Posts filed under ‘Laptop’

Laptop Battery Life: internal vs external battery

My Acer 3680 only last about 2 hours on a charge. Should I buy another internal battery or buy an external battery?

First, let’s examine the laptop’s battery and AC adapter:

  • Battery: 4000 mAh, 11.1 V, 44.4 Wh Li-ion.
  • AC Adapter: 19 V, 3.42 A, 65 W

The best way to measure a battery’s capabilities is Watt hour. The formula for Watt Hour is:

Watt Hour (wh) = Voltage x Amp-Hour

For the Acer battery, the Watt hour would be 4 A x 11.1 V = 44.4 Wh. So if you buy an external battery taht’s 44.4 Wh, you’ll get the same battery life as your internal? That depends on your internal voltage vs external voltage. If you look at the Acer battery specification, it list a voltage of 11.1 V, but if you look at the AC adapter, it list 19V. To get the same battery life on an external battery, you would need a battery with 4 A x 19 V = 76 Wh. Essentially, you need a much bigger battery because of the higher voltage.

Let’s compare the battery life with what is typically available on the market:

Capacity (Wh) Percentage from Baseline Est. Battery Life (Hours)
40 Wh 53% 1:04
50 Wh 66% 1:19
60 Wh 79% 1:30
76 Wh (baseline) 100% 2:00
80 Wh 105% 2:06
100 Wh 132% 2:38
120 Wh 158% 3:10
140 Wh 184% 3:41

Internally, the Acer has two battery options:

  • 4000 mAh, 11.1 V, 44.4 Wh Li-ion.
  • 7200 mAH, 11.1 V, 79.9 Wh Li-ion

So the battery life would be:

Capacity (Wh) Percentage from Baseline Est. Battery Life (Hours)
44.4 Wh 100% 2:00
79.9 Wh 180% 3:36

Amazon currently sale an 80 Wh external battery at around $205, which will give me another 2:06 of runtime. I could get the 44.4 Wh internal battery for $160 for the same amount of battery life. In the end, the internal battery almost always seem to be a better deal.


September 1, 2007 at 2:25 pm 3 comments

Installing an Aftermarket Internal Bluetooth Module on Acer 3680

All Acer 3680 have a bluetooth button on the front, but only some models of Acer 3680 actually have the internal bluetooth module. This has led people to spend hours trying to get bluetooth to work, only to discover that they don’t have bluetooth. This does mean that all or most model of Acer 3680 probably have a connector for the internal bluetooth module and an internal antenna. All we need to do is to find a compatible module to connect to the connector.

Acer does not sell the bluetooth module as a part. Since the connector is essentially a USB connector, I could have rewire a USB dongle if I can figure out the pin outs. However, I am not a hardware person and don’t really have the time to mess with solder and wires. I managed to acquired an aftermarket bluetooth module from a ebay vendor OldEgg Wireless. OldEgg mentioned that the part was not an original Acer part, but it was only about $34 with shipping. If it worked, the it was a much better option than USB dongle or PCMCIA cards. There are a few other vendors offering the part, but OldEgg at least was offering reasonable prices (one vendor wanted $150, why would I spend that much money for an accessory for a $400 laptop?)

The module arrived in a few days. The module is a tiny box size of a fingertip with a cable terminating in a 6-pin connector. There’s some double sided tape in the back of the box. I have no idea who the vendor is since the label on the box is in Chinese.

Internal Bluetooth Module

Installation is actually pretty easy for the Acer 3680. All you need to do is to remove the memory door panel, exposing a white 6 pin socket. All you need to do is plug the connector into the socket (it only goes in one way). You can remove the backing of the double-sided tape and stick it on some part of the motherboard. In my case, I just tucked into a crevice of the case.

Acer 3680 Memory Panel

To test it, I boot the laptop up and press the bluetooth button and the blue light lit up, indicating that it was working. After installing gnome-bluetooth under Ubuntu, I was able to scan and connect to my Motorola Razr from across the room. I assume that it probably works under XP and Vista, but I don’t have either OS on the machine to try it.

I assume that this trick will work on all models of Acer 3680, but you should open up your memory panel to make sure there is a 6-pin connector. I did notice that there seemed to be several models of Acer 3680, so there’s a small chance that this may not work with every model.

August 24, 2007 at 7:46 pm 75 comments

Installing memory on an Acer 3680 Laptop

The acer 3680 has two memory slots that takes DDR2-533/PC4200 or DDR2-667/PC5300. Because the Celeron M has a FSB of 533 Mhz, you’re limited to 533 Mhz even if you use DDR2-667. The computer typically come with a single 512 Mb module and can accept up to a maximum of two 1 Gb module for a total of 2 Gb. Since DDR2-667 and DDR2-533 are pretty much the same price these days, I chose a pair of G. Skill 2 x 1 Gb DDR2-667 from Newegg.

To install the memory, power off the laptop and remove the battery. Turn the laptop over. The memory module is located under the middle panel, the one with the Windows Product Key sticker. To remove the panel, remove the two screw on the bottom of the case. There is plastic washer underneath the panel holding the screw in. You will have to unscrew the screw all the way and then carefully use your fingernail to pry off the screw (be careful not to lose it).

Once you remove the screw, you will find resistance as you try to pry over the panel. The panel is actually being held in by plastic fingers that stick out to the back of the panel and some to the side. Pry open the cover gently so you don’t break the fingers. In my opinion, it’s a really bad design, since plastic get brittle with age and the fingers may break if you keep opening the panel.

Acer 3680 Memory Panel

After you remove the panel, you’ll notice 2 white plastic washers. Carefully remove them so they don’t get lost.

The memory module is toward the back. Examine the memory module carefully, you’ll notice that the memory module is being held by two clips. The clip fits into a notch on the side of the memory. Gently pry the arms of the clip outward, causing the memory module to flip up to about an 45 degrees angle. Remove the memory. Insert the new memory at an 45 degree angle and swivel the memory gently until it clicks into the clips. Since there is a notch on the connector, you cannot insert the memory in the wrong direction. Do not force the memory or you will break something.

Once the memory module is in, don’t close the memory door right away. Test it to make sure it works first. If you don’t get a BIOS welcome screen, then the memory is not installed properly. If you get a blank screen, don’t panic. Turn off the machine, remove the battery, and re-seat the memory. I find that I may have to re-seat the memory a few times before the memory works. If it still doesn’t work, try different combination of the memory module. You may have a bad memory module. Trying different combination allow you to discover which one.

Once everything is working, turn the laptop over again. Carefully put in the white washers on the screw hole. Reattach the memory panel door starting with the fingers in the back. Be careful you do not knock off the white washers. Once the panel is click in place, put the two screws back in.

Post Installation Booting Problems

After installing the RAM, I notice that occassionally, was unable to start up after a shutdown. Typically, I would turn on the machine. The power light would be on, but nothing happens. The problem is usually fixed by removing the battery and AC, killing all power to the laptop. After the power is restore, the laptop boots normally, only to have a similar problem again after shutdown.

After some research on the net, the problem is cause by a BIOS timing issue. According to Acer, the problem affects laptop with dual RAM. To fix the problem, download the BIOS 1.3505 or above (mines was originally 1.3502).

August 24, 2007 at 7:28 pm 36 comments

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