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HP82143A Printer, HP82033A pack, HP 820XXX Charger
Message #1 Posted by Guillermo Castarés on 4 June 1999, 6:19 p.m.

Few days ago I bought a HP82143A printer. It came with an old HP82033A battery pack, but without charger and without manuals. I measured the pack with a tester and it showed 0.00 Volts.

After I got some info, I took the risk of make a charger by myself. The transformer I used have this nominal values: 220V (the voltage here in Argentina), 9V AC. 500 mA. Connected without load it shows 10.0 V

Then I connected it to the printer (with the old pack inside) and when I measured the charger voltage, it showed about 3 V. ! I disconnected it, but maybe later. First question: Could it damage the printer ?

Then I took the old pack out and connected my charger again. With the printer OFF it measured 10.0 V AC, and the battery contacts measured 0 V. With the printer ON it measured ~8.5 V AC, and the battery contacts measured ~6.5 V DC. Second question: Is it Ok? Seems that it will not charge the battery if printer is OFF. Is this the normal condition or I damaged the printer?

After that, I decided to make a totally new pack. I made it with four new Ni-Cd 1700 mAh sub-C cells. Once my new pack was ready, it measured 4.8 volts without load.

I drop the new pack on the printer and tried a little printout. It worked Ok.

Then I connected my charger and turned the printer ON to charge the pack for the very first time. The charger measured 7.0 V. AC. I left it 8 hours and after that, the charger measured 6.5 V AC. I disconnected the charger, took the pack out of the printer, just to realize that it was really HOT (It was not possible to hold it firmly in your hand without get hurt ) . Part of the plastic cover of the cells was melted (I saw that original pack have paper cover instead of plastic cover). The pack measured now 5.11 V. without load. The printer worked still Ok on this battery pack. Third question: Is this high temperature normal ? Could this high temperature damage the cells? Or, What is wrong ?

As you can see, my knowledge about batteries, chargers and regulators is very limited. Anyway I guess the regulator was burned out when I connected the charger with the old pack, and then the damaged regulator couldn't operate properly with the new pack. What do you think ?

Thanks in advance, Guillermo Castarés.

Re: HP82143A Printer, HP82033A pack, HP 820XXX Charger
Message #2 Posted by Steve on 6 June 1999, 12:01 a.m.,
in response to message #1 by Guillermo Castarés

The appropriate charger for OZ (where I am) is HP80068B. It is rated at 8VAC 3W (375mA approx). My particular model reads 12VAC with no load.

I would not expect that a 9VAC transformer would cause any significant problems.

I am not certain what the charger circuit is, but I'm told it's not to clever.

I'm charging a rebuilt pack from scratch now, and if it gets hot I'll tell you.

If I can manage it I'll insert a thermocouple into the battery compartment and give regular readings of temperature...

Re: HP82143A Printer, HP82033A pack, HP 820XXX Charger
Message #3 Posted by Steve on 6 June 1999, 12:25 a.m.,
in response to message #2 by Steve

I just managed to insert a thermocouple into the battery pack pressed against one of the cells.

They have only been charging for 15 minutes and their temperature is close to ambient (maybe 2C higher).

The ambient temperature measured by the thermocouple was 18.1C, and is presently reading 19.7C.

I just checked and both the internal and external sensors are now reading 18.2C (my handling probably warmed the pack)

I did notice that a section of the Cassette drive near the front left corner was distinctly warm. This must be where the "regulator" is (I am told it is just a resistor)

If I notice any significant rise above ambient I'll write back...

BTW temperature rise may also be dependant on the type of NiCad. There are several types made, ranging from those designed to be rapid charged/discharged to those designed to be float charged for standby purposes. They have different characteristics and tolerance for temperature, overcharge, and capacity.

Rapid charge nicads do NOT respond well to overcharge.

