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martghh avatar image

BYD LVL 15.4 - High Battery Voltage Warning

Hi,

since 2 days i've connected new BYD LVL 15.4 (two units) to a single MP-II 48/5000 together with 2 MPPTs chargers. Installation and configuration went smootly, following the Victron provided docs. All components running the lastest SW and no connection problems exists. Since the initial full charge i saw Voltage Warnings from the BMU (and on the CCGX following) - the Battery voltage is displayed at 55.3V and thus slightly above the documented limit. I though that CCGX (venus) is dynamically controlling the DC voltage receiving the changing limits from the BMU ? Any other option to correct in order to avoid these warnings ?

best regards,

Martin

MPPT - Solar Charge ControllerMultiplus-IIVenus OSBYD
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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @martghh,

I have been running one of these LVL batteries myself for a while now, and with the current firmware, I haven't seen any warnings or alarms.

Can you please provide the VRM site id so I can have a look at the alarm log to see how often it is happening and what might be causing it?

The first thing I can think of, is with 2 units they might not be perfectly state of charge synchronised to be begin with, and could get some warnings until they are both balanced. I would expect this to happen within a few days, and a few charge cycles and plenty of time close to fully charged though.

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Hi Guy,

you mean this id ? edit- redacted - odin_island will do

-- Martin

Thanks @martghh,

I'll follow it up and get back to you.

Would you be willing to test my theory and isolate/disconnect one of the batteries to see if the warnings stop when only one is connected?

martghh avatar image martghh Guy Stewart (Victron Community Manager) ♦♦ ·

basically yes - i would consider waiting a few more charge cycles - if the warning do not disappear, i'll disconnect and see what happens then. By the way - according to various documentations it will be beneficial to 'not always' fully charge the batteries and leave them basically in a partly charged state. If this is true, how to configure this ?

-- Martin

Good, please keep us updated if anything changes.


At a fundamental chemistry level, you are correct. Pushing a battery beyond to it's limits regularly will come at the expense of battery cycle life.

However, one of the benefits of a sophisticated BMS like the BYD is that the cell life / useful energy / efficiency is managed for you. They collect cell data from millions of batteries over decades, and use that to optimise how their system behaves.

The consequence of that is you give up some controls. Effectively BYD is taking responsibility for the cycling of the battery, and backing that profile/algorithm with their warranty.

There are no supported ways to subvert the charging profiles of these batteries, without potentially compromising the warranties.

If you planned to leave the battery for a long time, you could discharge it to 80% by switching off the charge source, and running a load, before isolating the battery.

@martghh,

Is the BYD battery also connected to the internet via the Ethernet/Internet port on the BMU?

It would seem the battery itself could use a firmware update, though all Victron equipment is up to date.

If you could cycle the battery between 80% and 100% a few times, I expect the situation to improve as individual cells become balanced.

martghh avatar image martghh Guy Stewart (Victron Community Manager) ♦♦ ·

yes, they are

by the way - did you now how i could verify that the BMU connects correctly (to whom actually) ? the documentation is (still) crude and most stuff i could find on some australian site - did you know other sources of up to date documentation ?

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