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Want your house to be the only one in the street with lights on? Emergency backup power during blackouts Have you thought about how an extended blackout would disrupt your life? They may not be common where you live, but that will change, especially if a natural disaster occurs. A widespread, extended blackout could go beyond inconvenient, to life-threatening. But you can build a system to run some lights and critical appliances when mains power is not available, for days if necessary. A few months ago, we came home to find the power was out. While this is not a common occurrence, it does happen from time to time. I have experienced several blackouts over the last decade or so; mostly short (under one hour) but occasionally longer (three or four hours). Some of my family members who live in the Blue Mountains (west of Sydney) have experienced multi-day blackouts, which are annoying, to say the least! For us, the power came back on not long after we got home, and we were able to resume our regular routine. That included bathing my daughter and putting her to bed; something that would have been very difficult to do in the dark and with no hot water (our gas water heater has an electric igniter). 10 Silicon Chip This loss of power got me thinking about what I would do if there were a longer blackout, especially in the evening, when we rely heavily on electricity. An extended blackout would cause us a great deal of difficulty. So I started looking into possible solutions. A disturbing development This blackout caused me some grief beyond just that time without power. When we had a roller shutter installed which can block the rear exit to our home, I insisted that it must have battery backup so that a fire at the front of the house (where power comes in) could not result in both main exit routes being blocked. We paid quite a lot of money to have this battery backup system installed. by Nicholas Vinen Australia’s electronics magazine But only two-and-a-half years later, during this short blackout, it totally failed. Arriving home to the dark house, I tried to put the shutter up, but it didn’t respond. That weekend, I dismantled the cabinet in which it was housed, only to find the gel cell batteries in the UPS (interruptible power supply) had gotten so hot that they melted and were leaking acid! (See Photo1) I ran some quick sums and discovered that these two 7.2Ah SLA cells were expected to deliver upwards of 100A each when the UPS was operating. No wonder they failed so spectacularly! Anyway, I’m told that these SLAs, even in normal service, only last a couple of years. That’s hardly ideal for a safety-critical application, especially siliconchip.com.au Photo2: the APC SMX1500RMI2U is one of the commercial Uninterruptable Power Supplies I considered before discarding the idea and building my own. It costs around $2000. Many UPS data sheet give no indication of the expected runtime or battery capacity, only the maximum power. To APC’s credit, they do give you the battery capacity for this unit at 311Wh (approximately 25Ah <at> 12V) and provide a runtime chart, which shows a runtime of just under five hours at 50W. That’s better than your average computer UPS but not so great when you consider the price. Photo1: while not really obvious from this angle, the two SLA batteries in this UPS were badly distorted and buckled and it was very difficult to remove them. You can see some of the acid that was leaking out on the clear plastic sheet underneath them. all that high-end computer UPSes had pretty poor battery capacity given their high prices (see Photo2). I wanted something that would ideally last at least 24 hours, and I was becoming increasingly concerned that the SLA/gel cell batteries used in almost all UPSes are not good long-term prospects. There had to be a better way, so I started investigating other possibilities. This article is not intended to describe all the ways that you could provide emergency backup power. There are just too many options. But I will list some things I learned while researching my particular problem. I will also describe the backup system that I eventually put together. Backup power options Perhaps the ultimate way to insulate yourself from mains grid power fail- given their inaccessibility in my case. I had to find a proper solution to this. I looked online for higher-quality UPSes, especially those with a longer standby time at light load. The UPS that we had been supplied would last for less than an hour even with no load. That simply wouldn’t do as we can’t guarantee that we would be home if the power goes out again. I found some commercial UPSes online with a longer standby time; in some cases, eight to twelve hours, or more. They cost thousands of