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Battery Status LED not showing after rebuilding Powerbook G3 Pismo battery

fergycool

fergycool

6502
I've just rebuilt the battery for my Powerbook G3 Pismo. I used a spot welder and spent a methodical day putting the new battery back together as i've never done anything like this before (outside on a fireproof table, with a bucket of sand and plenty of protective gear!).

It all went OK except when assembled and I pressed the button to show the status of the battery it shows nothing at all! It was working before in the battery, albeit just flashing a single LED.

The voltage across the battery leads is coming out at 10.3v. However, if I measure across pin 2 and 6 of the battery pack plug it shows 9.4v. Which seems a bit weird to me!

Since the battery is three sets of three 18650 in series that means each set of three cells is at 3.4v. That's not discharged so I would have thought I should be seeing at least one or two LEDS.

I'm guessing that I've broken the board at some point? Before I go any further does the sound about right? I'm a little out of my comfort zone here :-)

Thanks!
 
Well I decided to proceed anyway! Glad I did. After redoing a few connections as it did not lay flat, I got the battery pack mostly assembled. Held together with a few pieces of Kaptan tape on the outside (rather than burning my bridges and glueing it back). As soon as I slid (well pushed!) the battery pack in the first LED started flashing. The laptop refused to boot though. However, I then went to remove the battery and went and broke the lever! I had to slightly unscrew the laptop in order to remove it. Now the battery is out it will still flash when I press the status button. So I guess I "reset" the BMS of the battery and it is connected OK. Just need to rebuild the battery pack to fit better (...and get myself a new lever!).
 
...and after a repack the battery inserts OK and now charges, and after ten mins of charge it will run the Pismo for a little bit. But wary so far of leaving it charging for longer. But I guess I should relax a little now :)
 
Exciting that you got it working! I'm planning to do this myself at some point in the future.. did you follow a particular guide?
 
cgp said:
https://68kmla.org/bb/index.php?threads/rebuilding-a-pismo-battery.39033/#post-538043 is a thread with assorted contributions on this topic … including my own.
Click to expand...
That's the main thread I followed! Thanks for all that.

I would add that I really recommend the FNIRSI SWM-10 spot welder. This is a lovely piece of kit and both easy and a pleasure to use! It's available online in the UK from about £35/£40.

Also I watched videos of 18650 batteries on fire to suitably scare myself. I wore eye protection, kept a pair of heavy duty welding gloves nearby, and also a large metal box (old gas bottle locker from a boat) with a bucket of sand in order to dump something if it went off. I also did this outside on a covered bench that I have.
 
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However, after that rebuild I'm afraid I messed up and discharged the newly rebuilt battery too much and now it refuses to charge!

After repacking the battery I got it into the Pismo fine. I put it on charge for 30 mins then booted from it. But it when I removed the power it would only run for ten mins then power off. I guessed the battery still had the old capacity of the previous run down pack.

With a massive dose of hindsight I should have taken it slower and stopped here. I should have rebooted and recharged a few times before doing this. Just so I know it was working. But I am far too impatient and instead I messed up :-)

After googling I came across a [few posts](https://www.reddit.com/r/VintageApple/comments/1efvovu/freshly_rebuilt_pismo_battery_anyone/) that suggested fully charging the battery, then booting from a OSX Tiger installer DVD and running the battery down. The idea being if you fully discharge the battery pack below a certain voltage then it will reset the BMS's stored capacity. Since the powerbook will go to sleep when nearing the capacity of the previous battery pack using the OSX Installer will stop the Powerbook going to sleep.

This [post](https://forums.macrumors.com/threads/rebuilt-a-clamshell-ibook-g3-battery-battery-only-charges-for-12-minutes.2274217/) in particular said that the BMS of the battery pack will only reset when the voltage drops below 12v. This was for a Clamshell G3 which has 4 sets of 18650 in series - the PBG3 has 3 sets of 18650 so I reckoned that would be 3 x 3v = 9v.

Charging the battery took about five hours. I monitored the voltage and current (using "system_profiler SSPowerDataType" in a terminal). The batteries were already half charged when I fitted them, so it started from there at 11.4v/1.4A. After a few hours the voltage had raised to 12.3v and the current had dropped down to 0.5A. The last reading I took (just before it got to 100%) was 12.35V/0.351A. That's 4.1v per cell.
(I have readings every 30 mins or so if anybody is interested).

Once it was at 100% I allowed it to discharge until it turned off and it took about seven hours to do so.

However, now when I plug the charger back in it recognises the battery and powers the Powerbook, but it says the battery is not being charged. The voltage is at 9.5v.

At this stage I do not know what to do. Have I completely messed up? That would be a real shame as I enjoyed rebuilding that battery pack and really took my time with it :-)
 
I took the battery pack apart and checked the voltages. The three sets of batteries are each giving 3.1v. The overall voltage of the pack is 9.4. I'm guessing that the discharge is too deep and the BMS has locked the pack from being charged. Whoops! I'm guessing that even if I replace these nine (new!) batteries then it's still not going to work. Damm my impatience :)
 
On a whim I took the battery pack apart and desoldered the +ve lead, hoping to reset it! I left it for 30 mins or so. Then resoldered, assembled the pack and reinserted into the Powerbook. Whaddayaknow! The LED on the battery pack flashed and it was recognised and started charging. I'd left it outside on a fireproof service, but it's got to 10.6V now so hopefully that's all good. Whooop! :-)
 
So another update. After getting it charging again the capacity was shown as just 236mAh. I was a little too nervous about letting it run down until it powered off, so I fully charged then booted the OSX Tiger installer again and let the voltage go down to 9.5v (previously it died at 9.0v). I turned it off and left it powered off for an hour. Thankfully it booted back up again when I reconnected the charger and said it was charging.
...and the System Profiler now says capacity is 2933mAh. Also for the first time the battery status LED is NOT flashing with just one LED lit. So now I am feeling very pleased with myself!

Will fully recharge again, then do the same just to check as capacity should be much higher than that as there are three parallel sets of three 3000mAh batteries in series. So surely that should give a final capacity of 9,000mAh. ..or am I missing something?
 
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