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360alaska

Lithium Polymer battery for PB100 (and maybe portable)

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Those 1200 mah are just for testing purposes, Once I complete the design I can use much bigger cells, but obviously they will take longer to charge.

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While I'm waiting for my custom pbcs and correct batteries for my pb100 battery, here is a test unit I made to fit in my portable, it seems to work well enough, it will switch into charge mode when the charger is connected and switch into operation when the charger is disconnected, the only problem is that the computer will reset, this is like due to the relay not switching fast enough. That would mean that unless I can find an electrical solution, one would have to reboot the computer to disconnect from the charger, not a bad compromise for having a working pb100 battery. 

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Here is the completed prototype, it will probably be 90% of the full design. It will also have a cover. I discovered through use that only one diode should be used. So I've made that adjustment. I've also got a faster acting relay on the way and I'm considering replacing LM 358 with LM393 which will require a slight redesign to accommodate LM393's open collector output.

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That's an impressive bit of work, and so clean too. Is it possible to use a giant capacitor to keep things alive while the switchover happens, or is the relay just super-duper slow?

Edited by ravuya

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It's probably possible to do that. I've also thought of incorporating a mosfet or transistor somehow. The old relay part "TX2-5v" has a 4ms release. The new one "EC2-5NU" has a 2ms release. I doubt that will make a difference at all but who knows. I'd like to fix that but I really don't see it as a major detractor given that there essentially are no other options for this little laptop. Right now if it's running and you yank the charger it resets.

Edited by 360alaska

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How trivial do you think this would be to adapt to other PowerBooks?

 

I would think that, now that you've mostly come up with the design, it could be used as a reference for other similar designs targeting models such as the 14x/150/170 and 500 series.

 

They all use NiCd or NiMH as opposed to SLA, but I wouldn't think it would require much of a change to adapt your design?

 

Nevertheless, this is a fantastic development, and if I had a PowerBook 100, I'd totally want to get one of these once you've finished it!

 

c

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8 hours ago, just.in.time said:

I know the 500 and 190/5300 NiMH packs also had their own “intelligence” on board the batteries.

Oh yeah, I forgot about that.  Has anyone been able to reverse engineer that "intelligence"?

 

c

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On 8/29/2020 at 2:02 PM, CC_333 said:

Oh yeah, I forgot about that.  Has anyone been able to reverse engineer that "intelligence"?

 

c

Having that intelligence offloaded to the battery itself is actually to our benefit. That way your not fighting against the internal charge controller when changing battery chemistry types and using your own BMS. 

 

Yea, it needs reverse engineered, and then a new BMS made that has the "smart" features built into its microcontroller 

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@techknight OK, that makes sense, because the BMS in the battery can be modified to basically look like whatever the computer expects, regardless of the actually chemistry of the cells.

 

I'm sure someone can reverse engineer the 5xx battery easily enough.  I mean, all kinds of things have been successfully re-implemented that were once thought to be prohibitively difficult to reverse engineer (Custom ROM SIMMs!  FloppyEmu!  SCSI2SD!  And now even a complete clone of the entire SE logic board!), so why would this be any different?

 

c

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Today I tested the voltage curve. I wanted to make sure the laptop would display a low power message before the BMS cuts off. I ran it for about 3 hours of mixed use and got a low battery notice I ran it for about 30 minutes between low power and critical power and the laptop was still going strong. My final design incorporates 3600 MAH batteries, the original battery had a 2500 mah battery good for 2.5 hours so I figure my lithium battery should be good for about 3.6 hours.

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Edited by 360alaska

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On 8/28/2020 at 5:45 AM, 360alaska said:

It's probably possible to do that. I've also thought of incorporating a mosfet or transistor somehow. The old relay part "TX2-5v" has a 4ms release. The new one "EC2-5NU" has a 2ms release. I doubt that will make a difference at all but who knows. I'd like to fix that but I really don't see it as a major detractor given that there essentially are no other options for this little laptop. Right now if it's running and you yank the charger it resets.

If you are doing switching with this relay from charge to discharge, vice versa. this really needs to be a series pass transistor set to do this. 

 

Case in point: I made a dual-port BMS for 24v. Charge comes in on a different port (solar applications). for LiFEPo4. This one is loosely based on a chinese version which when my supplier started screwing up the parts that were being assembled onto the board, I had to take matters into my own hands and study its design plus engineer a new one. This one even does cell balancing as well. 

