Charging while driving…Wild, irresponsible speculation...

[SpaceEVDriver]

Instead of working I’m thinking about wildly irresponsible ideas for EVs.

With the Harvester, the vehicle will be capable of charging while driving. It’s highly unlikely in my opinion that the Harvester will use a separate converter to charge the battery while driving. It would make little sense to add yet another, redundant (but not usefully redundant) converter to the vehicle. So I suspect that the Harvester engine will turn the generator motor which will produce single phase, 240 volts, probably 48 to 80 Amps (11.5 to 19.2 kW) that feed into the L2 onboard chargers. If they do 80 Amps, that will mean something like what the early Lightnings have, which is dual onboard charging (two AC-DC converters). Most EVs turn off access to charging while the vehicle is in motion because that would be a dumb thing to leave on. But an EREV, by definition, requires access to charging while the vehicle is in motion.

The possible implications of my speculation here are:
1) The Scouts will be able to take advantage of 80A Level 2 charging (not all EVs have dual onboard charging), which will be great.
2) The BEV Scouts might only require a small bit of software changes and maybe a bit of hardware to allow L2 charging while driving.

What kind of idiot would want #2?

Me.

I would love to build a trailer with a 60-120 kWh battery built into it—probably from a rescued totaled EV—and use it to charge the truck while on the road. With Level 2, 80A charging, I could push 19 kWh into the truck for every hour I’m on the road. Assuming 2 miles/kWh efficiency, that’s an extra ~60 kWh and ~120 miles of range for every 3 hours of driving. I would charge the trailer battery on DCFC when possible (park it at one DCFC station and the truck at another). That bit of extra range gets me to my favorite, very remote boondocking sites with plenty of juice left over. And I could leave behind the extra weight when I’m not camping. And I have significantly less maintenance than I would with a Harvester.

There’s zero real evidence this would be possible, so it’s all speculation.

 

[AlanL]

So I suspect that the Harvester engine will turn the generator motor which will produce single phase, 240 volts, probably 48 to 80 Amps (11.5 to 19.2 kW) that feed into the L2 onboard chargers.

Not knowing any facts about how the drive units feed regen power I have been assuming the Harvester would use the same path. Does that not actually work because of inherent electrical differences?

 

[SpaceEVDriver]

Not knowing any facts about how the drive units feed regen power I have been assuming the Harvester would use the same path. Does that not actually work because of inherent electrical differences?

We don’t know enough to say. It could work either way. Your assumption may be the way they choose to do it.

Like I said, I’m speculating wildly.

 

[BeerParty]

I love the idea of plugging in a range extending trailer. If there were a standard plug of some kind that allowed you to hook a trailer to the truck so they could share power while towing (and while not towing), I can see a lot of after market equipment that would take advantage of it. If set up properly, the truck could just treat it as "more battery" or you can have an user controllable configurations for the secondary battery.

I have seen some of the promo videos about the Pebble Flow, which includes a battery and motor to help with EV range, but I think it would be better to just have a way to feed the power to the truck rather than have the trailer drive itself.

 

[SpaceEVDriver]

I love the idea of plugging in a range extending trailer. If there were a standard plug of some kind that allowed you to hook a trailer to the truck so they could share power while towing (and while not towing), I can see a lot of after market equipment that would take advantage of it. If set up properly, the truck could just treat it as "more battery" or you can have an user controllable configurations for the secondary battery.

I have seen some of the promo videos about the Pebble Flow, which includes a battery and motor to help with EV range, but I think it would be better to just have a way to feed the power to the truck rather than have the trailer drive itself.

That’s precisely my feeling too.

I know of several people who run a 30A cable from the back of the Lightning to their trailer so they can keep their travel trailer powered while on the road. I no longer have a travel trailer, in part because I don’t enjoy towing them (even with gas tow vehicles). But if I had a way to feed power back to the truck while towing, that line of resistance to my partner’s desire for another trailer would fall...

