Re: Boot in 5 seconds
 

Because higher charge levels during storage increase the rate of degradation. 40% is more "stable" (while not skirting too close to a damaging discharge).

Also, I'm fairly certain the tablet batteries don't have a circuit board (as all charging logic is handled by BME). Somebody want to cut away the plastic casing on an old one to confirm?

Re: Boot in 5 seconds
 

Installed new OMWeather. Reboot. :p

Thanks for the explanation. So, say I have 2 laptop batteries. I should put the other one to 42% and then power off my laptop and use that battery as my backup battery? But, when I'll need it it'd be only 40% full. Hmm. Seems like a sacrifice.

Re: Boot in 5 seconds
 

All removable rechargeable lithium ion batteries in personal electronics devices have a "controller" to limit charge and discharge. They must have this to be safe. Short circuiting a lithium ion battery could cause an explosion or fire without such a controller, and so can overcharging. The controller manages these scenarios to keep things safe.

I believe Apple iPod lithium ion cells do not have this controller because that battery is not removable, but every lithium ion cell phone battery I have encountered, in a PDA, cellphone, laptop/notebook, etc. that has a consumer removable Li-ion battery has the controller circuitry I have described.

I have not cut open the Nokia N800 BP-5L batteries I have here but I remain confident there is a controller circuit board in there.

It is this controller which keeps the cell from being overly discharged, or overly charged. It also manages to limit current flow in the event of a direct short across the terminals to prevent a dangerous condition. Without controllers in these batteries, you would not be allowed to board an airplane with your N800, cellphone, or laptop computer, and the batteries would not be freely transportable (shipped). Without the controller circuitry the battery is hazardous material.

Re: Boot in 5 seconds
 

Approx. a year ago I disassembled a PALM PDA. Like the Apple iPOD the PALM also had a non-removable Li-ion cell. I do not think that battery had an integrated controller because, like the iPOD, it was not consumer accessible.

I caution anyone against "tinkering" with Li-ion cells removed from devices such as the iPOD or the PALM PDA. I also caution against tinkering with individual Li-ion cells removed from notebook computers. These cells are very dangerous when shorted and they do not tolerate overcharging in the way a NiMH or NiCAD does. The Li-ion will blow up in your face if you overcharge it. I was at an outdoor demonstration once where a trash can was blown high into the air when a lithium ion cell was intentionally overcharged to show just how hazardous these can be.

I am confident without cutting into the plastic of the BP-5L that there is a circuit board controller in there. The reason laptop battery packs are so hard to "open" is one of safety.

Re: Boot in 5 seconds
 

The Palm PDA batteries have an integrated protection circuit, which is not the same as a controller. The controller is in the device (the PDA itself). The protection circuit is there to cut off the charge if the voltage reaches past 4.30 V, and below 2.5 V.

This protection circuit is installed in even the simplest lithium-ion/polymer batteries, except those that are sold in "raw" form mainly for RC enthusiasts, they make their own battery setups and adds what's necessary.

I have replaced the non-removable battery in my Palm T3, and the original battery had a protection circuit. It's the same for the T, the T2, the E2, the T5 and the TX - you can read all about the battery-replacement project over on Brighthand.
The battery I bought and installed was a lithium-polymer RC type, the protection circuits (very small) can be bought from vendors and there is one such in my replacement battery.

See above - I'm nearly 100% certain that it has a protection circuit. It doesn't have a charging circuit. It's dangerous not to have them, because if the charging circuit in your pda or phone or whatever fails to stop charging then the battery would explode if it doesn't have that protection circuit. There have been cases where phones have exploded because cheap replacement batteries without that circuit had been installed. (There's a reason Nokia now prints a hologram on their genuine batteries..)

Re: Boot in 5 seconds
 

Very good. So there is a circuit board. This means it is best not to expose it to 100% humidity.

I have a question. Does the safety circuit in your PALM PDA battery only do under and over voltage, or is there a control of discharge current. Reason I ask is that externally shorting Lithium Ion or Lithium Polymer is dangerous.

Re: Boot in 5 seconds
 

I don't remember if it trips on short circuiting (or other overcharging), unfortunately. It's been a couple of years since I did the mod and since I followed the Brighthand discussion.

But there is some info over at batteryuniversity.com.
Scroll down a little bit on http://batteryuniversity.com/partone-10.htm
and it describes a lithium-ion battery protection circuit that trips on 4.30V, 2.5V, and it has indirect over-current tripper in that a separate fuse opens at 90 degrees C (194 F) - the battery gets hot very quickly if you short it.
That article is from 2006 (last update), so it was highly up-to-date when I did my battery mod. I don't think much has changed in this respect since then.

EDIT: Added:
Agreed. Here is some info cut&past'ed from a battery reseller - a lot of them seem to have included more-or-less the same advice:

Re: Boot in 5 seconds
 

I assisted to this sort of debate some 2 years ago, entirely between nokians and the demostration was done exactly by cutting open a battery (hell, why wasting time with Lotus Notes and schematics when you can rape a battery?) and the circuitry is there.