Harvester Battery Stage of Charge Question

[04Ram2500Hemi]

I’ll apologize in advance if this has been answered, but I don’t remember seeing this. I was watching the “Help me decide between BEV or EREV” subject, and after making a comment on switching modes, @cyure asked me a question that made me rethink the whole Harvester/EREV thing. I’m going to try to not ramble here with my thought/question as I’m still processing the question myself. So - here we go:

I know with a standard EV you get home, charge to 80%, drive until around 20%, and then repeat (at least that’s what I believe is true for battery life efficiency).

With the Harvester, the gas motor charges the battery when needed. What I’m wondering now is how/when does the engine know it’s supposed to come on? I’m guessing there’s math involved that I don’t understand, and I’m sure it also depends on what kind of driving is being done (in town or highway speeds). But if I fill the tank and then charge at home, and the rest of the week is just going to and from work in town in Auto mode, when or how does the engine know to run? Is there a healthy battery level/charge that it’s trying to stay at?

@Jamie@ScoutMotors - is there a simple answer to this? Am I overthinking it?

 

[04Ram2500Hemi]

And if I’m going to go down this rabbit hole, here’s an interesting scenario:
-I’m leaving in the morning for a 500 mile trip and plan to top off the gas tank on the other side of town before hitting the interstate (I’ve got 1/2 tank of gas). While packing and having dinner, I forget to charge and I’m at 25%. I get up hit the road, and realize I’m at 25% charge and a 1/2 tank of gas and it’s go time. Am I going to make it with gas stops alone, or am I already thinking about either charging before I leave (I hate leaving later than planning) or do I now need to add a charging stop along the way?

 

[R1TVT]

I forget to charge and I’m at 25%. I get up hit the road, and realize I’m at 25% charge and a 1/2 tank of gas and it’s go time. Am I going to make it with gas stops alone, or am I already thinking about either charging before I leave (I hate leaving later than planning) or do I now need to add a charging stop along the way?

Maybe - Maybe not... Depends on a ton of variables, but if you are driving like a maniac and have variables working against you, you may need to get more gas if you skip a charge. This is where all the testing needs to come in for the Harvester variant to help demonstrate different real-world driving scenarios. And we don't have any testing or even specs or data now.

There will also need to be a variety of settings for the Harvester. I would imagine that you can choose to override what the SW thinks if you want to preserve fuel or SOC, for example, and there needs to be a SW interface to accomodate that.

By default, the SW will be considering efficiency for any given drive, so long as you enter a destination into the native navigation and have the routing done, the software will take care of all of that for you (and will adjust on the fly based on changes to efficiency).

Same in the BEV, except it will just suggest a charging stop at the right time and based on the right SOC to MAXIMIZE EFFICIENCY for the entire trip. Theoretically, this is a more simplistic calculation in a BEV with fewer variables (no fuel / no engine).

The Harvester adds additional complexity to SW development and adds additional U/I considerations (think fuel gauge and battery gauge and how they interact to optimize range, and how you, as a driver, interface with the system). The Harvester SW and U/I may opt to route you to a DCFC or a gas station based on estimated distance to your destination and available infrastructure. Inherently, it will have more options for charging or fueling, but you obviously could reach a point where your travel time will increase or decrease based on what infrastructure is available.

For example - If you opt NOT to charge at a DCFC when recommended, and you just fuel up the tank on a LOW SOC, and then drive off up the continental divide at 80MPH into a headwind, well, you reap what you sow...

 

[6-ScoutFamily]

@Jamie@ScoutMotors has said the Harvester can be used as a gas-and-go hybrid if you wish. Presumably the software can manage for this scenario.

 

[cyure]

@Jamie@ScoutMotors has said the Harvester can be used as a gas-and-go hybrid if you wish. Presumably the software can manage for this scenario.

Okay but let’s say the driver selects battery only, could the battery get down to a point where the generator can’t charge it because it’s just been run too low.

 

[6-ScoutFamily]

Okay but let’s say the driver selects battery only, could the battery get down to a point where the generator can’t charge it because it’s just been run too low.

I doubt it. I would use battery only for most of my around town driving and leave the Harvester for trips. With the usual caveats about aging gas and critically low SOC. This is why I’m still on the fence regarding BEV/EREV.

 

[shutthefrontdoor]

There is a reserved buffer that is never available. So even if the display is at 0%, there is still enough battery left for cell balancing, thermal management and accepting a charge from the generator.

But the pack would not be allowed to drop below any SOC thresholds that affected any critical functions. It will probably do this at around 5-10% SOC. It was 6% for the BMW i3.

