Victron system with multiple batteries

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robertc asked Nov 5, '21

Victron system with multiple batteries

Hi, I have a Victron 3f setup - 3x Multiplus, 2x MPPT charger and 3x Pylontech 3000 and Cerbo. As a tech hobbyist I'm looking forward to extend my capacity with a custom 15S LiFePo4 pack to match Pylontech battery voltage and a BMS that can talk to the Cerbo via CANbus to provide the system with battery data similar how ie. Pylontech does that. Will the Cerbo work with both batteries together correctly calculating all the values together - like capacity, SOC, current draw and so on? I just could not find such an information anywhere. Thanks.

BMS 48v battery

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nickdb answered · Nov 05, 2021 at 06:33 PM

You have one shared DC bus, the system does not know what is hung off it, that is the role of the BMS to make sure all these modules balance/charge/discharge correctly.

Electrically you can’t treat banks of batteries differently when they share a common bus.

Internally all battery models are different and need to be treated that way.

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Modifications Space

Node Red Space

Answer 1 · 2021-11-05T16:59:30Z

nickdb answered · Nov 05, 2021 at 04:59 PM

No, you can’t mix the battery types. You can however add more of the same pylon model.

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Answer 2 · 2021-11-05T17:32:52Z

robertc answered · Nov 05, 2021 at 05:32 PM

I know that Pylontech no matter how much of those you have, you connect only one to Cerbo which acts as a master BMS aggregating the data from other modules to a single BMS connection to Victron. So the system then just thinks it has a single battery. Does that mean that Cerbo/ or VIctron in general does not have support for having multiple BMS connected?

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Answer 3 · 2021-11-05T17:45:11Z

nickdb answered · Nov 05, 2021 at 05:45 PM

it’s a bit more complicated than that.

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Answer 4 · 2021-11-05T18:20:40Z

robertc answered · Nov 05, 2021 at 06:20 PM

I read somewhere that technically the Cerbo can handle multiple CANbus BMS devices, but will only use for controlling MPPT charging and discharging one of the devices. Is that the issue? I would not mind that really, the BMS itselt can protect the pack, I just want the system to show the correct numbers on the GX dashboard. Although I'm not sure if the dashboard takes numbers from the battery BMS or from MPPT chargers.

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Answer 5 · 2021-11-05T18:57:58Z

robertc answered · Nov 05, 2021 at 06:57 PM

Ok, well then I'll go with more Pylontech batteries then I guess. Thanks!

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Answer 6 · 2021-11-06T03:03:49Z

shaneyake answered · Nov 06, 2021 at 03:03 AM

You can have diffrent LFP packs on the same bus. There are disadvantages to doing this but it is totally doable.

The problem comes in that the Cerbo won't understand what is going on. The Cerbo can have multiple battery packs on the CAN bus however the Cerbo expects there to be 1 master that combines all the data from the slaves and sends it to the Cerbo. If you want to spend a lot of time you could probably get this working using an Orion BMS or a custom board to act as your CAN bus interface. You could also write your own Battery Monitor Driver and use different CAN IDs for the diffrent packs this is all doable but will take some work and custom programing.

If you are okay with not interfacing the BMS data into the Victron system, you can treat the packs as dump batteries and use a Victron Smartshunt to get the relevant data to the GX, this would work but the BMS's would lose the ability to signal that there is a problem with a pack. and just to be clear, I only run CAN managed batteries and refuse to use anything else in my installations.

So I guess to answer the question, Yes, you can use diffrent packs if same chemistry on the same bus but the money saved on a homemade pack might not be worth the time it will take you to get full software integration. Plus Orion BMS is like $750 USD when all said and done.

https://www.orionbms.com/products/orion-jr2-bms/

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shaneyake commented · Nov 06, 2021 at 03:08 AM

On a side note, Pylontech uses RS485 to send data to one pack that sends that over CAN bus to Cerbo. Batteries from FreedomWon and others, have multiple packs on the CAN bus but they still only have 1 Masters that interacts with Cerbo.

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nickdb ♦♦ shaneyake commented · Nov 06, 2021 at 09:52 AM

It wasn't said that you can't have multiple packs on a common bus, that is after all how pylons scale out, just with a single BMS, care of their external hub.

What was asked here was two different models/makes of batteries each with their own BMS.

That is sailing in waters marked with "here be dragons".

If someone is a serious engineer and software developer, they could attempt a Frankenstein system but it would be off support and the warranties would most likely depart the building.

One bus and two masters is not a recipe for success.

I doubt the QA that gets done would consider this scenario, so any software/firmware update may undo the hard work.

And all this time, cost and risk to save a little bit of $ on what is already a good value battery.

The sums and headaches don't add up.

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