navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address. Following continuous spam/hack attempts on the forum, "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: [1] 2   Go Down
  Print  
Author Topic: EV chargers with PV  (Read 1321 times)
brackwell
Hero Member
*****
Offline Offline

Posts: 3267


« on: March 18, 2020, 09:24:25 AM »

I have had a EV for a 3yrs+ now but have been sitting on the side lines not being happy with where we are when it comes to chargers and PV. I have until now just been using the granny cable manually. The EV can be set with charging times and a MAX amps ie not a min amps.

I had a Immersun that went BANG after 2-3 yrs but it did show that i can run my HW on the excess PV except for about 25days a yr.  The Immersun experience makes me feel uncomfortable about buying electronic equipment for these uses when we need electrical equipment which is a mind set difference not appreciated by modern boffins i feel.

However to get the best value out of ones PV production then the leccy should be used for charging the car not for heating hot water.  For large parts of the day and yr there is not enough power to charge the EV but in some ways this does not always matter as one does not need to charge every day.  So the regime i want to follow is  -  the hot water is heated as long as the surplus is below 10amps (2.4kw). Below 10 amps it is not worth bothering.  Once the PV surplus is above the 10amps the EV is charged and vice versa.

Peoples first answer to this problem is a Zappi but unfortunately this does not seem to be possible (from Zappi themselves ) and then there is the problem can the EV be continually switched on and off as in cloudy weather or when a house appliance is used - not sure.

The charger can have a sensor to sense when there is surplus PV but in practice this would not happen if the diverter had switched to HW first as it would show nill surplus.  I have seen it suggested that the charger sensor be fitted to the immersion heater supply, after the diverter which i guess would work.

If the Zappi will not do what i want i not sure i have any choices.

Then we get onto the stupid costs of these chargers but i can envisage that one day they will become free with leccy cos and car suppliers.

As anyone had thoughts about this -it is slowly getting to me.

Ken
Logged
pantsmachine
Sr. Member
****
Offline Offline

Posts: 395


« Reply #1 on: March 18, 2020, 09:57:28 AM »

I'll throw out self built with smart switches acting as relays for normally open contactors alongside ct clamp (s) as sensors. I had similar thoughts in the ongoing process of convicting self that it's EV time. I watch with interest.
« Last Edit: March 18, 2020, 10:00:03 AM by pantsmachine » Logged

5.12kw PV system with Solar edge
7.2kwh Pylon tech battery storage
18kwh Heater Storage
Solar I boost charging 12kwh 210 ltr OSO system tank
Deep insulation, air leak controlled home
Zoned & Balanced CH wet system
Hive 2
Low energy bulbs
Wood fired cedar hot tub
Masanobu Fukuoka garden
Countrypaul
Hero Member
*****
Offline Offline

Posts: 1672


« Reply #2 on: March 18, 2020, 10:47:27 AM »

Ken,

Have you looked at the Eddi, as that has the ability to switch on a device once the PV excess exceeds a certain value. So for example it would heat HW until the PV production hit say 10A then switch on your charger (and HW off). You can also set a minimum amount of time that the device is switched on (aimed primarily at HPs so does not want to turn on/off that often), once it turns off your charger it would return to heating the HW.

I have an Eddi and a HP but have not yet set this aspect up so can't really comment on how well it works. You would need the extra relay card in the Eddi to turn the Charger/HP on/off.
Logged
M
Hero Member
*****
Online Online

Posts: 5303



« Reply #3 on: March 18, 2020, 11:28:00 AM »

Hi Ken, currently OVO are doing a free charger instead of the usual top up of 300 or so on the UK grant. But they aren't cheap for leccy.

How much PV do you have? As I've been pondering what we can get away with here, and 2kW+ sustained for 4-8hrs (as the length of sunny days improves towards June) seems highly predictable based on the weather forecast. I know that it can go up and down, but I'm hoping that for the better six months of the year, with an eye on the weather forecast, we will be able to do almost all charging off PV simply through the dumb use of a granny charger.
Logged

Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
brackwell
Hero Member
*****
Offline Offline

Posts: 3267


« Reply #4 on: March 18, 2020, 02:09:34 PM »

Ken,

Have you looked at the Eddi, as that has the ability to switch on a device once the PV excess exceeds a certain value. So for example it would heat HW until the PV production hit say 10A then switch on your charger (and HW off). You can also set a minimum amount of time that the device is switched on (aimed primarily at HPs so does not want to turn on/off that often), once it turns off your charger it would return to heating the HW.

I have an Eddi and a HP but have not yet set this aspect up so can't really comment on how well it works. You would need the extra relay card in the Eddi to turn the Charger/HP on/off.

