BYD battery and Atto 3 V2L off-grid charger

I have been reading alot of very useful information from Jason regarding setting up a off grid system for my garage, in conjunction with my BYD atto 3 V2L.
I am convinced that a separate Battery charger is the way to go.
My question is regarding my battery which is a BYD U3A-1 50P-1

I just read that it may not be possible to use a separate charger with this battery?

It may be possible, but only if you use a specific type of system, such as a DC-coupled Victron system which uses CANbus to manage the battery and regulate the charging from multiple sources.

What type of inverter do you have?

Hi Jason
Thanks for your reply. I haven’t bought inverter etc yet but was hoping to use victron multi plus 2 inverter/charger 5kw.
I have the battery as surplus to our house off grid system.
The idea is to have basic small solar array and use the car if needed. The garage will not require large amounts of power and will be left idle for most of the time so hoping the solar will keep the battery topped up.

Hi James,

Sorry, someone flagged your previous message as spam for some reason.

Anyway, a Victron system should work with V2L and a BYD battery as long as the battery charger is compatible with the BYD (CANbus) communications.

You will need to use a Victron charger since this will be fully integrated with the Victron VRM and CANbus control system.

Thanks Jason. Not sure what happened but relieved we are in touch again.
If I have a separate victron charger will I still need the inverter/ charger or just the inverter? Would the mppt charge the solar side?

Hi again
Just wondering if you do designs for off grid system? I am happy to pay for your time and expert advice, especially regarding my V2L BYD car. First person I have found with any decent information.
Thanks James

Yes, you will need the separate Multiplus inverter to supply AC power.

Where are you based? In some countries outside Australia, you can legally use the internal Multiplus Ground relay (link) function and may not need a separate charger.

I am in rural NSW on a farm. I am actually a builder. I have a good friend who is a electrician who will wire things up. He doesn’t know alot about off grid and V2L. I figure if I do the homework and get all the bits we need we can get it going.
While obviously wanting to be safe nobody will be inspecting or approving the system. If we used the multi plus ground relay link, then I just need to buy 48 volt inverter/charger?
The 48 volt charger is expensive. We are using the BYD batteries (10kw) at home through a multi plus 2, 48 volt inverter/charger 5kw, with a fronious 5kw. We have installed a zappi charger on the house to charge the car.

Where are you located?

Hi James,

I’m near Kinglake North of Melbourne. So a long way away. Since you are in Australia, you technically need to use a separate (isolated) charger for the V2L, which is compatible with the Victron GX unit (CCGX in your situation) and will be controlled using the DVCC control feature. (If you wanted to use the ground relay and disconnect the NEM in your SB, that’s solely up to you)

The DVCC control feature will already be enabled in your CCGX and it allows the BYD battery BMS to correctly manage the battery charging. If the V2L charger is not connected and managed by the CCGX you could destroy your battery. The problem is the Victron Skylla 48V charger is not compatible with the CCGX so it won’t work. I’m not sure if you can use a second Mutliplus 2 as a dedicated charger, but this is something worth looking into.

Another way it could work is to use a 48V battery charger (any brand) and stop the charging (via a contactor) once the battery is around 85 to 90% SOC using the built-in relay in the CCGX. This way, the charger would never be allowed to fully charge the battery, and there would be no risk of overcharging.

Thanks Jason
Now I am getting confused. Just getting back to the beginning, is it the BYD battery that is the problem or the V2L option?

Hi James, there are two problems…

  1. The V2L is a protected (grounded) supply, which means you cannot simply connect it to the AC input on the inverter, as it will not work due to the ground (MEN) link in your switchboard.

  2. The BYD battery is a ‘managed’ battery system that must be used with an appropriate (compatible) battery charger. You cannot simply connect any old 48V charger as it could overcharge and damage the battery.

There are solutions to these issues, but you really need to have some technical understanding of the Victron system and how it’s configured and managed.

Using the Multiplus inverter internal ground relay is one way to get around both of these issues but it’s not technically legal in Australia.