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Jornada 820 battery repair experiments

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kiwa Page Icon Posted 2021-03-08 2:26 AM
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Hi, just recovered this account and a friend (Karpour) told me to post this here.



a couple of days ago i got a Jornada 820, thankfully it was working except for the battery, that was reporting the "can't communicate" error, when i took it apart it was already leaked, but not badly, so i took the cells out and replaced them with two nokia batteries with their own controller removed.

Original battery:


Experimental battery:



i guess at this point i have to give the disclaimer of playing with lithium batteries can be dangerous, so this is not a guide, but just to share the experiment, but I'm dumb so i kept going.

so doing this did nothing, the controller still indicated comunication errors and i didn't get any voltage on the pins, so i have two issues to fix.


i repaired the no voltage on the pins by reading datasheets, i noticed it had a really fancy fuse meant to protect the overcharge of the cells, this was blown.





it's supposed to have continuity between the two top pins (and not the middle one), i had nothing, so i just bridged this with a wire (dangerous) and yeah, i got 7.4ish Volts on the output, plugging this back on the device got it running without external power! nice, but still, no communications and that means no charge and the annoying popup.

what i did now was kinda a coincidence, i found the linux for the 820 website Link copied the loader and the kernel to my cf card and booted, pretty fast, interesting but yeah, old linux.

i did this with the external power plugged and the battery, i rebooted the machine (issuing the reboot command) and after that i got windows ce again, no display, so i did a reset, that helped with the screen, i bypassed the welcome screen and restored a backup, and that's when i noticed that the battery was actually reporting a charge!



i unplugged it and it started going down, nice, looks like it's reading fine that info, so i plugged it back and bam! red light on the battery and the status started to go up.



it got stuck there and the red light went away, looks like probably it's reading maybe incorrectly, the batteries are probably not balanced at all, or who knows what kinda other issue can be, so right now I'm at the point of discharging the device, i connected a wifi card, dialled the modem and the brightness is on max and right now it has been sitting for like 2 hours




So, at this point i need to do some more experimenting and see if first it's possible to replicate this scenario (disconnecting the cells and seeing if the controllers fails, repeat procedure to revive it) and second see if i can source the fuse to do a more permanent repair and lastly see if it needs more calibration, if the controller is doing balancing correctly, test for over/under discharging, and other stuff.

I'm also interested to know if maybe someone has done this before, so we can compare info


i will update this when i get more info

Thanks for the space and I'm reading your comments.
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Mjolnir Page Icon Posted 2021-03-08 12:07 PM
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Nice! Please keep us informed of your experiments. If you want to play around with the linux install I added a 'userland' to the Fare' group kernel here: https://www.hpcfactor.com/forums/forums/thread-view.asp?tid=17185&po...
Still 'old' linux but fun. The Jornada '720' boys have a more current linux install going if you happen to also have one of those devices.

Edited by Mjolnir 2021-03-08 12:11 PM
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Karpour Page Icon Posted 2021-03-08 1:50 PM
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This is amazing, in all my years I have seen several attempts of people to re-cell a Jornada 820 battery, but no one succeeded. I always wondered if the fuse was internal in some IC or just a part on the PCB that could possibly be bypassed or replaced.

Finding a replacement for the fuse, as well as compatible batteries could breathe new life into many Jornada 820s!
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CE Geek Page Icon Posted 2021-03-08 6:01 PM
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If the solution is Nokia cell phone batteries, that's huge since they're still easy to locate online. I was able to hook up a BL-4C from one of my old Nokia phones to a Casio BE-300 which then charged properly through the motherboard and provided similar length of use on a full charge to the stock BE-300 battery. The battery just fits inside the space for the device's battery, but unfortunately it's just a little too wide to allow room to put the battery cover back on. (People in the BE-300 community found that the Konica/Minolta NP-200 camera battery fits just fine.)
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jamesaaron Page Icon Posted 2021-10-19 7:08 AM
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Piggy backing on this awesome thread, here's an album of photos of my Jornada 820 Battery Pack: https://www.flickr.com/photos/stegall/albums/72157720037157458/with/...

I ordered a couple of the Nokia BL-4D batteries from Amazon and I'm going to experiment with them, but as you can see from some photos, I've also got a single 3.7v, 2200mah battery from another project that fits very well. I could pick up a second of those batteries and experiment as well.

