Replace Ni-Cd with Li_ion on a drill

goixiz

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Dec 16, 2013
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I have an cordless old drill in perfect condition but the Ni-Cd battery barely holds a charge (14.4V dewalt).

I would like to replace the C size batteries in the pack with Li-Ion 18650 batteries from various laptops that i rescues through out dumpster diving.
Is it possible to group some of the similar 18650s to and solder the (+ / -) ends to the old battery pack (dispose of the Ni-Cd) and use it with the existing charger that comes with the drill kit.

Thanks in advance..
 

mattheww50

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Short answer: NO!

NiCd's are pretty tolerant of two things. You can run them down to zero volts, but as long as you don't reverse charge them, they tolerate it very well. They also tolerate slow (Trickle) overcharging very well, i.e. you can indefinitely charge most NiCd and NiMh cells at about C/12 almost forever. Li-Ions fail catastrophically if you do either of those things. The charging algorithm for Li-Ions is very very different than for NiCd or NiMh cells and requires very specialized charging equipment. While there are chargers out there than can do both, they are able to recognize the type of battery, and use the appropriate charging strategy. NiCd's also are characterized by very low internal resistance, i.e. even relatively modest sized NiCd cells can deliver a surprisingly large amount of power for short periods. The typical 18650 ICR Li-Ion has trouble delivery more than about 5 amps, however IMR type cells are capable of much higher current, and when you see a battery powered tool that claims Li-Ion power, it is a safe bet they are powered with IMR cells. You can find IMR cells that are good for up to 30 amps for short periods.You basically trade total energy storage for higher peak power output when you go from ICR to IMR. There are some hybrids of the two out there such as the Panasonic 18650BD that is rated for 10 amps.

So while it might be possible to replace the cells in your drill with Li-Ion cells, you WILL need a different charger to charge those cells.
 
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Lynx_Arc

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I agree 100% with matthew here, you cannot use a charger that isn't designed for the chemistry of the cells you are trying to charge without possible danger to the cells and/or the surrounding environment. I would also add I would NOT recommend mixing lithium ion batteries of various vendors and batches in a series circuit without proper protection involved and proper charging as you could have catastrophic results in both charging and heavy load usage. My advice is to get a part time job and make the money to buy a lithium ion based drill as you may find the amount of time and effort and parts required to adapt your drill to lithium ion would add up to more than just buying one and not have to worry about issues that could be unsafe in adaptation.
 

goixiz

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Dec 16, 2013
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12
Thanks for the info advice I just hate to waste a good drill and when i have so many Laptop individual Li ions on hand

Accept - i will look for Ni-cd c cells to replace it

Thanks again

BTW I do have a job and those comments bout "get a part time job" is not needed to clarify your point and does not add any value to my question - I rather keep answers to point
 
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