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MarioWagner avatar image

BYD - DVCC - Cold weather performance

Hello Guy (as this will probably target you :-) ),

we run several off-grid BYD B-Box/Victron combos.

Cold weather charge performance required me to switch off DVCC for now ... since we cant

recharge our batts properly if its temperature drops below 13°C.

But i got no good feeling having DVCC off. Especially since the allow to charge/discharge contacts arent wired.


Unfortunatly i got no reponse from BYD so far, as to what firmware changes regarding this topic they might have made for the b-box. U meantioned in your BYD/Victron manual that they did make some changes. Do u have info on that?


overruling the charge limit via a CCGX option would resolve it all ... but guess thats not in victrons interest?

BYDDVCC
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6 Answers
Guy Stewart (Victron Community Manager) avatar image

In terms of actual help, the current firmware version from BYD, will improve cold weather performance and allow additional current. But I suspect you will still find it to be insufficient.


12 degrees to 3 degrees charge current limits have been increased from 6A ( 0.12C ) to 7.5A ( 0.15C ) per module.


I am not confident yet to provide step by steps from updating BYD firmware to the latest, but there is a video and instructions from BYD’s Australian distributor:

http://alpspower.com.au/download/

https://youtu.be/ssSBTTxM53k

https://youtu.be/bXb5kr9TqGw

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Guy Stewart (Victron Community Manager) avatar image

You are walking on thin ice here :)


The DVCC system is in place to follow the instructions and specifications required by BYD.

You must have it on, and find another way.


Charging your batteries outside of their specified parameters is going to potentially void your warranty if you make a claim and they want to look at the data log inside of the BMS inside the module (which will indicate charge currents and temperatures).


Those limits are in place for a very good reason, though they are quite restrictive (in my opinion).

The real solution is to keep your batteries warm by insulating and heating the space that they are in.

You will get no help from me on how to more easily void your warranty bypassing Victron and BYD controls :)

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Chris avatar image

Weve been seeing some charge discharge limitation in line with the BYD manual. 6A charge at less the 12 degrees. Although possibly affecting the whole rack of 4 more than just what the individual specs suggest.

Also. the calculated SOC seems to drop as the battery temperatures drop. We have had reports of the SOC dropping when no (significant) load on the system.

To top this lot off.... disconnect of the Quattro on low battery voltage, and it not restarting again once they have been charged above the restart value.
Needing a plugs out restart once battery voltage has been restored.

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Hello Chris,


The SOC drop you mention must due to small load rather than the cold. Could you send me access to review this? agarcia@srenergy.co.uk


On the other hand, regarding the restart. I understand the batteries are being charged by an MPPT directly after the quattro has shut down due to a low battery alarm right? You shouldn't have reached the point of shutting down the quattro but I can see that from the VRM too.

Hi Alvaro - Literally just noticed your reply !! I do apologize. I didnt get a notification from the Victron support system it would appear...
Yes - i think i determined that low power draw is inefficient - and uses more battery than expected. Also possibly compounded by the 50w inaccuracy ?
Yes - charging directly by MPPT.
Site now has generator backup / top up so we shouldnt ever run the batteries completely out.

MarioWagner avatar image

hi mikael,


my opinion: byd b-box with its current firmware and parameters isnt suited for off-grid in our regions.

we will use smthing else. victrons lifepo4 arent as cheap but integ3ation is way smoother.


regards from austria

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Mikael avatar image

Hi


I have the same issue with an upcoming installation that will be in an off-grid vacation cabin that will be in subzero environment during some months of the year.


I was thinking if there it would be possible to use the BMV-712 with AUX input Temperature and then Relay option “Low temperature relay” that in turn would open or close a Battery Protect between the MPPT and the battery? And maybe even two Battery Protects one like above and the second one in reverse to use the power generated from PV (when battery is ti cold to charge) to heat the battery to correct temp to charge and then get disconnected when BMV-712 changes relay state.


Would this be doable?


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MarioWagner avatar image

thx for the info! awesome to have u around guy! very apreciated.


no 7.5A isnt a solution. im on it via our supplier. but i guess if nothing changes i need to run with dvcc off.


still dont undetstand why within 1 degree charge current needs to be limited to 1/5th. but anways.


thx a million

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It protects the battery. BYD is offering a very long warranty period for a battery.

They have been using these packs for more than 10 years. But in other more climate controlled markets.

I hope over time that as the residential lithium battery market grows they will gain more experience and suit the technology to this application. And increase performance.


Nevertheless, if charge current limits are bypassed the warranty will be void.