"David Billington" wrote in message news:sagndj$cm2$1...@dont-email.me...
On 17/06/2021 12:52, Jim Wilkins wrote:
> So does anyone have hands-on experience with replacement drill battery
> packs that use NiMH cells instead of the original NiCads?
I can't help with your query but last year I converted my 14.4V Bosch
NiCd battery pack to Lithium. I found 4 18650 Li cells was close at
14.8V and fitted beautifully in the Bosch pack, 3 fore aft, and 1
across, these were tabbed cells so I made a simple PCB to couple them
and hold them together, on top of the PCB I mounted a supervisory board
for over charge, over discharge sensing and wired to the standard
battery pack contacts. For the charger I used a 4 cell Lithium charger
wall wart and gutted the original NiCd charger to just leave the bare
PCB and charging contacts with leads to those and a socket to connect to
the Li charger plug with its lead going into the original charger in
place of the mains lead. I've had no problems and it has revived a
useful tool and the new pack is 3.6Ah as opposed to the original 1.2Ah.
Thanks. Were you able to determine the battery discharge rating and the
tool's current draw?
The tabbed 18650s I've collected are in outdated cell phone chargers, so
they may not have a high enough discharge current capacity, maybe only 2C. I
bought them to refurbish old laptop batteries and since a few had dropped
slightly below 3V and self-disabled, I recharged them directly with a lab
power supply, as I learned to do at Segway. Unlike a smart charger, a
current-limited power supply will try to recover a fully discharged battery.
I suppose I could measure the drill's stall current with a 20A power supply
or 12V battery and the 18650's max output (outdoors) with my 1 Ohm 1000W
I stopped testing the NiMH in the DeWalt charger when the voltage rose above
19V. They came at 16.5V and charged reasonably quickly at 17~18V 0.5A from a
power supply, to the endpoint of 0A drawn at 17V. Anderson PP45s fit
directly onto the battery contacts and I wired the charger contacts to