Rebuilding a Pismo battery

[gw280]

So I have a Pismo which had a completely busted battery. Taking it apart, three of the cells were leaking and pressing the charge indicator button wouldn't show any signs of life. Occasionally it'd show maybe 1 flashing light but most of the time it'd show nothing. The computer didn't recognise the battery either, I'd plug it in and it'd show the expansion bay as empty (except when it would show one flashing light, in which case it'd show a battery with a red X through it).

I took it apart and replaced the cells with Panasonic NCR18650 cells connected in the same configuration as the original ones. Before spot welding the cells together, I measured the voltage across each cell at around 3.15V. I'm seeing around 10V across the output pins and the battery actually powers the machine for a little while when I unplug the power. However, I cannot for the life of me get the machine to charge the battery.

I've tried a PMU reset using the button on the back of the machine, I've also tried booting into OpenFirmware and doing the reset-nvram, set-defaults, reset-all dance to no avail.

Does anyone have any experience with rebuilding these packs and know how to get them to charge after a cell swap?

 

[gw280]

Quick update: after some sleuthing I’m now reasonably sure the Pismo’s charger board is broken. OS X’s System Profiler shows the dreaded “AC adapter cannot charge battery: Yes” message, and says it’s a 26W power supply. I’ve ordered a replacement power board, and will tear the machine down tomorrow to see whether there’s anything visible going on. Hopefully it’s just a brittle solder joint that needs to be reflowed.

 

[gw280]

Replaced the DC input board and the charger board today. I'm reasonably sure it was just the DC input board but I ordered both anyway. The battery is now charging as it should, and I'll report back here with the results of the cell swap. My estimate is that it should have a working capacity of around 9000-10,000mAh, which would be a substantial upgrade from the OEM battery.

 

[desertrout]

Appreciate the updates

 

[gw280]

So after replacing the board, it showed a capacity of around 3800mAh, which is presumably what the old cells were at before the battery died. When I charged it, it hit "100%" relatively quickly, but continued to charge for several hours after that. I then ran a full discharge and a full charge again and now the battery is showing as 7600mAh - a little lower than I expected but still a huge improvement over OEM. With the screen brightness down and an SSD instead of a spinning HDD, I get around 7-9 hours of battery life.

One interesting source of information was this forum thread, where they identify the 26W charger issue and isolate it to a short-circuited zener diode on the DC input board: https://forums.macrumors.com/threads/blueberry-ibook-clamshell-1st-gen.2087119/. Testing the diode labelled DZ1 on my DC input board shows it as faulty, so I'm reasonably sure that's what happened in my case.

 

[beachycove]

7600mah is superb. I'd love to be able to do this myself. What kind of spot welder is right/ best for this sort of battery rebuilding work?

 

[gw280]

I used this one: https://www.amazon.com/dp/B08B4RJ58B?psc=1&ref=ppx_yo2_dt_b_product_details, and used these nickel strips: https://www.amazon.com/dp/B08RHP8NDD?psc=1&ref=ppx_yo2_dt_b_product_details

Be warned, this is a very very dangerous project, so be prepared for that. I made sure I had a fire extinguisher on hand for the entire duration and handled everything very carefully.

Here are some instructions I found very helpful for the project: http://fweb.wallawalla.edu/~frohro/Powerbook/Pismo/Battery/