hp67 82004A reserve power pack
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06-19-2015, 08:40 AM
(This post was last modified: 06-19-2015 08:46 AM by Sadsilence.)
Post: #6
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RE: hp67 82004A reserve power pack
(06-18-2015 05:07 PM)gfernval Wrote: It is the same charger circuit the one of the hp67 that with the HP 82004A Reserve Power Pack? DonĀ“t have the instructions of the HP 82004A Reserve Power Pack. Has not checked HP 67 curcuit so far, but HP 45 curcuit, which uses same battery packs. HP 45 inside curcuit is same as in 82004A charger. Both deliver 60 mA to 50 mA charge current, dwindling a little bit when battey pack is full, cause battery voltage goes up. Take a look at your power supply, too. 82002A or 82010A here. It has an 400 uF capacitor inside. In 2 of my 3 device it had to be replaced in order to get an stabilized voltage. Otherwise charging current is even lower. (06-18-2015 09:59 PM)Katie Wasserman Wrote: The charging rate/time on nicad cells is not critical, as they can tolerate overcharging pretty well. Newer nicads can charge at much higher rates (faster times) than old ones without damage. The best way to tell if a nicad battery pack is fully charged is to remove it from the charger and measure it's voltage. Fully charged, it should measure 1.45 volts x number-of-cells. (06-19-2015 01:48 AM)Dave Frederickson Wrote: So our 700 mAh battery has a charge rate (C) of 0.7A. 0.7/0.055 approximately equals 12.7 which is pretty close to the website's description of an overnight charger having a charging current of C/10. I seem to remember the chargers simply being used overnight and the website states that this is the easiest way to charge a NiCd battery but they do recommend setting a timer for 16 hrs. As Katie pointed out, newer NiCd's can charge faster and some of newer chargers have built-in timers and temperature sensors. Generally overcharging is a problem with any NiXX battery, but a charge rate around C/10 is uncritical for moderate overcharging. NiCD batteries tend to decrease their output voltage level when used afterwards, NiMH batteries gets hot with destruction of chemistry. At some point energy put into battery is completely transformed into heat. With C/10 charging rates and low capacities thermal energy can be dissipated over surface without much harm. Lately I rebuilt HP 41C battery pack with 170 mAh NiMH cells. Data sheet states, there is no harm when charging cell with C/10 (=17 mA) for ONE YEAR. Strange. Even before not all energy put into battery is transformed into electrical one. With C/10 charging rate 12 to 15 hours are necessary to reload a completely empty pack or cell. On the other side charging rates much below C/10 are not good either, so called trickle charge. Battery chemistry "drains out" and loses high current capabilities. No real problem for low current devices like calculators, but battery life time is decreased, too. Not to mention days of waiting time... So it makes no sense IMHO to charge a new > 2000 mAh battery pack (like Katie mentioned anything above 2500 mAh is not reliable) with original calculators charging curcuit or 82004A. Use an external charger like iMax B6 and a C/3 to C/2 charging rate. |
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Messages In This Thread |
hp67 82004A reserve power pack - gfernval - 06-18-2015, 05:07 PM
RE: hp67 82004A reserve power pack - Dave Frederickson - 06-18-2015, 09:11 PM
RE: hp67 82004A reserve power pack - Katie Wasserman - 06-18-2015, 09:59 PM
RE: hp67 82004A reserve power pack - Dave Frederickson - 06-19-2015, 01:48 AM
RE: hp67 82004A reserve power pack - Katie Wasserman - 06-19-2015, 02:34 AM
RE: hp67 82004A reserve power pack - Vjsilva - 10-03-2016, 01:56 AM
RE: hp67 82004A reserve power pack - Sadsilence - 06-19-2015 08:40 AM
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