I know that the Multi RS Solar (and new Multi RS) can’t be paralleled at the output because they can’t synchronise with each other – but what if the two AC outputs are kept separate? And if this is possible, rather than two Multi RS Solar or two Multi RS, can I use one of each?
Application is a series hybrid boat, ACIN switched between shoreline and 9kVA generator using external transfer switch, 2.5kWp solar, common 48V LFP battery bank, one AC output for hob/oven and the other for 230Vac ring main.
Would replace a Quattro 48/10000 which can’t provide enough battery charging current to fully load the generator, data sheet maximum is 140A but in practice this is around 120A when cold and 100A or less when hot – also Quattro losses when high power charging are quite bad (around 10%?).
Two RS would more efficient at high power (94%?) and should provide much higher charging current (170A?) to reduce generator running time.
This didn’t get any answer, so I’ll ask a similar question but about the Multi RS 19 Solar – can two be used with a common single-phase AC input and common Vbatt but with separate AC outputs?
Backing up to your original post, quick questions:
What’s the battery bank capacity and charge rating? 48V, but what’s the capacity e.g. 200Ah and 0.5C = 100A, just to determine if making a change is going to help matters.
it’s not clear (to me anyway) what is it that you’re actually trying to achieve?
e.g. More charge amps to the batteries? or faster charging? “Fully load the generator” consumes more fuel, and that generator is also powering house loads while charging battery, right?
If the generator is 9kVA at 230V, that’s 39A at best to the AC In - it has to serve BOTH the loads and the battery charging so are you willing to turn off loads to maximize battery charge rate?
How hot is the Quattro getting? eg in an area with poor ventilation? or are you “enjoying” 40C on the waters these days?
If its 48V 200Ah and 0.5C, that’s 100A, so no need to change out the Quattro 48/10000/140-100/100 (e.g. charge at 140A @ 25C.)
Generator 9kVA converted to battery’s 57.6V (with magical impossible 100% efficiency) is 156A. So basically the setup could already be at maximum.
Getting to the second part:
what’s the shore power input current? eg 50A max at 230/240V ? If so, you’re not going to be able to do much better, especially if running loads and charging… the Quattro already can bring in 50A AC In, and changing this to two units isn’t going to up the possible shore power, unless you are allowed to run TWO feeds in from shore.
Meant to add - If I understand correctly , you can have two multis charging the batteries, and then the AC side - one going to the loads, OR split the panel and have one AC out from each going to the different halves (eg one to Hob/Oven, other to rest of AC). But you’re shore power and generator power is limited and I don’t know how you can get past that.
Two things I’m trying to achieve – faster charging (lower generator running time) and reduced losses.
When the generator is running for charging (700Ah 51.2V LFP battery bank, can be charged at 420A) while cruising there’s usually negligible domestic load. The Quattro 48/10000 is specced at 140A maximum charging current but never achieves that, starts at 130A when cold and then drops off as the Quattro heats up, to 100A or less after a couple of hours. Also I measure around 12% loss in the Quattro when charging, so with 100A into the batteries (typically around 53V) that’s about 6kW out of the generator which it’s perfectly happy with. The quattro is in a fan-cooled electrics cupboard, inlet air temperature is always below 40C, usually lower, but with about 700W loss the Quattro gets pretty warm going by the exhaust air temperature.
Shore power isn’t really an issue, I’m usually on a 16A circuit which can supply around 3.7kW.
What I want to do is make better use of the generator capacity and reduce losses – 39A out of the generator (4.5kW/Multi RS) with lower loss (6%) would give 160A into the batteries, which is 80A for each Multi RS which they should be able to sustain looking at the data sheet. That’s 60% more than the Quattro (23% SoC/hr compared to 14% SoC/hr) which would mean a lot less generator running time – currently this averages about a third of cruising time, this would drop to about a fifth. The Multi RS should also run a lot cooler than the Quattro. Also time between generator services would be about 50% longer since this is done using running hours.
Yes the plan is to split the AC loads, one Multi RS for hob/oven and the other for the rest of the mains appliances (kettle, toaster, microwave, washer…). These loads are usually only there when the generator isn’t running and I’m not plugged into shoreline, so all the power comes from the batteries.
