Range % question

[ABjolly]

Look I failed second grade math so my pee sized brain cannot comprehend basic mathematics. If I have a 70kwh battery and charge to 100% can I then multiple average mi/kWh by % of charge to determine range.

please answer as condescending as you’d like. Thanks.

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[SpaceEVDriver]

That will get you a decent estimate if your driving habits and conditions for the upcoming trip are similar enough to what got you the average mi/kWh. Knock off 5% or 10% just for safety-sake.

 

[Mach-Lee]

Multiply mi/kWh by kWh remaining to find range. Personally I would use 65 kWh for your battery capacity instead of 70 to be more realistic. This number will be even less when it's cold out (e.g. 60 kWh).

Example:

You are at 75% charge. 65 kWh x 75% = 49 kWh remaining

49 kWh x 2.8 mi/kWh = 137 miles left.

 

[Maquis]

Look I failed second grade math so my pee sized brain cannot comprehend basic mathematics. If I have a 70kwh battery and charge to 100% can I then multiple average mi/kWh by % of charge to determine range.

please answer as condescending as you’d like. Thanks.

True as long as your driving conditions achieve “average M/kWh!”

 

[SnBGC]

Look I failed second grade math so my pee sized brain cannot comprehend basic mathematics. If I have a 70kwh battery and charge to 100% can I then multiple average mi/kWh by % of charge to determine range.

please answer as condescending as you’d like. Thanks.

Almost.
Charge percentage displayed on screen divided by 100 x 70 (kWh,) x average mi/kWh= estimated range remaining.

 

[ebeponyan]

A couple of points for the sake of further confusion:

• 100% won't always correspond to 70kWh. At low temperatures, a fully charged battery might only store 60kWh, so 3.1mi/kWh won't get you as far in winter as it would in summer. I believe this is represented by the external temperature portion the visualization in the Trips app, but I may be mistaken there.
• Power delivery and efficiency is not constant across all states of charge. This means that, while extrapolating the distance you're able to achieve over 10 or 20% of battery charge provides a decent estimate, it's still just an estimate. Regeneration on downhills and while braking is less effective at high states of charge, and generally propelling the Mach-E is less efficient at low states of charge.

 

[RickMachE]

Almost.
Charge percentage displayed on screen divided by 100 x 70 (kWh,) x average mi/kWh= estimated range remaining.

Not quite.

70% charged means 0.70. Already divided by 100.

.7 X battery size X miles per kWh.

 

[SpaceEVDriver]

A couple of points for the sake of further confusion:

• 100% won't always correspond to 70kWh. At low temperatures, a fully charged battery might only store 60kWh, so 3.1mi/kWh won't get you as far in winter as it would in summer. I believe this is represented by the external temperature portion the visualization in the Trips app, but I may be mistaken there.
• Power delivery and efficiency is not constant across all states of charge. This means that, while extrapolating the distance you're able to achieve over 10 or 20% of battery charge provides a decent estimate, it's still just an estimate. Regeneration on downhills and while braking is less effective at high states of charge, and generally propelling the Mach-E is less efficient at low states of charge.

Adding further confusion: discharge rate also impacts usable battery capacity. If you discharge at twice the standard rate, you have much greater losses (and thus less usable energy) than if you discharge at half the standard rate.

 

[Murse-In-Airy]

No heckling not condescension. You’ve got the basics better then 98% of the folks who show up here.
70 kwh x%State of charge (as a decimal where 70% is 0.7) gives you how many kwh you’ve got left in the tank. Then multiply that by your current efficiency.
70kwh battery @70% charge means
79kwhx0.7= 49 kwh left.
49kwh x 2.7 miles /kwh means you’ve got a range right around 132 miles.
You can make it a lot more complicated but this is the exact formula I use for a quick check.

 

[SnBGC]

Not quite.

70% charged means 0.70. Already divided by 100.

.7 X battery size X miles per kWh.

True. My formula is more complicated then necessary.
It is a good thing I don't teach for a living.

 

[Tom L]

Look I failed second grade math so my pee sized brain cannot comprehend basic mathematics. If I have a 70kwh battery and charge to 100% can I then multiple average mi/kWh by % of charge to determine range.

please answer as condescending as you’d like. Thanks.

This is going to be good. I look forward to reading the responses to your reasonable question. I suspect you will subsequently feel less alone with your thoughts.

 

[ckt]

Isn't cold weather already factored in the cars displayed mi/kWh avarage? I.e. if your car is already displaying 2.3mi/kWh in winter, can't one just take 70kwh*70%*2.3mi/kwh=112.7mi range left at 70%? Or does one have to also take into account that 70kwh might only have 60kwh usable in winter?

 

[SpaceEVDriver]

Isn't cold weather already factored in the cars displayed mi/kWh avarage? I.e. if your car is already displaying 2.3mi/kWh in winter, can't one just take 70kwh*70%*2.3mi/kwh=112.7mi range left at 70%? Or does one have to also take into account that 70kwh might only have 60kwh usable in winter?

Your battery's maximum kWh (100%) is temperature-dependent. The battery chemistry is impacted by temperature such that the battery is actually "smaller" in extreme cold than it is at its standard-rated temperature. So, not only do you use more kWh to drive in the cold, in the cold you have fewer kWh in your battery at 100%. The efficiency given on your trip meter isn't based on the kWh size of the battery, but on the kWh used while driving.

(Similarly, your battery's maximum kWh is dependent on discharge rate--if you discharge faster, you're not only less efficient, your "tank" is smaller.)

 

[Murse-In-Airy]

Isn't cold weather already factored in the cars displayed mi/kWh avarage? I.e. if your car is already displaying 2.3mi/kWh in winter, can't one just take 70kwh*70%*2.3mi/kwh=112.7mi range left at 70%? Or does one have to also take into account that 70kwh might only have 60kwh usable in winter?

I simplify things for my pea size brain all the time. So I look at the battery as a glass of water, where the water is my “fuel” or energy held. When it’s really cold out, my glass of water ices up inside a little. Therefore it no longer holds as much water as it does when it’s warm. I have less “fuel” available. So while the glass looks full (it’s holding all the water it can for the condition), my formerly 16oz glass may only be holding 14oz of water. The rest of the space is taken up by the ice.
Taking that analogy to my battery, what was once an 88 kwh battery, when part frozen, may only hold 78 kwh of power at 100%. There’s more room in there but some of the battery sludge is to cold to do anything. So it’s just taking up space like the ice in the glass.
Now preconditioning, will warm up the battery or melt the ice in the glass, restoring full capacity. But if I don’t precondition, 100% full is still full, but I’m not getting a 16oz drink (or all 88kwh to use).

 

[ckt]

anyone knows if level 2 charging in winter from 0 to 100 uses noticeably more from the grid than spring/summer?

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