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SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Jim Rowe – B.A., B.Sc. Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Nicolas Hannekum (resigned) Advertising Enquiries Glyn Smith Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Former Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $65 12 issues (1 year): $120 24 issues (2 years): $230 Online subscription (Worldwide) 6 issues (6 months): $50 12 issues (1 year): $95 For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: Editorial Viewpoint Low-cost UPSes are not worth the risk Ten or more years ago, purchasing an uninterruptible power supply (UPS) for a computer or other piece of critical equipment was quite expensive. Usually, you would have to buy a brand like APC. While their quality was reasonable, those units had very few features and cost a few hundred dollars for even a moderately-sized one. But more recently, many less-expensive units have come onto the market. These are very tempting because if you only need a basic UPS, you don’t want to pay hundreds of dollars more for what seems to be essentially the same thing. But these cheap units are usually too cheap. They come with low-quality batteries and have dumb charging schemes, often without proper battery management or thermal cut-outs. As a result, you’re lucky if the battery lasts more than a year or two. Even decent quality gel cell (SLA) batteries will generally not last more than a couple of years in these devices. When the battery inevitably fails, it can leak acid and overheat badly. While I haven’t heard of any such units catching fire, it doesn’t seem impossible. I had one of these fail on me, and it got stinking hot and reeked of acid. I had to disassemble the UPS to get the badly distorted and swollen battery out. More recently, I have heard from several other people who have had similar experiences with various low-cost UPS brands. I went into a bit more detail about my bad experience and what I did to prevent it from happening again in an article in the January 2020 issue titled “Emergency backup power during blackouts” (siliconchip.au/Article/12215). While it is a somewhat more expensive solution initially, buying an inverter/ charger and a separate, high-quality battery (AGM or LiFePO4) is much better. This approach lets you independently select the maximum power and backup time requirements. Battery replacement is easy, and the battery will last a lot longer. A decent AGM battery designed for standby use should have a useful life of at least five years, while a top-quality unit might last ten. Consider that most low-cost UPSes only offer a ‘runtime’ of around 10 minutes at full load. In contrast, the inverter/charger solution can maintain its output for hours without mains power. Even days, if that’s what you need. The long-term cost of this type of solution may not be that much higher than a cheap UPS because you won’t have to replace the battery as often. That means less maintenance and less chance of catastrophic battery failure. That’s partly because you aren’t stuck with gel cells but also because you can locate it outside the main unit, where cooling air can better circulate. If you must use a low-cost UPS, I suggest taking the battery out before you even use it and checking to see if it is a decent-quality unit. If not, immediately replace it with a higher-quality equivalent and either sell the battery that came with it or use it for another less-critical purpose. It would also be worth checking whether the UPS you buy has a thermal cutout to stop charging the battery if it fails. If you can’t see a temperature sensor near the battery, it probably doesn’t. I won’t suggest that you add a thermal cut-out if one is missing because I don’t have the space to describe how to do that properly. Ultimately, I think it isn’t worth dealing with a poorly-designed low-cost UPS. If possible, buy a better one or try the inverter-charger option I mentioned above. Ongoing mail delays Apologies to readers who received their May issues late (or not at all). They were mailed on-time but soon after came the Easter and Anzac Day public holidays, terrible weather and general postal chaos. Unfortunately, it seems that the postal system is not stable yet and might not be for some time. We mail out the magazines consistently in the middle of the previous month, but we are at the mercy of inconsistent delivery times. by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia's electronics magazine siliconchip.com.au