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I have a 14.4v NI CD power drill with a charger that outputs 18v 400mA (original charger for drill) but the charger supply lead no longer works. Looking to get a replacement but finding it difficult to get an exact match The charger voltage output (18v) is larger than the voltage of battery (14.4v) but does the output amps have to be the same as original (ie 400mA) if not what amps could i go upto?


marked as duplicate by PeterJ, Ignacio Vazquez-Abrams, Leon Heller, RedGrittyBrick, Michael Karas Mar 23 '14 at 13:15

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The charging current you can safely administer depends on the capacity of the accumulator.

Interestingly, the slower you charge the battery, the less effective the charging becomes, however you don't want to choose a current too high or it'll overheat.

Seems like a pretty surefire way of charging the battery would be at a current of C/10 for 16 hours. (C being the rated capacity (Ah or Ampere hours) of the battery)

For more information you might want to check out this link - http://www.powerstream.com/NiCd.htm

Wikipedia also offers some insights - http://en.wikipedia.org/wiki/Nickel%E2%80%93cadmium_battery

  • \$\begingroup\$ since found out that the battery will only draw amps required so seems to me as long as higher than original amps it will be ok \$\endgroup\$ – user39123 Mar 23 '14 at 14:26
  • \$\begingroup\$ @HOTDOGHARRY- when replacing a power supply, you are correct - the "toy" will only draw the current it needs. But battery chargers are a little different in that they tend to force a certain predetermined current into the battery, the battery doesn't draw the current it needs. So you do need to be careful on what you buy for a new charger. \$\endgroup\$ – Filek Mar 25 '14 at 4:06