phil.g00

Or borrow your existing system's shunt and a min/max voltmeter. Although a trace to show the current decay would be nice, you are probably not interested in the first second, so you can differentiate between inrush and starting current.

I think I'd forego this DC efficiency in favour of having the PV available for other things as AC.

There are VFD's and then there are VFD's. The first step in the VFD chain is full wave rectification and is normally done with 6 pulse diode bridge. Although at extra expense though there are VFD's that use fancy phase-shifting techniques to utilize 12, 18, 24 or 36 pulse bridges. Which considerably reduce the harmonic distortion. Top marks goes to active IGBT rectification though but at 250% cost premium apparently. Here is a nice paper for those that want to know what combos do what in terms of THD: http://www.aic-controls.com/fullpanel/uploads/files/abb-technical-guide-6-harmonics.pdf

Things have come a long way since star/delta starters I see. From what I understand a soft starter (cheaper) should halve the standing starting current surge, and a VFD (more expensive) could possibly limit it to 110% of full load. I have never used either, but it would be worth a few bob, if they can.

Basically, you have between 10AM to 2PM when solar can really work. That's four hours, I think the minimum pump size has to be governed by its ability to achieve what it needs to do in those four hours.

@plonkster, Picture the same set up (Venus with only Victron MPPT's) but with a Lithium battery. Would a canbus compatible bms still be able to control the charging? And could the Venus provide a low voltage cut-off contact to a third party device?

Agreed it's going to have a fair surge, as pumps need to be primed so they start under load. I would be pretty confident he already has a star/delta starter for a pump that size, so it may not be as bad as you say. Best thing is to measure it.

I know people have complained about them but Segensolar came through for me, confirming parallel compatibility of two 8kVA Quattro's on the bench beforehand. (I don't know if I could've specified the firmware I wanted, to expand my system in the future though). AC/DC didn't have a clue, just tried to upsell me a Venus as the cure-all. So credit where it is due.

Apparently not. How does one go about ordering a specific firmware version? Or is there a serial number visible on the box, that can be checked against a database?

I assume "eOrder" that is something Victron lets you see? Or is it visible to us mere mortals? I've had a helluva time over the years with ensuring firmware compatibility. Does what you see let you see firmware versions, or is it potluck? AFAIK, the firmware version is not visible on the box, and many resellers are reluctant to open the box, once you point out the importance of firmware compatibility. I know Victron advises that multipluses destined for paralleling should be bought together, but that is hardly a practical solution given their price. Or what would one do if a muliplus in a parallel or three phase system needs replacing? Dealings with resellers in the past, enlightened me that they didn't even know firmware versions existed.

Yes, I returned a second Phoenix inverter ( of the old type) because it could not parallel with my existing one. Bizarrely, the firmware difference was related to the transfer switch size of their respective Multiplus firmwares. As you state, Phoenix inverters don't have transfer switches, but there you go. Are the older 5kVA Phoenix's now phased out? I wish Victron would announce their end of line dates on products, as the ability to parallel and grow a system is a big selling point. They are pricey products and I am sure people plan to expand their systems, and rely on procuring parallel components in the future. At least if they know something is becoming end-of-line they can maybe move up their plans and get the component they will rely on in the future.

I was going to suggest that myself, you can also AC-couple to Phoenix inverters. Although, have Victron just come out with a new range? My phoenix inverter has a Multiplus firmware chip, I have always wondered if I could parallel it to a Multiplus? Thereby adding AC charging/blending, albeit a lesser amount. This would allow a smaller generator to supplement to the power. With Victron multiple 5kVA's also deliver more power as they start to derate at temperature, than a single big boy. I agree with you on this point. This ain't going to be cheap, if it's going to last.

AC coupling is nice, but along with the 1:1 rule ( Victron to PV inverter) there is a battery size component as well. If I recall correctly it is: 1kW PV inverter for 5kVA battery for lead acid & 1.5kW PV inverter for 5kVA Lithium. 15kW of PV inverter adds up to a pretty sizeable battery bank pretty quick. As much as I like Victron equipment, an SMA Sunny Island + Sunny boy combination may be worth looking into as well. SMA may also have a similar requirement, but they seem to allow a higher ratio of AC coupled inverters.

Mmm, a lot to read about Axperts, on this forum alone. I never had one, can't comment.

Unique combo, I hope those Growatt inverters are half-decent.

OK, that's what I was thinking you'd do. Interesting, it should work though.

Are you going to replace your existing panels and make two parallel strings, or how are you connect them to 1 MPPT?

I agree, in your instance it would seem the most attractive option. Although the MLT has 2 MPPT's, the Growatt only one?

Do have an inverter/charger or just an inverter? Or alternatively, can you use a PV inverter (PV straight to AC), but it only works when there is a grid supply. By that I mean only reduces the bill, it doesn't work when there is load-shedding. PV inverters are relatively cheap and have very high voltage MPPT's built in.

On the other hand, you are now into a size where you can keep your Outback where it is and size the MPPT just for the new panels if you go for either 6,8 or 9 panels. ( Depending on 72 or 60 cell variants).

I wouldn't size for 2400W, that will be a freak occurrence, but lets say 2200W. Then 2200/53 = 41Amps, (It is is OK to exceed the output current limit), so a 40A MPPT will do. (The charging voltage is probably closer to 55V anyway). One thing that will cost extra is you will need several wire runs to avoid the losses over that distance. You may want to consider 60 cell panels that will allow you to put 3 in series and benefit from the higher voltage.

Sorry I just want to correct my MPPT selection above. I would estimate your existing peak of your 235W panels at probably 200W ( unless they are perfectly aligned and spotlessly clean). So about a 1800W peak for 9 panels.. A 48V system probably charges around 53V ish, so 1800/53V = 34A, so a 150/35A MPPt is what you are looking for to free up your Outback. (The Outback history data will be more reliable).

OK, an MPPT voltage rating is a hard limit, based on open circuit voltages. Not only that it is such a hard limit that you have to factor the temperature coefficient of your coldest day on the Voc. Those panels have a Voc of 37.1V at 25C and a temperature coefficent of -.34%/deg So if your lowest teperature was say -5C, then the Voc would be 37.1V + 30C x ( .0034 x 37.1) = 40.9V An outback has a 150V limit, so the maximum panels in series would be 3 ( 3x 40.9 = 123V, which is less than 150V, so you're OK). So you can easily do 3 parallel strings of 3 in series of your existing panels and unless your panels are perfectly aligned, I bet you don't even peak at 20amps. So really you want to replace the Outback with a much cheaper 150V/20A or 150V/30A MPPT and reuse it for your more powerful panels. (There are many options in this range, the MPPT's dont have to be the same brand, just the same settings). Next thing, unless you really have to, don't buy an odd number of panels, and if you really have to buy an odd number, don't buy a prime number of panels. These new panels will probably have a Voc of too close to 50V for comfort ( unless you live at the coast), so for the outback you'll need 2 panels in series strings, but you could easily 4 strings of 2 in series, probably up to 8 strings or so. All the strings don't have to face the same way if you have future expansion plans.

Just checking, these voltages are open circuit voltages (Voc) and not Vmp ( maximum power voltage)? What is your DC battery voltage? What are the panel dimensions?

Yes there is a 600V MMPT that is hellish expensive, if you kept your max Voc of your string below 250V you would have many more options. That answers your question. It doesn't address the options available to you though. 1.) Is your Outback maxed out? - I don't mean on paper, I mean what is it's actual peak current? I have often found 30% headroom difference from theory and practice. 2.) If it is, why not get another and keep it, MPPT's can be paralleled on the battery side. I have 4 Outbacks in parallel.