question

mterman avatar image
mterman asked

3+3kW AC coupled system design

Hello,

We are designing 3+3 kW system. Because of financial constriction and pressing need to upgrade the current system we are planning to build our new system in two phases.

First phase would be 1 x Victron Multiplus II 48/3000, 1 x Fronius Primo 3.0-1 with around 4kW of PV, 320Ah 48V traction battery system (24 * 2V batterys) and Cerbo GX for system monitoring.

The second phase should be implemented next year. We would then add another Victron Multiplus II 48/3000 in parallel with the first one and another Fronius Primo 3.0-1 with around 4kW of PV.

This is a offgrid system, most of the power usage is during the day.

There is a 2kW generator for backup.

In addition to that we would probably add a micro water turbine (PowerSpout), also AC Coupled trough Ginlong Solis Mini string inverter. We could get from 500 to 1000W form the PowerSpout. I know that this takes the system over the 1:1 rule. But water turbine would be used when there is no PV power (bad weather or night).

I don't have the exact question, just need the sanity check for this long term plan.

Thank you!

Multiplus-IIoffgridAC PV CouplingFronius
11 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

shaneyake avatar image shaneyake commented ·

A few things that I would think about.

Why do you want the Multiplus-ii 48/3000 over the 48/5000, not that much more but almost double the power?

Why do you want to do AC-Coupled with the Fronius Primo vs an MPPT, Like the RS 450/100?

Please please consider LFP batteries, I know the up front cost is higher but the life and useable energy is so much better.

Small Water Turbines hardly make sense, unless your property meets unique requirements, I would rather spend the money and get more PV in 99% of the cases. Also less hassle and less materinace on PV.

If you did DC PV for phase 1 then you could add AC-PV for second phase. Would also look into Enphase micro inverters if you have any shading requirements.


0 Likes 0 ·
Show more comments
shaneyake avatar image shaneyake commented ·

@mterman I just saw that my battery supplier sells their batteries in Europe.

Batteries that we use
https://www.freedomwon.co.za/storage/2021/07/lite-home-and-business-spec-sheet-design-1.pdf
10/8 is proably close to your 320ah
We have only had good things with these batteries, lasting 10+ years getting cycled to 40% SOC daily and 10% occasionally.

European Distributor
http://www.esergetica.it/customized-solution/?lang=en

http://www.esergetica.it/energy-storage-3-reasons-to-choose-them/?lang=en

Might be worthwhile to get a price. In South Africa they are $3700, will probably be more but I don't know how much more.


0 Likes 0 ·
marekp avatar image marekp commented ·
Hi @mterman

If you want 2 MP-II to work properly in parallel, you better buy them at the same time.

They will have the same hardware inside.

I had a problem with two MP-IIs that were made more than a year apart.

They would not balance the load evenly.

I agree with @shaneyake. Go with LFP.

I got mine, made by Winston, from their Czech dealer GWL.

They are a bit more than Lead-acid but they can be safely discharged down to 20% SOC.

Lead-acit should not be discharged below 50% SOC if you want them to last.

If you compare the usable capacity to price ratio of PB i LFP, LFP wins hands down.

If you want longevity LTO is the choice but still expensive.

0 Likes 0 ·
Show more comments
0 Answers