2 wire bms assistant ignores aux inputs on Multiplus II

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Mike Dorsett asked Feb 25, '23

2 wire bms assistant ignores aux inputs on Multiplus II

I'm trying to configure the 2 wire BMS assistant on my Multiplus II 24/3000/70 inverter.

The BMS assistant configures and loads ok, with the following settings:

BMS has separate contacts of full and empty

battery full when AUX1 is open

battery empty when aux 2 is open

Disable charger and soc to 100% when full

When this configuration is uploaded to the multiplus, it turns off and will neither invert nor charge with any combination of aux1 / aux 2 open or closed.

Changing full/empty condition to closed rather than open, the inverter & charger operate normally, but will not turn off when the Aux input is closed.

AUX+ inputs are at +5v when open, 0v when closed. Aux- inputs are 0v.

A search of the forum shows a similar situation with a quatro, but no clear solution.

I have an assistant error report, but it is a .bin file, and can't be uploaded here.

Multiplus-II 2 wire bms

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Answer 1 · 2023-02-26T08:57:09Z

wkirby answered · Feb 26, 2023 at 08:57 AM

Is the Aux1 input configured elsewhere too?
An example can be where some grid codes, by default, enforce the use of Aux1 to be used for a "disable feed in" signal.

1677401730288.png (2.9 KiB)

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Mike Dorsett commented · Feb 26, 2023 at 06:39 PM

No, this is an island system, and grid code is set for none / no feed in.

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Answer 2 · 2023-05-25T20:33:36Z

Mike Dorsett answered · May 25, 2023 at 08:33 PM

I finally got the time to sort this out. I think there is a bug in the assistant, because if you change any of the battery voltage parameters after selecting lithium battery BUT BEFORE loading the assistant, the control inputs don't function.

This is cured by resetting the inverter to default settings, with no assistant loaded.

Select the Lithium battery option

Disable the virtual switch.

Install the 2 wire BMS assistant,

then trim the Battery voltage parameters, and it all works.

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Answer 3 · 2024-01-24T18:52:57Z

Jmarc answered · Jan 24 at 06:52 PM

Hi,
Do you have the Firmware version you where using when you encountered this issue?

Thanks

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