dollars, though, and I found oversiliconchip.com.au ures is to have an off-grid system, such as a solar-charged battery bank system. However, that brings up a whole new set of problems. As you will be generating your own 230V AC power, you need to make sure that you have sufficient redundancy that one component failure will not mean a total loss of power. After all, off-grid systems can fail, and if yours does then you will be without power until you fix it. If you don’t have spare parts on hand, that could take days or weeks, depending on how hard it is to get replacement parts. So you need to know what you are doing if this is your plan to improve the reliability of your home electrical supply. You will also need a big battery bank and big solar array, to ensure that it can meet your power needs, regardless of weather and usage patterns. That’s a Photo3: our 800W+ UPS project from the May-July 2018 issues would have worked in my situation, except that it was a bit large to fit in the space I had available. My eventual solution involved a much larger and different type of battery, partly because of my desire for a longer runtime, but also because I am told that AGM leadacid batteries last a lot longer on standby than the lithium-based (LiFePO 4 ) rechargeable batteries we used in this UPS. The LiFePO 4 batteries are very good in ‘deep cycle’ applications, but that is not so important when you only only have the occasional blackout. Australia’s electronics magazine January 2020  11 Photo4: the Jaycar MG4508 inverter generator is good value at $899 (retail, including GST). It runs off petrol (3.7l tank) and has a continuous power rating of 1.6kW, which is enough to run all but the biggest appliances. Depending on the load, a tank of petrol could last for many hours, and even a modest jerry can would have enough capacity to refill it several times over. However, you will need to make sure you have fresh petrol on hand to use a generator like this. It goes off eventually, so you can’t just fill a can and forget about it. You also need a well-ventilated area to operate a generator due to fumes. significant challenge, and such a system is likely to require a significant upfront investment. You could consider installing a small off-grid type system to run a limited portion of your domestic appliances, and retain the grid connection, so that you have two sources of power. Such a system could be a lot smaller and cheaper, and the chance of it failing on the same day as a loss of grid power is very low. But building such a system ‘just in case’ could still be quite expensive and time-consuming. Anyway, I don’t have any suitable places to mount solar panels, so I had to think of another solution. I considered a small battery system (charged from the mains and/or other sources), or a petrol/diesel generator. A generator is the cheapest solution. For example, Jaycar Cat MG4508 is a 2kVA petrol inverter generator which retails for $899 (Photo4). Providing you have enough fuel, this could keep you going for several days or even weeks without mains power (eg, during a natural disaster), keeping your fridge/freezer cold and running other critical appliances. The three main disadvantages of such a system are that most are not automatic (you normally have to fire up the generator and plug your appliances into it, ruling it out in my case), that petrol and diesel fuels cannot be left in the tank long-term and that a generator cannot be used in an enclosed space. So if you live in a unit, it may not be a practical solution for you. Fuel can go bad if left sitting for a long time (more than 3-12 months, depending on how it’s stored and the ambient temperature). So unless you are continually turning over a small supply of petrol, you will have to go out of your way to keep fresh fuel on hand in case you need it. I have an electric mower, so I don’t keep petrol at home. It may be possible to drain some from your car’s tank in an emergency, but anti-siphoning de- vices (to stop petrol theft) make that difficult. You could purchase a generator and wait until there’s a blackout to get some petrol; but if the blackout is widespread, the fuel station pumps may be non-functional which could leave you totally out of options. A small battery system cannot deliver anywhere near the total energy that a generator can, but does have a few advantages. Battery systems can automatically take over during mains power failures, and they can be augmented with a generator for longer outages. And batteries can sit around charged for years, ready to go, so they are low-maintenance. You will pay more for a decent battery backup system than a generator, even though it won’t run your loads for anywhere near as long. And batteries do need to be replaced eventually. So there’s no ideal solution. Other