Temp increaces above ambient for first 4 hours of charging
Message #4 Posted by Steve on 6 June 1999, 4:22 a.m.,
in response to message #2 by Steve

Ambient temperature has been between 18.1 and 18.4 degrees

Battery pack temperature during charging:

After 1 hour ~1 C above ambient After 2 hours ~2 C above ambient After 3 hours ~2.7 C above ambient After 4 hours ~3 C above ambient

I'm not expecting the battery pack to get too hot to handle any time soon :-)

By far the hottest thing is the charger. Another digital thermometer reports 24.5 C at the vents on the outside of the charger (The probe is too large to get into the charger)

The probe inside the battery pack is smaller, but I'm not going to poke that about inside the charger.

WOW! after 9 hours
Message #5 Posted by Steve on 6 June 1999, 9:05 a.m.,
in response to message #2 by Steve

I am somewhat surprised. After 9 hours (I went out for dinner, so no results for the last few hours)

External temperature (ambient) 18.4 C Battery Pack Temperature 34.8 C

Thats a 16.4 C rise above ambient!

could get interesting over the next couple of hours (I was planning on charging for 14 hours)

The charger is still at 23.4 so it's not dissipating significantly more power, and the side of the drive is no warmer than before (although the whole unit is a little warmer than ambient now)

The outside of the battery cover does not feel warmer than the rest of the case, so without the thermocouple in there I would not have been aware of the temperature rise.

After 12 hours (and it's time for bed)
Message #6 Posted by Steve on 6 June 1999, 12:20 p.m.,
in response to message #2 by Steve

Battery 37.8 C Ambient 18.0 C Rise above ambient 19.8 C

Voltage (unloaded) 5.67V (~1.42V/Cell)

The pack is warm to touch, but not warmer than I hope my bed is :-)

Certianly no melting plastic bits (I slipped the paper tubes around the cells, then put this inside the plastic)

I just measured the cell temperatures again (I may have repositioned the thermocouple into better contact with the cells after takink it out and masuring the voltage)

The cells are now at 40.9 C, a 22.9 C increace above ambient.

Re: HP82143A Printer, HP82033A pack, HP 820XXX Charger
Message #7 Posted by Dan Grelinger on 6 June 1999, 12:38 p.m.,
in response to message #1 by Guillermo Castarés

Steve gave the correct capacity of the original charger. 8 Volts AC, 375 mA. The extra volt on your homemade charger is probably not a concern, but the extra 125mA may be.

During the time that Ni-Cd batteries are recharging, the power input into them is converted to chemical energy and stored in the battery for later use. Once the battery is fully charged, the power input is converted to heat. Since your new battery pac was probably fairly well charged to begin with (4.8 volts), they quickly reached full charge, and then began dissapating the input power as heat, which is why they got hot. And no, this is not good for them. The electrolite is subject to evaporation and possibly boiling.

Steve's batteries had several hours of charging before they got fully charged and started dissapating the energy as heat.

The standard charger has a power output limit of 3 watts, you charger has a output limit of 4.5 watts. This is 50% higher than normal, which explains why your battery go so much hotter than normal (Steve's).

By the way, the charging circuit is supposed to charge the batteries even if the power is switched off. You should check this again to be certain of the measurement.

In summary, you should probably get the original charger for this printer.

Re: HP82143A Printer, HP82033A pack, HP 820XXX Charger
Message #8 Posted by Guillermo Castarés on 6 June 1999, 8:39 p.m.,
in response to message #1 by Guillermo Castarés

Thanks Steve and Dan for your time and information.

I have just opened the printer (an easy task to do), and I saw that the biggest resistor have one end unsoldered, so the circuit is open there!

I'll bring the printer to someone with good electronic skills, to know what else could be damaged and if it is possible to repair it.

I can use the printer charging the battery pack with an external charger, but what I really want is to have my HP items full working.

Re: HP82143A Printer, HP82033A pack, HP 820XXX Charger
Message #9 Posted by Steve on 6 June 1999, 11:59 p.m.,
in response to message #8 by Guillermo Castarés

From what you describe, it seems possible that someone has modified the printer to work with a dead battery pack by removing the resistor that limits the charge current and (probably) replacing it with a link somewhere.

That would result (probably) in far higher charge currents (that would heat the nicads and result in the reduced voltage you saw on the output of the transformer)

If you have any problems you might be able to convince someone with a printer to opern it up and see how things are usually connected. Unfortunatly that person would not be me because I have no printer :-(

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