PB170
Well-known member
Hi all,
I need a new battery for my PowerBook…
Short background (feel free to skip):
I built two batteries for my PowerBook 170 back in 2017 (briefly documented in this thread here and here) that I've been using regularly since then. However, all of a sudden at the end of 2020, they both went from working just fine to not being able to power the computer at all, unless all power saving features were set to the absolute minimum, and barely even then. At first I suspected something was wrong with either the PowerBook or the charger I'm using since it seemed unlikely that both batteries would fail at the same time, but after some testing that indeed appears to be the case.
When I built the batteries, I did a ton of research into NiMH battery technology to get the best use out of them, and I've been charging them at 0.1C and cycling them between 0–100% continuously. They both only had about 50 charge cycles each when they failed, so they should still have had plenty of use left. I suspect the problems might be due to internal crystallization. During the first half of 2021 I tried the best I could to revive them without taking them apart but didn't have much success and eventually gave up.
So I've been tethered to the wall ever since, which is starting to feel increasingly limiting since I often use my PowerBook when I'm out and about. It would be great to have it back running on batteries again now that summer is on its way, and avoid having to hunt for power outlets at cafés etc.
Meat of the matter:
When I was preparing to build the batteries in 2017 and considered different battery options, I quickly ruled out lithium based batteries because of the safety risks involved and went for gen 2 NiMh instead. They've served me well, giving me about 4–5 hours of use on average (more than double the capacity of the original batteries!). At this point however, it feels very tempting to leave the long charging times and the 0–100% charging schedule behind and go for the more convenient usage properties and energy density of lithium based batteries instead.
I enjoy tinkering, and it was a fun project to plan/design and build the two batteries back in 2017, but this time around I would very much just want to buy an off-the-shelf battery, if such an option existed. So I'm looking for the easiest possible path to a lithium based battery. At this point I'm contemplating taking a suitable USB power bank and build from that, should that turn out to be a realistic option. One challenge would be to find one with battery cells and circuity that will fit inside the PowerBook battery cases.
To begin with, these are my requirements:
Lithium Polymer battery for PB100 (and maybe portable)
PB 1[4-8][0,5]c? Li-ion Battery
I also watched this video (YouTube: How Does A Power Bank Work?) that I stumbled across, and briefly looked at a couple of other sources covering the basic circuity of USB power banks.
A couple of questions:
Would be happy to hear your thoughts. To recap, my priorities here are 1) safety and 2) the easiest/quickest possible solution
Sorry about the long post
I need a new battery for my PowerBook…
Short background (feel free to skip):
I built two batteries for my PowerBook 170 back in 2017 (briefly documented in this thread here and here) that I've been using regularly since then. However, all of a sudden at the end of 2020, they both went from working just fine to not being able to power the computer at all, unless all power saving features were set to the absolute minimum, and barely even then. At first I suspected something was wrong with either the PowerBook or the charger I'm using since it seemed unlikely that both batteries would fail at the same time, but after some testing that indeed appears to be the case.
When I built the batteries, I did a ton of research into NiMH battery technology to get the best use out of them, and I've been charging them at 0.1C and cycling them between 0–100% continuously. They both only had about 50 charge cycles each when they failed, so they should still have had plenty of use left. I suspect the problems might be due to internal crystallization. During the first half of 2021 I tried the best I could to revive them without taking them apart but didn't have much success and eventually gave up.
So I've been tethered to the wall ever since, which is starting to feel increasingly limiting since I often use my PowerBook when I'm out and about. It would be great to have it back running on batteries again now that summer is on its way, and avoid having to hunt for power outlets at cafés etc.
Meat of the matter:
When I was preparing to build the batteries in 2017 and considered different battery options, I quickly ruled out lithium based batteries because of the safety risks involved and went for gen 2 NiMh instead. They've served me well, giving me about 4–5 hours of use on average (more than double the capacity of the original batteries!). At this point however, it feels very tempting to leave the long charging times and the 0–100% charging schedule behind and go for the more convenient usage properties and energy density of lithium based batteries instead.
I enjoy tinkering, and it was a fun project to plan/design and build the two batteries back in 2017, but this time around I would very much just want to buy an off-the-shelf battery, if such an option existed. So I'm looking for the easiest possible path to a lithium based battery. At this point I'm contemplating taking a suitable USB power bank and build from that, should that turn out to be a realistic option. One challenge would be to find one with battery cells and circuity that will fit inside the PowerBook battery cases.
To begin with, these are my requirements:
- At least the same capacity as my first batteries (31.5 Wh), but preferably at least 50 Wh or more (I guess LiPo pouch-style batteries would be the given choice here)
- Able to use it safely in my PowerBook with the AC adapter connected, but with the actual charging taking place outside of the computer through a separate port (already in my first version of the batteries)
- Unregulated power so that the the PowerBook's power management will work correctly
Lithium Polymer battery for PB100 (and maybe portable)
PB 1[4-8][0,5]c? Li-ion Battery
I also watched this video (YouTube: How Does A Power Bank Work?) that I stumbled across, and briefly looked at a couple of other sources covering the basic circuity of USB power banks.
A couple of questions:
- Do you think using a power bank would be a good and safe starting point?
- Is it possible to safely and easily modify the circuity of USB power banks so that they output unregulated power at circa 7 V (preferably ≈6.95…5.85 V so that the PowerBook's battery management works correctly) rather than the, presumably, regulated 5 V? If not, would it be easy to bypass just the regulating circuity and add a separate boost/buck converter? Any recommendations on a suitable chip/circuit for that in that case?
- Unless power banks are already protected from current going the wrong way, is it possible and efficient to protect the output with a diode or some other solution? Any recommendations on a suitable part in that case?
Would be happy to hear your thoughts. To recap, my priorities here are 1) safety and 2) the easiest/quickest possible solution
Sorry about the long post
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