EV Discussion thread

Grumpy_chap

Grumpy_chap said:

Grumpy_chap said:

I am doing my first charge tonight with my power monitor plug so will have a figure to give some assessment of the accuracy of the energy assessed by the car versus actual plug power draw.
I am doing a 140-mile round trip tomorrow so will be able to measure that as well.  It will be all mileage and no "vampire loss" energy as charging overnight today and will charge again when I return home tomorrow evening.

OK, so here goes, my non-scientific mini-data set of two, but here goes:

Full charge on the car is to 90% (as TESLA manual suggests) and the car stops the charge once the 90% is reached as measured by the car.

Saturday 22/07 = charged to full

Monday 31/07 = charged to full

• 9 days of whatever "vampire drain" occurred
• 104 miles, of which 94 were in the return journey on the Monday 31st
• Power as measured by the car 24 kWh
• Power as measured by the power monitor plug 26.29 kWh
• Power delta 10%
• 3.96 mile/kWh as measured by the plug
• 4.33 mile/kWh as measured by the car

Tuesday 01/08 = charged to full

• No days of "vampire drain"
• 143 miles
• Power as measured by the car 33 kWh
• Power as measured by the power monitor plug 37.48 kWh
• Power delta 13%
• 3.81 mile/kWh as measured by the plug
• 4.33 mile/kWh as measured by the car

On this limited review:

• I need to add 10% to the power (and costs) for those charges where I have only the car data
• "Vampire Drain" does not appear to have been significant
• If I can drive with the in car display showing 220 Wh/mile then that will mean actual 4 miles/kWh achieved.  A useful target.

I now have the power monitor plug and the overall difference between power supplied and power recorded by the car is 15%.
That 15% represents charging losses.

I will add more charging commentary later as my posts are vanishing.

EricMears

Grumpy_chap said:

I now have the power monitor plug and the overall difference between power supplied and power recorded by the car is 15%.
That 15% represents charging losses.

Not necessarily.    Neither power monitor plug  or power recorded by the car  are likely to be absolutely accurate.  Hence the 15% might include some contribution from 'differences in opinion' about the levels being reported.  Hopefully the correction needed will be small.

Grumpy_chap

Thanks Eric,

There is a difference in opinion.  The plug shows 2 decimal places and the car only whole kWh.  On the latest charge that a change from 11% loss to potentially as low as 8% loss

I tried again to share my charging information, but the content simply won't post

EricMears

Grumpy_chap said:

I tried again to share my charging information, but the content simply won't post

Try writing whatever you want to say into a plain text file with e.g. 'MS Notepad'  then copying it from there and pasting it into the MSE   comment box.    

Grumpy_chap

EricMears said:

Grumpy_chap said:

I tried again to share my charging information, but the content simply won't post

Try writing whatever you want to say into a plain text file with e.g. 'MS Notepad'  then copying it from there and pasting it into the MSE   comment box.    

I am typing as plain text straight into the box - just like I am typing here now.
Something odd happens that when I type in the efficiency data about the car, I submit using the red "post comment" box and it all just vanishes.
Maybe something is flagging up an obscenity filter or something somehow (!?).  Maybe EVs are just too obscenely fantastic to allow the true experience to be shared with the uninformed.

I have written all that in the hope you can get to see any of it

Petriix

The 'granny' charger is always going to be the least efficient way to charge. 15% loss sounds about right. 

1961Nick

Grumpy_chap said:

Grumpy_chap said:

Grumpy_chap said:

I am doing my first charge tonight with my power monitor plug so will have a figure to give some assessment of the accuracy of the energy assessed by the car versus actual plug power draw.
I am doing a 140-mile round trip tomorrow so will be able to measure that as well.  It will be all mileage and no "vampire loss" energy as charging overnight today and will charge again when I return home tomorrow evening.

OK, so here goes, my non-scientific mini-data set of two, but here goes:

Full charge on the car is to 90% (as TESLA manual suggests) and the car stops the charge once the 90% is reached as measured by the car.

Saturday 22/07 = charged to full

Monday 31/07 = charged to full

• 9 days of whatever "vampire drain" occurred
• 104 miles, of which 94 were in the return journey on the Monday 31st
• Power as measured by the car 24 kWh
• Power as measured by the power monitor plug 26.29 kWh
• Power delta 10%
• 3.96 mile/kWh as measured by the plug
• 4.33 mile/kWh as measured by the car

Tuesday 01/08 = charged to full

• No days of "vampire drain"
• 143 miles
• Power as measured by the car 33 kWh
• Power as measured by the power monitor plug 37.48 kWh
• Power delta 13%
• 3.81 mile/kWh as measured by the plug
• 4.33 mile/kWh as measured by the car

On this limited review:

• I need to add 10% to the power (and costs) for those charges where I have only the car data
• "Vampire Drain" does not appear to have been significant
• If I can drive with the in car display showing 220 Wh/mile then that will mean actual 4 miles/kWh achieved.  A useful target.

