sony laptop battery replacement
April 23, 2018 7:43 AM Subscribe
I need to replace a failed Sony VGP-BPS26 battery, rated at 10.8 volts. All the replacements I can find online are rated at 11.1 volts. Will this be an issue?
Best answer: Short answer -- both will be fine.
It's mainly a marketing difference. Lithium battery voltages aren't really an exact number. It is derived from the average voltage at 50% charge under a specified test current load. The range during use is from 12.6 volts at full charge to 9.0 volts at full discharge. So your laptop is designed to handle all battery voltages across that range.
Some batteries are constructed to have a slightly lower internal resistance so that they will measure a slightly higher voltage under the specified test load. All of them are charged at the same 12.6 volts. You shouldn't notice any difference between a pack marketed as 10.8 volts or 11.1 volts.
The voltages for the pack are derived from stacking three single cells that have either a nominal 3.6 or 3.7 volt rating. Both will work fine in your laptop.
posted by JackFlash at 8:12 AM on April 23, 2018 [2 favorites]
It's mainly a marketing difference. Lithium battery voltages aren't really an exact number. It is derived from the average voltage at 50% charge under a specified test current load. The range during use is from 12.6 volts at full charge to 9.0 volts at full discharge. So your laptop is designed to handle all battery voltages across that range.
Some batteries are constructed to have a slightly lower internal resistance so that they will measure a slightly higher voltage under the specified test load. All of them are charged at the same 12.6 volts. You shouldn't notice any difference between a pack marketed as 10.8 volts or 11.1 volts.
The voltages for the pack are derived from stacking three single cells that have either a nominal 3.6 or 3.7 volt rating. Both will work fine in your laptop.
posted by JackFlash at 8:12 AM on April 23, 2018 [2 favorites]
Best answer: It probably* won't matter. Actual output voltage is a curve that varies with battery charge and the rate of drain. A 10.8V battery will generally output more than 10.8 volts when it's fully charged, will output around 10.8V for most of its charge capacity, and will drop below 10V when it's near its discharge limit. A nominal difference of a few tenths of a volt shouldn't matter, especially when the new battery's nominal voltage is rated slightly higher than the original.
Computers and other fancy electronics have internal voltage regulators that convert the battery's output voltage to the specific voltage needed by the various components (mostly 5V, but perhaps 3.3V or lower for the CPU, and possibly more for the display). Those regulators are designed to work with a pretty broad range of battery output, and 11.1V is almost certainly within the design capacity of your computer's voltage regulator.
* There's a very small possibility the computer's battery capacity readout will not accurately reflect the capacity of the battery. Laptop batteries carry their own "smart" charging circuitry that's supposed to monitor the health of individual cells and prevent overheating during charging or excessive discharge. If the computer only reads the battery's voltage and not the full reported capacity of the smart circuit, weird things could happen around the extreme ends of battery charge, like staying at 8 or 10% for a really long time and then dropping to nothing all at once. This is probably not going to be an issue in a computer, but it happens with aftermarket batteries in the cameras I own and it's super annoying.
posted by fedward at 8:31 AM on April 23, 2018
Computers and other fancy electronics have internal voltage regulators that convert the battery's output voltage to the specific voltage needed by the various components (mostly 5V, but perhaps 3.3V or lower for the CPU, and possibly more for the display). Those regulators are designed to work with a pretty broad range of battery output, and 11.1V is almost certainly within the design capacity of your computer's voltage regulator.
* There's a very small possibility the computer's battery capacity readout will not accurately reflect the capacity of the battery. Laptop batteries carry their own "smart" charging circuitry that's supposed to monitor the health of individual cells and prevent overheating during charging or excessive discharge. If the computer only reads the battery's voltage and not the full reported capacity of the smart circuit, weird things could happen around the extreme ends of battery charge, like staying at 8 or 10% for a really long time and then dropping to nothing all at once. This is probably not going to be an issue in a computer, but it happens with aftermarket batteries in the cameras I own and it's super annoying.
posted by fedward at 8:31 AM on April 23, 2018
Best answer: There's a very small possibility the computer's battery capacity readout will not accurately reflect the capacity of the battery.
For a laptop, that probability is zero. Cheap, small electronic devices attempt to estimate battery state of charge by reading the voltage of the battery. But as your link shows, the discharge curve for a lithium battery is fairly flat over most of its capacity, so there is little difference between 80% charged and 20% charged. This method is simple and cheap but very inaccurate.
On the other hand, a more sophisticated device like a laptop uses a circuit called a coulomb counter that actually counts the number of electrons going into the battery and coming out of the battery. It doesn't care about the nominal voltage of the battery. It only cares about full charge, 4.2 volts and full discharge, 3.0 volts. It doesn't need to know about the voltages in between to determine state of charge.
It is similar to measuring the number of gallons of gas going into your gas tank and the number of gallons taken out of your gas tank. If you do this accurately, you always know exactly how many gallons of gas are in your tank.
So your new battery should work fine and have no problems measuring capacity. You will have to do an initial calibration cycle. To do this you discharge the battery to zero capacity then charge it to full capacity. Once you do this, the coulomb counter has gone from zero gas in the tank to a full tank and can now keep track of everything in between.
posted by JackFlash at 8:50 AM on April 23, 2018 [2 favorites]
For a laptop, that probability is zero. Cheap, small electronic devices attempt to estimate battery state of charge by reading the voltage of the battery. But as your link shows, the discharge curve for a lithium battery is fairly flat over most of its capacity, so there is little difference between 80% charged and 20% charged. This method is simple and cheap but very inaccurate.
On the other hand, a more sophisticated device like a laptop uses a circuit called a coulomb counter that actually counts the number of electrons going into the battery and coming out of the battery. It doesn't care about the nominal voltage of the battery. It only cares about full charge, 4.2 volts and full discharge, 3.0 volts. It doesn't need to know about the voltages in between to determine state of charge.
It is similar to measuring the number of gallons of gas going into your gas tank and the number of gallons taken out of your gas tank. If you do this accurately, you always know exactly how many gallons of gas are in your tank.
So your new battery should work fine and have no problems measuring capacity. You will have to do an initial calibration cycle. To do this you discharge the battery to zero capacity then charge it to full capacity. Once you do this, the coulomb counter has gone from zero gas in the tank to a full tank and can now keep track of everything in between.
posted by JackFlash at 8:50 AM on April 23, 2018 [2 favorites]
Response by poster: Installed new battery, no issues, thanks all.
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