 

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Edited by techknight

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It's not that simple,

 

There simply is not enough voltage to charge the pack as a 2S so the relay switches the battery between 2S and 2x 1S for charging purposes. During operation cell 1's negative is connected to cell 2's positive but during charging cell 1's negative is connect to ground and cell 2's positive is only connected to the charger. The relay is connect to a comparitor which compares battery voltage to the voltage of the charge and energizes the relay whenever the charger is connected.

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Thats kind of oddball.... That leaves alot of room for error because the computer cant really use the battery pack as a part of the load if the AC Adatper gets weak. Not to mention switching. 

 

I would say use a boost converter, but we would need a clear way to tell if your into charge mode or not. Since, the load and charge are on the same terminals. could create this weird feedback scenario. 

Edited by techknight

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14 hours ago, techknight said:

Thats kind of oddball.... That leaves alot of room for error because the computer cant really use the battery pack as a part of the load if the AC Adatper gets weak. Not to mention switching. 

 

I would say use a boost converter, but we would need a clear way to tell if your into charge mode or not. Since, the load and charge are on the same terminals. could create this weird feedback scenario. 

Exactly! This is the only way I know how to make it work, but for a computer model that has not had any working batteries for sale in quite a while it's probably not a big deal to have to shut down before disconnecting, if you don't it's not like the computer is damaged or anything. Maybe I can use a small supercap, but how would I isolate it from the comparitor? I've thought about connecting an AND gate to the Status pins on each charger so the relay will open when both chargers give the signal but this battery is good enough.

Edited by 360alaska

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Well as long as it works properly and there are no ill-side effects, then its fine I suppose. 

 

I dont use my portable machines enough to warrant replacement batteries, at least not yet. Only functional batteries I have left are my Portable batteries, and I just float them every few months so they dont go bad, I havent used any of the machines for a few years now. 

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On 9/5/2020 at 11:48 AM, Fizzbinn said:

https://www.ebay.com/itm/313208553687

 

I think I get to be your first eBay buyer! Looking forward to having a PowerBook I can run off battery! (Let alone my PB100 that I’ve spent a lot of time restoring)

 

I guess so and thank you for that! It's nice to get some funding for research!

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Got my PB 100 battery from @360alaska this weekend and after replacing a failed fuse he helped me identify (that I didn’t realize was bad) I’m wire free on a 30 year old laptop! So cool!
 

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Very cool! I developed something similar for my Duo (separate thread over in the PowerBook forum), but although that platform has some of its own unique challenges (ID chips, current regulated charging algorithms, etc.), one critical factor made the single port charge / discharge steering easier than what you've overcome here: When plugged into the charger, the Duo's battery terminals see ~20vdc, which gets pulled down by a NiMh when inserted. That allowed for simple diode steering into a battery-internal Li-Ion 3S CC/CV charger (which requires a source voltage over ~13.5vdc to engage) when plugged into AC, but it isn't engaged by the battery alone when it's discharging and AC is unplugged. I have a functional 18650-based pack, but am not nearly brave enough to try selling them :)

 

I'm now in the process of developing a 2S pack with its own power-path steering circuity for my PowerBook 180c, and while in some ways its characteristics are more conducive (7.5vdc OE charged voltage is a great fit for a 2S Li-Ion's 7.4vdc), the single port charge / discharge switching is more complicated. I'm using a 2S CC/CV charge board (similar to the 3S part I used in the Duo pack), but with only 7.5vdc from the wall charger, a boost converter is necessary in this application (or a split as you've done, very creative!) I can't just let the Li-Ion cells / BMS back feed into the boost converter, and with a common charge / discharge port, some sort of sensing / switching is necessary to prevent that (as you're obviously well aware).

 

Ingenious approach with the split cells, comparator, and electro-mechanical relay. Love seeing resto-mod projects like this leveraging modern tech to augment these old 68Ks :) In my case, I'm planning to use an LT1494 (or similar) current-sensing opamp to drive the gate on a FET powering the internal boost converter / 2S charger only if current is flowing into to pack. Bench testing currently on-going with a thread to follow if it goes anywhere... 

 

Edited by sutekh

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Thank you for your encouragement! There was a bit of trial and error and research involved. I'm going to try and use the other half of the comparitor to release the relay when both charging ICs signal complete.

Edited by 360alaska

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