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Dell Inspiron 6000d
Components: Power and Thermal

James F. Carter <jimc@math.ucla.edu>, 2005-03-30

Battery and Power LiIon, 80 watt-hour
Fan and Thermal Issues Very cool, not noisy

Component Details: Power and Thermal

Battery and Power System

80 watt-hours (7.2 amp-hours at 11.1 volts, nominally). Lithium ion, probably a polymer anode, by Sony. I find that in normal use the battery lasts 3 hours (when new). High power activity such as compiling a kernel or watching a DVD can cut this lifetime in half. According to the Users Manual, the nominal lifetime of the battery is 500 charge-discharge cycles. This Users Manual does not discuss partial cycles, but on the Inspiron 4100 a life of 2000 partial cycles was noted. The operating temperature range is 0 to 35 C; non-operating is -40 to 65 C. The rest of the machine is similarly rated.

If you have a program that monitors the battery's charge level, remember that querying the battery requires 26 msec with interrupts off. I set mine to do one query every 5 seconds (rather than one per second). When attempting to burn CDs without DMA, you need to avoid dead time like this. The Inspiron 3800 and 4100 had a similar brain-dead battery query procedure.

As is common in PCs, there is an expendable lithium battery that powers the NVRAM and clock. Eventually it will need to be replaced.

My experience is that the mere passage of time makes LiIon batteries degrade. A similar battery from the Inspiron 4100, by Sony and probably with a polymer anode, went from 1.5 hours to 1.0 hours on a standard high power test over an interval of almost exactly 2 years. On the other hand, the previous battery with a graphite anode lost essentially all of its capacity in 1.5 years. The batteries were used occasionally away from AC power (e.g. in the library or machine room) and were given a full cycle monthly for life testing. Perhaps if I drained them daily the life would be used up faster. I tried to distinguish having the charger plugged in during non-operating times, versus only during actual use, and found no significant difference in the rate of capacity loss.

ACPI displays the voltage and the current into or out of the battery, allowing one to determine (within 50 ma) the current used by individual components. In preparation for testing the battery life, I found:
Component Current (ma) Comments
Lamp 365 Bright minus dim
Panel plus lamp 550 Bright minus off, per specs
Hard disc 502 Continuous reading vs. idle
CPU 823 Intense computation minus idle
Wireless 150 Sending by FTP, includes disc
Wireless 0 Turning off radio: too small to measure
Graphics 920 3D demo incl. moderate CPU, minus static X display
CDROM 928 At 24X
CD burning 345 At 4X
Base current 2150 With lamp bright
Max current 3085 CPU, graphics, disc, CD, for testing (but omitting CD due to DMA issues, so this is not the standard test)

The normal use test was started with a full charge. Conditions: the lamp was bright. No CPU intensive tasks, speed at 800 MHz. Lots of slogins to other machines, reading mail, etc. Typical current drain was 2.1 0.75 amps. After 1/2 hour of just sitting (lunch break), the current dropped to 1.6 amps. Most likely this is the difference between spinning the disc with the heads loaded, versus the disc being totally asleep. When the battery got under 10%, something conspired to run the current consistently over 2.4 amps. The test was stopped voluntarily at exactly 5% charge; coincidentally this lasted exactly 3 hours.

In an empirical test of suspend to RAM state, 867 mAh was used over 466 minutes, or 111 mA. The battery (if new, 7200 mAh) would last 64 hours or 2 2/3 days.

Windows estimates that a full charge will last 5 hours. I doubt this.

Here is a table of battery voltage at various charge levels. The voltage is not linear with the charge level; there is a broad range in the middle of near-constant voltage, which drops off quickly when the battery is empty and which jumps up when it is full. There is no memory effect in LiIon batteries; partial cycles aren't bad for it. Estimated self-discharge rate: 6% in 5 weeks, or possibly less.
Source Charge Volts Current (Amps)
AC (full charge) 100% 12.6 0.0
Battery 90% 12.0 2.0
Battery 5% 10.2 2.4
AC (charging) 5% 10.9 2.2
AC (charging) 50% 11.8 2.2

The AC power converter works on 100v to 240v AC; interchangeable cords can be purchased for non-USA plugs. (Or, more practical for travel, buy a plug adapter at a travel store.) The converter is able to feed at least 46 watts into the machine (its nameplate rating is 65 W); it is warm but not seriously hot. This is plenty for full power operation plus charging the battery on its normal schedule, which will take about 3 hours for a total recharge. The battery is also not hot, probably helpful for making it last longer.