possible solutions Having decided that I needed a battery system, my thoughts turned to how to extend its run-time in case of a long blackout, as might be caused by a natural disaster. The difficulty in keeping fresh fuel on hand (and getting fuel out of a car tank) put me off the idea of using a generator. So, what about using my car as a generator? I am constantly turning over the fuel in its tank, and it already has an engine and alternator; it just lacks the high-voltage output of a generator. Just about any 12V inverter will run from a car electrical system. This could provide 230V AC to run appliances and/or recharge a battery backup system during an extended blackout. But a typical car or SUV alternator is only designed to provide maybe 100A Photo5: this Jaycar 2000W pure sinewave inverter is under $500 including GST (catalog code MI5740). It could be useful as part of a battery power back-up system, or to connect in to an automotive electrical system to provide mains power from the vehicle’s fuel supply. But note the caveats presented in the article, especially that a car alternator generally cannot provide more than about 100A, so you risk flattening the car battery drawing upwards of 1000W from the inverter for long periods, even with the engine running! 12 Silicon Chip Australia’s electronics magazine siliconchip.com.au Photo6: Jaycar has a range of 12V solar panels (this is Cat ZM9058, 120W) which could be kept in your shed and pressed into service in an emergency, to charge a battery back that powers your appliances though an inverter. If you choose to go this route, make sure you have all the cables you need on hand. It would also be a good idea to have an MPPT Solar Charger. Jaycar sells inverters with built-in solar chargers (eg, Cat MI5722 & MI5724). If you are desperate, you can connect panels directly across a battery, if you monitor the voltage carefully and disconnect them if it rises too high. continuously; possibly a bit more or less, depending on the model. That’s barely enough to run a 1000W inverter at full load. Such an inverter could drain the car battery even with the engine running. There’s also the question of whether the car’s alternator will deliver full current with the engine idling. Many require 2000RPM or more for maximum output. That is something that would need to be verified for your vehicle. Despite these provisos, a 1000W pure sinewave inverter can be purchased for just a few hundred dollars (Photo5), so it may be a worthwhile investment as a last-resort method of recharging a backup battery during a prolonged blackout. You would need to periodically monitor the vehicle battery voltage if using such a rig. If you found that the battery was being discharged even with the engine running, you’d need to disconnect the inverter and allow the vehicle battery to recharge before connecting it again. Having to do this periodically could be quite annoying, but it would be better than having no means of keeping your appliances running at all. Temporary solar panels As I mentioned above, I don’t have any good locations for permanently mounting solar panels, but I did consider installing a mains-charged backup battery power system while also keeping some panels on hand for emergency use (Photo6). These could be laid out in our yard and wired up to an MPPT solar charger attached to siliconchip.com.au the battery when needed. That would allow me to power our appliances using solar power during the day (weather permitting) and possibly even recharge the battery during the day, to keep it going overnight, if we experience an extended multi-day blackout. The only disadvantages are the purchase cost of the panels and the solar charger, and the need to store both. But if you experience an extended blackout, I think you will be thankful to have them. So it’s an option worth considering. Determining power requirements So I set about researching a battery-based system with mains power to keep the battery on standby, and recharge it after a blackout. The first thing I did was measure the size of the space I had available, where the old UPS was fitted. I considered using the UPS design that we published, which was based on two 12V LiFePO4 batteries (May-July 2018; siliconchip.com.au/Series/323). But I measured our prototype and found that it was too large to fit in the available space. I could have probably built a smaller version of this design, but I wanted to take a different approach, for reasons I am about to explain. The next thing I did was to measure the maximum power draw of the motor powering our roller shutter, and found it to be just under 400W. So a relatively small inverter and battery would do the job, as long as the standby power Australia’s electronics magazine consumption was low enough. (Our 2018 