Jornada 820 Battery

Quote from Pete P:
"Make a pair of 2 parallel packs, each connected to a individual charge area. Ground the case to the common ground."

What do you mean by "connected to an individual charge area" ?

I have opened up the J820 battery pack. There are 4 cells inside. There is a black wire on one battery connected to the circuit board in the casing. The is another connection (metal strip) on the other end of the 4 cells, but there is a 3rd connection on the circuit board right in the middle. Any idea what that is or how I wire the batteries together to utilize this obviously essential piece of circuitry ?

I can get 4 batteries of 950mah each with red and black wires (same size as the original cells but only half as thick - and much lighter), and can wire them - but its that middle connector that is throwing me. But I think your quote above is probably the answer. But I don't know exactly what you mean.

Can anyone help ?

Thanks Richard.

Edited by lizsboy 2008-03-11 5:34 PM

I'm pretty sure the cells are charged in pairs (at 3.6V), but the two pairs are wired in series to supply 7.2V to the Jornada.

Didn't you buy four of them from him before? And as I recall, it was significantly less than the $70 Pete P's solution would cost.

Many thanks. I think that you are correct. So the middle terminal on the circuit board would be the common link between the two pairs. The batteries at the moment are on sale for just $9 a piece - 950mah, so in total with delivery only $57 for four. Interestingly because they are half the thickness of the original cells, there is enough room to put in 8 for a really extended performance. I am not sure I am willing to lay out over $100 however for something that just might not work.

Thanks for the input and if anyone else wants to add anything before I create a WinCe powered bomb, please let me know.

Thanks, Richard.

Okay, so I bottled it and have backed out of the repair idea for my battery. I have just purchased one from the following link:

http://prioritylaptopbattery.stores.yahoo.net/f1hpjo820and.html

However, I toyed with the idea of having it refilled for a little less cost, and increasing the capacity from the standard 3200 to 4400 mah. This second service looks good and the battery packs used would have been less than 1 month old. They say on their website that li-ion batteries last only 3 years before they become less effective - the oxidizing effect. Of course the new battery that I ordered might have been sitting on a shelf for a period of time. The refill service is at the following link:

http://www.batteryrebuild.com/laptops/hp/F1260-80068.phtml?gclid=CO-Hm-nrh5ICFSOCGgodIz1fEA

Well, it is done now. I will let you all know how it went.

Richard.

Yeah, the ones I got were significantly less than $70 - they were free samples for testing. (The actual price was mentioned in a previous post here, and yes, it was also a lot lower than $70.) Maybe Gordon will respond if he hears from more than one of us. You can try e-mailing him yourself and see what happens.

Well the Priority Batteries company came back and they are out of stock and do not know if they will be getting any more in. The Battery Refil company are quoting 4 to 5 weeks. So, if anyone is aware of the wiring details for the mysterious middle wire, then let me know. A DIY job might be back on the table.

Richard.

Apologies, did anyone come up with the wiring diagrams ?

Edited by lizsboy 2008-03-12 4:24 PM

I think I neglected to respond to this one: I'm pretty sure the red light did come on for me when I had completely dead cells installed. I haven't tried it with the cells removed.

Free is cool. But I'm willing to pay the price you mentioned earlier. I just sent an e-mail.

What ever happened to those samples, anyway? You had installed them, but they wouldn't charge, right? Did you do anything to test the PCB?

No, ledthrax offered to install them, so I sent the pack to him. He installed them fine, but neither of us was able to get them to charge. That's where he and I began to wonder if the real problem might be in the pack's PCB. Far from being an expert in electronics, I do not have a way to test the PCB.

Edited by CE Geek 2008-03-14 3:27 AM

I just tried it with the cells removed, and the red light does not come on.

I then connected (with alligator clips, not solder) a 2k Ohm resistor across the terminals, simulating a load for charging, and the red light came on.

Some battery PCBs will PERMANANTLY disconnect the batteries in the event of a catastrophic failure, IE disconnect of batteries :-D

There's permanent, and there's PERMANENT. Surely there's some sort of reset, eg, a hysteresis, and you just have to get a voltage above a threshold again to get it working again.

Permanent in this case means that the EEPROM or CMOS which stores the data about the cell's life (More likely CMOS or flash, perhaps) has been instructed "BATTERY DEATH: DISCONNECT". I cannot think of a way around it, without knowing more about the ICs on the board.

The board I found in my black proto Jornada battery was also a proto board :-P Hand soldered jumpers and wires everywhere. If somebody could provide a high-res scan of both sides, I bet we could all chip in and find which IC stores the battery information.

Or better yet, when swapping batteries, solder the new ones in parellel with the old ones, on long wires, remove the old batteries, solder the new ones in (again) with short wires, and then remove the long wires. No disconnects!!

Also, that was me "Wizzard1" as I could not recall if my login was my name or handle :-D

Edited by Pete P. 2008-08-28 9:25 PM