question

londonflatthing avatar image
londonflatthing asked

connect BMS to Multi RS Solar

Hi everyone I have a solar system with battery using a Multi RS Solar 48/100

The Multi RS doesn't estimate the battery state of charge correctly so I'd like to connect the RS-485 / CANBUS from the battery to the Multi RS Solar.


the technical details of the battery connection is as follows:

RS485 and CAN interface, which supports communicating with multiple machines in parallel and with the upper computer.
RS485 baud rate is 19200, CAN baud rate is 500K.
RS485 INTERFACE

8P8C RJ45 Pins Assignment (RS485)
Pins Definition
1,3 RS485_B
7 RS485_A
2,6 GND
4 CANH
5 CANL
8 N

it also has a jumper for "victron compatible" output.


this is the battery from aliexpress... I'm using the 7.7kWh version.
https://www.aliexpress.com/item/1005004370280988.html?spm=a2g0o.order_detail.order_detail_item.2.7c0cf19c7zX5id


Now how should I go about connecting the battery to the Multi RS?

Do I use a BBB (with an add on CANBUS transciever and VE.CAN to CANBUS cable)

or

buy a cerboGX and connect multi-rs with VE.CAN cable and BMS with "CANBUS" cable

or

Can I connect the BMS straight to the Multi RS VE.CAN using a CANBUS to VE.CAN cable of some sort?

any help / advice would be appreciated


BMSVE.Canmppt rs
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5 Answers
Alexandra avatar image
Alexandra answered ·

@londonFlatThing

Since it is not a supported battery you may or may not win

Use the pins can H, L and ground (battery side you know). The bms can will be the same as the GX.

The connection can also be done in the IO from what i understand.

I have the Inverter RS but have BYD connected to the bms can port. They are a supported battery though.

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londonflatthing avatar image
londonflatthing answered ·

Thanks for the reply.

so my understanding is that I can use a VE.CAN to CANBUS cable and connect directly to the Multi-RS Solar VE.CAN interface and then set it to use "2 wire BMS" ?


or


i should buy a cerbogx.

connect the multi-rs to cerbogx via ve.can port (using standard rj45 cable?)
connect BMS to cerbo-gx using the VE.CAN to CANBUS cable.

and try and configure it from there?


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Alexandra avatar image Alexandra ♦ commented ·

All three are an option. If the can works then you are set. If it does not then switch to the two wire option.

But one implemented at a time for a solution.

You can use the system without the Cerbo. Are you planning on expanding? do you want remote monitoring?

To be honest a cerbo is a great addition to any system, it opens up other things you monitor and control in the system.

But again your battery is not officially supprted so may or may not work.

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londonflatthing avatar image londonflatthing Alexandra ♦ commented ·
well i bought a cerrbogx.... but it doesn't seem to see my multi-rs 48... not sure if its the cable
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Alexandra avatar image Alexandra ♦ londonflatthing commented ·

Are you using the CAN connection?

Check you have it in the correct port for CAN and have the terminator in?

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gabius avatar image
gabius answered ·

I have a multi rs solar, with cerbo, it works pretty fine.

Do you need some help to wire it correctly ?

I have a bms from aliexpress connected to 15x306ah but I choose to use a smart shunt, I think it’s easier than try to make the Victron product understand the Chinese bms.

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londonflatthing avatar image londonflatthing commented ·
so actually the chinese BMS comes up perfectly fine on the cerbo GX using the "VE.CAN to CANBUS cable" connected to the VE.CAN port set at CANBUS 500kbps



however its the MULTI-RS that is not being detected at all now...

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Alexandra avatar image Alexandra ♦ londonflatthing commented ·
A few rhings to note. If the chinese battery has a higher charge voltage than Pylontecs normal ones of around 52 and 51v you may run into issues where they wont charge up fully.
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londonflatthing avatar image
londonflatthing answered ·

do i need to buy and use one of these cables instead of a "normal" ethernet cable? for the
https://www.amazon.co.uk/Victron-Energy-RJ45-UTP-Cable/dp/B06Y4T92H6
multi-rs ve.can to cerbo-gx ve.can connection?

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ejrossouw avatar image ejrossouw commented ·

Trying connecting the bms using the ve.can to canbus cable to the bms.can port on the cerbo and terminate on the cerbo. Then use a standard RJ45 cable to connect Multi to cerbo using VE.Can ports and terminate both sides. PS - There are many oem batteries using either components or are rebadged versions of the large manufacturers.

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londonflatthing avatar image londonflatthing ejrossouw commented ·
hi. yes i'd already done that and it works.. the only thing its not picking up is the multi rs solar on the ve.can port... (yes end terminators are fitted). i've tried every setting in there:

ve.can & lynx ion BMS 250k
ve.can & CANbus 250k
canbus BMS 500k
oceanvolt 250k
RVC 250k

cerbogx version 2.93,
multi rs version: 1.11

ironically it picks up the cerbo-gx and the pylontech batteries in the devices list in the ve.can settings... but never the multi-rs solar.




so i ordered a victron brand RJ45 UTP cable... and will retest when it arrives.

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ejrossouw avatar image ejrossouw londonflatthing commented ·
Fingers crossed it is just a cable and not the actual ports on the RS. If you had some spare broadband modem RJ45 cables you could try those. Maybe worth checking the pins are ok on the RS side too.
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londonflatthing avatar image londonflatthing ejrossouw commented ·
so just for the sake of anyone else who may face this issue.


I went and rebooted the Multi RS Solar 48 (along with the BMS and cerboGX... ) and lo and behold... everything is working now!

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ejrossouw avatar image ejrossouw londonflatthing commented ·
That is great and the feedback to the forum is appreciated. 101 principles apply yet again ;)
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londonflatthing avatar image
londonflatthing answered ·

hello all. I have another issue now... hopefully simpler.

so now both the "pylontech" battery and "multi rs 48/6000" are connected successfully to the Cerbo GX.

however, the Multi-RS still shows the incorrect "state of charge" for the pylontech battery in its own "victron connect connection".

what do I do to rectify?

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