I’d prefer to have a single 10kW output, but if that’s not possible two separate 5kW ones are OK.
Power usage never goes down…, I have the same: I could use second RS6000 in my home, but not possible, with three RS6000 is for now overkill… but then I will be ready for an EV.
Thanks for the details. Changing out the Quattro for two Multi RS 48/6000 would up the efficiency, although the manual is lacking on de-rating details for temperatures above 25C. That’s going to maximize the use of the generator as far as I can tell.
If you’re thinking about Multi RS Solar 48/6000/100, get two, instead of one solar/one non-solar, for redundancy and simplicity, and the solar side will get you more charge (eg go from 88 to 100A each) if you have the panels to do it.
Must be a pretty nice Yacht!
It might be a good idea to pay a professional for a bit of time for checking all the numbers work - eg VA vs W.
Anybody know what the temperature de-rating is like for the Multi RS or Multi RS Solar ? I could not find it.
Only have 2.5kW of panels (5x500W) so having two Solar doesn’t help – in fact given 120V minimum start-up voltage this would only be one string. Which is going to be a problem because the maximum current is 12A, not enough for the panels…
So I’ll have to keep the existing MPPTs, so that would mean using 2 Multi RS 230V then…
Which won’t really fit in the space where the Quattro 48/10000 is – but then having read that the Multi RS 19 has to be fitted horizontally (like in a rack) two of those wouldn’t fit either…
The other option I looked at was the Multiplus 20kW (250A max charging) but that’s also too big, as is the Multiplus II 15000 (200A max charging) – and two Multiplus II 6k5 (200A max charging) definitely won’t fit…
It’s a bit of a tricky situation trying to tick all the boxes.
It might be worth giving the system a bit of maintenance - eg clear out any dust bunnies, and give the cable terminals a bit of TLC - eg reseat fuses, retorque connections to spec, ensuring there is no corrosion or damaged cables etc. It might help with the operating temperature and efficiency.
I don’t think there are any issues like that, I’ve checked all connections for heating up after charging at full power for a couple of hours and there’s no problem – but I wouldn’t expect there to be, it’s a series hybrid boat where the motor can draw something like 16kW so all cables/connectors to the main battery bank are rated for something like 600A (the main busbar is a Lynx 1000). There’s no dust to speak of inside the Quattro or the cabinet, or in the ducting to the fans.
Excellent - sounds like you take good care of your boat. I use a small handheld FLIR infrared camera, and it works great for finding issues. From your photo, the only thing I could think would be a bit more space around the Quattro for airflow, if possible. Glad to hear you have everything done right with bus and cables.
There’s a 140mm 2000rpm Noctua fan blowing cold air in from outside at the other end of the cabinet, and a similar fan (will soon be 2 in series) sucking hot air out from the top to the right of the Quattro (where the hot air comes out) – all the gaps around it are plenty big enough for these not to limit the airflow.
According to the RuuviTag right next to the Quattro air intake, maximum inlet air temperature this summer was 38C when outside was at 25C, adding the second fan should double the airflow and drop this to the low 30s. That ought to minimise temperature derating and charge current dropoff with time – but I still think Victron specify this as 140A maximum is verging on deception, my boatbuilder says that they never sustain anywhere near that even when tested in a cool open space…
(after 2 hours genset was putting out around 5.5kW, battery was charging at 89A/54.5V which is 4.85kW, 12% loss is in Quattro which is what I typically see when hot)
If the Intake air temperature (after the input fan) is 10C hotter than the outside temp, that’s a problem - perhaps too much back pressure (sometimes called static pressure) for the fan - it might be spinning but it’s not able to move the air, or the air has nowhere to go. The question might be to figure out the cubic volume of the space and how much of that entire volume of air is being changed per minute?
The “inlet air temperature” is measured immediately in front of the bottom of the Quattro, you can see the white RuuviTag in the picture. With the Quattro dumping something like 700W into the cabinet there’s always going to be a temperature rise even with cool air in at one end of the cabinet and hot out at the other, the hot exhaust air comes out of the top of the Quattro and goes everywhere, there isn’t a nice clean one-way air flow.
