Surge Posted January 7, 2020 Share Posted January 7, 2020 (edited) I'd like to build a small, mobile battery, backup system (UPS) using a Victron Multiplus 500VA 12V inverter/charger with LiFePO4 batteries just to ease the pain of load shedding. I've ruled out the Ellies/Mecer units since they use lead acid batteries which do not last when deep cycled frequently (I have friends who've learnt this the hard way). What I don't understand is how the Ellies/Mecer/Sustainable battery backup systems implement earthing/grounding and if they are protected by an earth leakage unit. I don't see any mention of earth leakage being present on these portable UPS units. How do they protect against accidental electrocution when the inverter is running the load and there is no earth leakage in-line? The other thing that is not clear to me is whether the Multiplus 500VA to 1200VA units are bi-directional inverters or not and what isolation is present when there is a grid failure. They have a UPS mode which I presume will prevent any feedback to the grid but that's not an assumption I'd like to take for granted. Does UPS mode on these smaller units provide sufficient isolation from the grid or does one need to install isolation circuitry and possibly go down the ESS path like the bigger Multiplus II 3000VA+ models? I don't see any mention of additional mains isolation present on the Sustainable Power Boxes which also use the Multiplus 500VA/12V and 1200VA/12V inverter/chargers. Edited January 7, 2020 by Surge spelling Quote Link to comment Share on other sites More sharing options...
___ Posted January 7, 2020 Share Posted January 7, 2020 (edited) 20 minutes ago, Surge said: What I don't understand is how the Ellies/Mecer/Sustainable battery backup systems implement earthing/grounding and if they are protected by an earth leakage unit. I don't see any mention of earth leakage being present on these portable UPS units. How do they protect against accidental electrocution when the inverter is running the load and there is no earth leakage in-line? They don't. Just like most portable petrol generators don't. They will earth the whole system to the earth of the upstream connection (where the UPS plugs into the wall). 20 minutes ago, Surge said: Multiplus 500VA to 1200VA units are bi-directional inverters or not The Multiplus models are always inverter/chargers, they can both invert from the battery and charge it. I assume that is what you mean by bi-directional. The Phoenix models are inverters only. The Multiplus inverters can only feed energy into the grid when specifically configured with ESS (energy storage system). The inverter firmware can be extended with so-called assistants which are a bit like apps that run on top of the basic firmware, providing additional functionality. A Multi will not feed into the grid unless you install the ESS "app". By default it acts as a UPS. Further, no additional "isolation" is required even for the bigger models. They are NRS097-2-1 compliant and no extra anti-islanding or similar is required. You do need to put your own breakers on the input and output (to protect the cabling), and the output must have an RCD installed. Edit: I also have to add that the regulations don't require NRS097-2-1 compliance for a UPS. It is required only for embedded generators, and contrary to what most people expect, the inverter is NOT the generator. The PV modules are. No PV modules... no compliance required. You must however comply with the grid code if wire it to your house's distribution board. Edited January 7, 2020 by plonkster Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted January 7, 2020 Share Posted January 7, 2020 21 minutes ago, plonkster said: The Phoenix models are inverters only. I don't know about the smaller Phoenix inverters, but for the 5kVA version: I know it doesn't have an Grid AC input, but the Phoenix 5kVA is a bi-directional inverter/charger. ( It even has a Multi firmware chip) I have PV inverters on the AC out of a 5kVA Phoenix, and it does charge the batteries from them when there is excess power production. The settings are normally greyed out in VE.config, but they are there if you enable the charger. When the batteries are charged it also frequency shifts to control AC production. And it works very well. ___ 1 Quote Link to comment Share on other sites More sharing options...
Surge Posted January 7, 2020 Author Share Posted January 7, 2020 (edited) Thanks plonkster, that answers my questions. So fuses on battery cables, current limiting circuit breaker on mains input (to protect cable from wall socket), RCD on output to trip if there is an earth leakage + current limiting circuit breaker on output to protect output cable. Edited January 7, 2020 by Surge Quote Link to comment Share on other sites More sharing options...
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