My understanding from MyEnergi is that it cannot do that.  Firstly i think it is sequential ie heat HW and then if more spare switch on X .  It will not switch over once say 10amps is reached.
If a relay is fitted to the Eddi then it would send a signal to the relay in the charger but not sure the a charger, any charger can take that as its signal and that i presume this is where the Hub and Zappi come in and i need to take out a bank loan (not literally). However even with a Eddi,Hub,Zappi nothing can do the switching over at 10amps - it is just not programmed that way -seems a great error in my book.
Logged
Countrypaul
Hero Member
*****
Offline Offline

Posts: 1672


« Reply #5 on: March 18, 2020, 02:30:37 PM »

The relay on the Eddi is rated upto 16Amps (according to the manual), and is isolated from the mains, so can be used to turn on/off anything connected to it be that 12v, 110v or 240V, which could obviously include a contactor.

The instructions make it clear that it is an option to turn on a device (expected to be a heat pump) when the exess PV reaches a set point (user settable) and that the minimum time for the relay to be switched on is also user settable (to prevent short cycling the assumed heat pump).  The idea being that using the heat pump is far more efficient for heating water than an immersion (as we have both commented on in other threads).

I am not sure what the consequences would be of switching a charger on and off too frequently though, or whether as you suggest it could just be a signal to the charger that you switch.

Have a read of the Eddi manual - though I am not sure on the requirements of the charger side of things, it would not be the first time a support team member does not understand the more advanced capabilities of something they are there to support! (Nor would it be the first time a manual suggests it can do something it can't).
Logged
Robl
Jr. Member
**
Offline Offline

Posts: 72


« Reply #6 on: March 18, 2020, 02:56:25 PM »

I think that the days of using spare PV are limited - eventually, smart meters will be ubiquitous, and time of day pricing will be commonplace.  In which case, finally, the "green" thing to do will finally tie up with the financially sensible thing.  We have been in this strange period where PV electricity can be used for free - there are already at least two providers, Octopus Outgoing Agile, and OVO with their V2G trial, that pay more for this electricity than you would pay for night time electricity.  Likely if you got an Octopus Outgoing Agile account, I think you would be paid to export PV, and program the car to charge overnight - that would probably cost less than using your "free" PV, which as you say is difficult into a complex electrical load.  Disclaimer: I have none of the above products yet - I'm waiting for DNO approval to get on the OVO V2G trial.
Logged
brackwell
Hero Member
*****
Offline Offline

Posts: 3267


« Reply #7 on: March 18, 2020, 04:35:24 PM »

I think that the days of using spare PV are limited - eventually, smart meters will be ubiquitous, and time of day pricing will be commonplace.  In which case, finally, the "green" thing to do will finally tie up with the financially sensible thing.  We have been in this strange period where PV electricity can be used for free - there are already at least two providers, Octopus Outgoing Agile, and OVO with their V2G trial, that pay more for this electricity than you would pay for night time electricity.  Likely if you got an Octopus Outgoing Agile account, I think you would be paid to export PV, and program the car to charge overnight - that would probably cost less than using your "free" PV, which as you say is difficult into a complex electrical load.  Disclaimer: I have none of the above products yet - I'm waiting for DNO approval to get on the OVO V2G trial.

Not quite because the TOU is actual export wheras on FITS it is 50% deemed.  So on FITS you are payed a little less than the TOU export but are payed for something which you can then use. It is better than free it is negative cost if you like.  The FITS payment is indexed linked and tax free.  TOU export?
Logged
brackwell
Hero Member
*****
Offline Offline

Posts: 3267


« Reply #8 on: March 18, 2020, 04:43:29 PM »

The relay on the Eddi is rated upto 16Amps (according to the manual), and is isolated from the mains, so can be used to turn on/off anything connected to it be that 12v, 110v or 240V, which could obviously include a contactor.

The instructions make it clear that it is an option to turn on a device (expected to be a heat pump) when the exess PV reaches a set point (user settable) and that the minimum time for the relay to be switched on is also user settable (to prevent short cycling the assumed heat pump).  The idea being that using the heat pump is far more efficient for heating water than an immersion (as we have both commented on in other threads).

I am not sure what the consequences would be of switching a charger on and off too frequently though, or whether as you suggest it could just be a signal to the charger that you switch.

Have a read of the Eddi manual - though I am not sure on the requirements of the charger side of things, it would not be the first time a support team member does not understand the more advanced capabilities of something they are there to support! (Nor would it be the first time a manual suggests it can do something it can't).

Thanks for that Paul it seems doable put like that. I need to try again but i think the stubbling block is the "excess PV reaches a set point " because the HW is preventing it getting to that point. Perhaps it is a case of making the relay/charger No 1 priority and if then there is not 10 amps it will go to priority 2 ie HW.
Logged
brackwell
Hero Member
*****
Offline Offline

Posts: 3267


« Reply #9 on: March 19, 2020, 08:56:54 AM »

My reply from Myenergi is

Hi Ken ,
Yes, of course that can be done. The excess solar will initially go to the diverter for your hot water, and then in the zappi you can set the minimum pwm in compatability mode to 17% and power factor to 1 and it will work just fine.

As for
"minimum pwm in compatability mode to 17%"     What?

Ken
Logged
RIT
Hero Member
*****
Offline Offline

Posts: 2296

South West London


« Reply #10 on: March 19, 2020, 09:16:34 AM »

My reply from Myenergi is

Hi Ken ,
Yes, of course that can be done. The excess solar will initially go to the diverter for your hot water, and then in the zappi you can set the minimum pwm in compatability mode to 17% and power factor to 1 and it will work just fine.

