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Power Drill Battery Rebuild by Terry Byland

PostPosted: Feb 9, 2007 6:09 pm
by cavescom
Terry Byland sent me this article....feel free to forward to other cave groups. Power Drill Battery Rebuild or

Mark Passerby,

PostPosted: Feb 10, 2007 12:15 am
by tagcaving
Thanks a lot for that! I am also building a new battery pack for my Hilti 36v drill. Ordered the batteries last week. I plan put up a build page of the project and share it.

The original Hilti NiCd pack was just 1200mah and had a cut off of 85% charge so I only got 37wh out it and maybe 20 bolts on a charge. It weighed 5 pounds. The new pack will be made 10s3p from 18650 2200mah lithium ion cells. 244wh and enough power to set 100 bolts or drill 14 feet of 5/16 hole for rock shaving. Just 3 pounds and $166. An alternative is using A123 Li Phosphate or Emoli 3000mah 10c cells. The advantage being A123 will not explode and burn down you house if you mistreat them. Mistreat Lithium ion cells and kaboom....

Cells are made in 5 2s3p 7.4v blocks, shrink wrapped, tool dipped, and covered in a fiber glass shell, then tool dipped once more. The 5 packs are then put on a belt and hooked in series. Each pack is charged separate with one charger at 1C, so just 2 hours a pack. That takes 10 hours to do 5, but not a problem the week before a trip.

No PCB so a 14A poly switch is used to protect each pack from shorts. A low voltage cut off set for 30 volts to limit discharge to 3 volts per cell is a good thing also.

PostPosted: Feb 10, 2007 8:12 am
by Scott McCrea
Is anyone else having trouble getting the images at the link above to load, or is it just me?

PostPosted: Feb 10, 2007 8:59 am
by barcelonacvr
Scott McCrea wrote:Is anyone else having trouble getting the images at the link above to load, or is it just me?

All I see are x's too.

PostPosted: Feb 11, 2007 4:46 pm
by cavescom
Here is a link to a PDF version of the "Power Drill Battery Rebuild" by Terry Byland.

Mark Passerby,