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[KuRi]

Hi!

I want to do a trip to the beach this weekend, and there is 90km of distance. I can charge the bike at the destination, but not along the way. The problem is that the return to home is uphill during all the 90km. The specs says that I should be able to travel 126km at 113 km/h. I have checked this on a flat road and it is more or less accurate, but what about uphill???

It is too risky? xD

Thanks!

[PaulZero]

I can’t speak as a DSR owner but as an SRF owner I’d be ok with that trip so long as I started the return trip on 100% charge.  I’d have <20% neutral regen assuming the road is mostly uninterrupted (not start/stop) as coasting is more efficient and a high brake regen to claw back what I could when I need to slow down. I’d keep torque (acceleration) to a minimum or just be gentle with the throttle. I’d also keep top speed under 55mph if possible.  Elevation will be key though, if it’s a lot of climbing (>1km) without the downhill then it could be a risk, but my SRF would suffer more than your DSR I’d suspect as the SRF is heavier. 

[KuRi]

Yes, it is a constant climbing to the destination, that's my main concern

Thanks!

[Doug S]

Don't forget that you can almost always squeeze out a little more range by going slower. You can't eliminate the loss of charge due to elevation gain, but you can almost always reduce the loss due to wind resistance. If you're willing and able to reduce your speed without risk of being run over by faster-moving traffic, you're almost always capable of reducing your drag and increasing the range.

[DonTom]

Hi!

I want to do a trip to the beach this weekend, and there is 90km of distance. I can charge the bike at the destination, but not along the way. The problem is that the return to home is uphill during all the 90km. The specs says that I should be able to travel 126km at 113 km/h. I have checked this on a flat road and it is more or less accurate, but what about uphill???

It is too risky? xD

Thanks!

You probably get less than half the range going uphill (depends on how steep, of course) but you get around double the range by going half the speed.

So go as slow as possible on the way back.

-Don-  Reno, NV

[KuRi]

With my previous bike (BMW F800GS) I was able to go down and back with a single tank, and the range was about 220km on a single tank, but I guess electric bikes are completely different

I am not sure if I will take the risk but if I do, I will let you know the results xD

[Biff]

motorcycles are light, so the total amount of energy to move the bike up the hill is typically insignificant.  If the destination is 1000m (3300ft) higher than the starting point, that is  300*9.8*1000 = 2.94MJ of energy (about 0.8kWh) assuming total bike+rider weight is 300kg (660lbs)  Assuming 85% efficiency of converting battery energy to potential gravitational energy, that would use about 0.94kWh of battery to lift the bike up that evlevation change, so it takes such a large hill to become significant. 

Assuming going down the hill to the beach you "recover" potential energy at 100% efficiency, the difference of battery usage to get down the hill vs going up the hill would be about 1.75kWh. So if you make it to the bottom of the hill with 1.75kWh left in your battery, and you charge up to full while you are there, you should be able to make it back traveling at the same speed.  If you have less than 1.75kWh when you get to the bottom of the hill, you will want to travel up the hill more slowly than you came down, to spend less energy moving the air around you.

Again, that assumes a 1km (3300 foot elevation change). Also note this calculation assumes the elevation at the start and the end of the trip,  any increase / decrease in elevation between those two points roughly balances out and doesn't influence energy consumed that much (as long as you have enough energy to make it to the top of the highest point between the start and end).

Another thing to consider is prevailing winds and air temperature, which will both affect aerodynamics.  I believe typically, winds blow off the ocean, so you may have a prevailing tail wind going up the hill, since the bottom of the hill is a beach.  A 7-10kph wind can have significant impact on your range, especially if it is against you going one way, and with you going the other.  Also air temperature has a significant impact on range,  a study I read about bicycle racing and the effect of temperature on aerodynamics suggest that for every 10C temperature increase, the aerodynamic drag decreases by 3%.  And depending on your speed, the most significant influence is your riding position.  If you need to extend your range by 10-15% you can simply tuck to reduce your total cross section area,  the faster you go the more tucking will affect your range.

