{"id":360,"date":"2023-02-10T11:07:18","date_gmt":"2023-02-10T11:07:18","guid":{"rendered":"https:\/\/asdfghjkl.me.uk\/blog\/?p=360"},"modified":"2023-02-10T13:31:01","modified_gmt":"2023-02-10T13:31:01","slug":"multiplus-aes-node-red","status":"publish","type":"post","link":"https:\/\/asdfghjkl.me.uk\/blog\/multiplus-aes-node-red\/","title":{"rendered":"Disabling\/enabling AES (power saving) programmatically on Victron inverters with Node-RED"},"content":{"rendered":"\n

Want to do this yourself? Grab everything you need from my Github<\/a>!<\/em><\/p>\n\n\n\n

Living off-grid means we have to be pretty careful with our electricity usage, especially in the winter when solar output can be a tenth of the summer highs. We don't have a huge number of mains appliances (fridge, laptops, coffee grinder, blender) and run as much as possible off 12 volts. Despite this, I honestly don't think we're missing out on anything! We use around 1kWh of electricity per day, just an eighth of the average UK household that Ofgem reckons uses 2900kWh each year.<\/p>\n\n\n\n

One reason I chose to install Victron gear is that I am simply too lazy to turn an inverter on and off whenever I want to use mains power. Their inverters have a power-saving function they call AES (automatic economy switch), which keeps the inverter off and blips the power every second to see if a load is connected. If it detects a load, it switches on fully. This does restrict your choice of appliances to those without too many electronics, but for a fridge with an old-school bimetallic strip thermostat it works great.<\/p>\n\n\n\n

The energy savings from using this \"search mode\" can be quite significant. My Multiplus 1600W inverter uses 10W when switched on with zero load, and 3W in power saving mode. Just considering the fridge, it tends to run in a 1-hour-off, 20-minutes-on cycle. So that's 18 fridge cycles per day, saving 7W * 18 hours = 126Wh compared to the inverter being left on 24 hours per day. That works out to an eighth of our average daily consumption saved. It's a much bigger deal in the winter, where the average day only gives us around 250Wh of solar power, so we're saving fully half of that!<\/p>\n\n\n\n

The only downside is that picking the wattage thresholds to turn on fully can be quite finicky. These inverters don't have a current transformer on the AC output, so the power usage they report is just an estimate based on battery current and efficiency. Reactive vs resistive loads will also skew this figure. Choosing the threshold takes a bit of experimentation to pick the lowest wattage where the inverter will go into power saving with no load, but still switch on when something's plugged in. This seems to vary between inverters, but a good place to start is 25W and work upwards until it works well. Mine is just about right at 35W start and 67W stop (in reality this means a 10W load will keep the inverter on).<\/p>\n\n\n\n

It's still not quite perfect, though. I noticed that newer USB-C laptop chargers will draw just a few watts to begin with, ramping up to full power after about 10 seconds. Since the \"blips\" in search mode only last for one AC cycle, they don't draw enough power to fully turn on the inverter before they reset. My lazy solution was to run the coffee grinder for a few seconds, but ideally I'd like to briefly disable AES, allowing the charger to ramp up before re-enabling it.<\/p>\n\n\n\n

I've been playing with Node-RED a lot recently<\/a>, so I figured I could find a programmatic solution. Problem is, there's a (sensible) divide in what Victron lets you access externally - you can change state<\/em> but not settings<\/em>, and AES is a setting so no dice. Luckily I came across this hacky workaround<\/a>, which uses a digital input on the inverter to control the AES setting. The solution is described almost entirely there but took a lot of searching and keyword massaging to find, hence why I'm writing about it here!<\/p>\n\n\n\n

Alright, enough backstory. This isn't a recipe website. tl;dr:<\/p>\n\n\n\n