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Old 09-22-2019, 03:34 PM   #1
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Default Amazon Electric Vans 100K Rivian

https://arstechnica.com/cars/2019/09...limate-change/

Meanwhile people on the sprinter forum are still arguing about what oil type is the best
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Old 09-22-2019, 05:13 PM   #2
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Default Re: Amazon Electric Vans 100K Rivian

If only they'd hire a new design team. The R1T truck grills/headlights are ugly af. Rivian must be stoked, and I hope they're able to succeed. Amazon investment is no joke, but wow 2021? That's ambitious, they're only releasing their R1T's and R1S's next year I think? Looks aside (which is hard to do), their specs are actually pretty impressive (400 mile range, 0-60 in 3 secs, etc.) on todays market of gas/diesel powered offerings. Great range and payload/towing capacity. I can't wait for them to become more available/affordable over the years. I love the torque of turbodiesel, it's pretty much all I've ever driven, but the torque of electric motors is a whole 'nother ballpark.

Anyway for now Mobil1 0W-40 European car formula is all I ever feed her. No argument necessary...
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Old 09-22-2019, 06:20 PM   #3
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Default Re: Amazon Electric Vans 100K Rivian

They are great for what they are, but I will bet the 400 mile range is not at 75 MPH with the AC on, outfitted as RVs and Campers are. I will bet it is more like 200-300 miles if driven at highway speeds and outfitted with vents, AC, Solar Panels, etc. Charging will take more than an hour if the battery size ( 180 kWh )and stated charge rate (160 kW / h ).

Our use case of our RV is 800 miles in a day, with two refueling / pee break / driver switch stops of 15 minutes and two pee break / driver switch stops of 10 minutes. The extra pee breaks sometimes get extended. Food is self contained, so we don't stop for that. An EV that requires 3 or 4 hour plus stops for refueling won't work for us, even if the price was similar, which it is not.

Now, what they really need to do is to make a small, light EV that is designed to be charged by towing. That would be a fantastic tow vehicle, as the use case for that is to just tool around the local area wherever the RV is parked. Apparently, manufacturers don't support charging while towing, although some third parties have been able to accomplish it. The range would only need to be less than 100 miles. I'd seriously consider that, if it was not too expensive. Of course, then you can usually only go 65 MPH per posted speed limits for vehicles towing.

Regards,

Mark
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Old 09-22-2019, 06:28 PM   #4
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Default Re: Amazon Electric Vans 100K Rivian

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Originally Posted by marklg View Post

Now, what they really need to do is to make a small, light EV that is designed to be charged by towing. T

Apparently, manufacturers don't support charging while towing,

Regards,

Mark
Mark,

We used to regularly tow charge a 2011 Nissan Leaf as part of our testing at work.

You had to engage Drive before you fully flattened the battery, ie after a few hundred yards in 'Turtle' mode the whole car switched off and the only way to bring it back to life was to plug it in.

The only downside to tow charging was the effort required to actually tow the car! Think of trying to tow a car with the emergency/park brake fully on and you won't be far off.

We used to tow with a Land Rover Discovery Diesel and the mpg dropped from around 30 UK mpg down to 10 - 12 UK mpg towing the Leaf. You certainly wouldn't want to tow it far!!!

Keith (retired Hybrid vehicle design and test engineer)
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Old 09-22-2019, 06:38 PM   #5
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Default Re: Amazon Electric Vans 100K Rivian

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Mark,

We used to regularly tow charge a 2011 Nissan Leaf as part of our testing at work.

You had to engage Drive before you fully flattened the battery, ie after a few hundred yards in 'Turtle' mode the whole car switched off and the only way to bring it back to life was to plug it in.

The only downside to tow charging was the effort required to actually tow the car! Think of trying to tow a car with the emergency/park brake fully on and you won't be far off.

We used to tow with a Land Rover Discovery Diesel and the mpg dropped from around 30 UK mpg down to 10 - 12 UK mpg towing the Leaf. You certainly wouldn't want to tow it far!!!

