PV home battery storage and EV charge point conflicts.

EcoScruples

I couldn't find an answer anywhere on here,

If I have a Hybrid DC coupled battery set up with my PV, when I plug my EV in at night what's stopping the EV from emptying the home storage battery?
I've seen how this can be avoided with the Zappy by using the export margin but I'm talking about a bog standard wall point.
Is there a way it can be done or will the home storage battery always see it as import and therefore empty it?

QrizB

My immediate question is, why do you want to keep the hybrid battery full? What is the problem with it being drained to charge your car?

In principle, you've charged the battery for free from solar so putting it into your car is no better or worse than using it for your other household loads.

If you've got a time-of-use tariff like Octopus Go or one of the EDF EV tariffs, you might find there are settings on the inverter to lock out a time period where it won't discharge. I can do this with my AC-coupled inverter but I don't know about your hybrid.

Magnitio

If you are using FusionSolar, you can configure the battery so that it is not discharged during specific hours. For example, if you have cheap rate electricity from 1AM until 4AM, you can set it up as follows:

You also need to set up the AC charge cutoff SOC to an appropriately low value. As shown in the settings below, it is set to 60%, so if the solar battery is over 60% during this period, it will not continue to charge, but the grid will be used to provide energy for the house/car. If it is under 60%, then it will also be charged from the grid.

Exiled_Tyke

QrizB said:

My immediate question is, why do you want to keep the hybrid battery full? What is the problem with it being drained to charge your car?

In principle, you've charged the battery for free from solar so putting it into your car is no better or worse than using it for your other household loads.

If you've got a time-of-use tariff like Octopus Go or one of the EDF EV tariffs, you might find there are settings on the inverter to lock out a time period where it won't discharge. I can do this with my AC-coupled inverter but I don't know about your hybrid.

I'm guessing the reason is because the battery is needed  for household needs and to avoid using peak time electricity.   

I don't know of a setting to prevent discharge of my battery but I am wondering if the battery is set to force charge at the same time this may get round the problem when overnight cheap electricity is used. However  I don't know the solution when there's excess PV available and you want to hold the battery whilst charging the car with whatever is available. 

EcoScruples

QrizB said:

My immediate question is, why do you want to keep the hybrid battery full? What is the problem with it being drained to charge your car?

In principle, you've charged the battery for free from solar so putting it into your car is no better or worse than using it for your other household loads.

If you've got a time-of-use tariff like Octopus Go or one of the EDF EV tariffs, you might find there are settings on the inverter to lock out a time period where it won't discharge. I can do this with my AC-coupled inverter but I don't know about your hybrid.

Good question and the answer is because potentially the vehicle won't be mine, it'll be a company vehicle and I'll be reimbursed for the charge amount. 

Magnitio said:

If you are using FusionSolar, you can configure the battery so that it is not discharged during specific hours. For example, if you have cheap rate electricity from 1AM until 4AM, you can set it up as follows:

You also need to set up the AC charge cutoff SOC to an appropriately low value.

That's what I'll be using yes and has answered that question really well, I assume I'd have to import a few hundred watts during those hours to cover my base load but as it would be cheap rate then it's not a big one.

Exiled_Tyke said:

QrizB said:

My immediate question is, why do you want to keep the hybrid battery full? What is the problem with it being drained to charge your car?

In principle, you've charged the battery for free from solar so putting it into your car is no better or worse than using it for your other household loads.

If you've got a time-of-use tariff like Octopus Go or one of the EDF EV tariffs, you might find there are settings on the inverter to lock out a time period where it won't discharge. I can do this with my AC-coupled inverter but I don't know about your hybrid.

I'm guessing the reason is because the battery is needed  for household needs and to avoid using peak time electricity.   

I don't know of a setting to prevent discharge of my battery but I am wondering if the battery is set to force charge at the same time this may get round the problem when overnight cheap electricity is used. However  I don't know the solution when there's excess PV available and you want to hold the battery whilst charging the car with whatever is available. 

Yes, I don't want to use the battery until next next day yo cover the days load.
The bit about the vehicle not being mine though is the main reason, I'll still get paid for that electric that goes into it but don't want it to come from my battery.

Petriix

There are alternative solutions. You can configure the wiring and CT clamps so that the grid monitoring for the battery is after the supply for the EVSE (which could be branched off using a Henley block before the main consumer unit). That way the battery inverter would never 'see' the car charging and therefore not discharge.

For anyone with an existing solar setup and a Zappi or similar, I strongly advise going for an AC coupled battery rather than a hybrid inverter. It's less efficient but massively more versatile. 

Reed_Richards

I like my DC-coupled battery.  My inverter has a setting that controls the depth of battery discharge so I could manually set the battery not to discharge overnight then manually reset it in the morning.  I don't think I can schedule this but I have no incentive to try so it might just be possible.

Solarchaser

If you feed the negative lead from the charger through your CT for the hybrid system it won't see the draw, as the positive power use will be cancelled by the negative return.
This way it won't discharge into the EV