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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthortychwarel
    • CommentTimeApr 25th 2021
     
    Does anyone make an EV charger that can be programmed to pick up excess generation from PV panels?
    Functioning like the immersion heater diverters you can get.
    • CommentAuthorEd Davies
    • CommentTimeApr 25th 2021
     
    Yes. The Zappi springs to mind: https://myenergi.com/product/zappi/

    For a DIY-type setup https://shop.openenergymonitor.com/evse/ can work with another system to dynamically control the charge rate.
    • CommentAuthorjms452
    • CommentTimeJul 31st 2021
     
    Has any one tried the zappi?
    Good, Bad, Indifferent?

    It looks like the minimum it can charge at is 1.4kW so it's not quite like an immersion diverter that can eek every last drop out but still good for maximising self usage...
  1.  
    Posted By: jms452Has any one tried the zappi?


    Not exactly - we have an Eddi (by the same company) which charges our SunAmp DHW storage from PV excess.

    They are a small-ish company which tends to mean they are good at sorting stuff out but often experience server upgrade & beta release type issues etc. that a larger outfit maybe wouldn't. I recently lost a month's worth of monitoring data for instance. Not a big deal, just mildly annoying.

    The good part is that they have a very active forum much like this one where you can ask questions and get genuinely helpful advice.

    https://myenergi.info/zappi-v2-f46/

    I recommend looking on there for a bit before taking the plunge.

    p.s. the actual hardware is fine, no issues there.
  2.  
    Posted By: jms452It looks like the minimum it can charge at is 1.4kW so it's not quite like an immersion diverter that can eek every last drop out but still good for maximising self usage...

    Is there a limit on the minimum amount of energy you can stuff into an EV battery without getting long term degradation?
    I can see that for DHW putting in a few watts here and there when available is only going to help the gross energy contained in the tank however can you do the same to a Li-ion battery?
    • CommentAuthorRobL
    • CommentTimeAug 2nd 2021
     
    I’m not aware of a reliability issue with trickle charging li-ion batts. The 1.4kW thing is actually a 6A minimum level set by the J1772 connection protocol. J1772 is the slow charger plug that most ev cars have, and the ‘pilot’ pin on it has a PWM signal on it, generated by the zappi or the control box on a granny cable. This pilot signal tells the charger built into the car how much current it can draw - and the protocol only goes down to 6A - that’s why the zappi can’t take every last drop of power from PV.
  3.  
    Assuming the car does about 3 miles per kWh, is it worth bothering to charge at 1.4kW or even less? You could walk quicker....!

    Less tongue in cheek: is it still a good idea to self consume? Maybe better financially and environmentally to export the PV and then charge the EV at times of low demand, see JMS's comments up to Jul 3rd here
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17049&Focus=290383#Comment_290383
    • CommentAuthorjms452
    • CommentTimeAug 3rd 2021
     
    Posted By: WillInAberdeenLess tongue in cheek: is it still a good idea to self consume? Maybe better financially and environmentally to export the PV and then charge the EV at times of low demand, see JMS's comments up to Jul 3rd here
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17049&Focus=290383#Comment_290383" rel="nofollow" >http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17049&Focus=290383#Comment_290383


    This is a complicated one! My logic.

    I've stopped using the PV to heat the water when the price's high as there are times when I can export for 20p/kWh Early evening), these are also high CO2 hours.
    Given the amount of solar down our street we are probably doing the local transformer a favour using some of the PV to charge the car in the early afternoon when the export price is low (less than economy 7).

    When it's not sunny there's economy 7.


    Posted By: WillInAberdeenis it worth bothering to charge at 1.4kW


    Those shoulders give an additional 3-10 kWh/day so I think it does - that means the weekend or a day wfh charges up the car for next day's commute. It's better than a domestic static battery as the inefficiencies of the cycle are already baked-in.
  4.  
    Did you look at the Octopus Go import tariff that offers a few hours each night at 5p/kWh?

    Idea is to export the PV during the daytime (you mentioned getting paid 11p/kWh on average) then charge the EV and the DHW tank by importing at 5p in the cheap window, thus making an additional 6p/kWh compared to self consumption.

    Obvs would depend what other usage you have at other times. Would be interested how this stacks up in real life?
    • CommentAuthorjms452
    • CommentTimeAug 3rd 2021
     
    Posted By: WillInAberdeenDid you look at the Octopus Go import tariff that offers a few hours each night at 5p/kWh?

    Idea is to export the PV during the daytime (you mentioned getting paid 11p/kWh on average) then charge the EV and the DHW tank by importing at 5p in the cheap window, thus making an additional 6p/kWh compared to self consumption.


    Unfortunately Go can't be combined with agile export.
    Economy 7 is the closest you can get to that which is 13p but for longer.
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