MFG's don't allow a user-selectable mode to brick the vehicle.

 

[R1TVT]

Okay but let’s say the driver selects battery only, could the battery get down to a point where the generator can’t charge it because it’s just been run too low.

I only see something like that happening if you (also) lost all charge in the 12V system. Then the truck would essentially be a brick and require a 12 V jump. Then you could fuel-up, then charge or engage Harvester, and then go.

Will Scout even allow this scenario to happen in the first place, or will there always be some buffer. We don't know. In an EV, you could drive in safemode until you loose all SOC.

So, let consider this:

1. You have no fuel in the Harvester tank, and you run the battery to zero
2. You fuel up the tank
3. You drive away with the Harvester running.

Does the vehicle govern how fast you can drive while you start charging from the Harvester, so you can add SOC and outpace your usage? There could be some safety issues to consider here. Too many unknowns at this stage until Harvester testing begins and we know how Scout will implement the Harvester!

 

[Jamie@ScoutMotors]

I’ll apologize in advance if this has been answered, but I don’t remember seeing this. I was watching the “Help me decide between BEV or EREV” subject, and after making a comment on switching modes, @cyure asked me a question that made me rethink the whole Harvester/EREV thing. I’m going to try to not ramble here with my thought/question as I’m still processing the question myself. So - here we go:

I know with a standard EV you get home, charge to 80%, drive until around 20%, and then repeat (at least that’s what I believe is true for battery life efficiency).

With the Harvester, the gas motor charges the battery when needed. What I’m wondering now is how/when does the engine know it’s supposed to come on? I’m guessing there’s math involved that I don’t understand, and I’m sure it also depends on what kind of driving is being done (in town or highway speeds). But if I fill the tank and then charge at home, and the rest of the week is just going to and from work in town in Auto mode, when or how does the engine know to run? Is there a healthy battery level/charge that it’s trying to stay at?

@Jamie@ScoutMotors - is there a simple answer to this? Am I overthinking it?

<details here are subject to change of course>

The software will always consider your current power consumption, speeds, and destination (if you entered it into the nav system) to determine when to start the engine/generator to stay ahead of power consumption. Most often, the engine will fire up sooner if there is a heavy load (electric motors are very easy to measure resistance in tiny amounts), you are driving at high speeds for any length of time, or if you activate the mode to turn the engine/generator on. In all cases, the software will always try to maintain a minimum charge level (still being determined, but figure 15-20%), and under most normal driving situations, you will run out of fuel before you run out of charge. You then stop and refill the gas tank and keep driving.

With LFP chemistry, you can charge to 100% more often, and in most around-town driving you will be 100% battery-only for around 150 miles. You come home and you plug it in, just like a phone and you may rarely need to go to a gas station.

And if I’m going to go down this rabbit hole, here’s an interesting scenario:
-I’m leaving in the morning for a 500 mile trip and plan to top off the gas tank on the other side of town before hitting the interstate (I’ve got 1/2 tank of gas). While packing and having dinner, I forget to charge and I’m at 25%. I get up hit the road, and realize I’m at 25% charge and a 1/2 tank of gas and it’s go time. Am I going to make it with gas stops alone, or am I already thinking about either charging before I leave (I hate leaving later than planning) or do I now need to add a charging stop along the way?

Yes, you can top of the fuel and start driving. So long as the generator can stay ahead of the power drain, you will be fine. If you're driving 85mph, uphill for long, long periods with a strong headwind, then the generator may not be able to keep up. Generally, though, this would be temporary. You can also reduce speed (say, 85mph to 70mph) to conserve battery life. Once Scouts are out in the world, there will undoubtedly be a TON of YouTube test videos out there. Likewise, when the RAM, Jeep, and Ford full-size EREVs hit the market in the next year, we will all learn a lot about these systems and the various approaches. This should help people make a more informed decision about what they want and whether it will work for them.

@Jamie@ScoutMotors has said the Harvester can be used as a gas-and-go hybrid if you wish. Presumably the software can manage for this scenario.

Yes, under most normal conditions. But you could create a situation where the engine/generator can't keep up (towing max, 8 percent grade, 90mph for two hours straight as an extreme but not very common example). In that case, you could slow down to a lower speed to conserve battery drain or stop and let the generator charge the battery back up (or even stop at a charging station and top off).

Okay but let’s say the driver selects battery only, could the battery get down to a point where the generator can’t charge it because it’s just been run too low.