design could deliver twice this power, so it would have worked, if it had fitted.) After some more thought, I decided that while a 400W inverter would do the job, it wouldn’t cost much more to get a bigger inverter and battery. That would let us run other appliances during a blackout. I considered whether it was feasible to build a system which could keep the fridge and freezer cold for about 24 hours, and maybe run a few other appliances intermittently, such as lights, a television etc. It would have to fit in the cabinet space available, though, and I didn’t want to spend a huge amount of money on it. I also wanted a system that would need minimal maintenance over a long period; ideally, 10+ years. One reason for this is that, as I mentioned above, the electronics would be sealed inside a cabinet which would make regular maintenance difficult. I also could easily forget to check the battery as it would be “out of sight, out of mind”. Choosing a battery I quickly ruled out using flooded or gel-cell (SLA) lead-acid batteries, as they have an insufficient lifespan. Many UPS vendors recommend replacing even good-quality SLAs after 2-3 years (mine didn’t even last three years!). After some research, I also rejected LiFePO4 lithium-based rechargeable batteries. This is because, while they are well-suited to deep-cycle applications, they do not last so well on January 2020  13 Photo7: this Fullriver 200Ah AGM battery is good value, if a bit unwieldy. I was told to expect a 6-7 year lifespan. I was hoping for a system that could be left alone for around ten years, hence, my decision to buy a slightly more expensive battery. standby. There is some talk online that if kept constantly on charge, LiFePO4 cells degrade significantly within a few years. Also, they have much lower continuous discharge current ratings compared to similarly-sized (and priced) lead-acid batteries. That meant that an LiFePO4 battery suitable for my application would be well over $1000. Consider that a 100Ah LiFePO4 battery, typically around the $1000 mark, is only rated to deliver 50A. That’s barely enough to run a 500VA/400W inverter, just barely adequate to power my shutter and nothing else. I didn’t want to use a lithium-ion battery due to their reputation for catching fire if there’s a fault, especially considering it would be inside a timber cabinet. That left me with only one real choice: one or more lead-acid AGM (absorbed glass mat) batteries. A good AGM battery has a very high charge and discharge current for its size and can have a long life on standby; typically more than five years and, in the case of top-quality batteries, up to ten Some back-of-the-envelope calculations showed that a 100Ah 12V battery or 50Ah 24V battery would be able to power my fridge/freezer for around 24 hours in typical weather, based on the figures on its Energy Star sticker. Such a battery would also last days on standby, assuming an inverter idle current of no more than about 1A. I made a shortlist of suitable batteries. Two of the best options were the Chinese-made FullRiver HGL200-12 200Ah standby AGM battery (Photo7) and the American-made Lifeline GPL30HT 150Ah deep-cycle AGM battery (Photo8). 14 Silicon Chip Photo8: this is the battery I wound up with, a Lifeline 150Ah deep-cycle AGM unit. It’s rated for around 500 full discharge cycles and can be charged or discharged at up to 150A, or discharged a bit faster, at the risk of a shorter lifespan. That’s enough to support a 1500-2000W inverter with just the one battery. It should be able to deliver an average of 100W, enough to run a typical fridge/freezer for more than 24 hours. Both batteries came to me highly recommended as being of good quality. The FullRiver battery is cheaper, despite having a 33% higher capacity. I was told to expect a 6-7 year working life while the Lifeline battery might reach the 10-year mark that I was hoping for. That, plus its smaller size and lower weight (43.5kg compared to 57.6kg) clinched it for me, despite the higher cost. Interestingly, the 150Ah Lifeline battery supports charging at up to 150A (and presumably, discharging at a similar level; enough to run a 1500VA inverter) while the higher-capacity FullRiver battery is only rated for charging at 40A. The maximum specified discharge rate for the FullRiver battery is 120A for 1 hour. So it would be suitable for running an inverter up to about 1200W, although you can see that you lose a fair bit of its usable capacity at such a high discharge rate – 120Ah is 40% less than when discharging at the 20-hour rate where capacity is 200AH. permanently connected to the battery. This would be a cheap approach, as a basic but decent charger can be had for around $100 and a similar quality 1kW inverter is just a few hundred dollars. But the main problem with