Speak EV - Electric Car Forums banner
1 - 20 of 26 Posts

·
Registered
Joined
·
142 Posts
Discussion Starter · #1 ·
I'm hopefully receiving an ID.3 soon and I'm trying to sort out my charging in the (however long it will take) before it arrives.

Initially I will be charging with the granny charger as I've been told the wait time for a walk box in my area is around 4 to 6 months.

While it's on the granny charger, is there anyway to see how much energy is being drawn by the car and how much that costs? Other than the obvious of reading the meter and working it out by hand.

Eventually I'll have a walk box and the same question would apply.

If possible I'd like to be able to see the usage on an app on my phone.

Just to note, it's not possible to get a smart meter at my property at this time point.

My thanks in advance.
 

·
Registered
Joined
·
1,636 Posts
You could use one of these, other companies produce similar - I would keep an eye on it to be sure it doesn't get hot (good practice with the plug on a granny charger anyway).


Smart EVSEs (wall boxes) will be able to tell you how much electricity has been consumed (my Zappi does)
 

·
Registered
Hyundai Ioniq 28
Joined
·
8,746 Posts
While it's on the granny charger, is there anyway to see how much energy is being drawn by the car and how much that costs? Other than the obvious of reading the meter and working it out by hand.
Much depends on how accurate you wish to be. Some kind of meter on the supply would give a true reading of energy supplied but wouldn't tell you how much of that actually arrived in the car's battery due to transmission losses. On the other hand, measuring what arrived at the car would not tell you how many kWh's were sent from the house supply for the same reason.

A rough guide is easy to check though. Just note the SOC % at the start and end of a charge session, and note the difference. If the car has the 58 kWh battery then multiply that by the 'difference' % and that will give the kWh increase by that charge session. Then multiply that by the cost per kWh from your energy tarrif to give the cost of that charge.

For example.
Start - 30%
End - 80%
Increase 50%.
58kWh x 50% = 29 kWhs. ( increase in kWh's in that session)
29 kWh's @ €0.15 = €4.35. ( adjust the price per kWh for your own tarrif)

This will give a very approximate answer and cost because the battery isn't actually 58kWhs and will be around 55 kWh's usable really. And the kWh's leaving the house will be slightly more than what will arrive as explained above. But as one factor underestimates slightly and the other overestimates the result won't be a million miles from what you want to know.
 

·
Registered
Joined
·
712 Posts
Could try one of those clip on electric monitors? A bit low tech based on your initial description (no app etc)

I know they're not super accurate, but if you just want a rough idea what's happening, this will be transferrable between your granny and your EVSE when fitted.

 

·
Registered
Joined
·
168 Posts
I’ve got a similar question, and am not electrically minded In any way! I’ve got a 22kw 16 reg Zoe and a 3.3kw home Podpoint installed, and a year or so ago, our builder accidentally knocked the cable to the Podpoint unit, which ‘broke‘ the unit. I took the whole unit off the wall and found someone relatively local to me and he repaired it, and it’s now working fine. However, the Wifi functionality of the unit isn’t working now, which doesn’t affect the charging ability, and didn’t bother me initially, but I am quite interested in how much it costs me to charge at home, as I used to be able to check the Podpoint app on my phone and find out how much it used to cost per charge. I always program the car to charge between 12.30-4.30am when we have cheap rate 5p per unit. Can anyone tell me how I can calculate the cost of charging?
Thanks,
Simon.
 

·
Registered
Joined
·
153 Posts
I’ve got a similar question, and am not electrically minded In any way! I’ve got a 22kw 16 reg Zoe and a 3.3kw home Podpoint installed, and a year or so ago, our builder accidentally knocked the cable to the Podpoint unit, which ‘broke‘ the unit. I took the whole unit off the wall and found someone relatively local to me and he repaired it, and it’s now working fine. However, the Wifi functionality of the unit isn’t working now, which doesn’t affect the charging ability, and didn’t bother me initially, but I am quite interested in how much it costs me to charge at home, as I used to be able to check the Podpoint app on my phone and find out how much it used to cost per charge. I always program the car to charge between 12.30-4.30am when we have cheap rate 5p per unit. Can anyone tell me how I can calculate the cost of charging?
Thanks,
Simon.
Why not use one of these clipped around just the "Line" i.e. brown wire of your granny charger (might need a short extension lead with cable core wires exposed for a short length). geo Minim Energy Monitor - Self-Installed - CT Clip Sensor for Single Phase Electricity Meters: Amazon.co.uk: DIY & Tools
 

·
Registered
Joined
·
1,636 Posts
Why not use one of these clipped around just the "Line" i.e. brown wire of your granny charger (might need a short extension lead with cable core wires exposed for a short length). geo Minim Energy Monitor - Self-Installed - CT Clip Sensor for Single Phase Electricity Meters: Amazon.co.uk: DIY & Tools
Please don't do this. Cable has two layers of insulation for a reason. Cutting into the outer insulation to expose the inner cores is a bad idea and completely unnecessary - just buy a plug in energy monitor like the one I posted above.
 