Just like any vehicle, if you are getting low on fuel or battery, the vehicle is going to give you ample warning. Even in ECO mode to try and use only batteries as much as possible, you will have a limit at which the vehicle will want a charge from the engine or a charger unit. Our engineers can only do so much to protect you from yourself.

Generally, you would have to purposely run the battery down to zero after a crazy amount of warnings/chimes/lights. I don't know if our system will force the engine/generator to come on at a certain low state of charge no matter what (I would guess likely). Even offroad, if you were climbing a steep ascent with heavy rocks and ran the battery down, you can still run the engine/generator. Likewise, if you ran the battery down to 10% by some extreme means, you can stop and let the generator charge and start moving again fairly quickly.

Lastly, we will be producing a ton of videos about the Harvester system as we finialize specs and get our hands on test units. I would imagine software tweaks (which can have BIG impact on efficiency) will be happening all the way through launch and likely after as well. One thing we haven't talked about is that there are cases where you could drive more than the EPA-rated number we have quoted.

 

[cyure]

<details here are subject to change of course>

The software will always consider your current power consumption, speeds, and destination (if you entered it into the nav system) to determine when to start the engine/generator to stay ahead of power consumption. Most often, the engine will fire up sooner if there is a heavy load (electric motors are very easy to measure resistance in tiny amounts), you are driving at high speeds for any length of time, or if you activate the mode to turn the engine/generator on. In all cases, the software will always try to maintain a minimum charge level (still being determined, but figure 15-20%), and under most normal driving situations, you will run out of fuel before you run out of charge. You then stop and refill the gas tank and keep driving.

With LFP chemistry, you can charge to 100% more often, and in most around-town driving you will be 100% battery-only for around 150 miles. You come home and you plug it in, just like a phone and you may rarely need to go to a gas station.



Yes, you can top of the fuel and start driving. So long as the generator can stay ahead of the power drain, you will be fine. If you're driving 85mph, uphill for long, long periods with a strong headwind, then the generator may not be able to keep up. Generally, though, this would be temporary. You can also reduce speed (say, 85mph to 70mph) to conserve battery life. Once Scouts are out in the world, there will undoubtedly be a TON of YouTube test videos out there. Likewise, when the RAM, Jeep, and Ford full-size EREVs hit the market in the next year, we will all learn a lot about these systems and the various approaches. This should help people make a more informed decision about what they want and whether it will work for them.




Yes, under most normal conditions. But you could create a situation where the engine/generator can't keep up (towing max, 8 percent grade, 90mph for two hours straight as an extreme but not very common example). In that case, you could slow down to a lower speed to conserve battery drain or stop and let the generator charge the battery back up (or even stop at a charging station and top off).



Just like any vehicle, if you are getting low on fuel or battery, the vehicle is going to give you ample warning. Even in ECO mode to try and use only batteries as much as possible, you will have a limit at which the vehicle will want a charge from the engine or a charger unit. Our engineers can only do so much to protect you from yourself.

Generally, you would have to purposely run the battery down to zero after a crazy amount of warnings/chimes/lights. I don't know if our system will force the engine/generator to come on at a certain low state of charge no matter what (I would guess likely). Even offroad, if you were climbing a steep ascent with heavy rocks and ran the battery down, you can still run the engine/generator. Likewise, if you ran the battery down to 10% by some extreme means, you can stop and let the generator charge and start moving again fairly quickly.

Lastly, we will be producing a ton of videos about the Harvester system as we finialize specs and get our hands on test units. I would imagine software tweaks (which can have BIG impact on efficiency) will be happening all the way through launch and likely after as well. One thing we haven't talked about is that there are cases where you could drive more than the EPA-rated number we have quoted.

Thanks Jamie for chiming in on your Sunday!

 

[LonnyMacD]

Okay but let’s say the driver selects battery only, could the battery get down to a point where the generator can’t charge it because it’s just been run too low.

Obviously I can’t speak for Scout, but . . .
Once upon a time I did a trip LA to Boston (Medford) and stopped at a friend’s place in TN. He and Tesla warned me that there were few charging stations near him. The charger before the jump to his house brought me to 10%. Not a big deal, I thought 30+ miles to get to another station, I should be okay. I charged up on 110v the night I stayed there. I estimated that I’d get maybe 5-10% in 12hrs. We get up the next morning and find that the outlet had tripped and the battery went down to 5%. Without much of a choice, I headed out with 2 rabbits feet, 4 leaf clover and a dozen hail Marys. My car got to the station at 0% (I had hit 0 25mi earlier). As soon as I plugged it it, the car started charging without hesitation. I believe EV’s have people like me in mind when it comes to how far down you can run the battery. These are my thoughts