this is that any time the attached appliance(s) are used (eg, the shutter put up or down), this would draw tens of amps from the battery, likely reducing its lifespan. Worse, this would almost certainly cause the charger to switch from float charging to bulk/absorption, and if that happened regularly, the battery would not last long. The other problem is that I didn’t know how long the charger and inverter would last when powered 24/7. Low-cost devices might fail in less than 10 years, making the purchase of Charger and inverter choices I then had to figure out what charger and inverter to use. I briefly considered buying a battery charger and a separate inverter, and leaving both Photo9: my Victron Multi Plus Compact 1500VA 12V inverter/ charger (what a mouthful!). It comes with the battery cables and NTC thermistor prewired. It’s also supplied with pluggable terminal blocks for the mains input and output, but these need to be wired up (in my case, to the ends of a bisected extension cable) before it can be used. Australia’s electronics magazine siliconchip.com.au an ultra-reliable battery a bit pointless. What I really needed was a UPSlike scheme where the appliances would run off mains when available, only switching to inverter power during blackouts. That way, the battery would have no load most of the time and could just be kept in float/maintenance mode. And ideally, the hardware to achieve this should be designed for long-term use, to meet my longevity goal. I subsequently noticed a local shop (Battery Business – a few doors down from our office) [www.battery-business.com.au] advertising Victron Energy Compact Inverter/Charger units on their website. While a little expensive, these would do precisely what I wanted. They contain a large toroidal transformer which charges the battery fast when mains power is available. That same transformer is then used in reverse for the inverter function. So they have a battery charging capability that’s well-matched to their inverter power. And as I later discovered, a deeply discharged battery recovers best if it’s recharged with the maximum available current. Another useful aspect of this Victron “Multi Plus Compact” series of inverter/chargers is their relatively small size. Their 800VA, 1200VA, 1600VA and 2000VA versions are all just 375mm tall, 214mm wide and 110mm deep. That’s only slightly wider than the Lifeline battery I chose (at 170mm), and would just fit into my cabinet. Photo10: the MK3-USB interface, needed to connect a computer to the Victron inverter for configuration or monitoring. Photo11: the cables after being terminated and clamped in the supplied plugs. They plug straight into the bottom of the unit, effectively making it into an appliance. The inverter chassis is Earthed via the plug’s Earth pin. The 500VA Multi Plus Inverter is somewhat smaller, and there are also larger models (up to 5000VA or even higher), but the “Compact” series seemed right in the sweet spot for me. So that left me with the choice of the four models mentioned above. While all four would run my shutter, I found the higher-power models attractive for a few reasons: 1) The 1200VA and 1600VA models are not that much more expensive than the 800VA (depending on where you buy them). 2) While 800VA is enough to run a fridge, it might not be enough to start the compressor reliably. Stalling it could lead to motor burn-out. The peak power of these inverters is twice the VA rating, but I wasn’t sure if that would be enough on the lower-power models. 3) The watts rating of each model is slightly lower than the VA rating (as you would expect), but it falls even further at elevated ambient temperatures. At 65°C (which the inside of my cabinet could reach), the 800VA inverter can only deliver 400W, which is barely enough for my needs. The 1200VA unit can deliver 600W under the same conditions, with the 1600VA (800W) and 2000VA (1000W) units doing even better. So I decided to purchase the 1600VA inverter/charger (Photo9), plus the separate USB interface module needed to configure and monitor it (Photo10; more on that later). While these units have reasonable default settings, and there are DIP switches for changing common options, I wanted to be able to set it up to match my battery requirements as closely as possible. I could have saved a little bit by buying both the battery and inverter/ charger online. But given that the staff at the shop down the road had already given me helpful advice, and I was likely to get better after-sales (and warranty) service from them, I decided to pay that little bit extra. This came out to $1126 for the battery, $1440 for the inverter/charger and $90 for the USB interface, for a total of $2656 including GST. So this is not a cheap system, but I am hoping that I can rely on it