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Old 02-07-2011, 08:21 PM   #1
Registered: Jul 2007
Location: Chicago Illinois
Distribution: SLES 10 SP2/SP3, SLES 11 SP1, OpenSUSE, Sabayon, Gentoo, Fedora 14, RHEL 3/4/5/6
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Replacement battery for Asus eee 701?

Not sure if this fits better in Linux - Hardware or Linux - Laptop and Netbook as my questions kind of fit in both.

I have an Asus eee 701 that needs a replacement battery, as it can only hold a charge for about 10 minutes before it starts warning me that the battery charge is too low. Looking at different batteries, there are models with 4400mAh (what the laptop currently has), 6600mAh, and even one that claims 8800mAh, but it's enclosed by '*' in the title, so I'm a little weary of that. Some of the descriptions also say how many cells they have, while other descriptions don't mention it.

My questions:
1. Does getting a battery with a higher mAh increase the life of the battery before it needs to be charged? If so, does the increase in mAh directly proportional to how much longer the battery will last before needing recharged?

2. Does the amount of cells matter in determining the best battery to get?

3. I have been monitoring /proc/acpi/battery/BAT0/state, and noticed a couple things. Here is a sample output from cat'ting the file:
present: yes
capacity state: ok
charging state: charging
present rate: unknown
remaining capacity: 90 mAh
present voltage: 8471 mV
I have been using the "remaining capacity" as a way to determine the percentage of life left before needing recharged. It's always decremented in units of 10, and it goes to 100 mAh usually when fully charged. But if it's a 4400mAH battery, shouldn't it go up to 4400mAh?

4. Also the present voltage usually changes a bit every time I read the info in proc, just curious what the present voltage means. For example if I run more apps, does the voltage increase, or is it almost always going to run within a certain range no matter what?

5. I kept the laptop plugged in almost 99% of time. Did that hurt the battery at all? It's really not that old, and I barely used the laptop in a battery only state. So I'm just curious if I did something wrong that made the battery go prematurely.

Thanks for your help!

Old 02-08-2011, 06:57 AM   #2
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In a nutshell mAH is the amount of current the battery can supply in an hour and so the higher the value the longer the laptop will run. The number of individual batteries is not real important. The batteries are combined in series and parallel to get the desired voltage and current to run the laptop.

The battery probably needs to be calibrated since you never use it might be the reason the readings are off. You need to fully charge, discharge, recharge. Yes, never discharging the battery will effect its useful life but from a bit of searching on the internet it appears that this is a common problem.
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Old 02-08-2011, 08:41 PM   #3
Registered: Jul 2007
Location: Chicago Illinois
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Thanks, michaelk; I'll try charging, discharging, and recharging a few times to see if I can get the battery to last longer before purchasing another battery.

Old 02-09-2011, 01:38 PM   #4
Registered: May 2003
Location: London, UK
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Modern batteries don't need the "regular deep discharge" that the older ones needed.

I have an EEE701 bought the moment it came out (3-4y ago?). Mostly I use it with the charger plugged in. Sometimes I take it out for a walk. The battery still lasts 2-3Hrs+.

If you are regularly using it on battery, it could be that it is just worn out (just too many charge - discharge cycles). Time to do some experiments as above.

That EEE701 was, and still is, a brilliant piece of (cheap) hardware. The original OS - Xandros has been replaced many times. Currently ubuntu 10.04. Magic
Old 02-09-2011, 07:06 PM   #5
Registered: Jul 2007
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OpenSuSE 10.3 for me. I was really into compiz at the time and Xandros didn't have the updated version. After I tried adding regular Ubuntu repo's, installed all the packages, rebooted, and got a white screen where no input could be issued. I hosed the install. So that's when I switched. So I got compiz running on my Eee

I have also used the Eee as a router, where the wireless received the signal from my Linksys and then I routed that out the wired connection. That allowed me not have to run a cable from different floors in my house.

Old 02-13-2011, 02:30 AM   #6
Registered: Jul 2008
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Check web for information about lithium ion batteries


The mAh rating is the nominal capacity of the battery calculated as the integral of milliamperes it can supply for how many hours. Hyphothetically, if you discharge the battery at twice the current (milliamperes), then it should supply current for half as much time (hours). Of course it does not really work out that way in R.L. Most batteries will provide less mAh at higher discharge rates than at lower discharge rates. The nominal capacity is usually rated at a 20 hour discharge cycle. Of course, your computer will almost certainly discharge them faster than that, and you will get less mAh at the usual operating conditions. None the less, the ratings provide a comparative capacity rating for the different batteries. You should expect that a 6600mAh battery should give 50% longer run time than the 4400mAh battery.

Lithium-ion batteries eventually fail. Some place I looked at said they lose about 20% of their capacity per year. So your 4400mAh battery will become a 3500mAh battery after a year, and lower capacity as time goes by. Unfortunately I can not remember well enough to cite the source. My experience indicates that a lithium ion battery in constant use in a computer will provide useful capacity for only about four years and in a very hot running notebook they may become unusable with as short a lifetime as two years.

Completely discharging a lithium ion battery can destroy it. If you have multiple batteries, the best storage condition for the unused battery to maintain its capacity is about 40% charged. A higher state of charge accelerates loss of capacity due to aging. Naturally, if you want to alternate batteries on a field trip or while traveling, you would want them to be fully charged.

A full discharge cycle with the computer, however should not damage the battery. The computer shutdown is configured so it will not discharge the battery into the damaging low charge state.

Higher temperatures speed both the self discharge and the loss of capacity with aging. The hottest environment your battery will encounter is in your computer, because the power dissipated by the computer makes it warm (in some cases, even hot). If you run your portable computer on the charger most of the time, your battery will last longer if you remove it from the computer while you are on charger.

Keeping the batteries cooler slows both the self-discharge and loss of capacity due to aging. The cooler you keep them, the longer they maintain both their charge and their capacity. However, they should never be permitted to freeze. The electrolyte in the battery freezes at a lower temperature than water, but the freezing point depends on the state of charge. Household refrigerator temperature is close to optimal long-term storage condition. If you put the batteries in the refrigerator, enclose them in a ZipLock freezer bag. Wrap the battery in a paper towel and put some dry rice in the bag to act as a dessicant. The paper towel keeps the rice off of the battery. Allow the batteries to warm back up to room termperature before removing them from the freezer bag.

Remember that the batteries self discharge slowly in storage, even if you refrigerate them. If they discharge completely, that will ruin them. If you keep them out of the computer, be sure you put them in the computer to recharge them at least about once every 6 months or so. If you have more than one battery pack for your computer, trade them off from time to time so that all the batteries get recharged. Avoid letting the batteries get below 20% charge in storage.

Some battery cells are constructed to provide more capacity than others. Aftermarket replacements often offer higher capacity than the OEM battery by using slightly larger cells. They may use a thinner battery pack shell and tighter packing or prism shaped cells rather than cylindrical cells. Another modification to the battery packs is a larger pack with more cells. This provides even more capacity. A six-cell pack provides 50% more nominal capacity than a four-cell pack. Actual performance is even better, because the individual cells provide more capacity because they are being discharged at a lower current rate. However, the six-cell pack is physically larger than the standard battery. My six-cell aftermarket battery in my EeePC 900a protrudes slightly below the bottom of the computer in the rear, which lifts the rear of the computer and tilts the keyboard slightly forward. I do not find this to be a problem.

Trading battery packs may confuse the computer's estimation of remaining run time. My computer does not give very good guesses in any case. It still gives me a timely shutdown alarm unless the batteries have degraded to very low capacity.


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