BEV charger questions

[Countrypaul]

Apologies if this has been mentioned, but my skim read this morning noticed quite a few mentions of Zappi (or similar). Not in any way knocking the tech nor idea, and the same for water heater diversion switches, but ....... if anyone has a battery, or will be getting one in the future, then is the technology needed?

The diversion devices avoid export of spare PV, a great idea, but if the battery is catching that excess, then you can charge the car, water tank, or A2A unit from the battery (buffer)?

Hope that makes sense.

Mart not sure I really follow what you are getting at. If someone has a Zappi, then presumably their main reason for getting one is to charge an EV. It will, surely, make more sense to charge an EV directly rather than charge batteries to then charge the EV. If you are going to heat water then again why charge batteries to then heat water?
If the PV is producing a high amount then choosing which to put the energy into first will, presumably vary, if a long trip is planned then chrging the EV fully may be the priority, if not expecting to go out for a couple of days then charging the batteries first may be most beneficial, if expecting to have a famiy all needed a bath due to muddy activity then hot water may be essential. If everything is fully charged then exporting the remainder, even if you get nothing for it, benefits others.
Depening on what tech you have installed on the RE sie it might be that the batteries cannot take all the PV power you are producing so diverting to a secondary, or even tertiary destination would make sense.
Like most technology, it is needed or just wanted, do we really need to have home batteries or could we just rely on the grid? Giving flexibility to how we utilise what we are producing is surely beneficial, but not everyone will need every option.

Just my tuppence worth on what is probably a very philisophical question rather than a technical one.

[Mart]

My only advice is get a longer cable than the basic 5m. The 7.5m means that you can charge a car parked in any possible configuration on our drive. a 5m would be more sensitive.

100%. Our first charger/cable was 5m. The website said ~5m or 5m, but the installer info says 'about 5m'. Leading to an interesting discussion on what about means, could it mean 4.3m, possibly, whereas ~5m suggests to me, something much closer to 5m.

The problem being that 0.7m of the cable is inside the charger, and the full length of 5m included the nozzle. So we were unable to charge a tesla model 3 parked nose in, as the cable wasn't long enough, and the nozzle length sticks out to the side, so doesn't contribute to the distance.

Struggle to reverse in as our driveway is very steep, and narrow, so the passenger door is blocked, or the driver door if reversed in. Driver has to climb across, but doors are heavy to open, due to extreme angle.

Wifey criticised on a charger forum, then a bod came along and quoted the installer length of 'about 5m', and asked where she'd seen 5m or ~5m. She linked to the charger company site pages, and he said he was the boss of the company, and after checking the pages apologised, and arranged for a 7.5m cable to be installed instead.

May sound silly, but even at 5m, as Smegal explains, you don't get much choice about how/where you park. Even the charger location becomes important, if it's central to the car nose, then that reduces overall length, and if it's to one side, make sure it's the side your charger flap is on, otherwise Pythagoras makes life harder, and worse still, if you don't want the cable laying across the car.

First World problems I know!

[Mart]

Apologies if this has been mentioned, but my skim read this morning noticed quite a few mentions of Zappi (or similar). Not in any way knocking the tech nor idea, and the same for water heater diversion switches, but ....... if anyone has a battery, or will be getting one in the future, then is the technology needed?

The diversion devices avoid export of spare PV, a great idea, but if the battery is catching that excess, then you can charge the car, water tank, or A2A unit from the battery (buffer)?

Hope that makes sense.

Mart not sure I really follow what you are getting at. If someone has a Zappi, then presumably their main reason for getting one is to charge an EV. It will, surely, make more sense to charge an EV directly rather than charge batteries to then charge the EV. If you are going to heat water then again why charge batteries to then heat water?
If the PV is producing a high amount then choosing which to put the energy into first will, presumably vary, if a long trip is planned then chrging the EV fully may be the priority, if not expecting to go out for a couple of days then charging the batteries first may be most beneficial, if expecting to have a famiy all needed a bath due to muddy activity then hot water may be essential. If everything is fully charged then exporting the remainder, even if you get nothing for it, benefits others.
Depening on what tech you have installed on the RE sie it might be that the batteries cannot take all the PV power you are producing so diverting to a secondary, or even tertiary destination would make sense.
Like most technology, it is needed or just wanted, do we really need to have home batteries or could we just rely on the grid? Giving flexibility to how we utilise what we are producing is surely beneficial, but not everyone will need every option.

Just my tuppence worth on what is probably a very philisophical question rather than a technical one.

