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$ave money: replace failed batteries in emergency lights Recently a building owner I know had a problem by with his emergency lights – you know the ones, ROSS TESTER where an exit route is illuminated to show the way out of the building in a blackout. When power goes out, an internal battery keeps the light on for some time. T here are many different types of emergency lighting. The ones we’re talking about here look just like standard fluoro fittings. In the electrical trade they’re called luminaires and can be “maintained” and “non maintained”. The difference is that maintained emergency luminaires are “on at all times” – normally powered by the mains so they light an exit route 24 hours a day; whereas non-maintained fixtures only come on when power fails. Neither type can be turned off (except by cutting mains power to them, usually at the switchboard – and even then they stay lit courtesy of their inbuilt batteries) and in both types those batteries are continuously “tricklecharged” from the mains supply. Until quite recently, when LEDs started to take over, these were fitted with one or two 18W fluoro tubes which, especially in the case of the maintained type, had a quite respectable tube life. Fluoro tubes will always last a lot longer if they’re not subjected to the rigours of frequent starting. Of course, the non-maintained types have a tube life approaching shelf life because they are so very seldom on – They look just like an “ordinary” fluoro lamp fitting. 80  Silicon Chip they only light up in a blackout or other power-cut emergency (eg, a fire). While on the subject, there are other “emergency” lights often found in buildings which show either a running man and an arrow, showing the exit route, or simply the word “EXIT” if that’s the way out. Similarly, they’re normally on but switch over to internal batteries in a blackout. There’s yet another type with two tubes, one of which is powered by the mains and the other which comes on when the mains fails. Now back to the building owner’s quandary: of the half-dozen or so emergency luminaires in the twentyyear-old building, two had recently failed their annual “fire” inspection (required by insurance companies). It wasn’t so much that the lights themselves had failed, as they worked perfectly when power was on and immediately switched over to their inbuilt batteries if the power was cut . It was the backup battery circuit which earned the big cross from the fire inspectors, as they didn’t power the lights for the required 90 minutes without mains power. Even though one lasted 45 minutes and one over an hour, that wasn’t “up to spec” and therefore the building insurance would not be renewed without that vital certificate. Never mind the fact that it was only a two-storey building, and maximum egress would be (at most) one minute. Them’s the rules! He contacted the electrician who looked after things electric in the building, asking if the luminaires could be repaired. He was told that they were never repaired; simply replaced with a new fitting. Now I’m not saying that the building owner was named Scrooge McDuck, but he baulked at the quoted price of $295, plus GST. Each! Fitting involved removing the old luminaire, mounting a new one, then re-wiring the mains. But as this also required mains power being disconnected, it could be quite inconvenient if done during working hours . . . and even more expensive if it had to be done after hours. Being of a somewhat technical “bent”, our hero reasoned that the backup supply must be a rechargeable battery and would be either a sealed lead-acid (SLA), nickel-cadmium (Nicad) or (possibly) nickel-metal-hydride (NiMH), presumably with a simple trickle charger running from the mains plus an inverter to boost the voltage back up to power the tubes when required. Unless someone wasn’t playing by Hoyle, such a battery should be significantly less than what the electrician quoted. It was only a matter of a couple of minutes up a ladder with trusty screwdriver in hand to whip off the emergency light cover and his suspicions were confirmed – a “stick” of five Csized NiCd batteries, shrink- wrapped and mounted on a plate, with a quickconnect terminal attaching them to the charger/inverter. Indeed, there was even a label attached telling him that it was a 5-cell, 6V, 1000mAh Nicad. siliconchip.com.au Who’s dat a comin’ down MY driveway? BUILD THE DRIVEWAY MONITOR – See SILICON CHIP July/August 2015 Alerts you when any vehicle uses driveway. PARTS AVAILABLE from the SILICON CHIP ONLINE SHOP (www.siliconchip.com.au/shop): While it would appearDetector that the vast majority of emergency lights use NiCd PIC16F88I/P IC (programmed): ...