One thing I'm wondering is if it would possible to go with a different charge controller board altogether? I know I've seen them for other handheld projects, but can't seem to google the right terms to find an example for 7.2v.

I'll post more when my batteries arrive and I attempt to replicate Kiwa's experiments.
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jamesaaron Page Icon Posted 2021-10-25 10:58 PM
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My Nokia 3.7v batteries came this weekend. I also ordered some rosin-core extra-fine solder which I had read would make the battery work easier (I wish I had discovered this sooner. It's by far the easiest electronics soldering I've done using the new solder).

Got extension wires added to the batteries and then set up in parallel to get 7.2 volts. Then I soldered a bridge on the thermal fuse that Kiwa mentioned. I had 7.2v across the circuit. What was difficult to tell from Kiwa's photos is how they wired the BA1 battery connector in the middle of the charging board. Are both the pos/neg leads from both batteries soldered to that?



I'm also not sure about the voltage I should be reading at the terminal connector into the 820. It appears to be back to 3.2 there. The Jornada wouldn't start with the setup connected, so I think it's definitely not getting enough juice.

One issue with the setup was that it was getting hot. This section on the bottom of the board was too hot to touch:



Edited by jamesaaron 2021-10-25 11:03 PM
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hassilon Page Icon Posted 2023-09-05 12:44 AM
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I would just like to say I, too, have failed to repair a Jornada 820 battery. I got about as far as kiwa: the j280 will run from the recelled battery, but it will not charge it.

Tried booting linux as suggested by kiwa, and a charging icon appeared in the tray after getting back to WinCE. But I still get error popups about not being able to communicate with the battery and the battery status remains at 0 percent.

I'm using 2 2000mah 3.7V batteries I had lying around to test. Might have bought bigger batteries if this had worked.

If you do not jumper the fuse, the j820 does not see the battery at all. With the fuse jumpered, it gets power from the battery but will not charge.

btw, the wiring photos posted by jamesaaron are wired wrong: do not follow his wiring if you attempt this. If you check the pack with a multimeter before tearing the batteries out, you can see that BA2 should be connected to a negative battery terminal. (Even if the batteries are completely trashed, there's usually a few mV left. Try both ways and you can see if there's a minus sign to indicate you have the meter's leads reversed.)

I can post correct connections if anyone still cares....
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AximUser Page Icon Posted 2023-09-05 3:19 AM
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Why not ping the EEVBlog repair section for ideas? There are some great engineers there that like helping out hobbyists. The flickr link of jamesaaron has a ton of helpful photos making it easier to post.

https://www.eevblog.com/forum/repair/

I don't like bypassing the fuse. Diagnose and Replace.

Some modern devices typically have several layers of protection (on the circuit board plus "backup" protection attached to the cell). Plus physical protection. I don't know how HP did it back in the day.

Karpour - 2021-03-08 1:50 PM
I always wondered if the fuse was internal in some IC or just a part on the PCB that could possibly be bypassed or replaced.

Finding a replacement for the fuse, as well as compatible batteries could breathe new life into many Jornada 820s!

Ekriirke replaced the 5A fuse and shows what a blown one looks like inside

To rebuild his Jornada battery pack, he removed 2 failed cells. So his Jornada runs just on 2 OEM cells now (half capacity). This might be a short-term option for some. Here are a few of his repair photos
https://imgur.com/gallery/isQjbsE

Edited by AximUser 2023-09-05 3:21 AM
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hassilon Page Icon Posted 2023-09-05 6:48 PM
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I took apart a second battery and this one seems to be charging properly with the fuse jumpered. Charged from 1 to 90 percent, light went from red to amber, and no excessive heat anywhere.

I think there is something else wrong in addition to the blown fuse with the first one .

Both Jornada battery packs had leaking batteries and melted tar-like glue all over the charging boards. I chose the one that looked less bad first; guess I was wrong.

Anyway, I probably will eventually replace the fuse. As soon as I figure out where to get one. (Radio Shack disappeared years ago and it seems like Adafruit and Sparkfun are most interested in hocking pretty colored LEDs....)


The batteries I used are "Maker Focus" 2000mah. I found a deal on a bunch of them on ebay a while back and have been putting them in Handspring Visor Prisms and Palm IIIc PDAs. I left the protection circuitry on the batteries and just cut off the JST connectors.

To add more amp hours--I currently only have 2000mah in there--you need to connect more batteries, in PARALLEL.