Sorry Paul, maybe I've completely misunderstood. I thought the main benefit of a Zappi charger (and a HW diverter), was to use low levels of excess PV that would otherwise be exported? They can modulate to vary the rate of charge in line with the varying amounts of exports.

That sounds like a great idea to me. However, if you have a home battery, then it can do the buffering, and removes the need (perhaps) for such a device.

For example, before I had batts, I would look to see if PV generation was enough to cover house demand, and if enough excess on top I could switch on the A2A unit, or charge the BEV.

Now, the problem would be that I had to consider the lowest generation, especially on days with clouds flying over. So say the house was exporting an average of 2.2kW, but varying from 1.1kW to 3.3kW, then a Zappi varying charge would work great (if I had one), but instead I'd set the car to charge at 5A (~1.1kW), since at a higher rate I'd be buying in expensive day rate leccy at times. But the lower charge rate, meant that I was also exporting.

Now with a battery, I can run it at 10A (2.2kW) in that situation, or even just wait for a build up of battery storage before charging. [Edit - Just to be clear, you don't have to charge the battery first, before the BEV or HW tank, you just need enough to buffer the varying PV generation. The majority of the charge/heating would actually be direct. Sorry I didn't make that clear.]

Hope that makes sense. And I wasn't suggesting getting batteries instead, I mentioned that if you have batteries, then a diversionary switch may not make sense?

but ....... if anyone has a battery, or will be getting one in the future, then is the technology needed?

[And of course, if you have a good export rate, then maybe not bother with daytime charging at all, and do it all on cheap night rate.]

[sharpener]

The round trip efficiency of batteries is only about 80-90% so you lose a lot by going through a battery system.

Very few people will have a battery system with the capacity to charge an EV.

Totally agree, I was addressing the diverter switch/charger issue. I thought the idea behind them was to only charge from excess PV. So a battery (buffering) allows for low rate charging (such as granny charging) during these excess periods, but without the need for the diverter switch. [Also, don't the BEV chargers have a minimum charge rate, so a diverter may cut off at say 1kW, and export excess, whereas a battery could buffer that excess, and be run when it has built up an adequate amount.]

The same for HW tank, rather than diverting excess, you can wait till the battery has a suitable buffer, then charge the tank at say 1kW.

There are several issues with the full setup so you have to be careful how you use it.

• the house battery is much smaller than the car battery and as said upthread the round-trip efficiency may be as low as 80%

• to charge during the day the zappi needs to be set to ECO+. But if you forget to turn it off at dusk it will then charge during the night on any off-peak timetable you have set up even if you don't want it to

• yes, car chargers take a minimum of 1.4kW, it's apparently written into the standards. So in practice you need to give that priority when the sun is at its highest especially on a day when there are clouds in the sky

• then you need to remember to turn the immersion diverter back on and there is a risk there will not be enough sun remaining to heat the tank

Some of this could perhaps be automated better. But the zappi needs about 100W of export to switch on, so setting the immersion diverter to have a higher threshold than that would mean significant unwanted exports when the car was not being charged. I suppose I could add an extra switch to it but I am loath to muck about with something that I built in 2012 and has not needed any attention since(!)

[Moxi]

Look at the late model hypervolt. The late model is Octopus intelligent compatible. I'm still hoping my V2 will be in the not too distant future.

Yes the Hypervolt 3 Pro looks like it does the job, checked it on the Octopus website along side the EV6 and its a matched pair and suitable for IOG, I put an enquiry in with my preferred local supplier last night to see if they would quite me for an install, lets see if they are up to the task of a slightly non standard install ?

Moxi

I've generally been critical of Hypervolt, it's irritating that my V2 isn't compatible *yet*, but we've had it since feb 22 and apart from a few software issues at the start which were resolved quickly, it's been fine.

Hypervolt are also one of the better looking units if you're into that sort of thing.

My only advice is get a longer cable than the basic 5m. The 7.5m means that you can charge a car parked in any possible configuration on our drive. a 5m would be more sensitive.

Thanks Smegal I appreciate the experience, I was thinking of getting the 10m cable option because we have three parking positions all nose in tail out and the 10m cable would reach every conceivable position. I just hope the installer get back to me and its a positive discussion, I get way too many trades not interested if a job is even remotely unusual?

Moxi

[Mart]

The round trip efficiency of batteries is only about 80-90% so you lose a lot by going through a battery system.

Very few people will have a battery system with the capacity to charge an EV.