Keith (retired Hybrid vehicle design and test engineer)
You are probably one of the third parties I'm talking about. They should design them to be tow charged, maybe over 300 miles, with a special low regenerative braking force mode for that. They don't need to be recharged in 50 miles. It will likely be more efficient if the batteries are charged at .25C or so also.

I did a quick calculation.

25 kWh battery
4 hour charge
6.25 kW draw while charging
746 w / hp
that is a little over 8 hp. Assume some inefficiencies and maybe 10 hp.

Is that reasonable?

Regards,

Mark

Last edited by marklg; 09-22-2019 at 06:45 PM.
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Old 09-22-2019, 10:35 PM   #6
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Default Re: Amazon Electric Vans 100K Rivian

I was mentally mulling the numbers for the 180kW battery, and using 1kW per HP as a way of allowing for some losses ...although i expect having the tow doing "regenerative braking" would entail 100% losses (2kWh of tow power to yield 1kWh of charge).

Let's see ... a typical 2nd alternator on a Sprinter is 250 Amps, so that's 250*14v= 3500 W ... 50% of your proposed rate due to towing your 25kWh example. So that would be an 8 hour charge rate, if done simply by wiring the EV to the 2nd alternator.

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Old 09-22-2019, 11:14 PM   #7
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Default Re: Amazon Electric Vans 100K Rivian

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Originally Posted by autostaretx View Post
I was mentally mulling the numbers for the 180kW battery, and using 1kW per HP as a way of allowing for some losses ...although i expect having the tow doing "regenerative braking" would entail 100% losses (2kWh of tow power to yield 1kWh of charge).

Let's see ... a typical 2nd alternator on a Sprinter is 250 Amps, so that's 250*14v= 3500 W ... 50% of your proposed rate due to towing your 25kWh example. So that would be an 8 hour charge rate, if done simply by wiring the EV to the 2nd alternator.

--dick
I would hope not for 50% losses if designed right, but I did see the claim from Victron that alternators are about 50% efficient. I have no idea how efficient EV motors are as generators.

8 hours would work for me. Having it automatically charge while being towed would not require an extra alternator or wiring, so it could be done by many more people just by setting up to tow. For many, they would have to pay someone to add an alternator and a charging port. I would assume the charging port would also have to conform to some standard, so some sort of controller would have to be installed besides the alternator.

A Smart Fortwo Electric Drive has a 17.5 kWh battery, and a 58 mile range, so that would be about right. But it is not designed to be charged while towed. Also, it would be an all Mercedes rig!

Regards,

Mark

Last edited by marklg; 09-22-2019 at 11:24 PM. Reason: added Smart Car comments
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Old 09-23-2019, 10:47 AM   #8
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Default Re: Amazon Electric Vans 100K Rivian

You could wire the tow car into the brake light circuit so it only charges while braking. So you get free braking and free battery power.
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Old 09-23-2019, 02:04 PM   #9
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Default Re: Amazon Electric Vans 100K Rivian

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Originally Posted by Cheyenne View Post
...

The only downside to tow charging was the effort required to actually tow the car! Think of trying to tow a car with the emergency/park brake fully on and you won't be far off.

...
Electric vehicle power isn't the somethin' for nothin' that many think that it is. Just the size of the cables at the charging stations should give some clue. Significant power is being supplied by the grid to allow those multiple hundred mile EV ranges.

I recommend 10C mineral oil for your electrical needs.

vic
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Old 09-23-2019, 02:49 PM   #10
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Default Re: Amazon Electric Vans 100K Rivian

Quote:
Originally Posted by owner View Post
You could wire the tow car into the brake light circuit so it only charges while braking. So you get free braking and free battery power.
I hardly use the brakes, but connecting a brake controller to a towed vehicle is common for safer towing. The brake controller would have to increase the regenerative braking when the main vehicle brakes are on so the towed vehicle doesn't jackknife.

The electric motor appears to not require maintenance, but there could be some nice arguments over cooling and brakes.

Regards,

Mark
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