Charge time guesstimator (web app)

[iainfm]

Hi,

I was finding that a lot of my brain capacity was being taken up with mental arithmetic gymnastics trying to estimate how long my car needed on the public chargers before it was full.

So, I came up with this: http://cpsdash.iainfm.co.uk/calc.html

It's quick-and-simple - just bang in your usable capacity, % charge etc and it'll give you an estimate of how long it will take.

It's formatted for mobile phone screens, so will look stupidly massive on a PC (side note, if there are any CSS experts here who'd like to help please get in touch ).

If anyone want to check my working, the details are in my (increasingly messy) github repo.

Comments/suggestions welcome

 

[Jomarkh]

Is this on fast EVSE or rapids?
Some of the rapids I have used give you an idea when at 100%.
On rapids the charge rate can vary and some free PodPoints don't always give you the full 7kW.

 

[iainfm]

It's on anything - you enter the charge rate you expect and it works it out from there.

The estimate on the chargers themselves will be more accurate as they'll have a better idea of what the drop-off is as the car is charged, and be able to adjust the estimate continuously depending on how much the car is drawing.

Mine is just an estimate of how long it would take based on a constant draw. For rapids I'd recommend putting in 80% as the target charge, as actual charge rates drop off after that.

It's a ready-reckoner, no more.

 

[bloggsy]

It's on anything - you enter the charge rate you expect and it works it out from there.

The estimate on the chargers themselves will be more accurate as they'll have a better idea of what the drop-off is as the car is charged, and be able to adjust the estimate continuously depending on how much the car is drawing.

Mine is just an estimate of how long it would take based on a constant draw. For rapids I'd recommend putting in 80% as the target charge, as actual charge rates drop off after that.

It's a ready-reckoner, no more.

Thanks very much ianfm - it's a good idea and very generous of you to share. It will save my fingers and toes from being counted!

Any chance of making this as a downloadable 'app' or something which I can save on my phone and use without connecting to the internet, please?

Cheers

Bloggsy

 

[iainfm]

Erm, that'd be quite involved and there's the whole hassle of supporting Apple and iOS versions. Plus Apple charge you £100 or so for the honour of being able to put apps on their store.

It's only just over 2kb (html+css), so not going to break the data bank, and once the page has loaded there's no data transferred in or out - the calculations are done by javascript within the page.

My ususal suggestion is to open the page and add it to your homescreen (or iOS equivalent), but I don't know if the phone would cache it for use when there's no 'net connection.

 

[Headgas1]

Hi,

I was finding that a lot of my brain capacity was being taken up with mental arithmetic gymnastics trying to estimate how long my car needed on the public chargers before it was full.

So, I came up with this: http://cpsdash.iainfm.co.uk/calc.html

It's quick-and-simple - just bang in your usable capacity, % charge etc and it'll give you an estimate of how long it will take.

It's formatted for mobile phone screens, so will look stupidly massive on a PC (side note, if there are any CSS experts here who'd like to help please get in touch ).

If anyone want to check my working, the details are in my (increasingly messy) github repo.

Comments/suggestions welcome

Nice one this is very useful

 

[5teep]

Mental arithmetic gymnastics is good for you though

 

[rotorhead]

I'm totally new to this, but thought that a 61.1kWh battery would get 10% @ 7kWh per hour..

 

[Jomarkh]

If you add 7kWh that is more than 10% of the 61.1kW battery and is that the usable capacity?

 

[Lguk]

I get approx 10% an hour in a 5LR at 7kw. By the time you calc in conversion losses and its not far off.

 

[iainfm]

I get approx 10% an hour in a 5LR at 7kw. By the time you calc in conversion losses and its not far off.

Yep, that's a pretty good reckoner for a 5LR on a 7kW charger.

Rearranging the how-long-will-it-take-to-charge equation, and setting d=1 (hour), the percentage increase (as a decimal fraction) is given by:

dP = Cr / Uc

(Cr is the charge rate in kWh and Uc is the usable capacity in kWh).

So, with no losses, a 57kWh usable capacity on a 7kWh charger would increase by approx 7/57 = 0.123 or 12.3%

ie 10% an hour is a great estimate when losses are figured in. Other vehicles will, of course, have their own characteristics.

When I get a few minutes I might add another option to the site giving the option to calculate 'if I charge for n hours on an xkWh charger how much will my % go up?'. Which is just dP=d.Cr/Uc.

Who said you'd never need maths again after leaving school?

 

[Gomev]

Yep, that's a pretty good reckoner for a 5LR on a 7kW charger.

Rearranging the how-long-will-it-take-to-charge equation, and setting d=1 (hour), the percentage increase (as a decimal fraction) is given by:

dP = Cr / Uc

(Cr is the charge rate in kWh and Uc is the usable capacity in kWh).

So, with no losses, a 57kWh usable capacity on a 7kWh charger would increase by approx 7/57 = 0.123 or 12.3%

ie 10% an hour is a great estimate when losses are figured in. Other vehicles will, of course, have their own characteristics.

When I get a few minutes I might add another option to the site giving the option to calculate 'if I charge for n hours on an xkWh charger how much will my % go up?'. Which is just dP=d.Cr/Uc.

Who said you'd never need maths again after leaving school?

Just look at the car when it first starts charging on a 7kw, Screen shows an estimated time to full, which is 10%/hour almost bang on.