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Jornada 820 battery options

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Karpour Page Icon Posted 2018-05-17 10:00 PM
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Sooo, long ago I killed my Jornada 820 battery, by letting it sit uncharged for too long. No way to replace it, and no way I know of to fix it.

I really want to make it portable again though, so I was thinking of other options to replace the battery.
The easiest idea I could come up with was ripping out the guts of the stock battery, putting in AAA eneloops and hooking those up to a voltage regulator with a diode (to prevent the charging circuit from doing anything)

Is this something that could work or a really stupid idea? Is there any reason it wouldn't work? I don't know if there's any communication between the J820 and the battery, or if it's just the standard extra pin with a thermistor attached.
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CE Geek Page Icon Posted 2018-05-18 4:24 AM
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There've been a ton of threads on this very issue here. Search "Jornada 820 battery" in these forums and see.
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Karpour Page Icon Posted 2018-05-18 9:55 PM
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Lots of threads, but no solutions sadly! Sadly no one did an in depth analysis of how the circuitry inside the battery works and whether it might be possible to "reset" it, but my question was about whether it would be viable to completely ditch the guts of the stock battery and replace it with my own battery circuit.
While I've been working with embedded hardware for a while, i never really did anything with power supplies, so my knowledge there is limited.
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HPC:Fan Page Icon Posted 2018-05-18 10:54 PM
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Wouldn't be finding two similar batteries but in higher mah's and just replace them and allow the circuitry to do it's job?
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Karpour Page Icon Posted 2018-05-18 11:07 PM
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Well, according to previous threads, finding a matching battery is nearly impossible, and the circuit inside the battery pack permanently stops working once the battery voltage is under a threshold. So that would require figuring out how to reset that, if that's possible at all.
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HPC:Fan Page Icon Posted 2018-05-19 12:27 AM
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Well shoot, they have to make thing so complicated huh? What about just ripping out the internals of the battery pack and convert it to a standard AA compartment and use rechargeable AA's with their own charging station? Not a perfect solution, but you'd be able to use regular AA's too if you're ever out and a bout without the ability to charge it.
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C:Amie Page Icon Posted 2018-05-19 8:20 AM
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Karpour - 2018-05-18 11:07 PM

Well, according to previous threads, finding a matching battery is nearly impossible, and the circuit inside the battery pack permanently stops working once the battery voltage is under a threshold. So that would require figuring out how to reset that, if that's possible at all.
Does anyone have any insight, electrically, as to how you would get an electrical circuit to do that?
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Nuketank Page Icon Posted 2019-04-19 2:35 AM
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In my personal experience having rebuilt more than one battery, it's not actually the circuit DYING, so much as these old devices were not equipped with a "rescue" mode.
The REAL problem is a chicken-and-egg situation:
The safety circuit is blocking charging because the cells are undervolted. But the cells are undervolted because the safety circuit is blocking charge.

You SHOULD be able to wake it back up though by recharging the cells inside of the battery yourself.
TAKE EXTREME CARE if you want to do this.

Alternatively, you can replace the cells themselves manually. The only time I've had this fail on me was when I damaged the safety control board itself in a moment of inattention.
If you go this route, the best way to protect against damaging your safety circuit (especially if the J820 has a multi cell battery) is to connect the main power wires to the + and - of the assembled batteries first, and then connect the balance/detect wires to each cell once the circuit is powered up.

That said, because this is such an old computer, the safety circuit is likely doing nothing except playing interference between the computer and the cells themselves.
You can tell by if there are any narrow data pins going from the circuits to the connector that goes to the computer. If there are, this trick won't work - the computer will think there's a failure and refuse to recharge.

If ere AREN'T any data or sense lines present, you can bypass the safety system completely and direct-wire the battery's outputs to the terminals going to the computer, but you ARE taking your H/PC's proverbial life into your hands doing this. CLOSELY monitor the repaired computer during charging to make sure it's not going to overcharge and burn your house down, or worse, destroy your J820!
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C:Amie Page Icon Posted 2019-04-19 7:22 AM
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Like Nuketank says, anyone following this advice with Lithium Ion: be VERY careful.
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Rich Hawley Page Icon Posted 2019-04-19 2:15 PM
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AA batteries wouldn't work. The US103463 battery cells are 10.2mm in thickness while the smaller AAA batteries are 10.5mm thick. You could probably grind down a little of the plastic enclosure to make them work however.