If you want an adventure, go for it, do some math to prepare yourself to adjust your riding style if you find it necessary, and have a backup plan should things not work out the way you hoped. Without adventure life is boring.

-ryan

[Crissa]

Yeah, I can confirm about half range going up hill.  Going up to skyline (about a climb of a little more than 2000' in about five miles) I use about 25% of my SoC while I use about half that or less the other way.

Of course it depends how steep.  And how cold.  Yesterday my bike was acting like it was freezing out and was just chewing through charge and used about 50% more SoC than the day before to do the same thing.

-Crissa

[KuRi]

Very nice explanation Biff, although it is contradicting what others are saying about half range going up hill. However it is similar to what I was thinking.

The total height diff is about 700m, and there are about 10km of flat roads (now that I recap).

Thanks all!

[TheRan]

It depends on the grade of the hill. It's going to require the same amount of extra energy to climb 700m whether it's over 10 miles or 100 miles. Using Biff's math it would require an extra 0.56kW/h, so if it's over a distance that would require that amount of energy on flat ground you've just doubled your energy consumption, if the distance would instead require 0.056kW/h then you've only added 10% onto your consumption.

Going with an approximate energy consumption of 75w/h per mile the climb would have to be over a distance of about 7.5 miles to double the consumption. Over your 90km distance it's an increase of 13.6%.

[DonTom]

You can figure out the range yourself by looking at the KWH consumption on the Zero app.

I was surprised how much energy it takes to go DOWNHILL at 75 MPH. I was just checking that on my Energica. I was drawing 7KW so the bike would not slow down at all, at 75 MPH down a fairly steep hill on the freeway. Then I had to climb up the next hill, about the same grade. Then I was drawing  24 KW.

Let's say you have a ten KWH usable capacity battery. If you see the draw at 20 KW, you know you can ride  at that speed for 30 minutes. If you draw only 5 KWH, then you can keep  that up for two hours.

The math you can do in your head. You can see what speed you need to go a distance and such by using simple math, after seeing the KWs being drawn. But what ever that speed is, try to keep it steady, such as a cruise control would do.

I find the KW being used to be the most handy info. IMO, that should be in large digits on  every EV screen, but usually it's small.

-Don-  Cold Springs Valley, NV

[Curt]

Several times I've done a 90 km loop on my FX 6.5 with over 1000 m elevation gain. I found that I get home with 5% remaining if I had it in sport mode, or 12-15% remaining if I had it in eco mode. I believe you'll be able to do this conservatively, starting with 100% at the bottom, if you're sparing on the throttle and keep a speed of around 60 kph.

700 m is not much of an altitude difference. However, are you sure it's strictly uphill? If there's any downhill then you'll have more cumulative uphill. If 10 km is flat then you're taking about an average grade of 0.875% for the rest, which is very mild compared to the area around the Zero factory. Note that any time you brake or regen kicks in, it means you're consuming more energy than you otherwise would have.

Welcome to range anxiety (I admit that when I was experimenting, I knew that if I ran out I'd be close to home and could pick up the bike in my truck.) The nice thing is that once you've done this trip once, you'll know how much power you have left over, for next time.

[KuRi]

Hi! Yes, it is a constant uphill for at least 60km-70km. It is a highway, so minimum legal speed is 60kph but going at that speed will get me a lot of angry car drivers using their horns against me xD

[Curt]

The specs says that I should be able to travel 126km at 113 km/h

You know, after noting again that the 126 km spec is for full highway speed, I think the elevation isn't a big deal and you'll be able to do the 90 km easily at say 100 kph. I say do it!

[Crissa]

Yeah, I do a 60km route over a pass 795m high with a median speed of 60kph (maximum 80kph, min 40 kph, mostly in the middle) and I use 50-60% of my five-year-old 8.5kW pack, even in winter.

Take that what you will.

-Crissa