Totally agree, I was addressing the diverter switch/charger issue. I thought the idea behind them was to only charge from excess PV. So a battery (buffering) allows for low rate charging (such as granny charging) during these excess periods, but without the need for the diverter switch. [Also, don't the BEV chargers have a minimum charge rate, so a diverter may cut off at say 1kW, and export excess, whereas a battery could buffer that excess, and be run when it has built up an adequate amount.]

The same for HW tank, rather than diverting excess, you can wait till the battery has a suitable buffer, then charge the tank at say 1kW.

There are several issues with the full setup so you have to be careful how you use it.

• the house battery is much smaller than the car battery and as said upthread the round-trip efficiency may be as low as 80%

• to charge during the day the zappi needs to be set to ECO+. But if you forget to turn it off at dusk it will then charge during the night on any off-peak timetable you have set up even if you don't want it to

• yes, car chargers take a minimum of 1.4kW, it's apparently written into the standards. So in practice you need to give that priority when the sun is at its highest especially on a day when there are clouds in the sky

• then you need to remember to turn the immersion diverter back on and there is a risk there will not be enough sun remaining to heat the tank

Some of this could perhaps be automated better. But the zappi needs about 100W of export to switch on, so setting the immersion diverter to have a higher threshold than that would mean significant unwanted exports when the car was not being charged. I suppose I could add an extra switch to it but I am loath to muck about with something that I built in 2012 and has not needed any attention since(!)

Many thanks.

For me, I can look at the weather forecast, and battery level, and say PV gen is enough, then I can put the Tesla on (the older IONIQ is not so clever), and set the charge level for X%, say plus 10%, so after say 3 or 4 hrs, it will stop charging. Hopefully the charge will come from PV, but the battery will buffer, so I no longer need to aim for the lower safer level, nor keep an eye out for clouds. [And that's where I can see a Zappi, or similar being brilliant.]

In the better PV months, I can now use the main 7kW charger, but dial the Tesla down from 32A to ~14/15A, since my large PC system and DC battery run through a 3.68kW inverter. That's fun. And the batt catches all the DC excess that isn't wanted, or can't be 'processed' at that time. I have actually seen gen hitting 6kW. Nice.

I was chatting yesterday at the Baxi stand about electric boilers and HW tanks. The guy asked if I had PV and talked about adding a smart diverter, but when I said I have batts, he said no point then ...... but crucially, we use about 100kWh of gas per month (when not heating), so allowing for poor boiler efficiency when cold, I'd guess our needs are around 2.5kWh(t) per day, hence why PV and battery buffering would negate the need/expense of a diverter switch. I think 1kW would suffice for us, but presumably we'd want a seond 2 or 3kW too, just in case. [But again, not knocking their idea, however, perhaps even just cheap rate charging these days may off set the additional purchase cost .... really not sure?]

[Ken]

If relevant,
Having a CT clamp on the grid supply and one on the immersion heater and then joining them together before entering the Zappi the immersion heater will charge until such time the measured current at the Zappi reads min 6amps when the Zappi will charge the car and disconnect the immersion and vice versa when clouds or evening. This utilizes all the surplus PV until they are full and then goes on to export or charge the batts.

However this is old thinking because with TOU tariffs i would demand shift EV,HW,HP, batts and others to the cheap rate and export the surplus PV at the 15p. I would not use the batts for arbitage as i consider that poor value after hammering the batts.

With enough PV then you get to a zero leccy bill as per Nowty.

I note that Octopus Agile seems to get close to zero once a week so with judicious use i wonder how close or easy to get to zero leccy bill, or perhaps IOG is the better route particularly if you fool it with the EV charging.

[sharpener]

Having a CT clamp on the grid supply and one on the immersion heater and then joining them together before entering the Zappi the immersion heater will charge until such time the measured current at the Zappi reads min 6amps when the Zappi will charge the car and disconnect the immersion and vice versa when clouds or evening. This utilizes all the surplus PV until they are full and then goes on to export or charge the batts.

However this is old thinking because with TOU tariffs i would demand shift EV,HW,HP, batts and others to the cheap rate and export the surplus PV at the 15p. I would not use the batts for arbitage as i consider that poor value after hammering the batts.

Not sure I understand the theory of this. Yes you can add the (signed) current draw of two devices using two CTs but does the control aspect rely on the immersion controller being a Myenergi eddi? Mine is home brewed, needs 50W export to turn on fully so has priority over the zappi (set as per MIs to 100W) but frankly CBA to modify that threshold.

Particularly as am expecting to be moved from deemed export to Octopus Fixed Outgoing when they get round to it, then I will as you say benefit from 15p/kWh and it will be cheaper to heat the immersion at night at 12p than sacrifice exports.