Impact of long sustained climb on battery, motor, range

[TexaCali]

Approx 20 miles from my driveway is the Lick Observatory, atop Mt Hamilton. The observatory sits at about 4,000 ft, but the total climb is closer to 5,000 ft (there are two valleys on the way up), and the average grade is 6%. I've been toying with the idea of trying to drive the FFE to the observatory, but I'm wondering if such a sustained climb would stress the battery or the motor. And of course I'm also wondering if the car would even make it!

Does anyone know the consumption rate for going 30mph up a 6% grade? Is there a way to keep an eye on the battery and motor temps? Thoughts, suggestions?

Thanks!

 

[ElSupreme]

Elevation is somewhat easy. You lose a bit of efficency but energy is Mass * gravity * height.

So assume 1800kg (about 4000# fully loaded car) * 10 (m/s^2) * 1200m (4000'). That gives you 21,600,000 J(oules).

Which is the same as 6 kWh. So I would expect the mountain to take about 1/3 of the availaible energy of the battery pack (which should be doable after only 20 miles). Most of which you should get back on the way back down.

 

[ElSupreme]

The up and downs drain your battery, but in generally you get most of what you put in back on the way down. So basically if you make the top of the mountain, the energy you get back driving down you can use to get home. So only the net elevation is really important.

 

[michael]

The FFE has a published curb weight of 3640 pounds, call it 3800 with driver.

So per thousand feet climbed, and assuming 100% efficiency, the energy requirement just to lift the car is 1.43 kWh. So for a 4000 foot climb, just under 6 kWH as ElSupreme suggested. However, I'd apply some efficiency factor (80%??) which takes it to maybe 7 kWh.

Add to this the energy just to drive the 20 miles on the level (5 kWH at 250 wH/mile) and I think you should make it easily (12 kWh vs approx 19 usable).

I don't know how to monitor motor temperature, but you could monitor battery temp, if worried, with an OBD scanner. At 30 mph, the trip will take 40 minutes or so, and your average power will be 12 kWH/0.66 hr = 18 kW. This is less than 20% of the motor's rating. Seems no prob.

I'm going to guess, and only guess, that you will recapture perhaps half of that 7 kWh on the descent. So if I'm right you will reach home with slightly less energy than you had at the top.

Please give it a try and report the results....Energy at top and back at home, average speed, etc. This would be really useful information.

 

[TexaCali]

Thanks Elsupreme and michael. I agree, basic energy calcs say it should be no problem. I probably won't get the time to try it this weekend, but hopefully soon - and I'll certainly take notes (and pictures) and post the results here.

BTW - I've noticed several folks on this forum are in the San Jose area. If anyone local wants to join me in this adventure, shoot me a PM. Would be fun to have a small caravan of FFE's headed up the mountain. The view is spectacular at the top, and the observatory is very interesting - housing one of the largest refractor telescopes ever built.

 

[jmueller065]

Took my FFE to a CAT scale not to long ago. It weighed in at 3620 lbs. without me in it.
FYI.

If a bunch of you make the trek...take pictures!

 

[v_traveller]

Took my FFE to a CAT scale not to long ago. It weighed in at 3620 lbs. without me in it.
FYI.

Perhaps you were low on charge?

TexiCali - that's my kind of fun, wish I were in the SJ area. If you have buddies with other types of EVs, would be interesting to see how their ride performs, and then compare notes...

 

[kmaluo]

So I would expect the mountain to take about 1/3 of the availaible energy of the battery pack (which should be doable after only 20 miles). Most of which you should get back on the way back down.

I wish this was the case. From the past year of hitting the same hill on my semi-daily commute, I get about 25% regen efficiency coming back down that hill.