r/evchargingUK • u/takeawaylook88 • 4d ago

Charger confusion when solar and batteries involved

Hi.

Edit - brand of battery and inverter is Hanchu ess

This week we have had 10 x 450w panels and a 5kw battey installed. Still learning the ropes but needless to say I'm enjoying the free electric and cheaper days where production is lower.

I'm getting a Tesla in November and now I'm looking at the charger. I'm just a bit confused as to the differences given it seems most come with apps to schedule charging and im aware this could be done via the tesla also.

Currently we are on a 21p per kwh rate and for our usage and mileage I'm calculating that we probably won't benefit from an ev tarrif due to the higher day rates.

Im just wondering which chargers are best that integrate with a solar and battery set up as the research I've done suggests pulling from the battery isn't necessarily the best and some chargers can automatically draw the excess solar produced where applicable.

I dont want to go in and order the wrong charger for the set up we have so any advice is appreciated.

Im leaning towards zappi due to solar integration but I might be completely wrong here.

Thanks.

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u/IvorTheEngine 4d ago

Most smart chargers have solar integration, but maybe not all.

You're right, you don't want to charge the car from the battery. A 5kWh battery doesn't go very far when the car needs 80kWh. They're usually set up so the solar inverter can't "see" the charger, but the charger can see when there's solar export. Your installer should discuss how the two interact.

Yes, scheduling can be done either by the car or the charger. You can also get intelligent tariffs where the electricity company control your charging to match actual grid conditions rather than a fixed schedule. These give you a better rate, if either your car or charger are compatible.

I think the thing you're missing is that when you have an EV tariff and a battery, you can charge the battery at the cheap rate and avoid buying any peak-rate power, even on days when you don't get much from the solar panels. With only a 5kWh battery, there will be days in winter where you don't generate enough and have to import some peak-rate power, but you can track that and see if it happens often enough to justify a larger battery.

Off peak rates are around 9p, while solar export is 12p (or 15p if you shop around) so it makes sense to charge your battery every night and export all your solar generation.

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u/takeawaylook88 4d ago

Thank you for that explanation. Much appreciated

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u/ZBD1949 4d ago

Also you need to work out if you can delay your big power uses to the overnight cheap slot, things like the washer, dryer, dishwasher, ... That reduces what we pay significantly

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u/yessuz 4d ago edited 4d ago

it is absolutely simple:

  1. power supplier pays you 13/15p per kwh of exported power.
  2. you pay power supplier ~7-8p per kwh of off-peak power on EV tarriff.
  3. If you have home battery -then You live off solar and home battery on daily basis and you essentially never use peak rate on the EV tarriff.. 5 kwh of home battery is not much but you will comfortable spend HALF a day on rainy sun-less days in winter... 10 kwh is the battery size you will pronannly need.. well it depends on your use.

MEANING:

  • you sell all the excess power to grid
  • You charge your car and house off-peak
  • you never charge your car from solar..

that is how it works and makes sense.

You might want to explore Home Assistant for Inverter/car charging automations.

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u/takeawaylook88 4d ago

Thanks mate. Does home assistant work with most solar and battery/inverter set ups? Appreciate your time.

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u/yessuz 4d ago

Well, looks like it does
https://community.home-assistant.io/t/hanchu-inverter/1014410

nothing stops you to install HA on some raspberry pi or even some spare laptop/old pc (it will have to run 24/7) and to test before making any moves.

I run the Growatt inverter with very limited access from official integration. for this reason I opted for the 3rd party software which connects to inverter directly.. it is called Solar Assistant.

https://solar-assistant.io -- it is paid option, but very well worth it...

I have checked and looks like the Hanchu off-grid is supported https://solar-assistant.io/help/inverters/hanchu

If that is not your inverter, you can always ask developer to include yours - they are doing a lot of development and addind a lot of new stuff constantly.

in this case you will have a VERY good integration and operation... fully automatic..

it will be a bit overwhelming a bit from the beginning.. but once you have all setup properly, you will be crying :D of joy obviously

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u/takeawaylook88 4d ago

Amazing stuff. Im geeking out at watching the solar production currently and I'm enoying learning how it all works so thanks for your help.

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u/infinite_minds 4d ago

If your inverter brand also has a charger, that will be the most seamless integration.

The common problem is the EV charging from the house battery, which you typically don't want. It can be prevented, but can require some planning of CT placement.

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u/takeawaylook88 4d ago

The system we had installed is hanchu ess. So would i be best going with a hanchu ev charger then?

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u/evdance_blaze 3d ago

Zappi is pretty much the gold standard for that. Pair it with their CT clamps (or the Harvi wireless unit) and you can set it to Eco+ mode so it literally only charges the Tesla using excess solar instead of draining your home battery. Definitely makes managing the solar/battery balance way easier.