I’m wondering what’s the best option for a three-phase ESS: the newer MultiPlus-II 4k5 or the older MultiPlus-II 5000VA. In terms of output power, there’s no difference; both can deliver 4,000 W. However, the MultiPlus-II 5000 has a respectable battery charging current of 70 A, whereas the MultiPlus-II 4k5 can manage only 55 A. The 6k5 seems like overkill to me, with the risk that it will be very inefficient as an inverter at low loads.
The MultiPlus-II 5000 will charge the battery (48 kWh) faster, which is especially important in winter, as in future I plan to use peak shaving to buy electricity at a low tariff for my own use. This will become interesting once we start using variable grid tariffs in the Netherlands. In winter, daily consumption is high, averaging 40 kWh per day.
The most important thing for me is any potential difference in efficiency at low and average loads when used as an inverter. In winter, this will be 300–500 watts per phase, and in summer 100–200 watts. Efficiency at peak power isn’t that important, as this doesn’t happen very often.
In homes, an ESS will operate at a low load for much of the time and at higher power for a limited period. Higher power levels occur during peak hours: in winter, when the heat pump is running at full capacity (max. 1 kW per phase), and in summer, when you want to charge your car overnight using stored solar power.
A three-phase system with three Multi RS units costs around €1,400 more, and you won’t make that back in efficiency gains.
I don’t have room for an ESS in my house, and I don’t want one inside due to the fire risk either. I’m installing the system in a Rittal VX cabinet in my garage. I won’t be bothered by the noise inside the house.
So the MultiPlus II 5000VA seems like the best choice to me. It’s also a proven workhorse.
Yes, I’ve allowed for approx. 2,000 W of heat loss, with a room temperature of 35 degrees and a cabinet temperature of 45. Around 450 m³/h of ventilation is required, and approx. 650 m³/h will be installed. I checked the figures using Rittal’s thermal calculation software. This situation is unlikely to occur often, but with outdoor temperatures of 35 degrees and the inverters running at half power, it does indeed get very warm.
I’m using a speed-controlled fan with a thermostat from the same manufacturer. I may also install a standby heater at the bottom for the batteries in winter. The garage is heated, but it’s not yet clear whether the temperature in this cabinet will stay above 10 degrees.
I don’t know whose figures for the RS you are looking at mine is definitely not that high 35-40 watts. And I have a bunch of other devices like the Ekrano (screen on all the time) and a few mppts.
What I can see here is that up to around 25%–30% of the nominal power, efficiency is mediocre, just as with the MultiPlus, and ranges from 70% to 90%. The RS and MultiPlus only reach their operating point, where efficiency is optimal, at around one-third of nominal power. The main difference is that the RS maintains its high efficiency at high power levels, whereas the MultiPlus drops off a little. For ESS use, I don’t think it makes much difference whether you use a Multi or an RS; the RS only has a clear advantage if you often run at high power. In any case, that doesn’t justify the substantial price premium for an RS. The main argument would be that the RS is said to be much quieter. I can’t comment on that, but my system will be installed in a cabinet in the garage, so it won’t make much difference.
I do think it’s a shame that Victron doesn’t make these kinds of curves available, as they would help people build the optimal configuration.
Hi everyone, I’m also struggling to find arguments for or against the RS models.
So far, noise levels seem to be the main argument.
I’m curious whether the RS models can handle a high inrush current just as well as the transformer models. The large circular saw starts up fine on my MP2 3000. The lights flicker quite a bit when it starts, but it handles the brief current spikes. I’d be interested to hear about people’s experiences with the RS.