Edited by hassilon 2023-09-05 6:55 PM




(j820.png)



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hassilon Page Icon Posted 2023-09-06 4:25 PM
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Well, even with only the two 2000mah batteries, the run time is pretty good. I may not bother to add more batteries if it really goes 5+ hours.

I ran this thing for maybe 45 minutes before I remembered to install battery monitor. Was afraid it was stuck at 100 percent. The battery only started to drop from 100 after firing up XT-CE, connecting a USB mouse and inserting 2 storage cards as a stress test.

I keep getting this popup every half hour saying there is about 30 minutes left. Is this normal behavior when the battery has been replaced? Should I run it all the way down or just do what it asks and plug it in?

Not sure I believe the percentages.

The J820 has been running for a while:


Edited by hassilon 2023-09-06 4:28 PM




(IMG_20230906_105124.jpg)



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torch Page Icon Posted 2023-09-06 5:21 PM
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Nice work all around, by the way! That's amazing
hassilon - 2023-09-06 9:25 AM


I keep getting this popup every half hour saying there is about 30 minutes left. Is this normal behavior when the battery has been replaced? Should I run it all the way down or just do what it asks and plug it in?


I believe there's some kind of monitor "chip" inside the battery, for reporting the percentages, I wonder if the OS is detecting something different than what it expects, and that's why it keeps popping up a flagged message?
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AximUser Page Icon Posted 2023-09-06 6:29 PM
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hassilon - 2023-09-06 4:25 PM
Well, even with only the two 2000mah batteries, the run time is pretty good. I may not bother to add more batteries if it really goes 5+ hours.

Not sure I believe the percentages.

Great!

With the new batteries, will the Jornada run when plugged into mains too? Will it also charge?

Some laptops will learn battery life by fully charging/draining a few times. The new built-in protection circuits may confuse things a bit but I would not remove them.
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hassilon Page Icon Posted 2023-09-07 4:54 PM
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Seems to charge normally; runs fine plugged in or not, but for the spurious low battery warnings. They seem to happen most around 90-100 percent; once it is down to 50-80, the warnings stop. There is also some confusion about estimated time left: sometimes the Power control panel says 20 hours, sometimes 1 hour, sometimes it just doesn't say. The Power meter looks reasonably in agreement with common sense(goes up when plugged in, down while discharging) and the percents reported by Battery Monitor.

I'm just ignoring it and using Battery Monitor (available in SCL w/reg code) to keep track of the battery. It works better than the control panel. I measured about 5-6 hours of run time when the battery percent reached the mid 30s, which is reasonable. Maybe there's a registry edit I can do to stop the warnings.

It might be worth it to replace the batteries with two 4000mah batteries (8cm x 5cm x 0.8cm) to get up to the original battery life.

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AximUser Page Icon Posted 2023-09-07 8:38 PM
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Something like this should work back to CE 3.0. Maybe it helps get you started on 2.11
http://www.hjgode.de/wp/2011/03/05/windows-mobile-disable-low-batte...

I don't think StopPowerNotifications is on point but it was used on newer devices in any case.
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hassilon Page Icon Posted 2023-09-12 4:53 PM
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I decided to try a pair of 4000mah batteries in this pack to see if it made any difference. It made no difference at all: you still get 30-minutes-left warnings now and then. The battery percentage seems to be correct and charging behaves normally.

Then I decided to take a second look at my other battery, the one with the charging board that will not charge batteries. I gave it a bath in isopropanol, wiped off the glue and battery muck as well as I could, and let it dry out for a day. Well, it started working! It charges the batteries and reports time remaining but the battery percentage reading slowly drifts to 0, taking about minute after disconnecting the power even though the battery is fully charged. At 0, there are no low battery warnings and the 820 stays on with "20 to 21.5 hours left."

I think both of these charging boards were damaged when the original batteries started leaking and shorted out various parts. Both had blown fuses. One charging board has several ICs whose black plastic casing got so hot it cracked. That's the one with the bogus 30 minute warnings. The other seems to charge ok but is unable to tell WIn CE the battery percentage. I've tried both sets of batteries (2x 2000mah; 2x 4000mah) with both boards and it does not alter their behavior.

I can't try the battery packs in another Jornada 820, because I only have one that works.


I'm not sure how to apply the registry change above as it is for a much newer version of Win CE: I don't have a Notifications key in the reg.
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