My system has been chronically under fed with the solar panel bank we have so we have had to charge a lot with our generator. Not fun and gas is expensive.
We are about to invest in another bank of panels and I’d like to know if the Multiplus II 3000w 24v we currently have can:
Handle two PV array inputs? I remember when I bought it that the answer to that was yes, but I’d like to double check with the community.
What total watts can the PV arrays be and do they have to be equal?
What MPPT will I need for the new array?
My system is:
4 x LONGI 375W Mono Black/Black/White 35MM Frame Solar Panels
MULTIPLUS-3024 Victron Pure Sine Wave Inverter Volt Victron MultiPlus Inverter 3000W 24V
with Battery Charger
SMART SHUNT Victron Energy
Victron Smart Solar MPPT Controller 100/50A
Cerbo GX
I have sunny days this time of year about 5 days a week so that’s 2 days of autonomy. In the winter, we will be using microhydro to charge our bank since we are installing that over the summer.
My bank is 904ah of FLA’s at 24v that I’m upgrading to 1200ah of lithium instead. So, I’m aware that the panels we have now are not sufficient for the 904ah bank.
I’m planning to buy 8 more panels at 400w each. So one array will be 1600w which the current MPPT 100/50a is using.
The new array will be 3200w and the Multiplus takes that in at 24v so that means I need an MPPT that can handle 133ah + some wiggle room so 150ah should work? Is there a Victron MPPT that can go that high?
Thank you community, I’m so grateful I have invested in our Victron equipment.
the Multiplus 3000/24-70 only cares about AC-coupled PV arrays like micro grid inverters or Fronius inverters and can load at 70A, e.g. ~1600W. You could use one Hoymiles HMS-1600 with four panels and 4 mppts build in, one for each panel.
If you add victron MPPTs, they charge directly into the battery and have no dependencies to your multiplus.
Most efficient is a combination of AC-coupled inverter and MPPTs.
4 existing panels with our your MPPT 100/50 (1200Wp, DC: 50A)
4 panels AC coulped, like HMS-1600-4T. (1,600Wp, DC: 70A)
4 panels at 2p2s with Victron Smart MPPT 150/60 (1,600Wp, DC: 60A)
Sum: 4,800Wp, DC: 180A
A Li-Ion battery should not loaded with less than 1C, e.g. 1,200A for a 1,200AH babttery.
Use Victron’s MPPT calculator to size your system and get best matching MPPT based on your location and panels.
Thank you so much Björn. Any chance there is a Victron component that I could use instead of the Hoymiles HMS-1600? I’m trying to keep my entire system VE. Also given that my existing panels are 375w (24v) wouldn’t the numbers on my bank look instead like 1500Wp, DC: 62A? I’m curious how you got to 1200/50? Are the extra two banks of four panels assumed at the same panels that I already have? It’s looking like I will be able to purchase either 455w or 545w. How would your numbers look at either of those on the second and third bank? Please can you tell me if my math is correct below?
Option 1: New panels are 455w:
Series: 4 existing panels with my MPPT 100/50 (1500Wp, DC: 62A)
Series: 4@ 455w (1820Wp, DC: 76A) with a SmartSolar MPPT 150/85-MC4 VE.Can
Series: 4@ 455w (1820Wp, DC: 76A) with a SmartSolar MPPT 150/85-MC4 VE.Can
Sum: 5140Wp, DC: 214A
Option 2: New panels are 545w:
Series: 4 existing panels with my MPPT 100/50 (1500Wp, DC: 62A)
Series: 4@ 545w (2180Wp, DC: 90A) with a SmartSolar MPPT 150/85-MC4 VE.Can
Series: 4@ 545w (2180Wp, DC: 90A) with a SmartSolar MPPT 150/85-MC4 VE.Can
Sum: 5860Wp, DC: 242A
I realize though that in series puts my system in a bad position in terms of if one panel on each bank is shaded. I’m confused as to how to wire it in parallel to get me the best possible operation. I suppose that is where the Hoymiles HMS-1600 comes in handy since it seems to keep each panel independent (parallel) so that they can each be monitored in terms of performance… but how do the numbers work if done in series and then parallel?
Please let me know if I’m completely off track here. I’m learning and you are helping, so thank you.
Just select your panels in the mentioned MPPt calculator. It will consider temperature gradients and recommend the appropriate MPPT.
My numbers are based on charge limit of MPPTs. If you have an MPPT 100/50 it means:
Max PV voltage is 100V.
Max battery current is 50A.
Max charge watts is battery voltage 24V multiplied by max MPPT charge current 50A
24V*50A=1200W.
The MPPT calculator will consider over paneling, e.g. the MPPT has lower charge watts than the panels have peak performance. This costs 2-3% over the year, but reduces equipment cost.
The main limit is the max voltage at low temperature usually in April. This is considered by the temperature gradient in the tool. Just use it and you are save.
If you would have a 48V system, the MPPt can handle twice the watts as the voltage is twice as high. If you upgrade the battery maybe considere moving to a 48V system.
In Germany a MP2 5K cost around 600 EUR.
A 15kWh battery from Gobel-Power GO-SR1-PC200 including a heating pad is around 1800 EUR.
With 48V the current is only half resulting in thinner cables. For 300A you will need at least 95qmm. For 150A a 50qmm cable is enough and standard for car batteries.
You should get 450Wp Panels at 60 EURs.
With 48V you might be able to use the RS450 which has 450V PV strings reducing cabling and lighting protection. The panels are the cheapest parts today.
The MPPT 150 can handle two string in parallel, each string having two panels in series.
A MPPT might be able to handle 4 panels in series, but this needs to be calculated based a the panel’s parameter.
There are many discussions how well MPPTs can handle different orientations and partial shading.
A single panel in a string limits the current in the string. The shorter a string the better is the performance with shadows.
A micro grind inverter with one MPPT per panel has advantages from a design perspective as the string length is 1 and each string has it’s own MPPT.
Other brands use “optimizers”. Victron is. It compatible with those devices.
The RS450 can handle strings with 450V or 6-7 panels.
Short:
the system design depends on your roof and shadow situation.
I have a lot of shadow and different directions/angels and went for 5 micro grid inverters serving 16 panels and von MPPT 150/45 serving 2p2s.
Maybe you can elaborate a little about your requirements.
Are you living completely off grid?
I live in one of the main cities of Germany with a stable grid, but decided for a 3-phase system with 3x MP2 5K, 8,5kWp PV and 56kWh LFP battery. I am autonomous April to September gaining 30-40 kWh/day.
We are a family of four with two having home office. Normal load is 12-20 kWh/day depending on amount of clothes to be washed and dried and 2-3 dish washers a day.
Depending on PV earnings, I decide to heat water (12kWh/day) and the house either via gas or PV.
Awesome sized bank. Thank you I did miss that piece of information in the original post.
I agree with you, a more efficient upgrade is to move to 48v inverter. And still add more solar.
@katefraser
Depending on how your build your battery bank, consier balancers if they are 12v.
But if you can - get a battery at the voltage system. You want to use a bus bar to current sharing in place as well.