·
Registered
Joined
·
712 Posts
Yes, to add and clarify, when I suggested a clip on monitor from ebay, I meant to the cables coming into your meter as per the manufacturer's instructions (so you could see how much it changes when the car starts charging), not stripping the cables :eek::eek:
 

·
Registered
Hyundai Ioniq 28
Joined
·
8,746 Posts
Can anyone tell me how I can calculate the cost of charging?
As I said in post #6 above. It just maths. Deduct the starting % SOC from the ending % SOC. Multiply the car's battery size by that % difference to give the kWh's taken on board in that session, and then multiply that by 5p.

eg- Start 32% - end 78% - difference 46%. Battery size 40 kWh x 46% = 18.4 kWh's. 18.4 x 5p = 92p.
 

·
Registered
Joined
·
79 Posts
I'm hopefully receiving an ID.3 soon and I'm trying to sort out my charging in the (however long it will take) before it arrives.

Initially I will be charging with the granny charger as I've been told the wait time for a walk box in my area is around 4 to 6 months.

While it's on the granny charger, is there anyway to see how much energy is being drawn by the car and how much that costs? Other than the obvious of reading the meter and working it out by hand.

Eventually I'll have a walk box and the same question would apply.

If possible I'd like to be able to see the usage on app on my phone.

Just to note, it's not possible to get a smart meter at my property at this time point.

My thanks in advance.

What charge point do you have - if its a rolec just put in a din mounted meter €20 in the charger next to the rcbo. This gives a kWh counter of what is being used by the car and charger.
 

·
Registered
Peugeot e-208
Joined
·
847 Posts
I doubt those Energy monitors are rated for continuous 10A draw.
If you’re charging overnight, when very little else is in use, I would think reading the meter before and after is the easiest, if most boring, solution. It will catch all the charging losses too, which you wouldn’t get by monitoring the % in the car.

Just remember to account for your house’s base load (mine is 60W).

the Ohme cable tracks usage too - maybe other chargers do.
 

·
Registered
Joined
·
2,386 Posts
I doubt those Energy monitors are rated for continuous 10A draw.

the Ohme cable tracks usage too - maybe other chargers do.
As BMW has issued a recall on my Delphi Granny Charger because of plug concerns, I would think twice before I used a TP Link smart plug. All granny chargers have built in thermal protection.

For continuous energy monitoring with CT clamps then buy a Zappi2.
 

·
Registered
Joined
·
1,636 Posts
As BMW has issued a recall on my Delphi Granny Charger because of plug concerns, I would think twice before I used a TP Link smart plug. All granny chargers have built in thermal protection.

For continuous energy monitoring with CT clamps then buy a Zappi2.
Granny chargers are prone to cooking up their plugs, or cooking up the socket they are plugged into - plenty of threads on the subject here, with the general view to use the minimum possible current and keep an eye on it.

I have used the tp-link plug with a continuous 10A resistive load for extended periods without any issues, but I checked it regularly.

The OP has not indicated why he wants to measure the power consumption - if it is just curiosity I agree that they should just wait until they have an EVSE that reports the power consumption.
 

·
Registered
Joined
·
5,086 Posts
Here's what my sparky fitted at my request when EVSE went in: as suggested above, standard meter inline with EVSE. No reason one of these couldn't be built-into a small extension plug+socket. Am thinking of making myself one so I can use it when charging at holiday lets (with owners permission!) at 6A, & I can then reimburse them at end of the week.
142279
 

·
Registered
Joined
·
142 Posts
Discussion Starter · #18 ·
Some really valuable information here.

I liked the idea of the TP plug, working in tandem with Alexa, but the heat issues of the granny plug are enough to put me off. It's something that worries me anyhow!

I think, when all is said and done, a measure of my base load of my house at the meter, then a measure of what happens when I plug in the charger is probably the best and safest way forward.

My reason for doing this is to compile a record of how much electricity my car uses over a year. I'd like to have this for various reasons, including possible installation of solar.

My thanks for everyone's input.
 

·
Registered
Joined
·
5,086 Posts
Most losses likely to be in the charging process inside the EV.
ID.3 acc to my neasurements is around 90-93% efficient, charging at 6,10, or 32A, doesn't seem to matter which you choose. So call it 10% losses and you're close enough.
 
1 - 20 of 26 Posts
Top