BYD Atto 3 V2L load testing - Vehicle-to-load power output

Hi Svarky, I’m hoping I can borrow of your bountiful knowledge again. Last year my electrician installed a backup power input to my (grid connected) house swicth box, but only for a group of essential circuits (excludes oven, stove top, etc)…these circuits can either be powered by the backup power input or via mains and an ACT40 automatic transfer switch does the switching …backup power is primary and mains is secondary, so if backup is connected the essential circuits run on that and as soon as it’s disconnected the circuits instantaneously return to mains. I currently use the Atto 3 VTL as backup power input, and it works fantastically ……EXCEPT that maybe 1/3 of the times I connect the V2L and the ACT40 switches across the car trips out and resets and I need to try again! At the same time a few appliances in the house like printer reset and sometimes it triggers the TV to switch on from standby??. There seems to be no consistency to when it will/wont work…I never connect when high loads are connected (never more than 500 watts load when connecting) so it isn’t an overload. Sometimes it will successfully connect 4days in a row and then will start the intermittent tripping/resetting the next few times I connect. It’s frustrating for family and also seems to trigger Sonos speakers to need to be cycled on/off sometimes. My electrician and I have no idea why it’s happening completely unpredictably??…is it a VTL fault or maybe a dicky connection somewhere on my house? I’d be very grateful for your suggestions? Cheers,Chris

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@chris1 that is a tricky problem. I suspect the transfer is somehow creating a voltage spike or small surge. Where this is coming from is hard to determine, but it may be a problem with the ATS.

Another possible cause is the large voltage difference between the two AC supplies. The V2L output from the Atto 3 is only around 220V, while the grid supply could easily be 250V or greater, depending on the local demand. You could test this by operating the transfer switch in the middle of the day when the grid voltage is typically higher, then test during the evening with large loads on the grid supply.

@chris1, how much did your backup setup cost? :thinking:

Hi Svarky, thanks for your feedback. I haven’t been sure how to respond so I apologise for the delay. I will try to monitor my daytime and nighttime mains voltage but I haven’t previously noted that the trip-outs are more likely at any particular time of day. I wish there was some way to diagnose what is actually causing the car to trip intermittently on connection ….do you have any idea if/how one can access diagnostic data on the V2L?…so I can actually see what causes the trips? At present it feels like I’m flying blind. There may be some dicky connection in my house or an appliance that has only become evident due to the V2L tripping and it frustrates me that there appears to be no way to diagnose more deeply. I once clumsily plugged an appliance into a power point which was already switched on while the V2L was active…I heard a tiny spark within the power point and the V2L tripped out immediately. I therefore realise it is quite sensitive, as I have heard sparking like that occasionally before when on mains power and nothing tripped. It’s really frustrating that no data seems to be available on the V2L or what parameters make it reset. Thanks again.

Hi GJOESQ, it’s actually a bit hard to answer as I had the backup power input added at the same time as I had 2 solar air conditioners, a heap of solar panels and a new inverter installed, plus some other electrical work. The electrician was already rewiring elements in my switch board as part of the job and I thought it was a great opportunity to add a backup power supply for some of the circuits. The costs were grouped into a much larger job. I don’t think it’s very expensive to get a backup power input installed. I selected an automatic (rather than manual) transfer switch and a smart relay in addition to the mandatory CB but these weren’t very expensive. I suspect the main cost variables relate mainly to the work in the switch board, wiring a sensible selection of “essential” circuits and the mains supply to the transfer switch, etc… I’m no electrician and all this work was scoped and done by a professional electrician. It’s not unusual, however, to install a backup power supply input to a switch board and that’s really all this is. I’d imagine most electricians (particularly those who maybe have off grid experience) can quote you on installing a backup power input.

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Hi, I need som help. I tried to make a V2L adapter, using first 2,7kohm resistor as on the schematic, next time the 2kohm what was shown on the photo above, but in both case the discharge not started. if the car opened but not started, nothing seen, if started there is a plugged cable icon on the small dashboard, and thats all.
the car is a BYD Atto3 Comfort where the V2L adapter is not attached to the car, but they said the function is installed. Is there any other trick I should do?

Hi again,

Here are some details on how the transfer switch is designed to work

I was assured that it is specifically designed to safely and seamlessly switch between two unmatched AC power sources (eg mains and generator input, within quite a wide voltage range…see the manual) without endangering household electronics. It is supposed to switch back seamlessly to secondary (mains) power automatically if the primary (generator) voltage becomes unstable or is disconnected. The manufacturer say the tripping must be related to something in the car as the ACTS40 will not allow a spike during the switching. So far I can’t find any useful info about the car to explain what may be causing the occasional drop-outs during changeover and I don’t understand why the ACTS40 doesn’t switch back to mains “seamlessly” fast enough when these occasional changeover drop outs occur. It normally transfers seamlessly from one source to the other as advertised UNLESS the V2L does the unpredictable drop-out during changeover. In this scenario the dropout is longer than normal and enough to trip stuff off and on again in the house.
I guess I was really hoping for guidance on how to determine what is unpredictably causing the car V2L to trip…i.e. some explanation as to what is in the car V2L and maybe how to diagnose? Latronics appear to be bringing forward the end of support for the ACTS40 and my electrician has kind of given up trying to work out why it works flawlessly most of the time but then trips unpredictably when connecting sometimes. The light of the V2L unit does go out and come back on immediately so it does seems to be a temporary trip/reset in the car rather than a ACTS40 malfunction. I’d love to get this remedied before Latronics cease supporting :confused:

The V2L is a protected supply that works the same as an RCD (residual current device). RCDs are safety devices that are designed to trip immediately if there is any earth leakage in the circuit due to an old or faulty appliance. It is not uncommon to have nuisance tripping to occur, even with regular RCDs.

You might have a faulty connection somewhere, which is causing the V2L to trip. Additionally, I assume your circuits are already protected by RCD, so when they are powered by the V2L-protected supply, it increases the sensitivity and could cause the V2L to trip off.

Thanx Chris1. I think all this is beyond me at this stage. Things are working fine and not costing too much and we are CO2 positive. All the best with your endeavours! :hugs:

Hallo Svarky.

I’ve been reading through this and thanks for sharing resourceful knowledge. I have Byd seal and bought Deye inverter (haven’t installed yet). The plan is to connect v2l to gen port of it like your Victron. I want to make sure i can do what i want with this inverter before opening box.
So my Seal will trip the power as well because of Neutral Earth bond in my home, right? Disconnecting it will disturb safety system, wont it? Can we find a way to disable RCD on the EV instead? Would it be easier safer and solve the issue?


@Thanwintun, I believe this will work as the Neutral on the generator AC input is not connected to the grid AC input. Refer to the diagram below from the Deye user manual and you can see the separated inputs. (Generator input on the left)

I have not tested this personally, but you should be able to easily verify whether the two neutral inputs are isolated by doing a simple continuity test (buzz) using a multimeter.

Note that you cannot disable the RCD on the EV. This is not possible.

2.7 MOhm is also what I measured