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weltverloren avatar image
weltverloren asked

System12/24V

Good afternoon, I'm in a difficult situation. I have a 24 volt solar panel, I want to connect the batteries in parallel to save 12 volts, since I already have a very good inverter for 12 - 220 volts.


Will the BlueSolar MPPT 100/50 controller (for example) work in such a system? And in general, is it possible that the panels are 24 volts, and the batteries are 12 volts?


And one more question, I have seen many controllers with the ability to connect a load, but the output voltage of the load is not indicated anywhere. Does it depend on the voltage of the panels, batteries or the controller itself?

MPPT ControllersSolar Paneldc system
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4 Answers
steffen-graap avatar image
steffen-graap answered ·

Actually there is no 24V solar panel. This is still a relic from the days of shunt regulators, where panel and battery were matched to one another in order to minimize losses in the regulator.

With modern MPPT controllers, the solar panel voltage is relatively unimportant. You should only meet two conditions.

1. It must be greater than the starting voltage (battery voltage + 5V) for charging to start

2. It must be smaller than the maximum input voltage of the solar controller. In this example, MPPT 100/50, i.e. max. 100V.


The charge output corresponds to the battery voltage, which the charger "learns" when it is first connected to the battery. In principle, it is just a switch that passes the battery voltage on to the charging output and switches off when the battery voltage falls below the set value. So an integrated battery protect.


If you only use a 150W panel, an Mppt 75/10 is sufficient, depending on the battery used (end-of-charge voltage).

With the MPPT Calculator Excel sheet you can calculate the combinations.

https://www.victronenergy.de/upload/software/VE-MPPT-Calc-4_0.xlsm

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Kevin Windrem avatar image
Kevin Windrem answered ·

The load output on the Victron solar controllers is battery voltage

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weltverloren avatar image
weltverloren answered ·

I chose this configuration for myself:

Risen RSM144-9-535W - 1 pcs (I plan to buy another one in the future)
1 pcs - open circuit voltage - 46V * 2 = 92V

1 pcs 535W * 2 = 1070W


Based on the panel data, I chose the controller BlueSolar Charge Controller MPPT 100/50

Nominal PV power, 24V - 1400W

Maximum PV open circuit voltage - 100V


+ two batteries for 200 ampere / hours at 12 volts each, connected in series, and a 12 - 220 volt inverter is already connected to them.






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kevgermany avatar image
kevgermany answered ·

Not sure how this is going to work.

You're setting up a 24V battery system, but have a 12V inverter. You must not connect the inverter to a single battery if the battery is in series with another.

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weltverloren avatar image weltverloren commented ·

I'm sorry, the batteries are connected - in parallel.

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kevgermany avatar image kevgermany ♦♦ weltverloren commented ·
Sorry, but then there's a different problem.

The 50 of a 100/50 MPPT is output current.

Assuming you charge at 14.4V, this is a maximum of 50*14.4V or 720W per MPPT. This may or may not be acceptable for the controller, probably isn't, but you won't get the power you're expecting from the system.

Also you need to account for the effects of temperature. The panel specifications will give a temperature compensation factor. This shows how much the panel vtage increases as temperatures drop.

This may help:

https://www.victronenergy.com/mppt-calculator


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kevgermany avatar image kevgermany ♦♦ kevgermany ♦♦ commented ·

And this

https://www.victronenergy.com/blog/2014/03/28/matching-victron-energy-solar-modules-to-the-new-mppt-charge-regulators/


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