As for
"minimum pwm in compatability mode to 17%"     What?

Ken

"The Min PWM setting in Compatibility Mode screen is the lowest charge current that zappi will declare as available if the measured power factor is lower than the Power Factor setting. Some EV's have poor power factor and cannot charge at very low currents without the harmonics being too high. This setting ensures that zappi can support these EV's. "

I know the above is 'as clear as mud' but its the best answer I could find.

One issue with charging at or near the minimum charge rates is that it can be very inefficient. I've not found any published figured from a manufacture, but posts on the internet claim that effiency can drop to as low as 40% when charging at the lowest charge rates (around 1.5kWh).

Do you have a mains gas boiler? If so would it not make more sense to focus on charging the EV first and then using an excess to heat water?
Logged

2.4kW PV system, output can be seen at  - https://pvoutput.org/list.jsp?userid=49083

Join the fight against human malware at https://stats.foldingathome.org/team/259956

Why bother? - well, there is no planet B
Countrypaul
Hero Member
*****
Offline Offline

Posts: 1672


« Reply #11 on: March 19, 2020, 09:32:00 AM »

The relay on the Eddi is rated upto 16Amps (according to the manual), and is isolated from the mains, so can be used to turn on/off anything connected to it be that 12v, 110v or 240V, which could obviously include a contactor.

The instructions make it clear that it is an option to turn on a device (expected to be a heat pump) when the exess PV reaches a set point (user settable) and that the minimum time for the relay to be switched on is also user settable (to prevent short cycling the assumed heat pump).  The idea being that using the heat pump is far more efficient for heating water than an immersion (as we have both commented on in other threads).

I am not sure what the consequences would be of switching a charger on and off too frequently though, or whether as you suggest it could just be a signal to the charger that you switch.

Have a read of the Eddi manual - though I am not sure on the requirements of the charger side of things, it would not be the first time a support team member does not understand the more advanced capabilities of something they are there to support! (Nor would it be the first time a manual suggests it can do something it can't).

Thanks for that Paul it seems doable put like that. I need to try again but i think the stubbling block is the "excess PV reaches a set point " because the HW is preventing it getting to that point. Perhaps it is a case of making the relay/charger No 1 priority and if then there is not 10 amps it will go to priority 2 ie HW.

The set point is based on the excess PV ignoring that used by the HW diverter within the Eddi from my reading. So I think that already can do what you are suggesting.

I have no idea about the Zappi, but looks like you have got MyEnergi to think a little more before replying, so they may have an acceptable solution, but need some help to get there.
Logged
dan_b
Hero Member
*****
Offline Offline

Posts: 4832

SW London


WWW
« Reply #12 on: March 19, 2020, 09:32:41 AM »

Also, why is heating hot water below 10 amps not worth bothering with? Genuine question?
Logged

3.06kWp SolarEdge system with a split array:
2.18kWp 10x South facing, plus 4x West facing 880W

Mk1 ImmerSUN DHW diverter
4kW PowerVault Battery

Tesla Model 3 Long Range
Countrypaul
Hero Member
*****
Offline Offline

Posts: 1672


« Reply #13 on: March 19, 2020, 09:43:46 AM »

Also, why is heating hot water below 10 amps not worth bothering with? Genuine question?

Heating HW below 10Amps is worthwhile (10Amps may not be the optimum figure), but charging the EV when there is less than 10A may not be, due to inefficiencies and also not wanting to swich the charger on/off too frequently if there are continuous cloud interuptions.
Logged
brackwell
Hero Member
*****
Offline Offline

Posts: 3267


« Reply #14 on: March 19, 2020, 09:47:12 AM »

[quote author=RIT link=topic=31557.msg35407

"The Min PWM setting in Compatibility Mode screen is the lowest charge current that zappi will declare as available if the measured power factor is lower than the Power Factor setting. Some EV's have poor power factor and cannot charge at very low currents without the harmonics being too high. This setting ensures that zappi can support these EV's. "

I know the above is 'as clear as mud' but its the best answer I could find.

One issue with charging at or near the minimum charge rates is that it can be very inefficient. I've not found any published figured from a manufacture, but posts on the internet claim that effiency can drop to as low as 40% when charging at the lowest charge rates (around 1.5kWh).

Do you have a mains gas boiler? If so would it not make more sense to focus on charging the EV first and then using an excess to heat water?
[/quote]

RIT thanks for that. For many days in winter etc there is not any excess to charge the car at 10amps or greater (not interested in less than 10amps for the reason you give.) but there is enough for the DHW.  Thats why i think this feature is so important. I need to do the HW daily (it destratifies too much and cools down otherwise) but the car can take or leave it.

I feel the Zappi is too clever for its own good, too light weight to be left outside (have they heard off electrolitic corrosion) and too expensive and will end up the same way as Immersun.
Ken
Logged
Pages: [1] 2   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!