Lynx Smart BMS 500 - Remote On/Off - No Load

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Rob Howdle asked Jul 20, '22

Lynx Smart BMS 500 - Remote On/Off - No Load

Hi,

Can anyone clarify the highlighted comment attached?

" When the battery current is low enough the contactor will open so that the DC system is disconnected from the batteries"

I have tried to carry out a few initial tests, but get varying results. When no load is present (on the outgoing contactor terminals) and the Rem On/Off is opened, the safety contactor opens immediately (as expected). If I generate a load (e.g. a Quattro inverting with 2-3kW), the contactor can take anywhere between 5 and 20 seconds to open. Presumably the BMS 500 isn't intelligent enough to command external loads (such as a Quattro/Multi) via VE.Can -> Cerbo -> VE.Bus, so how will the shunt determine what is an acceptable current level to open?

lynx distributor smart lithium

lynx500-rem-onoff.png (69.7 KiB)

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Answer 1 · 2022-07-20T13:17:49Z

Stefanie (Victron Energy Staff) answered · Jul 20, 2022 at 01:17 PM

Hi @Rob Howdle,

The (dis)charge current needs to be at 40A or less before the contactor opens. This is to protect the contactor.

FWIW, there is always a 2 second delay for the contactor to open, which you also need to take into account.

>>Presumably the BMS 500 isn't intelligent enough to command external loads (such as a Quattro/Multi) via VE.Can -> Cerbo -> VE.Bus<<

It depends on how the loads and chargers are controlled, via ATC/ATD or DVCC. For ATC/ATD it is the Lynx Smart BMS in command, for DVCC it is the GX device in command (which receives DCL and CVL from the Lynx Smart BMS).

edit: in case the Multi/Quattro is late in replying the DVCC request, there is a timeout of 20s, which is what you are experiencing.

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Answer 2 · 2022-07-22T07:46:24Z

Rob Howdle answered · Jul 22, 2022 at 07:46 AM

Hi @Stefanie and thanks for your response,

Loads/chargers will be controlled by DVCC. I am confident that the majority of equipment will shutdown (even if there is a 20 second delay), however, I am also powering a 48V motor used for propulsion. So, it would appear that if the motor was consuming >40A and the Remote On/Off was OPENED, nothing would happen until motor current became <40A. The reason I am investigating this, is that I was potentially looking to use the Rem On/Off as a form of isolation - but it appears it can't be relied on, under certain conditions. I fully understand the need to protect the contactor, but this then removes the option for operator isolation of the system. I will need to look at interlocking the 48V propulsion system with any potential shutdown of the Lynx 500.

Many thanks.

Rob

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