Sony Battery Info

This is generic information about Sony LiIon batteries from their catalog. As with all such documents, be alert to updated versions (this one is dated June 2001) and changes in web addresses. Specifically, the above catalog has been taken off the web, hiss, boo.

Characteristics: LiIon batteries have three technology variants: hard carbon (the oldest), graphite, and polymer (the newest). The cathode is lithium cobalt oxide.
Quantity Polymer Graphite Hard Carbon
Volts per cell at 50% 3.75 V 3.75 V 3.75 V
Voltage change, 25% - 75% 0.25 V 0.20 V 0.55 V
Series resistance* 0.06 V 0.09 V 0.08 V
Recommended charge time 1 hr 2 hr 1.5 hr
Capacity loss
after 500 full cycles
19% 16% 13%

* Series resistance: the voltage drop occurring when you draw a current that would discharge the battery in 2 hours.

Charging behavior: The recommended charging schedule is current limited so as to fill the battery in a specified time (see table) or more. When the battery is 80% full it will reach a voltage of 4.200.05 V, at which point it should be voltage limited, the current declining exponentially. It will reach 99% of full charge within one more hour. There is no indication in the catalog that holding the battery at 4.20 V has any deleterious effect, but overcharging or reverse charging is clearly not good for it. The battery must not be discharged below 3.0 V per cell; in the Inspiron battery this is sufficient to prevent reverse charging any cell.

Transport regulations: LiIon batteries containing no more than 1.5 gram per cell and 8 grams per battery of lithium can be treated as ``non-dangerous goods'' under the United Nations Recommendations on the Transport of Dangerous Goods, Special Provision 188. ICAO Special Provision A45 replicates the U.N. Recommendation, IATA follows ICAO in this, and US DOT regs are based on the U.N. Recommendation. The amount of lithium is 0.3 grams per amp-hour per series cell. The Inspiron 6000d's battery has 3 parallel strings of 3 series cells, and 7.2 amp-hours, so 6.48 grams of lithium.

Safety precautions: (See the catalog for the complete list.)

Fan and Thermal Issues

Unlike on the Inspiron 4100, the fan always runs at low speed, almost but not quite inaudibly. This keeps the machine much cooler: typically 10 degrees C above ambient (i.e. 28 to 32 C), whereas the Inspiron 4100 runs at least 25 C above ambient (45 to 50 C), and even so it has to turn on the fan occasionally in winter and frequently in summer. The lower temperature should improve reliability.

Thus, the Inspiron 6000d is not so useful as a lap warmer, whereas the Inspiron 4100 could get uncomfortably hot, so I got in the habit of putting a towel under it.

Under heavy CPU load, e.g. a kernel compilation, the CPU temperature will be about 10 C higher and the fan will run at medium speed. This is noticeable but not particularly obtrusive. The temperature will drop promptly when the job is over, as soon as the powersave daemon turns the clock speed down to 800 MHz (from 1600). So far in real life I have never provoked the fan to go at high speed, but the Dell diagnostic will do so, and it blows some serious air, and noise.

The air intakes are at the left bottom, side and top, so the Inspiron 6000d should be quite resistant to having the intakes blocked. Exhaust is to the rear.

The ACPI BIOS does not reveal the fan status, same as on the Inspiron 4100. Hiss, boo. I'd like to be able to display the fan status somehow. At the start and end of a CPU intensive task you see a delayed staircase effect in the temperature. It looks to me like the BIOS only reviews the temperature every 30 seconds.

According to the datasheet for the ICH6PM chipset, the internal temperature sensor is accurate to 13 C, which is not particularly accurate.


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