 

[Hedrock]

Sounds like there’s a market for someone to convert m110 trailers to have a Tesla battery and some charging equipment, in addition to an RTT and supplies!

Honestly, I’d think about a full BEV Scout with that sort of trailer option. Even if it’s a case of parking to plug into the external battery, that’s pretty much my use case

 

[SpaceEVDriver]

Sounds like there’s a market for someone to convert m110 trailers to have a Tesla battery and some charging equipment, in addition to an RTT and supplies!

Honestly, I’d think about a full BEV Scout with that sort of trailer option. Even if it’s a case of parking to plug into the external battery, that’s pretty much my use case

A park-and-charge option is actually pretty easy for DIYers today.

One can get a new 32kWh LiFePO4 (LFP) battery pack for about $5500.
An high-voltage DC / solar inverter (240V AC) for about $1500.
An L2 charger for $600.

The trailer can be charged via the grid input on the inverter:
A 30A plug will take (32kWh / (240 volts * 30 A) = 4 hours.
A 50A plug will take 2.7 hours.
You can also charge the trailer (a bit) from the truck while the truck is on a DCFC or on L2 charging (for example at a hotel while road tripping). This would, of course, add time to your charging stops.

If you toss in some solar panels, you could charge the trailer while out on the road and camping, etc. How long that take will, of course, depend on how much solar you bring with you.

A 32 kWh battery would give an extra 25% range to the vehicle.

The truck can be charged by the trailer's L2 charger at an 80A rate (if the truck has the dual chargers installed), which would take about 1.7 hours. If you have an L2 that maxes out at 48A, it would take about 2.7 hours.

The total cost ($7k-$8k), not including the trailer, is less than what I expect the Harvester will be (I would expect the Harvester model to be about $10k more than the BEV). The weight added to the trailer would be about 800 pounds, round up to 1000.

This is the plan if we do ever go back to trailer camping.

 

[rfk]

With the Harvester, the vehicle will be capable of charging while driving... Most EVs turn off access to charging while the vehicle is in motion because that would be a dumb thing to leave on. But an EREV, by definition, requires access to charging while the vehicle is in motion.

Re: speculation -

Suppose your battery is exhausted. Can Harvester (presumably) generate enough to power the vehicle normally? Charge the battery while in motion? Or is some degree of draw from battery necessary for normal operation? So you'd need to park & charge if battery exhausted?

I've reserved Traveler BEV, but might consider switch to Harvester if it effectively has indefinite range on a long roadtrip w/out charging available. But we already have a Grand Highlander hybrid, also depends on what other LR PHEV / EREV / BEV options hit the market in the coming few years, etc.

 

[LastDayScout]

Instead of working I’m thinking about wildly irresponsible ideas for EVs.

With the Harvester, the vehicle will be capable of charging while driving. It’s highly unlikely in my opinion that the Harvester will use a separate converter to charge the battery while driving. It would make little sense to add yet another, redundant (but not usefully redundant) converter to the vehicle. So I suspect that the Harvester engine will turn the generator motor which will produce single phase, 240 volts, probably 48 to 80 Amps (11.5 to 19.2 kW) that feed into the L2 onboard chargers. If they do 80 Amps, that will mean something like what the early Lightnings have, which is dual onboard charging (two AC-DC converters). Most EVs turn off access to charging while the vehicle is in motion because that would be a dumb thing to leave on. But an EREV, by definition, requires access to charging while the vehicle is in motion.

The possible implications of my speculation here are:
1) The Scouts will be able to take advantage of 80A Level 2 charging (not all EVs have dual onboard charging), which will be great.
2) The BEV Scouts might only require a small bit of software changes and maybe a bit of hardware to allow L2 charging while driving.

What kind of idiot would want #2?

Me.

I would love to build a trailer with a 60-120 kWh battery built into it—probably from a rescued totaled EV—and use it to charge the truck while on the road. With Level 2, 80A charging, I could push 19 kWh into the truck for every hour I’m on the road. Assuming 2 miles/kWh efficiency, that’s an extra ~60 kWh and ~120 miles of range for every 3 hours of driving. I would charge the trailer battery on DCFC when possible (park it at one DCFC station and the truck at another). That bit of extra range gets me to my favorite, very remote boondocking sites with plenty of juice left over. And I could leave behind the extra weight when I’m not camping. And I have significantly less maintenance than I would with a Harvester.

