Kohjinsha SC3 – Battery life breakdown and tips.

Posted on 28 July 2008, Last updated on 11 November 2019 by

As you might have read, I have been very disappointed with the battery life figures on the Kohjinsha SC3. I was expecting a lot lot more from an Ultra Mobile PC built on Intel’s latest battery-optimised Menlow platform but it turns out that under normal use, this device is just as bad as many devices based on the previous platform. Over the last 24 hours I’ve spent a lot of time trying to analyse why and have finally come up with the reason. Invetec, the OED for this device, have cut corners. While the background drain (on the motherboard and power board) is better than on previous Kohjinsha’s, it’s no better than the HTC Shift, Q1 Ultra. All these devices can match the SC3 for background efficiency. About 4W minimum or 5-hours, is what you can expect with everything turned off but the processor.

OK, 4W is good but once the screen is on, boom! Up goes the battery drain by between 80 and 150%. This is exceptionally high drain for what appears to be a LED-backlit screen. Thank goodness that using the screen in a bright room requires only 3/8th brightness but it’s still about 3W of drain which is much higher than it should be.

The second shock comes when you turn the VIA, yes VIA!,  USB Wifi module on. Connecting to a hotspot will push the drain up by over 3W. It will settle back to 2W after connection but this is, quite frankly, pathetic. A wifi module that takes more power than the processor is a joke. There are far more efficient Wifi modules out there. Did Inventec think they were designing a cheap netbook?

So from a background drain of 5W, if you want to surf the net in a bright room over Wifi, the battery life drops to a depressing 2hrs. This is an average drain of 10W which is no better than the devices mentioned above.

Breakdown, tips and summary follow…


Here is the breakdown using Windows Vista Ultimate. 1GB RAM. Optimisations done. SP1 installed. ‘Balanced’ battery mode.

  • Background drain: 4-5W
  • Wifi: 1.5-3W
  • Screen: 3-6W
  • Other radios: (BT, GPS): Max 1W
  • CPU: Max 2W.
  • GPU/Chipset: Max 2W.

Apart from the CPU and Chipset, its a horrible set of figures. The Wifi should be around the 0.5W mark and the screen well under 1W. [Here’s some more detail of where I think it should be with Menlow in 2008.]

How to get 3 hours browsing / typing time.

The SC3 has a good range of component control available through on-screen icons, keyboard shortcuts and BIOS settings. The trick, for mobile use, is to set all radios to off and to set ‘silent’ mode on the fan. Ideally, you should set this in BIOS so that the device boots up in this state by default. There’s even a ‘long-term-mobile’ BIOS setting that does this for you. (Obviously Kohjinsha knew how much the extra components affect the battery life!)

Setting all components to OFF and setting the screen to 3/8ths, the SC3 will sit doing nothing and give you well over 3 hours of typing time on a word processor. That’s if you really fancy typing for 3 hours on the tiny keyboard. E-Book reading (which is fairly comfortable on the hi-res, high-brightness screen, will give you 2.5 hours of battery life at the 50% setting. Outdoor use will see that drop to 2hrs as you pump up the backlight.

If you need to go surfing though, the big trick is to use a mobile phone modem over Bluetooth. Bluetooth takes very little power and if you’ve got a 3G contract, you’ll be happily surfing for up to 3hrs. Keep those flash-heavy pages closed after you’ve used them though! Single-tab browsing is the answer. Its a compromise but it works.

Vista and Disk.

I have a suspicion that the disk never spins down under Vista. I’ve been watching the read/write figures under Vista’s performance monitor and it seems that pagefile, logging and software services processes are always accessing the disk. One answer to this could be more memory. It would certainly reduce the need for the pagefile which seems to be the worst offender. Alternatively, moving to a simpler OS might be the trick. I’m tempted to try out XP to see how that affects the figures. Once I’ve taken a disk image, I’ll do it.

Further tests.
  • Removing the TV module. Its possible that this is draining some power on the USB bus.
  • Updating drivers for screen and Wifi. The screen is currently using a generic driver. There may be drivers that support extra power-saving features.
  • Switching to Windows XP. When I did this on the Q1 Ultra, I saw big gains. 10-15% battery life savings. Drivers for GPS and camera could be a problem but for mobile surfing, this could be worth trying.

The Kohjinsha SC3 is no showcase for the Menlow platform. The screen and Wifi take far too much power and negate any gains that might have been had from the Intel silicon. Adding an extended battery is an option but its a compromise that shouldn’t have to be made. Kohjinsha should have built the SC3 with a minimum 3-hour Wifi-on surfing time and users should not be expected to pay extra and compromise on size and weight with an extended battery. In fact, I don’t think pro-mobile users are going to make any compromise at all. They’re just going to walk right past the SC3 and look for a different solution. Unless I unlock significant advantages in further testing, i’m going to be doing exactly the same thing.

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