Dell laptop : Batteries
The disadvantage of buying old laptops is, that you get a lot of old batteries as well. Some of my machines have batteries that are still as good as new. In most cases, these were batteries that were replaced by the former owners. But some others are in very bad shape. On 5 old beasties, I have 6 batteries (one came with a spare battery), of which one is in awful condition (less than 10 minutes runtime) and most are in reasonable shape (40 - 60 minutes runtime).
So the thought crossed my mind to get some 'new' batteries. First I skimmed Marktplaats.nl, a dutch used-goods site. Either the offerings were suspicious, or the seller wanted almost the newprice. And I don't want to pay newprice on this kind of tricky product. Especially not on marktplaats, which is famous for its return policy: after you paid, all waranty is out the window.
Dell laptop : Batteries on Ebay
On Ebay my kind of battery (75UYF) is very well represented. At least, that's what they say. If you read the
fine print, 99.9% of the lots are for 'generic' or 'OEM' batteries that are drop in replacements for the
75UYF. With the advantage that these batteries are 4500 mAh, whereas the original was 3800 mAh.
Most of these replacement batteries are from China. In itself that does not mean a thing. Everything is made in China, nowadays. Still, China is not always China. There are lots of copy cat companies that mimmick a battery casing and then hope for the best. The trick is to filter these out. And I don't have a clue how to do that, without inviting a few batteries over for the weekend.
So I chose an Ebay supplier that looked trustworthy (feedback score) and had a good shipping policy. I ordered two replacement batteries (Brandnew and with 6 months of warranty) for €35 each. A steal, when compared to other shops that sell batteries for more than €120 a piece. I ordered the batteries on Friday and received them home on Tuesday. Not bad for an international shipment.
Dell laptop : Battery experiences
For some reason I had a bad feeling when I received the envelope with the two batteries inside. I put this aside. I'm an engineer and engineers don't feel. They experience and measure. These are my findings:
Dell laptop : Once more
After this nasty experience at Ebay I started a massive websearch (Yahoo and Google) for 75UYF batteries or replacements. Dell stopped producing them. Major second source parties (Duracell, EverCell) stopped as well. For the rest, it is difficult to seperate the sheep from the goats. One experience:
A webshop told to be reseller of the brand 'Yanec'. A new Yanec would cost around €100. I did a 'whois'
on the webshop and on the Yanec website. They were identical (some hillbilly township in the middle of
nowhere, of which I am 100% sure there is NO battery factory or research facility).
The webshop cannot be 'simple reseller' and 'battery developer'. So the Yanec brand is not trustworthy to me.
It can only be a cheap clone with a sticker attached by the Yanec development engineers (doing so when the
kids are at school).
It may well be that Yanec IS a good brand. It may be so that Yanec knows its way in battery-land and did find
a trusty source of OEM batteries. But at the moment I just don't want to set my money on it. Once is enough.
Still, I definitely wanted to get some real Dell 75UYF cells which were in a reasonable state. So I again ended up on marktplaats.nl. The day before someone placed an ad for three batteries in reasonable state. I had to ask the seller some details, did some websearching and came to the conclusion that this would be an acceptable risk. For €50 I will get three cells.
Battery health and battery status
On the backside of the 75UYF is a shallow button. If you press it shortly, the status of the battery is shown: 5 LED's is 100% and each LED less is 20% off. This is the battery status. The battery guesses the status on the basis of the battery pack voltage.
If you press the button above and hold it depressed for 3 - 5 seconds, the status LED's will turn off and
during half a second, a series of LED's will blink once. The longer the LED bar that blinks, the worse the
health of your battery is. So, if no LED's blink, your battery is brandnew. If 4 or 5 LED's light up, it's
time for a reconditioning attempt. Or the toxic waste disposal.
Of course this check only works if there is some charge in the battery (i.e. the status is not zero).
Dell laptop : logging battery state
When discharging a battery, this may take some time. You may do a game or two but soon it starts to be boring. So you want to automate this. I made a program called 'show':
cat /proc/acpi/battery/BAT0/state uptimeor, for older kernels:
apm uptimeand ran 'crontab -e' with this line:
* * * * * /home/jan/show >>/home/jan/keepup.logwhich runs the 'show' script every minute and the output is appended to the log file. Now I can just start the computer, start X and go do something else. Wen the power gets too low, the battery low voltage protection system will cut off power and the laptop will stop logging as well.