I now have the power monitor plug and the overall difference between power supplied and power recorded by the car is 15%.
That 15% represents charging losses.

I will add more charging commentary later as my posts are vanishing.

For comparison, since the beginning of July my car reports 3.96 miles/kWh. Measured at the meter this drops to 3.2 miles/kWh. My charging/vampire drain/pre cooling loss is therefore 19.2%.

Tbh, the cost of electricity @ 7.5p/kWh is so cheap that anything lost when it's plugged in is unimportant. What really matters is how frugal it is with the energy once it's onboard because obviously that impacts range.

Glad you're enjoying it.

JKenH

1961Nick said:

Grumpy_chap said:

Grumpy_chap said:

Grumpy_chap said:

I am doing my first charge tonight with my power monitor plug so will have a figure to give some assessment of the accuracy of the energy assessed by the car versus actual plug power draw.
I am doing a 140-mile round trip tomorrow so will be able to measure that as well.  It will be all mileage and no "vampire loss" energy as charging overnight today and will charge again when I return home tomorrow evening.

OK, so here goes, my non-scientific mini-data set of two, but here goes:

Full charge on the car is to 90% (as TESLA manual suggests) and the car stops the charge once the 90% is reached as measured by the car.

Saturday 22/07 = charged to full

Monday 31/07 = charged to full

• 9 days of whatever "vampire drain" occurred
• 104 miles, of which 94 were in the return journey on the Monday 31st
• Power as measured by the car 24 kWh
• Power as measured by the power monitor plug 26.29 kWh
• Power delta 10%
• 3.96 mile/kWh as measured by the plug
• 4.33 mile/kWh as measured by the car

Tuesday 01/08 = charged to full

• No days of "vampire drain"
• 143 miles
• Power as measured by the car 33 kWh
• Power as measured by the power monitor plug 37.48 kWh
• Power delta 13%
• 3.81 mile/kWh as measured by the plug
• 4.33 mile/kWh as measured by the car

On this limited review:

• I need to add 10% to the power (and costs) for those charges where I have only the car data
• "Vampire Drain" does not appear to have been significant
• If I can drive with the in car display showing 220 Wh/mile then that will mean actual 4 miles/kWh achieved.  A useful target.

I now have the power monitor plug and the overall difference between power supplied and power recorded by the car is 15%.
That 15% represents charging losses.

I will add more charging commentary later as my posts are vanishing.

For comparison, since the beginning of July my car reports 3.96 miles/kWh. Measured at the meter this drops to 3.2 miles/kWh. My charging/vampire drain/pre cooling loss is therefore 19.2%.

Tbh, the cost of electricity @ 7.5p/kWh is so cheap that anything lost when it's plugged in is unimportant. What really matters is how frugal it is with the energy once it's onboard because obviously that impacts range.

Glad you're enjoying it.

Thanks, Nick, for making that distinction clear. As you say, if the majority of charging is done at home then whether the cost per mile works out at 1.5p or 2p doesn’t really matter in the grand scheme of things. Over 8,000 miles it’s £150 against £187.50 the difference is less than a tank of petrol. 8000 miles in my Golf costs me about £1,000 in fuel at current prices. 

If though you don’t have access to home charging and are paying, say, 50p/kWh then it’s the difference between £1,000 and £1250 or the difference between a 40mpg car and a 50mpg one. 

Not all EVs are as efficient as Teslas. Cars like the Kia EV6, Toyota BZ4X, Audi e-Tron or the Ford Mustang use 50% more electricity per mile so the difference is greater. https://ev-database.org/uk/cheatsheet/energy-consumption-electric-car

I think it would be helpful if the motoring press took the trouble to point out that what the car indicates it is using when driving and what it costs to recharge are two different things. Before anyone refers to petrol cars this issue is not the same as the discrepancy between mpg indicted by the car and calculated from the pump. It is not about the accuracy of the onboard consumption gauge, it is about the extra fuel you have to put into the car to cover the vampire drain, battery conditioning, preheating etc and the losses in converting the AC electricity from the plug/charger to DC.

Petriix

Losses are definitely lower when charging faster. It's hard to precisely measure but 10% seems typical. That might add 2p per mile to the most expensive rapid charging but it's more like 0.2p per mile for home charging. Whenever I talk about the running costs for my EV, I'm always talking about the actual cost of charging for the miles covered so any losses are baked into the calculations. 

Grumpy_chap

1961Nick said:

For comparison, since the beginning of July my car reports 3.96 miles/kWh. Measured at the meter this drops to 3.2 miles/kWh. My charging/vampire drain/pre cooling loss is therefore 19.2%.

Tbh, the cost of electricity @ 7.5p/kWh is so cheap that anything lost when it's plugged in is unimportant. What really matters is how frugal it is with the energy once it's onboard because obviously that impacts range.

Glad you're enjoying it.

I did another response that disappeared when posted.
I copied it before posting so I will drip-feed in a few threads...