XPost: rec.crafts.metalworking   
   From: Snag_one@msn.com   
      
   On 6/17/2021 6:52 AM, Jim Wilkins wrote:   
   > I bought a $35 pair of replacement battery packs for my 14.4V DeWalt   
   > drill that contain NiMH instead of NiCad cells like the original. Amazon   
   > reviews claim the original DW9118 charger handles them without problems,   
   > but having been a battery test tech I wanted to know more.   
   >   
   > DeWalt says their chargers need a true sine input so for remote job site   
   > solar+battery use I bought a 300W Bestek inverter which gets decent   
   > reviews. Mine shows a nice 113V sine wave on a scope and cuts off at   
   > 350W. Some users wrote that a modified sine inverter blew their   
   > charger's fuse or worse. The AC input feeds a capacitor rather than a   
   > transformer.   
   >   
   > I recorded the voltage and current while charging the old NiCad and   
   > found that the charger ignores the small negative steps as each cell   
   > tops off and begins generating oxygen, instead it cuts off the current   
   > once a minute and measures the battery voltage. Charging ends when the   
   > zero-current voltage reaches 17.0V, or ~1.42V per cell. The charging   
   > current of 1.3A raises the voltage almost to 18V before the individual   
   > full-charge cell drops begin, ending at 17.65V. When the NiCad pack was   
   > new (or new-old-stock) it measured 17.13V at full charge.   
   >   
   > Internet sources suggest without firmly stating that constant-voltage   
   > charging to 1.4V~1.45V per cell is acceptable, though the last part of   
   > the charge is slow.   
   >   
   > So does anyone have hands-on experience with replacement drill battery   
   > packs that use NiMH cells instead of the original NiCads?   
   >   
      
      I bought 2 aftermarket NiMH batteries for my 18V DeWalt , the 9118   
   charger worked fine . Until a couple of weeks ago when I let the magic   
   smoke out of it . Probably moisture in/on the PCB . The new aftermarket   
   unit will only charge batteries that have the 3rd contact on the center   
   fin , so 3 of my batteries are now useless .   
   Snag   
   Race only matters to racists ...   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)