longterm. Ventilation          Photo12: two internal RJ45 sockets are provided for the VE.Bus interface. You can use either one. I cut a patch cord in half and ran it out through the supplied rubber grommet, then terminated it to an RJ45 wallplate so I can configure the inverter without having to open up the cabinet it’s inside. siliconchip.com.au Australia’s electronics magazine AGM batteries have vents, but I am told that they will not outgas during normal charging or discharging; only if they are abused or about to fail. Still, I had some concerns about the buildup of hydrogen/oxygen gas in my cabinet. It isn’t a totally enclosed January 2020  15 space, but neither is it especially well ventilated. As recommended in the Victron manual, I managed to avoid installing the inverter above the battery; instead, it is behind it, so any gas evolved will not flow directly into the inverter. I also mounted a small, low-noise, longlife fan in the cabinet, blowing air out through the only gap. This would help remove any gas which did build up in that space. This is something you have to keep in mind with lead-acid batteries. They can generate hydrogen gas, and if it builds up in an enclosed space, it’s an explosion hazard. So don’t forget to consider that when designing a backup battery system. The fan I fitted will also help reduce the temperature in the cabinet if the inverter/charger is working hard. Setting it up It took a couple of weeks for the inverter/charger to arrive, and as soon as it did, I went about setting it up. Before purchasing it, I was aware that the user manual stated that “This product should be installed by a qualified electrician”. In Australia, if such a device is installed with fixed mains wiring, you do need a licensed electrician to install it (the rules in New Zealand are different). However, other than the lack of internal battery, this device is essentially just a UPS (interruptible power supply). So if it is fitted with a standard mains plug and socket via a method which complies with the wiring rules, then it can be treated as an appliance. In this case, it is legal (and safe) to install without any special licenses, in NSW at least (other states may have more strict rules). The inverter/charger’s mains input and outputs are supplied with pluggable terminal blocks that have integral cable clamps, but no cables attached. So all you need to do is cut an extension cord in half, unplug these terminals, open them up, wire the Active, Neutral and Earth wires where indicated, then attach and tighten down the cable clamps to ensure the cables are properly retained (Photo11). There are two essential things that you must make sure of when you do this: one (and this is critical), the plug end of the extension cord must go to the terminal designated as the mains input, and the socket end must go to the terminal designated as the mains output. These are clearly labelled. The other is that you need to make sure that the cable you’re using has a sufficiently high current rating and that it is thick enough to be firmly clamped by the mounded plastic of the pluggable terminal block covers. I found the 10A cables I used a little thin to compress securely in the cable clamps, so I added a couple of layers of black heatshrink tubing around it to bulk it up a bit. It was then clamped nicely in place. Once you’ve wired up the plug and Screen1: the initial VEConfigure screen with charger and inverter status at left and some basic options at right, including the all-important maximum input current, which I’ve set to 10A to suit my cable. 16 Silicon Chip socket, plug them in and verify that you have low-resistance continuity from the Earth pin of the plug to the socket, and also from the plug to the inverter’s chassis. It’s also a good idea to check that there is a very high resistance from the Active and Neutral pins on the plug to the Earths. By default, the inverter/charger can draw up to 16A, however, there is a DIP switch to reduce this to 4A and with the USB interface, you can set the maximum current draw to just about any value, including 10A or 15A, to suit normal extension leads with either standard 10A or 15A plugs and GPOs. This is one of the main reasons I decided to purchase the USB interface; so I could set the maximum current draw to 10A, to suit the GPO and cable I am using. Given that the 1600VA inverter can charge the battery at up to 70A, drawing around 4.5A from the mains, that leaves me with about 5.5A or 1250W available at the output. That’s more than enough for me, and that’s about how much power my inverter can deliver at 40°C anyway. So for me, standard 10A input and output cables are suitable. USB interface Victron Energy uses a protocol they call “VE.Bus” to interface between various devices including inverters, control