Laptops forum


Do I have a 10400 or 8800 mAh battery?

by talksthetalk / January 16, 2013 4:40 AM PST

I purchased a new 10400mAh lithium replacement battery for my Acer Aspire 5740-5513 laptop on eBay. The battery is labeled as a 10400mAh, 11.1 V battery. BatteryBar Pro is reporting a maximum capacity for this battery of 97680 mWh. This seems more like the number I would expect from a 8800mAh battery. I contacted the eBay seller, who responded with this message:

"this is a brand new 10400mah battery. acer system bios will not detect anything over approx 8700mah since that is the highest battery they make."

Is the seller correct? Is there a way to reliably measure the true capacity of this battery?


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Clarification Request
Did you need an Amp Hour to Watt Hour conversion?
by R. Proffitt Forum moderator / January 16, 2013 6:16 AM PST

All Answers

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Get out your graph paper.
by R. Proffitt Forum moderator / January 16, 2013 4:46 AM PST

Now write down the 10400 at the top left and half that on the bottom left. Put the date of manufacture on the bottom left and a date 18 months later on the bottom right.

Draw a straight line from 10400 top left to the bottom right. Now find today's date along the bottom and about where did it land on today's date?

Batteries lose a little capacity every day. If you feel cheated, return it.

PS. I kept this simple on purpose. Apologies to my electronics and chemistry professors.

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Still need an answer
by talksthetalk / January 16, 2013 5:03 AM PST


While I appreciate the time you took to write your somewhat patronizing response, it does not answer my question or even address it. I am not asking if the battery is old (it isn't), but if its capacity is being correctly reported.

If you don't know, that's fine, but please don't answer a question I didn't ask, as a person who might actually be able to help me may look for unanswered questions in the forum and skip over mine.


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I offered a way to figure out the current capacity.
by R. Proffitt Forum moderator / January 16, 2013 5:59 AM PST
In reply to: Still need an answer

And I'm sorry to have offended you. I find it odd that you feel offended as I tried to make this as simple as I could and apologized for doing so.

-> You do have a valid complaint and need to have the vendor answer it. I did not sell you this battery but am only an electronics designer. So I tend to rush folk to the answer when they really want longer answers.

I really like BatteryBar. I have it on my laptop here but it's unlikely it can get the exact capacity in all models. If you find it in error be sure to report it to the author.


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PS. More about capacity.
by R. Proffitt Forum moderator / January 16, 2013 6:04 AM PST

Battery capacity is a finicky thing to measure. If you lower the temperature a few degrees, most batteries lose capacity so if some measurement is done, it would rarely match the number printed on the battery. You also have variances in manufacturing.

Your post is also comparing mWh to mAH which is not going to match up. I elected to ignore that and maybe that upset you as well.

Again, it sounds close and in batteries, close is all you get. Those that are accountants will always be unhappy as a 12 Volt battery is never 12 Volts.

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Perhaps I was unclear
by talksthetalk / January 16, 2013 9:03 AM PST

My apologies, Bob. I shouldn't have taken offense at your reply, and I do appreciate your efforts to help me. It may have been my fault in not being clear with my question. I will try to be clearer.

The battery is labeled 10400 mAh and 11.1 V. I know the formula for mWh, and I expect that it will report a maximum capacity of 115440 mWh. Battery Bar Pro should show this as "Battery Wear: [X]% of [Maximum Capacity] mWh.

After calibration, Battery Bar Pro is showing the following: Battery Wear: "2.6% of 96,780 mWh"

96,780 is EXACTLY 11.1 * 8800. EXACTLY.

There are two possibilities - either the seller sold me an 8800 mAh battery, mislabeled as a 10400 mAh battery - or the seller is correct in telling me that the problem is with my computer. The seller is claiming that because of a limitation in its BIOS, my computer will not detect, or will not report, a 10400 mAh battery correctly. I have never heard of such a limitation, but I was hoping that someone on this forum might know more about this issue.

I have an Acer Aspire 5740-5513. I am running Windows 7 64-bit and BIOS V1.28 from Phoenix Technologies.

The original battery was a 4400 mAh battery.

I do not need to know whether my battery is dying, or cold, or how to convert Amp Hours to Watt Hours, or whether a battery really gets its full rated life. I need to know whether I have been defrauded.

Thanks again!


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Let's watch their answer at link.
by R. Proffitt Forum moderator / January 16, 2013 9:24 AM PST
In reply to: Perhaps I was unclear
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Just a thought.
by R. Proffitt Forum moderator / January 17, 2013 4:15 AM PST

Remember that the battery's little computer chip that reports all this is something that some companies do not have the ability to update. In my travels to that land where they make such things it was not uncommon to ask if they can change a setting and discover they were unable to find the source code or program a part. They seem adept at copying and production but "getting it right" seems to be elusive.

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