There’s zero real evidence this would be possible, so it’s all speculation.

Love the idea. Sounds like a fun project. What do you think that would make your range?

 

[Hedrock]

Re: speculation -

Suppose your battery is exhausted. Can Harvester (presumably) generate enough to power the vehicle normally? Charge the battery while in motion? Or is some degree of draw from battery necessary for normal operation? So you'd need to park & charge if battery exhausted?

I've reserved Traveler BEV, but might consider switch to Harvester if it effectively has indefinite range on a long roadtrip w/out charging available. Depends on what other LR PHEV / EREV / BEV options hit the market in the coming few years, etc.

Scout has stated that the target is a 70mph steady state while running harvester.

 

[AlanL]

Scout has stated that the target is a 70mph steady state while running harvester.

Yes, here are quotes from the Jay Leno interview saying that. Keep in mind this is probably steady state on reasonably flat ground, you should expect to also draw some from the battery going uphill and hopefully the Harvester will be big enough to restore some charge on the level or slow down from 70 to 60 and put the reduced drag waste into the battery.

Jay Leno at 13:40: … I'm an old school guy I can just get in this and just run it on gas, just pretending it's a gas engine and the two will work side by side …

Followed by Scott: … 100%. And how it's designed is we've designed it for this thing to always hold a steady state, a steady state in our definition on a highway 70 miles per hour, so that's the combination of the battery and the gas working together when you're not able to hold the steady state it's going to say dear Jay time to go get gas, by the way just like you would do in a gasoline car so you go get gas it holds that steady state …

 

[SpaceEVDriver]

I'm skeptical the Harvester will reach steady state at 70 mph. Maybe 60 mph on the flats. There's no chance it'll do it while towing a travel trailer or going uphill.

 

[Hedrock]

I'm skeptical the Harvester will reach steady state at 70 mph. Maybe 60 mph on the flats. There's no chance it'll do it while towing a travel trailer or going uphill.

Why are you skeptical it will be steady state at 70 on the flats?

Doesn’t take much power to run steady state.

 

[SpaceEVDriver]

Love the idea. Sounds like a fun project. What do you think that would make your range?

A 32 kWh battery would not take up much space or trailer load and would add ~25% range to a 131 kWh main battery (for ~400 miles total range in the Lightning). Trailering would cut range by about 30-60%, depending on the height, width, and length of the trailer. I wouldn't do this with a large travel trailer, so my guess would be a loss of 40% for a total 240 miles range while towing. If I took the slower highways to maintain 55-60 mph, I might be able to retain 320 miles range.

It's all theoretical at this point, of course.

 

[AlanL]

I'm skeptical the Harvester will reach steady state at 70 mph. Maybe 60 mph on the flats. There's no chance it'll do it while towing a travel trailer or going uphill.

I think you're too skeptical for the base case and overly pessimistic in the towing case. I agree that steep grades will probably draw from the battery too. (Personally I would say "almost certainly" for grades.)

150 miles at 70 mph is 2.14 hours. Using 65 kWh in 2.14 hours is a steady draw of 30.3 kW, a straight energy conversion is 41.2 hp. Double that for towing (using the 65 kWh in 75 miles) is 82.4 hp. Towing at 60 mph would take a steady draw of 52 kW. Do you think there is "no chance" Scout will find an ICE in the 130 to 150 hp range for the Harvester? That seems like adequate power to cover losses, slight grades, recharging after steep grades.

 

[SpaceEVDriver]

Why are you skeptical it will be steady state at 70 on the flats?

Doesn’t take much power to run steady state.

The 70 mph range test of similar vehicles (the Lightning), for example, net about 2 miles/kWh in good conditions. That's an average 35 kW draw from the battery.

