hp67 82004A reserve power pack

[gfernval]

A quick question: when we remove the hp67 battery pack and put it
on a HP 82004A Reserve Power Pack (who is attached to an HP 82002A
transformer), what is the time to fully recharge the battery pack?
The hp67 manual states that the battery pack will be fully charged after 14 hours
if we connect the hp67 to a transformer. It is the same charger circuit the one of
the hp67 that with the HP 82004A Reserve Power Pack? Don´t have the instructions
of the HP 82004A Reserve Power Pack.
The original hp67 battery back is composed of 3 NiCd 700mA batteries.

thanks

[Dave Frederickson]

(06-18-2015 05:07 PM)gfernval Wrote:  A quick question: when we remove the hp67 battery pack and put it
on a HP 82004A Reserve Power Pack (who is attached to an HP 82002A
transformer), what is the time to fully recharge the battery pack?

It's unlikely that your original NiCd battery is still good. Replacement packs on eBay range from 1000 mAh to 3000 mAh so whatever charging time was originally published for 700 mAh batteries will need to be extrapolated. The other option is to monitor the charging current or the power with a Kill-A-Watt or equivalent.

I recently acquired a 82004A and am curious about the charging times myself. I'll conduct some tests this weekend and report back.

Incidentally, the charging time for a Topcat battery in an 82037A Reserve Power Pack is "about 6 hours".

Dave

[Katie Wasserman]

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.

NiMH cells are not as tolerant of overcharging and hence the HP calculator charging systems aren't the best for them but they still work and you should measure about 1.6 volts fully charged, but you really should never fully charge them to maximize their lifespan.

[Dave Frederickson]

I did some further investigation and this webpage came up. In addition, there's a sticker inside the compartment of my Power Pack with 55 mA written on it so apparently the previous owner measured the charging current.

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.

So with one of those 3000 mAh batteries on eBay, does that mean it would take over 68 hours to charge in the Power Pack?

Dave

[Katie Wasserman]

(06-19-2015 01:48 AM)Dave Frederickson Wrote:  So with one of those 3000 mAh batteries on eBay, does that mean it would take over 68 hours to charge in the Power Pack?

Dave

Yes. But my guess is that the 3000mAh rating is overstated, it's probably closer to 2000mAh.

[Sadsilence]

(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? Don´t have the instructions of the HP 82004A Reserve Power Pack.
The original hp67 battery back is composed of 3 NiCd 700mA batteries.

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.

NiMH cells are not as tolerant of overcharging and hence the HP calculator charging systems aren't the best for them but they still work and you should measure about 1.6 volts fully charged, but you really should never fully charge them to maximize their lifespan.

(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.

So with one of those 3000 mAh batteries on eBay, does that mean it would take over 68 hours to charge in the Power Pack?

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.

[Vjsilva]

Warning Will Robinson *** I purchased two of those so called 3000mAh NiMH packs for HP on ebay and less than 9 months later they turned into 300mAh packs (Seller ID: sarmatius).

I attempted to contact the seller to find out what was going on and he was silent to my queries. I tried to find out what kind of cells he used in his packs.

Anyway I took matters into my own hands and completely disassembled his packs and found BTY cells inside. A quick Google search yields universally unflattering comments regarding BTY cells.

One BTY cells weigh less than half of high quality Panasonic cells. I took his packs apart and used the materials to assemble a quality pack with Panasonic Eneloops. So from his packs I was able to salvage a few cents worth of brass jumpers and contacts.

I would steer clear of this guy's packs.

--Victor

(06-19-2015 02:34 AM)Katie Wasserman Wrote:  

(06-19-2015 01:48 AM)Dave Frederickson Wrote:  So with one of those 3000 mAh batteries on eBay, does that mean it would take over 68 hours to charge in the Power Pack?

Dave

Yes. But my guess is that the 3000mAh rating is overstated, it's probably closer to 2000mAh.