The OLPC XO BTest-1 battery
Have you wondered how well the XO battery would hold up under constant use? Or if you really can measure battery life in days, not hours? Did you even know OLPC is using LiFePO4 battery technology?
Well the amazing teapot was not content to enjoy one of the world's most energy efficient laptops. He's gone about testing the actual XO power consumption to have a benchmark at which we could start the battery life discussion. His Ubuntu'ed XO discovery:
Configuration #1: external power, battery is charging at maximum current.
External power supply, powering XO and charging the battery:
Voltage: 11.6-11.7V
Current: 1.2-1.3A
Power consumed: 14-15.2W
Battery being charged:
Voltage: 6.8V
Current: 1.1A
Power consumed: 7.5W
Power consumed by laptop and charging circuitry: 6.5-7.7W
Then Gabey8 decided to see how well the XO battery lasts after one year of constant use. The best response to her query? Peter Ruhe's XO performance:
When my XO was new (22-Jan-2008) the battery lasted about 3 hours. Ten months later (22-Nov-2008) with 8.2-767 software, it still lasts about 3 hours. I use my XO intensively, usually surfing the web, with backlight at max, averaging 3 hours per night. I go to bed just before the battery is going to die.
Wow! If only a normal laptop battery could be so resilient. Now I wonder, has anyone bought a replacement XO battery?
My experience with the XO battery has been similar to Peter Ruhe's. But I can also note that if you use the "Extreme Power Management" setting (from the 8.2.0 control panel's "power" applet), the battery life is closer to four hours than three -- wifi is a power-hog! -- and you can push to about four and a half hours if you can shut off the back-light as well.
After a year of use, the battery performance is virtually the same as it was when the machine was new.
I've purchased one replacement XO battery (from xoexplosion) and will probably purchase a second one eventually because on coast-to-coast flights, a single battery is not quite sufficient. For flying from Boston to Honolulu without a layover long enough (about 90 minutes) to recharge at least one battery, even having two batteries isn't enough. But three would handle both flights just fine.
I had my XO on my desk running the xubuntu distro (thanks teapot) with agressive power management turned on. It wasn't doing much, but was connected to the wireless network. Screen was in black and white mode. 8 hours later it was down to 10% or so and I realised it wasn't plugged in.
The design of the XO protects the battery pretty well.
The battery is far from heat sources so it is not "roasted" continuously as with normal laptops. The XO battery practically never gets extra heat at all.
Also, the LIFEPO chemistry is quite different from the LCO chemistry of the normal laptop. Both are lithium based but LCO has higher energy density and lower cycle life than LIFEPO. It is said that a good LIFEPO battery should provide 80% its capacity after 2000 full discharges and may be used for another 4000 cycles before becoming unusable.
A normal, LCO battery is good for 1000 cycles without roasting. With roasting, it will get 100-300 cycles or worse depending the amount of heat it gets.
My experience is something else. When I visit a school in India with olpc laptops about 30% of the batteries where nearly broken and the others lasts at maximum 1 1/2h .
It was a school with just 30 laptops and about 600 pupils so it was indeed quite suboptimal..
Another prob was, that there was just one plug to load the laptops.
Alex,
I've experienced XO batteries not charging completely even though the light goes green. Take a look at http://wiki.laptop.org/go/Battery_Charging and see if it helps. I've revived a couple of XO batteries this way. Its basically a way to reset the EC on the XO and see if it will recharge properly.