You don't run a genset engine at peak power for 5 hours. You want a ~20% duty cycle for peak power or you "oversize" the engine by a commensurate ratio. If they undersize the engine, it will be loud and buzzy, inefficient, prone to overheating, and unreliable. If they oversize it too much, it'll be inefficient and add more weight than necessary.

I think a 125 kW engine may be larger than necessary. They probably need a 100 kW peak power engine to meet that 35 kW battery demand. I don't know which naturally aspirated engine they'll choose, so I don't know what the efficiency of that engine will be. They may be able to get 23 mpg average efficiency from a 100 kW engine, so I might be too pessimistic. I'll remain skeptical until I have more details.

 

[SpaceEVDriver]

I think you're too skeptical for the base case and overly pessimistic in the towing case. I agree that steep grades will probably draw from the battery too. (Personally I would say "almost certainly" for grades.)

150 miles at 70 mph is 2.14 hours. Using 65 kWh in 2.14 hours is a steady draw of 30.3 kW, a straight energy conversion is 41.2 hp. Double that for towing (using the 65 kWh in 75 miles) is 82.4 hp. Towing at 60 mph would take a steady draw of 52 kW. Do you think there is "no chance" Scout will find an ICE in the 130 to 150 hp range for the Harvester? That seems like adequate power to cover losses, slight grades, recharging after steep grades.

If they’re planning to run the Harvester at peak power and 100% duty cycle for 350 miles (5 hours), they’re going to end up with a lot of blown engines.

 

[LastDayScout]

A 32 kWh battery would not take up much space or trailer load and would add ~25% range to a 131 kWh main battery (for ~400 miles total range in the Lightning). Trailering would cut range by about 30-60%, depending on the height, width, and length of the trailer. I wouldn't do this with a large travel trailer, so my guess would be a loss of 40% for a total 240 miles range while towing. If I took the slower highways to maintain 55-60 mph, I might be able to retain 320 miles range.

It's all theoretical at this point, of course.

Pretty cool. I could see the aftermarket coming up with something like this. I do not think Scout will produce it themselves. I wonder what it might cost and weigh? Single axle trailers do not require brakes, dual axle trailers do. Most decent 5 lug single axles have a 3500lb gvw.

 

[AlanL]

If they’re planning to run the Harvester at peak power and 100% duty cycle for 350 miles (5 hours), they’re going to end up with a lot of blown engines.

But the majority of those 350 miles will be at the much lower loads, not at peak.

 

[SpaceEVDriver]

Pretty cool. I could see the aftermarket coming up with something like this. I do not think Scout will produce it themselves. I wonder what it might cost and weigh? Single axle trailers do not require brakes, dual axle trailers do. Most decent 5 lug single axles have a 3500lb gvw.

Yeah, I hope Scout doesn’t do any development on a trailer like this—I’m a huge proponent of letting the experts do the thing they’re expert at, and I want Scout’s expertise to be developing and building a fantastic EV. The key to being able to use this setup in-flight, as it were, is that Scout would have to provide a mechanism (with a whole lot of safety checking) for receiving 3rd party power while moving.

Or we could do as discussed above and make it a park-and-charge option. For example here in the desert southwest, I have several routes that I can do unloaded just fine but if I attach a trailer, I’ll find myself having to use an L2 charger to charge partway through the route. If I can set up an 80A charger on my trailer, I can dump the auxiliary trailer battery into the truck while stopped for a long lunch, and that extra 25% will get me to my destination or to a DCFC.

The gear as I’ve specced it would be 800-1000 pounds. A 3500 lb single-axle GVW would have to be relatively light-weight on the rest of the build for this to work. In AZ, I think anything lower than 3000 lbs doesn’t require brakes but anything heavier does. I would imagine a 4500 pound trailer GVWR would work just fine. I have a 16-foot flatbed dual-axle trailer that I am slowly rebuilding. If I decide to move forward with this build, I may build a teardrop-style habitat that can be removed from the trailer when necessary.