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So, I want to be able to hotswap batteries in my thinkpad. My idea was to use a supercapacitor; I only need enough time to pull one battery out and put in another.

Are there any immediate issues with this? Some problems I can think of are:
- space and properly packing away wires
- on linux, how will the acpi stuff react when there's no AC power AND no battery? will it just say "unknown power source" or will it cause other issues?
- safety issues? I know some tantalum capacitors will quickly catch fire if you exceed their acceptable voltage, but I don't know about the materials used in supercaps
- do I need to worry about voltage spikes on V+ when I plug in AC power?

If supercaps aren't viable I'll probably just use a small lipo & trivial charging circuit, but that has its own issues.


Ever thought about connecting battery to charger jack? its much simpler than hotswapping.


How would I guarantee that the backup battery on the charger doesn't get drained first? When you unplug the computer, it will still think AC is in because of the battery, and will start draining the backup.

Also, an extra battery strapped to the side will add a lot more weight than a simple supercap setup. I carry this thing around a lot, that''s why I want to hotswap batteries.


> when there's no AC power AND no battery

your computer is in the "off" state.


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I mean if I had a supercapacitor in there. I guess it comes down to how the computer detects if there's AC -- if it's by voltage, then the computer will think the supercap is just the AC power. If it's a mechanical contact in the barrel jack or something like that, thenthat's where I'm not sure what the ACPI stuff will do.


You drain the charger baterry first. The on inside laptop IS backup.

For supercap, you would need DC-DC converter, where would you stick it?


That's a good point, I'd mount it to top of the lid -- but at this point it makes more sense to use another battery. For some reason I thought there were compact 20+V supercaps, but of course that doesn't make much sense.

I guess I could grab a broken motherboard off of ebay and salvage the charging circuit and battery slot from that, and mount them to the lid.


Newer thinkpads already have hotswap batteries. I keep one in my t460 and one in my bag
>inb4 newer thinkpad = garbage


Yeah, I know newer ones have internal batteries that let you do that. Unfortunately I'm poor as dirt and can only afford a t400.

Guess I'm looking forward to 2020 when current thinkpads drop to that price...


Instead of a complicated setup, Why not just jury-rig a second battery adapter so you can plug the second battery in before taking the first battery out?


my x41 has 2 batts - 1 underside and the main one - I only engage the underside batt to enable me to hot swap out the main batt. I dont think they do that any more - maybe a 2.5" drive bay batt?