I was browsing for other information, but came across this thread and just wanted to drop in some details regarding batteries. There's some great information on here already, but I just had a few points make :-)
The voltage difference between the 10.8 and the 11.1 batteries is negligable on any laptop. There are changes in voltage in 'all' batteries as a natural part of what they are, but beyond that, batteries drop in power anyway as they discharge and only the circuit they are fitted to will decide if it's flat or not enough to work it (until the battery just cannot work any longer).
How does any laptop know the battery is going flat? It tests voltage, amd when it finds it's getting too low, it shuts down (or just goes off without warning - that's it's 2nd layer of auto-off, 1st level is a warning with OS shut down, 2nd level is full off to avoid lower voltage causing data problems while reading/writing. To leave a circuit on a laptop struggling on a low battery with (for example) 7 volts, could cause all kinds of data corruption, so the best thing is just instant off - then it's far more likely to just stop what it's doing.
Losing power slowly could cause a hard drive to smear data (in theory) across a drives platter ARRGGGHHH disaster!
It had been mentioned here about voltages on laptops being 19v, so why is that? Well this isn't mentioned much but is important to realise....
No circuit uses 19 volts. Check on components and you instantly see 1v, 3v, 5v 9v, 12v etc. Now where does your 19v laptop fit in then?
Well its for power and safety - no laptop uses more than 12v, and most voltages are 5v, or lower like 1.3 for CPU's and things like RAM. If that 12v part needs power and your charger was 12v, you'd be straining the whole circuit - that's no good. So you have 19 volts, to power the 12's, and the 5's, and the other lower voltage parts, and also, of course, that all important trickle charge to the battery (usually between 1.5 and 3.5 volts to charge things with, 3.5 being Fast Chargers - not used on laptops).
The bit to note is, all the voltages are 'nearly' things. None of it is precise at this level, only things like RAM, data lines and CPU/GPU have 100% precision on voltages. The rule on such techinical circuits is - always have a little more power than you need just in case, but always have a protected voltage level anyway.
Consider the old fashioned and well used 7805 voltage regulator - you can slap 35+ volts into them, and the just casually give you 5volts output and laugh while doing it. That's your circuit protection from high voltages right there.
Laptops, both battery and mainboard, all have more modern versions of the same kind of thing inside them.
And also, I happily put 11.1 or 14.4 batteries in several makes of laptops without any difference or problem. As an example, I have here on my desk a Packard Bell MIT-SABLE-C, that happily uses either voltage, and I have 6 batteries I've been testing on it, All do the same thing, because the higher voltage battery has less amp, so the power level at the end all stays about the same.
4If both are Li-ion batteries, then 11.1 is just an advertising gimmick. Each Li-ion cell varies from 4.3V (at full charge) down to about 3.4V at maximum safe discharge. But the discharge curve isn't linear, it is about 3.6V (three in series are 10.8V) for most of the useful range of charge. Some companies call their batteries 3.7V (three in series are 11.1V) just to make them sound better, but it's the same voltage with the same chemistry. Whether you want to buy a battery from a company engaged in deceptive marketing is a different question entirely. – Ben Voigt – 2012-06-23T12:24:44.470
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@BenVoigt No advertising gimick. Lenovo itself sells multiple batteries for different models rated at 11.1v http://shop.lenovo.com/SEUILibrary/controller/e/web/LenovoPortal/en_US/site.workflow:SimpleSiteSearch?lang=en&q=11.1v&cc=us&ff=2 none of which is for this particular laptop. So unless you are saying that Lenovo itself is practicing those deceptive marketing techniques for only some of their battery sales, it would appear that even Lenovo believes there is enough of a difference.
– Bon Gart – 2012-06-23T12:32:49.0801@BonGart: Seems all the Lenovo search results for 11.1V are "Li" and for 10.8V are "Li-ion". The chemistry difference, which requires a completely different charger circuit, is far FAR more important than the nominal voltage, since voltage varies substantially with charge state. Marking Li-ion as 3.7V/cell is a marketing gimmick, but that's not what Lenovo is doing. – Ben Voigt – 2012-06-23T12:35:53.337
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@BenVoigt No, I'm finding 10.8v LI-ion and 11.1v LI-Ion batteries listed at Lenovo. check http://shop.lenovo.com/us/itemdetails/0A36292/460/A5EB9DB8B66C416083597E397599C2A4 and http://shop.lenovo.com/us/itemdetails/57Y6493/460/A5EB9DB8B66C416083597E397599C2A4
– Bon Gart – 2012-06-23T12:42:42.723@BonGart: Yep, that's marketing gimmickry. – Ben Voigt – 2012-06-23T12:44:22.160
@BenVoigt so you can't even trust Lenovo and what they say, since they are practicing that same deceptive marketing technique... that's what you are saying, since they sell both 10.8v Li-ion batteries, and 11.1v Li-ion batteries. Just trying to be clear about this. – Bon Gart – 2012-06-23T12:49:08.100
1@BonGart: All those batteries listed are 6 cell Li-ion, arranged with 3 in series. That means they are actually the same voltage, regardless of what the marketing team put on the box. – Ben Voigt – 2012-06-23T12:59:11.117