panels, computers etc. This operates over a Cat5-type cable up to 10m long. As I mentioned, I purchased their Screen2: the grid configuration screen. I’m not feeding power back into grid but this inverter apparently supports that. You would need an agreement with your power company before enabling this, and the unit would also definitely have to be installed by an electrician if connected to the grid. Australia’s electronics magazine siliconchip.com.au MK3-USB interface so that I could connect to the VE.Bus port on my inverter/ charger from a laptop computer. The required software is a free download (see links below). I had no trouble getting this up and running, and the software is quite easy to use. In addition to changing the inverter settings, you can monitor its operation, including battery voltage, charging mode etc. This is quite handy for me, given that my inverter is inside a cabinet. I can plug in the MK3-USB interface via a panel-mount RJ45 socket and check what the inverter is doing. This should also let me reset it if there is a fault (eg, an overload), although I believe that the inverter will auto-reset after a fault by default. The screen grabs below show the various options and displays available via the free VEConfigure software. Battery connections The Victron inverter/charger comes pre-fitted with 1.5m-long, thick battery cables pre-terminated with eyelet lugs suitable for the M8 screw terminals on my Lifeline battery. The battery came with matching hardware, so connecting up the inverter was easy. The inverter/charger has an internal fuse; however, they recommend fitting one at the battery as well. Jaycar has a range of bolt-down and battery terminal fuses which are suitable for this purpose. The inverter/charger also comes pre- wired with an NTC thermistor for sensing battery temperature, for temperature compensation during charging. This is encapsulated in an eyelet lug, which is placed over the ground lug on the battery to make physical contact, for temperature sensing. I then set about wiring up the RJ45 panel-mount socket I mentioned earlier. You have to open the inverter’s front panel up to make the connection, which is something I did before powering it up for the first time (Photo12). I cut a Cat5 patch cable in half, opened up the inverter (which involves the removal of just four screws) and plugged it into one of the two internal sockets; either will do. I then cut a small hole in the multi-size rubber grommet supplied with the inverter and fed the cable out through the bottom. I was then able to re-install the cover panel. I used a ‘toolless’ RJ45 wallplate socket from Jaycar. This has punchdown style connections at the rear, but it comes with a plastic cover plate which also serves as the punchdown tool. Wiring this up is a little confusing; while they show which colour wire goes where, there are unfortunately two colour coding schemes for Cat5/ Cat6 cable. So I had to check the order of the colours in the existing plug, then make sure that I had the wires connected to the socket terminals labelled 1-8 in the same order. Once you’ve fed the bare wires Screen3: the inverter settings. I left these all at the default values, except that I raised the low-battery cut-out from 10.5V to 11.0V to protect my battery from over-discharge, as that is the manufacturer’s specification. siliconchip.com.au through the appropriate terminals, you firmly push the plastic block down over them, which cuts through the insulation and makes the connections. The rear clamshell of the socket then locks together, stopping it from coming apart. This left me with an RJ45 wallplate socket ‘captive’ to the inverter/charger, which I connected to the Victron USB interface via another short patch cable, and plugged it into my laptop. Once I had downloaded and launched their free software and powered the inverter up, I was able to access the control panel and confirm that it was charging the battery. I could then configure various parameters related to battery charging, inverter operation etc. I didn’t change any settings I didn’t fully understand. I adjusted the maximum mains current to 10A and chose an appropriate charging profile for my battery. One of the excellent features of this device is the fact that once the battery has been on ‘float’ charge for 24 hours (typically around 13.8V), it will drop into ‘storage’ mode, holding the battery terminals at around 13.2V (2.2V/ cell). This extends battery life. It will then periodically bring the battery back up to 14.4V (2.4V/cell) for around one hour a week, which helps to prevent electrolyte stratification and also ensures that the cells remain evenly charged. All of this should mean that the battery lasts as long as possible. Screen4: the charger configuration. I chose the Victron AGM profile