Sunday, March 28, 2010

New UPS Battery

When I moved into the Smart Apartment I was one of the first residents. The power would go off occasionally as building work was done. So I installed a small Uninterruptable Power Supply (UPS). This is a SOLA UPS 305 520. It looks like an oversize power board, with three sockets for equipment protected by the UPS and two ordinary power sockets. It has a small gel lead acid battery (Panasonic UP-RW12200CH1) which can supply power to a typical desk top computer for a few minutes while it shuts down in an orderly fashion (there is a data port on the UPS to tell the computer it is on battery power and should shut down). In practice the UPS would run for about half an hour with my modest computer set-up, longer than most power outages.

Recently the power went off and the UPS failed to operate for more than a few seconds. The battery needed replacing (they last only a few years). There is a separate battery compartment with a cover held n by one screw, so they are reasonably easy to replace. Care should be taken with a UPS, as it can generate dangerous high voltages, even when disconnected.

Gel lead acid batteries are sold by electronics shops, so I thought it would be reasonably easy to get a replacement. Unfortunately the commonly avialable batters are the same dimensions as the Panasonic, but 10 mm longer. As a result the replacement would not fit in the case.

Rather than buy the batter 10mm larger, I decided to buy an even bigger one. The Panasonic unit has no capacity marking on it but appears to be about 4 AH (Ampere Hours). I noted that there was a sweat spot at 7.5 AH: the smaller batteries did not seem to be much cheaper and the larger batteries got significantly more expensive from this point on. The 12 volt 7.5 AH batteries are the size used by many UPS, home burglar alarms and the like.

So I bought a battery from Adelong in Sydney for AU$22.85. This has the same connectors as the smaller battery. I then just need to cut a hole in the side of the battery compartment to fir the larger battery. It will not be elegant, but should work longer than the original.

By the way, you should, in general, not replace a rechargeable battery for one of a different voltage, size or chemistry. Also you need to take care you connect the battery terminals the right way around. The gel batteries have no polarised connectors: you can connect it the wrong way around. If you use the wrong battery, or connect it the wrong way, the result could be an explosion and fire. However, for those with the skills and confidence, replacing the battery in the UPS can save a lot of money.

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Tuesday, February 02, 2010

Train Sleep Mode to Reduce Energy Use

Class 380 Desiro Electric TrainThe new Class 380 Desiro Electric Trains for Scotland will have a "sleep mode" to save power. Apparently trains are not simply switched off overnight when not in use. Also the air conditioning system will sense if a carriage is empty, thus saving further energy.

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Friday, January 15, 2010

Black screens save power on some smart phones

The Google Nexus One and Samsung SGH-i8000 Omnia II smart phones have Active-matrix organic light-emitting diode (AMOLED) screens. Web pages and apps using white text on a black background should save power on these devices.

The Blackle website, launched in 2007, claimed to reduce power consumption by reversing the usual Google search screen, providing a black background. The amount of power saved was not large, as most LCD screens have one back light which is on at the same brightness (and using the same power) regardless if most of the screen is black or white.

AMOLED screens have thousands of individual LED lights. For black, all lights are off. So using a black background should save power. This is significant for a battery powered device such as a smartphone.

The black background could be achieved for web pages and for applications written for the phones.

Currently AMOLED displays are prohibitively expensive for large computer and TV displays. But some larger LCD screens have multiple LED back lights which will save some power with a black background. For this to work there have to be large areas of black, as even one non-black pixel requires the back light for that area of the screen to be turned on.

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