inconvenient. If you open it up, you'll probably find a bunch of single cells (likely 'tab batteries') in there wired in series to make 18v. If you have access to discarded battery packs, you might find a bad pack will have one or 2 bad cells and the rest are good. You could scavenge the good cells and solder them together in series to make a battery pack whatever voltage you want, in multiples of 1.2 volts for nicad/nimh, 3.2 for lithium. So 15 nicads make 18 volts. Two 18 volt packs in series would make 36 volts. Additional ones in parallel would increase the amp-hours. If you look on ebay or a place like Only Batteries The Rechargeable Batteries and Battery Charger Store on the web, you can see tab batteries individually or in packs. There are also Bosch Fat Packs that are compact lithium packs if you want to go that route. I’m thinking about making a few battery packs using regular rechargeable D cells (probably nimh) stacked in a piece of PVC pipe. Ten cells would make a nice 12v pack a little over 2 feet long and I wouldn’t have to worry about soldering anything. I don’t know much about soldering batteries and I think it might be dangerous, especially lithium, so if you are thinking about that, check with somebody who knows that stuff.

I’m not sure what the 18A means but most of the rechargeable cells I have seen are rated in milliamp hours (mAh). I have seen D cells up to 10,000 mAh which is 10 Ah, so using them, each of my 12v tubes would be 10Ah - jd

jimraysr · #3 (**permalink**) 10-31-2009, 06:02 PM

I suggest you check out the D Ni-Cads and NiMH ones as many are just AAs in a large case. The truth is in the MAH rating of each. AAs now are running in the 2500MAH range, so a D cell should be 4 - 5KMAH rating.

Of course Lithium Polymer are much higher density and lighter. I still am concerned about using Lit-Ion cells that are not a part of a factory pack. They really need a circuit
to measure temperature to control charging and an internal fuse to protect against runaway and fire.

The Ryobi Lit-Ion 18 volt batteries are great and make all the difference in operation of their tools, but pretty hard to justify the expense.

Jim

Quote:

Originally Posted by jdcburg

Hi sojudave - There are people using power tool batteries for ebikes - nicad, nimh and lithium. The holder is kind of clunky and inconvenient. If you open it up, you'll probably find a bunch of single cells (likely 'tab batteries') in there wired in series to make 18v. If you have access to discarded battery packs, you might find a bad pack will have one or 2 bad cells and the rest are good. You could scavenge the good cells and solder them together in series to make a battery pack whatever voltage you want, in multiples of 1.2 volts for nicad/nimh, 3.2 for lithium. So 15 nicads make 18 volts. Two 18 volt packs in series would make 36 volts. Additional ones in parallel would increase the amp-hours. If you look on ebay or a place like Only Batteries The Rechargeable Batteries and Battery Charger Store on the web, you can see tab batteries individually or in packs. There are also Bosch Fat Packs that are compact lithium packs if you want to go that route. I’m thinking about making a few battery packs using regular rechargeable D cells (probably nimh) stacked in a piece of PVC pipe. Ten cells would make a nice 12v pack a little over 2 feet long and I wouldn’t have to worry about soldering anything. I don’t know much about soldering batteries and I think it might be dangerous, especially lithium, so if you are thinking about that, check with somebody who knows that stuff.

I’m not sure what the 18A means but most of the rechargeable cells I have seen are rated in milliamp hours (mAh). I have seen D cells up to 10,000 mAh which is 10 Ah, so using them, each of my 12v tubes would be 10Ah - jd

deacon · #4 (**permalink**) 10-31-2009, 08:48 PM

I have been looking at tool batteries lately and it's not going to happen for me. The highest tool battery I can find is 36v 3.5 ah rating. for over a hundred bucks. To get to 20ah I need for my 600watt motor I have to have 20ah so they say. It would cost about 600 bucks plus to do it.

Also they say that the BAS circuit gets screwed up from the parallel circuit or some such. Sorry