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Andy F avatar image

Off Grid 48V System options

Hello

Sorry if this is a bit long winded, I would appreciate some advice on Equipment selection and Integration for a 48V off grid system. I have been going around in circles Googling youtubing etc on Victron, Solar, Batteries etc.

I am going to be living temporally in a farm location whilst Renovating a Barn for a future house and also setting up a Camping/Glamping/Cabin site. This is all in the same Farm Location.

The 48V/5000 Multiplus 2 (GX ?) seems ideal as I can feed with a generator if required supplying 2 x Ac outputs and also feed via an MPPT from Solar (20 x 370W ish of Ground mounted Solar giving around 7 to 7.5 KW) and with Lifepo4 Batteries.

I have narrowed MPPT options to the 250/100 or the MPPT-RS ?

The advantages of the 250 is it is Multi Voltage and I could use Later in a 12 or 24V Camping setup with Some of the Panels. However it is limited to 5800W.

The RS can use more Solar and it has 2 x MPPT Trackers (2 x serial strings of 10) Disadvantage 48V and more expensive.

I would like to top up a water heater if the system is full (load shed?)

Looking at a couple of Friends rough Data (from a 6KW and 50Kw grid systems it seems the more Panels the better for the UK winter.

For Batteries was thinking of a 16s 280aH aliexpress type, but BMS selection seems to be a nightmare looking at all the reviews.

In my Understanding of this could I use a BMS to balance the Cells and the Victron setup to deal with the high and low voltage and temp sensors.

From online it seems some are using the BMS to deal with the total load, I don't know why.

Could use an expensive decent BMS if required.

I would consider Pylontech Batteries but they are more expensive and I would like to learn the system.

In addition the 16s cells could be later split to create 12V or 24v for the Camping area (to match the 250 MPPT).

Really it is the Integration and communication with the Kit I need help with, plus brushing up on my theory.

For Instance am I better off Having the Multiplus and a Cerbo or a multiplus GX, do I need a battery Monitor? or which one would one be better over the other in terms of temperature sensors and relay outputs for generator etc. (I don't want multiple items capable of doing the same thing)

The system will be located at the top of a hill around some old Barns so was considering a small wind turbine in the future unless its too much hassle.

In an ideal I world not have a grid connection for my future house (or just export/ use as much as posssible) so I could use the system or expand it for this.

This is a big learning process... and I am an Electrician ! (Never been involved with Generators, Solar or Battery storage though)

Thankyou

Andy

victron communitysolar sizing48v battery
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2 Answers
seb71 avatar image
seb71 answered ·
For Instance am I better off Having the Multiplus and a Cerbo or a multiplus GX, do I need a battery Monitor? or which one would one be better over the other in terms of temperature sensors and relay outputs for generator etc. (I don't want multiple items capable of doing the same thing)

For sure go for distinct/separate devices:

- inverter (non GX)

- Cerbo GX (don't get the display for it)

- SmartShunt + VE.Direct cable to connect it to Cerbo GX

- temperature sensor for SmartShunt (BMV type)

- MK3-USB interface to program the inverter (and a Windows PC/laptop)

- solar charger(s) and connection cables to Cerbo GX (probably VE.Direct cables).


Use busbars. You can DIY the busbars from copper bars.

Make sure you use proper section for wires. Even oversize a little.

All connections to the battery must be fused (positive wire). I use HRC (NH) fuses.


It is riskier, but you can "Bottom Ballance" the LiFePO4 cells and use them without a BMS. But with a stricter voltage range and some manual cell voltage monitoring over time.


Generators are problematic. Read this.

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Andy F avatar image
Andy F answered ·

Thankyou seb71 for the reply,

So multiplus 2 and Cerbo as the Central "brains"

I see what you mean on the Generators. I Was thinking of fitting a change over switch and isolators to by pass the multi should I ever need to go Generator only to the ac load or if there is an equipment failure.

No problem with cables, i'll look into NH Fuses (not used these before).

Annoyingly a while ago I scrapped some copper busbar bits and pieces when tidying up my Garage.

Ill probably be checking on the battery frequently to start with anyway so could bottom balance.


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