X40 monster battery pack?

[phr]

I'm wondering how to externally power an X40 for ultra-long runtime, like 24 hours. What I really wish IBM would make is an extended battery base that looks like the X4 Ultrabase but has no drive slots or ports and instead is just packed with batteries. They do make an Ultrabase-like battery base, but it has just 4 cells inside, which is completely silly.

Anyway, the alternative seems to be an external pack, that plugs either into the regular AC adapter socket, or else into the Ultrabase connector. I suppose I'd consider hacking up my X4 Ultrabase for this purpose.

Ideally I'd like the external pack to use Sony-compatible camcorder batteries. The six-cell version (generic brand) is only $25-30 on ebay and two of them should be able to power the X40 for around 12 hours. That's a much lower cost per cell than the IBM packs ($100 for 4 cells or $150 for 8 cells). They all have basically the same 18650-type li ion cells inside, so the camcorder packs are over 3x as cost effective as the IBM packs.

It would be great to have an external box that had 4 hot swappable camcorder packs, sort of like the old Thinkpad 235 a/k/a Hitachi Visionbook Traveler. You could remove two of the four packs without having to shut off the computer, and swap in fresh ones. So you could run without power interruptions as long as you had a supply of charged packs.

Does anyone know how fussy the AC adapter input is to input voltage? Cell voltage of li ion packs does vary with the charge state, so the computer wouldn't be getting 15 regulated volts. Another problem with going in through the AC jack is the external pack would then be trying to charge up the internal pack, which isn't so great. Workarounds would be either remove the internal pack, or make sure the internal pack is fully (or almost fully) charged before plugging in the external pack.

[Nebelfelsen]

You can also watch out for an external battery on eBay and connect it to the power supply of the thinkpad.

Or just take more than one external battery with you and replace it on the fly with the one in the X4 Ultrabase (the X4 has a battery slot like the X3, hasn't it?). So you can extend the power on time of your thinkpad as long as you which. To charge the external batteries, there is an IBM battery charger available. IBM sells it for more than 150 $ but on eBay you can buy it for less than 30.

[JohnDrake]

If you do use some external power supply, funnel it through the IBM Auto/airline adapter...so if you feed it 12v (automobile current) it will be "adjusted" for you.

It might be better if you just get multiple extended batteries...