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5jwx avatar image
5jwx asked

MultiPlus-II GX with Tesla batteries & Simp BMS

I've ordered a MultiPlus-II GX 48v 5000 earlier today but after reading the manual I'm not sure if I should have bought a non GX & a separate Cerbo GX???

Planned System
MultiPlus-II GX 48v 5000
4 x Tesla Model S Batteries
Simp BMS linked to Victron

The manual states
4.3.2. Li-ion batteries
Compatible BMS-Can lithium batteries can be used with MultiPlus-II GX however it is a requirement that those batteries to be connected via the BMS-Can port of the GX device (such as the Cerbo GX), and not to the MultiPlus-II GX communications interface directly

Have a bough the wrong Multiplus???? Thought it was simpler to have the built in GX


Thanks

multplus 2 gx
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2 Answers
Jason - UK avatar image
Jason - UK answered ·

@5JWX You will have the same set up as me but I have no dedicated BMS, I have a simple over / under voltage protection with cell balancing and a 2-wire 'BMS' single wire to stop the charger / inverter in a over / under voltage situation. Multiplus GX is fine to use but not that the tesla modules are 22.2v nominal, 25.2v max. On the below link are some photos of my installation in the photos section. I prefer the tidiness of having a Multiplus GX over the separate components but I also have maxed out my connectivity on my Multiplus whereas if I had the separate GX device, I would have more options.

https://vrm.victronenergy.com/installation/171934/share/db6807bb


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Jason - UK avatar image Jason - UK commented ·
@5JWX Also forgot to mention my batteries are also heating (no cooling ever required on my set up) as I lose about 25% useable capacity in the winter when they get really cold.
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5jwx avatar image
5jwx answered ·

Thanks for the info Jason

I don’t yet have solar, understand about the built in GX having limited connections for other devices but hopefully won’t be an issue.

I’ll have a look at your diagram this evening, can’t see it on my phone.

Are your batteries in a garage? I know it’s considered a risk but I’m planning on putting mine in a utility to keep at 20 degrees without cooling/ heating fluid connected & the Victron on the other side of the wall, which is the garage. Which is why I need the simp BMS to minimise risk.

I figured as I’m happy driving a Tesla & been in a metal box with the batteries they are safe enough to be inside, as long as they are monitored.


I may be in touch with some questions if you don’t mind. Currently waiting for the Victron 7-10 working days.

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Jason - UK avatar image Jason - UK commented ·
@5JWX yer sure, let me know if you have any questions but make sure you @ me otherwise I wont be aware you have posted a message for my attention.

My batteries are in my garage of which I have my 2 wire 'BMS' wired thought the fire alarm in the garage via a relay base so if there is a fire or smoke, the fire alarm breaks the 2 wire and therefore stops the inverter charger. I advise the same if going inside your utility room.

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