Dell laptop : experiences with the used Dell's
The 75UYF's arrived today. I've been running tests with them which are assuring:
I did a full discharge (until the battery cut out), recharged and discharged again (with a log file). After 40 minutes the battery reported to be dead (0%) but still managed to run the laptop for close to an hour!
present: yes capacity state: ok charging state: discharging present rate: 26152 mW remaining capacity:So I should run this battery on a system that does not have acpi and low battery warnings running. Still, it is strange.49280 mWh present voltage: 14792 mV 15:10:01 up 17 min, 5 users, load average: 0.18, 0.13, 0.15 present: yes capacity state: ok charging state: discharging present rate: 23330 mW remaining capacity:37310 mWh present voltage: 14029 mV 15:13:01 up 20 min, 5 users, load average: 0.70, 0.27, 0.19 present: yes capacity state: ok charging state: discharging present rate: 23355 mW remaining capacity:22990 mWh present voltage: 13927 mV 15:14:01 up 21 min, 5 users, load average: 0.92, 0.42, 0.24 present: yes capacity state: ok charging state: discharging present rate: 23447 mW remaining capacity:10840 mWh present voltage: 13825 mV 15:15:01 up 22 min, 5 users, load average: 1.05, 0.55, 0.30 present: yes capacity state: ok charging state: discharging present rate: 23706 mW remaining capacity:1950 mWh present voltage: 13735 mV 15:16:01 up 23 min, 5 users, load average: 0.94, 0.61, 0.33 ................. present: yes capacity state: ok charging state: discharging present rate: 14417 mW remaining capacity:1740 mWh present voltage: 14121 mV 15:59:01 up 1:06, 5 users, load average: 0.00, 0.00, 0.00 present: yes capacity state: ok charging state: discharging present rate: 16736 mW remaining capacity:1110 mWh present voltage: 14041 mV 16:01:01 up 1:08, 5 users, load average: 0.00, 0.00, 0.00 present: yes capacity state: critical charging state: discharging present rate: 15480 mW remaining capacity:660 mWh present voltage: 14035 mV 16:02:01 up 1:09, 5 users, load average: 0.00, 0.00, 0.00 present: yes capacity state: critical charging state: discharging present rate: 14788 mW remaining capacity:260 mWh present voltage: 14071 mV 16:03:02 up 1:10, 5 users, load average: 0.00, 0.00, 0.00 present: yes capacity state: critical charging state: discharging present rate: 14531 mW remaining capacity:0 mWh present voltage: 14067 mV 16:04:01 up 1:11, 5 users, load average: 0.00, 0.00, 0.00 ................. present: yes capacity state: critical charging state: discharging present rate: 14743 mW remaining capacity:0 mWh present voltage: 11229 mV 17:10:01 up 2:17, 5 users, load average: 0.00, 0.00, 0.00
Dell laptop : CPU loader
I want to test my batteries under load. So the CPU must do something silly. That's why I made the following program in C:
int main (void)
{
here: goto here;
}
compile it with
$ gcc run.c -o run
$ strip run
$ ./run &
and run the program while discharging the battery. It will load the CPU for the full 100%.
Dell laptop : my batteries
Below is a table with my batteries plus some details.
| Nr | type | mAh | Whr | Health | Minutes | Remarks |
|---|---|---|---|---|---|---|
| 1 | 75UYF | 3800 | 55 | Very good | 180 | This was a replaced battery (in the CPx). |
| 2 | 75UYF | 3800 | 55 | Dead | 15 | This battery was in the C600, after the repair... It is dead. |
| 3 | 75UYF | 3800 | 55 | Very good | 200 | - |
| 4 | 1691P | 3600 | 52 | Poor | 80 | For the first 60 minutes everything goes smooth. And then the system goes from 60% to 10% within minutes. This battery has a high self discharge (empty within three weeks on the shelf). |
| 5 | 53977 | 2700 | 38 | Good | 90+ | Tested in the CPiA running at 100% CPU load (twice the 'run &' command, and then 'startx') |
| 6 | 3149C | 3000 | 43 | Good | 100 | Tested in the CPiA 366XT with 100% CPU load |
| 7 | 75UYF | 3800 | 55 | Doubtful | 50 | Good for 20 minutes at first. After a full discharge: 50 minutes when fully loaded. Battery gauge malfunction. Good enough for keeping one of the oldies alive. This was a €20 as well. |
| 8 | 75UYF | 3800 | 55 | Good | 120 | Good enough for a €20 battery. |
| 9 | 75UYF | 3800 | 55 | Very good | 200 | Another €20 battery. Dead on arrival. Suddenly started charging. Now as good as new. Strange. |
Page created on 10 January 2009 and
Page equipped with FroogleBuster technology