Laptop life has been constant-ish, for years. You can get three or four hours out of a decent modern laptop; it used to be one or two, but it’s all of that order. Not enough for a full day without recharging. Do modern laptops use more power? They certainly do more stuff—CF readers, CD readers, better screens. Could you take a battery from a brand new laptop and use it to power your old P200 laptop for eight hours?
Well, of course you couldn’t, because they’re all different shapes. This is (charitably) because laptop designers need to craft everything specifically for each new model so that it all fits together as tightly as possible, to minimise size, or (uncharitably) so that you have to buy a new battery every time you buy a new laptop. But ignore that; imagine the shape and connections issues don’t come into it. Does a modern battery produce more power from the same size of battery? I imagine they do; technology marches on, after all. So if I took the battery from a brand new laptop and I put it in my old Toshiba Tecra 520CDT, which is a P166, would it run for eight hours? Or ten hours? Or 24 hours? It would be great if it would. Who knows about battery stuff?
All I know is that when I had to buy a new battery for the three- year-old Silver Surfer, it lasted half again as long as the old battery ever had.
Posted by Dorothea Salo on February 10th, 2005.
Your Toshiba Tecra 520 used a 2600 mAh (milliamp-hours, roughly a measure of capacity) battery. According to this page anyway.
http://www.priorityelectronics.com/laptopbattery/toshibabattery.htm
If you look at other models on the page, Toshiba has made some with as high as 8800 maH batteries. So all things being equal, it might run four times as long.
I think if you looked at it, though, you’d find that battery capacity is directly linked to laptop size, not how new it is. My brand new iBook uses a 4000 MaH battery, not much bigger than your old one. The bigger the screen, the bigger the battery needs to be (and the more room there is for it.)
You could certainly attach some kind of battery with four times the capacity to your new laptop, but I’m guessing it would weigh 4 times as much. In fact, they make some for this purpose—here’s one I found on a quick Google search.
http://www.sarrio.com/sarrio/12voltlaptop.html
Posted by Michael Moncur on February 10th, 2005.
Michael: ah, right, I get it. mAh, eh? That’s useful. I’ve always harboured this secret belief that I could take a new battery from a new laptop and my old Tecra would run for about 16 hours on it, and all that was stopping me was the nasty nasty Toshiba Corporation’s money-grubbing nature. If in addition the laws of physics stand in my way, I shall give up on one more dream :-)
Posted by sil on February 10th, 2005.
It also depends on the chemistry of the cells, practically all of the modern battery packs use Lithium Ion (LiIon) cells of one sort of another. The older packs would be Nickel Metal Hydride (NiMH) or even Nickel Cadmium (NiCd).
LiIon has a higher capacity (mAHr) than NiMH for a given size of cell, which in turn is greater than NiCd. Though NiCd has a much better (read lower) cell resistance, so can handle higher current discharges better without the cells over-heating.
All 3 cell chemistries have different charging characteristics as well, though NiMH & NiCd are a lot closer to each other than LiIon.
This means there is not really a straight plug in replacement.
LiIon has certain properties, because of the energy density in the cells, these require normally a complex protection circuit to ensure the cells are not over charged or discharged and to ensure excess current is not drawn from the pack. In addition because battery packs for laptops are have more than one cell in it, this circuit should perform “cell balancing“, to ensure each cell gets the same amount of charge in it, otherwise the cells after repeated charge/discharge cycles, end up with different charges present on them, so reducing the life of the pack. Unfortunately it appears this does not take place very often, so this reduces the service life of a laptop battery pack.
Hope this is useful information for someone.
Bruce S.
Posted by Bruce S. on February 15th, 2005.