post #21 of 21
Quote:
Originally Posted by EvanPitts View Post
In the real world, if there is a single point of failure, a Li-Ion battery will not explode - the built in safety circuit will shut it down far in advance. However, if there were two failures, that of the charger to overcharge (or go tango uniform and connect the battery directly to the AC line) - and the safety circuit fails or was punted to start with - there could be a very real explosion problem.

Most PC makers use isolated power supplies - so that even if the charging circuit entirely fails, the output will not be carrying full line voltage. This makes for a large "brick", which is not so classy for design. Higher end PCs use TopSwitch, which in inherently fail safe. Apple wanted a slimmer design without the cost of the license for TopSwitch - so they do their own thing, which is an online switcher that if it fails, can place line voltage across the output of the charger.

Apple machines have had some pretty dramatic failures. Lithium Ion has high energy density (which allows for small, light batteries) - but they are brutal when they fail. One of the main problems is that if a LiIon pack splits, moisture can get in, and Lithium and water do not get along, at all.

Lithium Ion also ages - so packs are built with charge counters that shut the pack off before the "estimated" time for cell failure - generally 1000 cycles - but some designs will allow for 1000 charge cycles, followed by a further 1000 cycles of "reduced capacity". However, in the real world, many LiIon packs will fail in as few as 300 charge cycles - and even less. There are other Lithium based batteries that are better for this, longer life and higher charge density - but are more unstable and not appropriate for uncontrolled conditions.

It is a bad thing that Apple even has built in such ability - the battery system should be entirely separated from the machinations of the CPU. If anything, the charging system should have a PIC processor for monitoring purposes, and with only the ability to view the state of health of the battery - with no ability to manipulate it unless it is lashed to a machine that can properly analyse battery performance, such as a Cadex.

Exactly! Rep+

What you say in the last paragraph were exactly my toughts on the matter when another thread on this forum was created. With all the dangers associated with Li-ion batteries, the charging mechanism should be tried and tested to be as close to 100% reliable as it can be, and then be hard-coded into some sort of ROM.

The fact that it can be tampered with indicates that Apple didn't fully test it and reserves therefore the right to make improvements to the firmware. In my opinion, when dealing with such critically sensitive things, there should be no possibility to change any parameters outside of the factory.

If there is a problem, it is always safer to do a recall. This is not BIOS upgrading we are talking about here.
 
Metro 2033 review
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Metro 2033 review
Metro 2033
CPUMotherboardGraphicsRAM
Core i7-3820 Asus Sabertooth X79 MSI GTX 750 Ti TF Gaming 16 GB Corsair DDR3 1866 Mhz Dominator 
Hard DriveOptical DriveCoolingOS
Samsung SSD 830 128GB + WD Caviar Black 1TB Sony Optiarc DVD-RW Corsair A70 + Noiseblocker M12-P Windows 7 Home Premium 64-bit 
MonitorKeyboardPowerCase
BenQ RL2455HM Cooler Master Octane Corsair AX750 Professional Modular 80 Plus Gold Cooler Master HAF 912 Plus 
Mouse
Cooler Master Octane 
  hide details  
Reply