If I were going to rebuild an 820 battery pack, I would probably use use CR10280 cells, about 10 of them wired in parallel. That would give you about 2000mAh capacity. I would remove the internal battery circuitry from the existing pack and disconnect everything except the ground and the positive feed line back to the Jornada. I would probably install a simple jack in the battery case to connection to an external charger, separate from the a/c adapter for the Jornada for charging purposes. That is assuming you buy the LION cells with the charging circuit end cap on them. If you buy straight cells, then some other overcharging method will be necessary.

I would probably have to make some registry changes so I didn't get low battery alerts, and certainly none of the applications that check battery power would work any longer, not that I care.

And you all keep talking about a "safety circuit" but in my experience all that these old battery packs had in them was a fusible diode that permanently blew once one of the cells died to keep from ruining your Jornada's a/c adapter and to keep the remaining cell from overcharging...but that is easy to test. Just hook up a multimeter to it and measure the reverse bias...if it's bad, you should be open in both directions. If that's the case, then just jump it. You won't have any protection afterwards...but...

I remember the fun I had when I made my own AAA adapter.
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Nuketank Page Icon Posted 2019-04-23 3:35 AM
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Rich Hawley - 2019-04-19 8:15 AM
And you all keep talking about a "safety circuit" but in my experience all that these old battery packs had in them was a fusible diode that permanently blew once one of the cells died to keep from ruining your Jornada's a/c adapter and to keep the remaining cell from overcharging...


Most of my experience is based in newer devices. It sounds like you've been inside one of these battery packs before, Rich, so I'll yield to you there.
My T5200 (vintage 1999) has a proper safety circuit in its battery, but it IS a ruggedized high end machine...
My Compaq H3630 PPC (similar vintage) has something more similar to what you were mentioning.

That said, reading the number there, the IEC cell code (if you can turn this into anything meaningful) is lCP10/34/63.
My Google Fu finds that size 103463 (the "US" isn't necessary) cells are a bit hard to find, only revealing wholesalers on a casual glance.
Maybe your Google Fu is better than mine. I hope it is. Good luck, Karpour. (Look for "Lithium Polymer 103463" or "lithium prismatic 103463" or something similar.)

(*Edit: Oops, typoed your name. Sorry dude.)

Edited by Nuketank 2019-04-23 3:38 AM
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Mjolnir Page Icon Posted 2019-04-23 1:12 PM
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I have no idea if any of these are compatible but they are the only 'close' search results for '103463' batteries I could find:

https://www.powerstream.com/liprism.htm
Rechargeable Prismatic Lithium Ion
H103463---10.3 x 33.7 x 63 (mm), 1700 mAh, 55 g

http://www.dmi-international.com/pages/Li-Ion-Prismatic.html
Li Ion Prismatic Batteries
Model # 103463S - 3.7v, 1850 - 1900 (mAh) , 10.0 × 33.7 × 63.8 (mm), 54.8g

https://www.smallbattery.company.org.uk/sbc_industrial_lithium_recha...
LIR103463
Li-Ion Prismatic Cell
3.7v, 1800 (mAh), 20~60 Internal Resistance (mOhm), 53.0g, 10 x 34 x 63 (mm)
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Rich Hawley Page Icon Posted 2019-04-23 4:30 PM
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I know it defeats the idea of being small and compact, but always thought it would be fun to 3D print a new bottom case half of my Mobilepro to be large enough to hold a bunch of LION batteries that I could externally charge and swap out like a flashlight. Make the case half tall enough to fit an 18650.

I didn't ever understand the "US" or other letter codes on batteries Nuketank.
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C:Amie Page Icon Posted 2019-04-23 6:54 PM
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Rich,

Why don't you download Sketchup free and give it a go. By the time you have a design, I'm sure someone will help you print it!
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Nuketank Page Icon Posted 2019-04-23 11:07 PM
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It's all cool, Rich. I had to look it all up to be able to interpret the code, lol.
So I'll help you learn how to read them!

The US is the manufacturer, in this case.
The number code is its dimensions in millimeters, in height/width/length format.
So applying this, the US103463 in the J820 is manufactured by a company that identifies itself as "US", is 10 millimeters tall, 34 mm wide, and 63 mm long.
Either a pouch (LiPo) or prismatic (the ones Mjolnir found) will fit in that space.
As for benefits, a Lipo is lighter and can fit a little more capacity.
A prismatic is a little more durable, both physically and electrically.
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