$10.00 batteries, theyPIC12F675I/P are not all the same. Indeed, within Receiver IC (programmed): .$10.00 the same building there were about half with a 6V stick, made up......$10.00 of 5 “C” size Nicads, but the other Detector/Transmitter PCB (15105151) PCBor (15105152) half had fourReceiver “D” size, 4.8V (as.....................$5.00 seen in the photo above). We would hazard P&P formay any/all above parts (one order) a guess that there beofother variations on$10.00 the theme. However, when he asked Battery Business ORDER if this would cause NOW AT any problems, the manager smiled and said “we can replace any battery for anything.” Nuff said! www.siliconchip.com.au/shop So one night when everyone had gone home, he turned off the appropriate lighting circuit at the switchboard and removed the cover/diffuser and the fluoro tubes (which of course was still lit). He then undid the two screws which held the Nicad stick in place. Carefully unplugging the stick (which was a very simple, ten second job) he replaced the tube and diffuser, then turned power back on. Measuring the output voltage revealed that the voltage was less than the 7.5 or so volts he would have expected; in fact it was about 5.2V which does suggest one or more of the cells was at least a little sick! Placing the battery on a suitable load showed that it had dropped markedly even after 15 minutes, so the stick definitely needed replacing. A quick search on line revealed that these batteries were available but quite a bit more expensive than he expected – more than $100+. He was hoping for perhaps half that. But one thing he did notice was a company called “Battery Business” who promised that they can replace any battery for anything. He remembered seeing one of their outlets only a few streets away from his building – so much the better. They didn’t quote any prices on line but it was worth the ask. So next morning, on the way in, he called into Battery Business with the old unit. siliconchip.com.au The manager told him that if they didn’t have it in stock, they’d simply make up new ones and shrink-wrap them to the old bases, then weld the old connectors on. The price? $40 each, including GST. That made him smile. It turned out that they didn’t have any in stock but it only took them a day to have the replacements made up. He duly picked them up – and noticed they even came with a similar label to the old one! Fitting the replacement battery to the emergency light fitting was just as simple as removing the old one – screw it in, plug it in, replace the fluoro tubes and put the cover/diffuser back on. As he put one of the fluoros in, it instantly came to life, indicating that they had supplied a charged battery. This was repeated for the second fitting. With the power back on, he left them for a day or so, then after hours turned the power back off. And after two hours they were still lighting the way, so he called the inspector who duly checked them for himself, passed them as A-OK and issued the insurance certificate. So for just a few minutes work, both of the old emergency exit fittings were brought back to new condition (in fact, probably better-than-new, because he replaced all the tubes at the same time – to be sure, to be sure, etc), saving a bit of landfill but more importantly for him, saving several hundred dollars in the process. SC Got a long driveway? Want to know who is coming to visit? Our driveway monitor will alert you when any vehicle enters. You can use it to sound an alarm, turn on a camera, lock doors and gates . . . anything! It will even work up to 200m away! BUILD THE DRIVEWAY MONITOR – See SILICON CHIP July/August 2015 PARTS AVAILABLE from SILICON CHIP ONLINE SHOP (www.siliconchip.com.au/shop): PIC16F88I/P Detector IC (programmed): ...$10.00 PIC12F675I/P Receiver IC (programmed): .$10.00 Detector/Transmitter PCB (15105151) ......$10.00 Receiver PCB (15105152) .....................$5.00 P&P for any/all of above parts (one order) $10.00 ORDER NOW AT www.siliconchip.com.au/shop LOOKING FOR A PCB? PCBs for most recent (>2010) SILICON CHIP projects are available from the SILICON CHIP PartShop – see the PartShop pages in this issue or log onto siliconchip.com.au/shop. You’ll also find some of the hard-to-get components to build your SILICON CHIP project, back issues, software, panels, binders, books, DVDs and much more! Please note: the SILICON CHIP PartShop does not sell kits; for these, please refer to kit supplier’s adverts in this issue. March 2016  81