as it most closely matched my battery. It specifies a charge voltage of 14.4V and float of 13.8V, compared to my ideal settings of 14.3V±0.1V and 13.2V, but it does incorporate a 13.2V storage mode after 24 hours. Australia’s electronics magazine January 2020  17 One slight disappointment is that I discovered that if you set your own battery charge voltages, the unit disables temperature compensation entirely. Temperature compensation can only be used by selecting one of the pre-set charging profiles. My battery specifies a bulk charge voltage of 14.3V±0.1V at 25°C, so the built-in profiles that charge to 14.4V are only just within spec. But I think using one of those is probably better than setting the charge voltage to 14.3V and losing temperature compensation. That could lead to severe overcharging at high ambient temperatures, above 35°C, where the charge voltage should ideally drop down to around 14.0V. Extra features I also bought a Jaycar PS2011 panelmount 15A ‘cigarette lighter’ socket, SZ2042 inline blade fuse holder, 15A fuse, 25A automotive power cable and 8mm ID eyelet connectors. I mounted the cigarette lighter socket on my cabinet and wired it back to the battery terminals via the fuse. I also purchased a Jaycar MP3692 dual USB car charger with voltage display. Plugging this into the cigarette lighter socket is a really easy way to monitor the battery voltage, and it also means I can charge USB devices without the inefficiency of the inverter. In future, I can potentially even charge the battery from solar panels wired in via this cigarette lighter plug (although only at 15A/200W, but that’s better than nothing). Conclusion So far, my backup power system has been running well. The shutter worked identically before and after I switched off the mains power to the inverter/charger. I had no clue that it was running off the battery, except for the change in the status LEDs. I haven’t tested the ‘fridge yet, but with a 3000W inverter surge rating, I’m confident that it will start up and run just fine. References & links Lifeline GPL-30HT 150Ah battery source: siliconchip.com.au/link/aava Lifeline GPL-30HT 150Ah battery data sheet: siliconchip.com.au/link/aavc Fullriver HGL200-12 200Ah battery source: siliconchip.com.au/link/aavd Fullriver HGL200-12 200Ah battery data sheet: siliconchip.com.au/link/aave Victron Energy Multi Plus Compact Inverter Charger (12V/1600VA/70A) source: siliconchip.com.au/link/aavf Victron Energy Multi Plus Compact Inverter Charger (12V/1600VA/70A) user manual: siliconchip.com.au/link/aavg Victron Energy MK3-USB interface: siliconchip.com.au/link/aavh VEConfigure software download: siliconchip.com.au/link/aavb Screen5: the inverter incorporates a “multiswitch” relay which can be triggered upon various conditions such as loss of mains power, battery voltage low etc. I haven’t wired mine up to anything but it appears to be a very flexible feature. 18 Silicon Chip SC DO YOU OWN AN ELECTRIC CAR? If so, you could well be driving an emer-gency home power supply right now! As some readers may recall, five years ago I purchased a Nissan LEAF. And for most of those five years, every time there was a blackout I thought about that BIG, powerful battery sitting down in my garage, wondering how I could press it into service as a source of power. I’ve always dismissed the idea because the thought of getting across ~360V DC made me shudder! But, as it turns out, I’ve been looking at a glass half empty instead of a glass half full! I came across a website not long ago which pointed out that, in common with many electric vehicles, the Nissan LEAF also has a 12V lead-acid “house” battery which powers all the “normal” 12V vehicle functions excepting, of course, the traction motor. This battery is kept fully charged (when the car is running) by the high voltage DC battery via a DC-DC converter – so it should always be ready to use. The website demonstrated how to fool the car into believing it was turned on and running so that the 12V battery would be kept charged until the high voltage battery was discharged, so its protective circuitry would kick in. All I needed to do was to buy a 12VDC to 230V AC inverter – as in this article – and connect it to the 12V battery. Doh! Why didn’t I think of that before! So now, 1kW inverter at the ready, I’m anxiously(!) awaiting the next blackout to put the theory into practice. You’ll find the website I’m referring to via siliconchip.com.au/link/aavi Ross Tester Screen6: this control panel can be launched from the VEConfigure software. It mimics the physical control panel which you can purchase for use with the inverter/charger, allowing you to switch the inverter on and off, change its current limit and monitor its state in real-time. Australia’s electronics magazine siliconchip.com.au