question

mhammer avatar image
mhammer asked

SmartSolar 150/45 setup w. 4 * 365W panels

Total beginner here.
This is for a hobby project, which, for a start, would not be connected to the main grid. I am aiming for a 24 V battery system, but I am not certain. I want to attach a inverter at some point in the future, but for now I am only going to use 24 V appliances.

It's for a home usecase and I have it all witin my small isolated garage. So it should not get colder than 10°C at the winter. (Location Denmark, EU)

What I have got:

  • SmartSolar 150/45
  • 4 x 365 W panels (In a 2s2p config)
    • Pmax: 365 W
    • Vm: 34,00 V
    • Im: 10,74 A
    • Voc: 41,30 V
    • Isc: 11,30 A
  • 2s2p setup
    • 2 x 2 series
      • Voc: 82,60 V
      • Isc: 11,30 A (Factor 1,56 * 11,30 A = 17,63 A)
      • Connected with 6mm2 wire from panels to Y-splitter
    • Overall
      • Voc: 82,60 V
      • Isc: 22,60 A (Factor 1,56 * 22,60 A = 35,26 A)
      • Connected with 10mm2 wire from Y-splitter to SmartSolar
  • Fuse/Breaker box 40 A between panels and SmartSolar
  • Manual switch between SmartSolar and future batterypack (100 A)

What I haven't got yet:

  • Batteries (LiFePO4, AGM or other?) (No high wattage demand appliances as of right now)
  • Inverter (Future project)
  • BMS (Is it needed if the batteries have one?)
  • Shunt
  • Energy battery monitor

My questions:

  • If I buy a/multiple batteries with built-in BMS, do I need to get one seperate for the system (Between SmartSolar and the batteries?)
  • Should I get a SmartShunt or other similar device?
  • Do you ahve any recommendations for other equipment for my project?

Bonus info:

I want to have a RaspberryPi 4 runnning the Venus GX OS or similar, so I can integrate it to my Home Assistant setup. (I believe it's a cheaper alternative to the Cerbo GX, and I have the RPi laying around)

MPPT SmartSolarSmartShuntEnergy Meterleisure batteries150/35
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3 Answers
snoobler avatar image
snoobler answered ·
  • If the batteries have internal BMS, you need no additional hardware, though you may benefit from balancers IF you are placing 12V in series to get 24V.
  • Yes. It's important to actually know the state of charge of your battery.
  • Yes. DC powered appliances usually command a hefty price premium with minor advantage over AC. Before you commit to a configuration, run both options. In almost all cases a right-sized inverter + efficient AC appliances represents a substantial cost savings with a very small efficiency penalty.

Concerning the Bonus info: How do you connect a RPi running Venus OS to Home Assistant? I didn't know they were compatible. Generally, you run Venus OS for VRM and interconnectivity of the Victron components instead of Home Assistant.

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Duivert NL avatar image Duivert NL commented ·

There is an home assistant victron integration, so you can do all sorts of automations and controls from home assistant!

But yes you will need an gx or pi with venus os to control the victron system itself

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mhammer avatar image mhammer commented ·
Thanks for your reply.
  • BMS: I've been reading a lot since I posted the thread, and I am certain that it is going to be a 24 V system, so I need to look into getting a BMS for two batterier in series.
  • Shunt: Same goes for a shunt so I can track the SoC.
  • Inverter: I am going to buy an inverter for the system.


  • RPi: I have only come across an article at one point and a youtube video that explained it was possible. But it seems that I need the VE.Can>USB dongle for it to work.
    I need to do some more digging in reagrds to the VenusOS on a RPi.


//Hammer

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snoobler avatar image snoobler mhammer commented ·
There is no such thing as a BMS for two batteries in series. I made reference to "balancers" - devices that seek to equalize the two 12V battery voltages. That is the closest thing you can get.


If you need 24V it's better to select 24V batteries.

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mhammer avatar image mhammer snoobler commented ·
I've bought two 24 V 100 Ah batteries I plan to mount in a parrallel connection.
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jetlag avatar image
jetlag answered ·

What is the usecase of this setup? Is it a RV or is it a home installation? I ask because of the temperature, - this might affect the battery selection. If it can get lower then ~5°C, then you should better use AGM. Otherwise I would take LiFePo4. If you chose a "out of the box" battery with included BMS, then you most probably don't need other hardware. The BMS should be able to count the State of Charge and is protecting the battery accodindgly. So no additional shunt or battery monitor needed. If you chose to build a DIY battery, take a good BMS like e.g. JK BMS, than again no other external additinal HW is needed. The JK can be connected via a RS485<->USB adapter to the RPi and Venus OS. You can display all Cell voltages, temperatures, SoC, etc.

The "Y-Splitter" for the module dc cables, - please use solid clamps with according cross sections to avoid problems with the higher currents.

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mhammer avatar image mhammer commented ·

Thanks for the reply.

I've updatede my thread with the usecase.

But the intended use is for home installation and it is installed in my small isolated garage. (Min. 10°C at winter times.)

I'm looking at LiFePO4 batteries, but I'm a little afraid to go the DIY route (Safety/Fire concerns).
So it would be some "out-of-the-box" batteries with BMS. @snoobler wrote that maybe a BMS is a good thing, if I acquire two 12 V batteries and connect them in series.

Regarding the Y-splitters. I've bought a set of beefy spiltters, that, according to the datasheet, have 10mm2 copper wire.

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kevgermany avatar image
kevgermany answered ·

If you intend to go to 24V, get 24V LFP from the start.

Most BMSs report SOC from voltage, not current measurements and can be inaccurate, but good enough for most purposes.

For proper integration, make sure the batteries/BMS are supported by Victron.

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mhammer avatar image mhammer commented ·
Thanks for your reply.

That's a good thing to know. I see if I can find ones that support the Victron protocol of communication, within my budget.

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snoobler avatar image snoobler commented ·

Most BMSs report SOC from voltage, not current measurements and can be inaccurate, but good enough for most purposes.

In dealing with multiple BMS of different brands on LFP and NMC batteries, I have yet to see a single BMS report SoC based purely on voltage, and all count current to compute SoC. They will use voltage as an initial estimate of SoC and the voltage limits as triggers for 100% and 0%, but in between these events, they report SoC based on Ah in and out.

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