sweyn avatar image
sweyn asked

Lynx Smart BMS still needs Battery protect?

From reading the manual, the Lynx Smart BMS combined with a CerboGX does not seem to need battery protect as it performs that function itself, yet all the circuit diagrams I can find seem to still include battery protect.

Can anyone explain?

BMSBattery Protectlynx shunt
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1 Answer
Stefanie avatar image
Stefanie answered ·

Hi @Sweyn,

Can you please link to those circuit diagrams?

In general, there would be no need for a BatteryProtect in a system with Lynx Smart BMS. The contactor in the BMS should be seen as a fallback (or secondary) safety system, if for example ATC/ATD fail to disable loads or chargers.

Every system is different and so are the circumstances that lead to the installation of further safety measures, for example with a BatteryProtect.

There may be good reasons to add a BatteryProtect, for example if you want to control individual chargers (especially those that are not DVCC compatible or missing a remote on/off port and thus not controlled by the BMS and the GX device) or individual load circuits, you can certainly do this with a BatteryProtect.
In addition, a BatteryProtect switches off at a voltage to be defined and switches on again at another voltage. The Lynx Smart BMS does not do this. It only (unless you switch it in Off or Standby mode) opens the contactor when the battery reports an alarm state (eg low cell voltage) in order to protect the battery from further discharge.

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bbfb3eed-15b5-4505-8865-657f8558db46.pngThis from the marine system booklet.

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67c78b4d-993c-4935-82b6-bd2922f63250.pngOr this one from victron

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Thanks! I have updated my answer above to explain some more reasons, including why it might be a good idea to build additional security measures into a system. However, as mentioned in the beginning, there is no absolute need for additional security, especially for loads, if you agree that the contactor will only open on a defined alarm condition. If you are a little more cautious, a BP would be an option. If only because it integrates perfectly with a Victron system ;-)

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sweyn avatar image sweyn Stefanie ♦♦ ·
Ah, I see the advantages from having that extra layer. I suppose you could have non essential loads dump earlier than the essential.


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