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Old 01-12-2011, 02:41 PM   #1
business_kid
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Battery spec Question.


I have a HP 6715S laptop, and the battery is dying fast. It's 10.8V & specified as
Quote:
6 Cell, 2.20Ah, 47Wh
in the handbook which has to be b.s. and has 47Wh printed on it.

acpitool verifies it as 473mAh (=0.473Wh), the box uses 2 - 2.5 amps and a full charge vanishes in 15 minutes like water down a plug hole. But I did get an hour out of it in a Fedora install previously. But it took a lot longer to recharge then.

It strikes me current is very high, and capacity is very low. I can buy 2200mAh AA sized batteries these days in a joke shop, and this claims to be Li-ion which is supposedly better :-O. If I stuck 8 nicads together, I'd have the 2.2Ah, wouldn't I?

Do I
1. Buy the battery and shut up moaning?
2. Check my power supply is charging it fully (i.e. by charging it externally)? I have the technology.
3. Attack the slackware install to start saving current?
4. All 3?
 
Old 01-12-2011, 02:51 PM   #2
szboardstretcher
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I would throw it on a battery analyzer like a Cadex or similar tester.
 
Old 01-12-2011, 07:07 PM   #3
jlinkels
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Quote:
Originally Posted by business_kid View Post
I have a HP 6715S laptop, and the battery is dying fast. It's 10.8V & specified as
in the handbook which has to be b.s. and has 47Wh printed on it.
That is nonsense. 2.2 Ah @ 10.8 V = 23 Wh.
You are not even allowed to discharge such a battery with 2.2A, usually you have to discharge it with 220 mA and then measure the discharge time which should be 10 hours. In other words, 2.2 Ah may only be measured at 0.1 Inominal. Therefor the 47 Wh is nonsense, it cannot be that discharging at 2.2A yields 2.2Ah and discharging at a lower current would yield a higer Wh. The spec is already using a lower current.

Quote:
Originally Posted by business_kid View Post
acpitool verifies it as 473mAh (=0.473Wh), the box uses 2 - 2.5 amps and a full charge vanishes in 15 minutes like water down a plug hole. But I did get an hour out of it in a Fedora install previously. But it took a lot longer to recharge then.
acpitool is surprisingly accurate, 2A during 15 minutes is 0.5Ah.

Quote:
Originally Posted by business_kid View Post
It strikes me current is very high, and capacity is very low. I can buy 2200mAh AA sized batteries these days in a joke shop, and this claims to be Li-ion which is supposedly better :-O. If I stuck 8 nicads together, I'd have the 2.2Ah, wouldn't I?
Your assumptions are correct. I often bought those 2200mAh AA sized batteries for my cameras. Most of them did not even reach 20 recharge cycles before they would loose 80% capacity. Therefor the notebook batteries are constructed differently and consequently bigger.

Quote:
Originally Posted by business_kid View Post
Do I
1. Buy the battery and shut up moaning?
I wouldn't put it rude like that, but it often helps to replace the battery. Whatever they specify, a notebook battery has lost 50% of its capacity after 1 year. My HP NC6230 has 10 minutes battery time left after 2 years.

Remember, both battery and notebook manufacturer's interest is that you buy their products, not that the battery lasts longer than the warranty time. Isn't the battery most often excluded from warranty?

jlinkels
 
Old 01-12-2011, 08:17 PM   #4
jefro
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How old is the battery?
 
Old 01-13-2011, 03:48 AM   #5
business_kid
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@jefro: I think it was made in 2008, I got the pc (new) in 2009. Bankruptcy proceedings interfered.

@szboardstretcher: I don't have a Cadex

@jlinkels: Hello again. We are agreed the spec is B.S., acpitool can multiply, although we are left wondering about the accuracy of it's figures - it certainly looks right.As for those 2200mAh batteries, change your nicad charger or your joke shop. The ones I buy work pretty good for at least 100 cycles. There is the 'memory effect' on nicads, but of course you know that. 20 cycles will be enough to invoke it.

The other sign of aging I have met (On lead acid mainly) is a larger internal resistance. The battery is then recharged on a charger limiting @ 15V and has low capacity, and takes no more current. But if allowed up to 17-17.5V (for a 12V), they will consume current, and then start dropping the internal resistance as the internals normalise. Lead acid is not li-ion, and I gather that's not a wise approach here.
 
  


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