question

matthias-nagel avatar image
matthias-nagel asked

Does the Lynx Smart BMS really only report start/stop charging to the Cerbo GX?

In some other thread it was stated that Victron's own LiFePO4 batteries ironically do not well integrate with the Cerbo GX. The Victron BMS are said to only report start/stop charging to the Cerbo GX while VE.Can compatible BMS from other manufacturer report a lot more like optimal charging voltage/current, internal temperature, etc., pp.

Is that so?

Of course, for the smallBMS there is no other option, because the smallBMS only has two digital output ("load" and "charger"). However, the Lynx Smart BMS provides VE.Can. For me, it seems unbelievable that the Lynx Smart BMS should be so primitive.

I haven't checked the connection options for the other BMS made by Victron.

cerbo gxBMSlynx bms
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Justin Cook avatar image
Justin Cook answered ·

In this case I would advise reading the product manual rather than the various random threads, as there can easily be a lot of misinformation in these threads - "primitive" is definitely not a term that could possibly be applied to the Lynx Smart BMS, LOL.

Lynx Smart BMS Manual

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matthias-nagel avatar image matthias-nagel commented ·

I read the manual. The manual does not contain any detail about the communication between the Lynx BMS and the Cerbo GX which either confirms or contradicts the claim.

Please note that the question is not whether the Lynx BMS can display detailed values via VictronConnect and Bluetooth. The question is whether the Lynx BMS also uses those value to determine the optimal charging strategy or if the Lynx BMS reports those values to the Cerbo and then the Cerbo uses those values to determine the optimal charging strategy.

Unfortunately, it seems that one cannot link to comments directly, but only threads. Here the link: https://community.victronenergy.com/questions/231821/welchen-lifepo4-speicher-nehmen.html. It is quite recent. @Matthias Lange - DE wrote:

Zum anderen daraus, das ironischerweise die eigenen Akkus gar nicht so gut mit dem System kommunizieren, wie man es vielleicht erwarten würde.
Da gibt es nur die Grundsignale "Laden stopp" und "Entladen stopp", wo es bei anderen Herstellern mit BMS-Can Kommunikation da z.T. sehr feine Abstufungen bei der Ladestrom/Spannungsbegrenzung und Entladestrombegrenzung gibt.
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pwfarnell avatar image pwfarnell matthias-nagel commented ·

Whilst I do not have the Lynx Smart BMS, I have been reviewing different BMSs as I am considering changing to lithium on my boat, hence I can not be categoric on how it works, but I had expected the LSB to take full control of charging Victron devices as well as the Wakespeed WS500 controller on the engine alternator.


From Section 2.1 of the LSB manual

DVCC controls compatible devices via Lynx Smart BMS and a connected GX device. Charging current and voltages are set automatically, thus Bulk, Absorption and Float algorithms are no longer used. Charging or discharging are stopped at low or high cell voltage or low temperature.


From Section 2.1 of the LSB manual, and my assumption is because the battery charging parameters are being put into the LSB, then the LSB is running the charging, not the DVCC compatible devices.

DVCC settings:

DVCC is forced on and cannot be turned off. However, a few settings can be changed, which are described below.

Please note that these settings only affect compatible DVCC devices such as Victron inverter/chargers and Solar MPPT chargers.

  • Discharge Current Limit at pre-alarm (default "No"): if set to "Yes", the discharge current limit is already set to 0A in the event of a pre-alarm, while the ATC contact remains closed. In this way it’s possible to save some battery power for essential DC loads, for example on boats such as lighting, bilge pump and navigation.

  • Absorption time: is set to 2 hours by default. This can be adjusted if necessary.

  • Repeated absorption interval: in days at which a new full charging cycle is started, if the battery SoC does not fall below the SoC threshold. The default is every 30 days and can be adjusted if required.

  • SoC threshold: is set by default to 70%. This is the threshold at which the Lynx Smart BMS starts a new full charging cycle. This can be adjusted if required.

    A new charge cycle means that the CVL (charge voltage limit) is increased from 13.5V (for a 12V battery) to 14.2V.

    In addition to the SoC threshold, a new charging cycle is started after a firmware update, when the battery voltages are below 12V/24V/48V (3V per cell) or when a low cell voltage is detected.

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