Q: battery not charging, power supply not reliable

First try reseting the PMU. If no improvement then it is likely either the battery or charger at fault.

http://reviews.cnet.com/8301-13727_7-10330118-263.html

http://my.safaribooksonline.com/book/operating-systems/9780321544872/learn-basic -troubleshooting-procedures/reset_pmu_smu_smc_nvram_or_pram

AH, I've basically had the same problem and found a fix! It is most likely a DC-Inboard issue with your iBook as my iBook would boot from the AC Adapter and if it did it would last a mere 20 seconds. The DC-Inboards are old now and die, the part is $10 on eBay, if you want to know for sure its the DC-Inoard plug in the Ac-Adapter and if it turns green you're good (It may be a other issue), it turns a yellow-ish color (Not ORANGE) then it is the DC-Inboard, the orange color can be both good or bad. The yellow-ish color is due to the DC-Inboard not being positive if it charging or not, and when this happens you can "Jiggle" the power cord to get it to boot (However it must stay on a desk and not move!) and if you're lucky you'll have enough time to back up any info you may have (Just for safety incase the DC-Inboard doesnt do the job!)

Here is a link for the DC-Inboard replacement- http://www.ifixit.com/Guide/iBook+G4+12-Inch+1.33+GHz+DC-In+Board+Replacement/69 9

Cheers, -JP

Generally speaking, it is not unusual to find computers (both Mac and PC) that have difficulties with the DC-in jack. Merely one example is the PowerBook 190/5300 series. The problem is that solder joints at the connector work loose. Often, this can be solved by a simple resoldering operation.

So, once the DC-in-board for the iBook is out (as under the link provided by JP), and if a replacement board is not available, you may want to ask someone with basic soldering skills to have a look at it.

Jan