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[SpaceEVDriver]

SORRY! Correction...I purchase OBDLink CX. If you plan to use the OBD2 reader with ABRP, be sure to check inside the ABRP app for compatible devices. OBDLink MX+ is not recommended for ABRP.

Choosing an OBD device - A Better Routeplanner

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Thanks for the correction. I don’t use ABRP in the vehicle, and rarely even for planning, so I’m not familiar with its requirements.

 

[SpaceEVDriver]

I saw a poll, “we’d like your feedback about range anxiety."

I haven’t got it.

I use the full capacity of my battery. Because I can charge at home, I’m freed from the constraints of having to reserve something “in the tank” to make it back to the gas station. I just charge at home.

And to be clear: This is a choice. I’m not regularly running to <10% without making the decision to run down the battery that low. I purposefully bring the state of charge that low so that I don’t have to pay extra for DCFC costs when I can easily make it home and pay sometimes 1/10th the cost to recharge.

 

[bwdavis7]

For me, it's more to do with how familiar you are with the vehicle whether it's ICE or EV. For an ICE vehicle, you tend to know if the "needle" can go past the "E" and sometimes even how far past. I tend to get anxiety even with my ICE vehicle when it approaches empty since it gets around 12 MPG. There's not a lot of margin and I start looking to fuel up.

I'm not familiar enough with my EV to go too low yet. Is there any "margin" after 0%? I'm not tempted to find out just yet. Not on purpose anyway.

 

[SpaceEVDriver]

For me, it's more to do with how familiar you are with the vehicle whether it's ICE or EV. For an ICE vehicle, you tend to know if the "needle" can go past the "E" and sometimes even how far past. I tend to get anxiety even with my ICE vehicle when it approaches empty since it gets around 12 MPG. There's not a lot of margin and I start looking to fuel up.

I'm not familiar enough with my EV to go too low yet. Is there any "margin" after 0%? I'm not tempted to find out just yet. Not on purpose anyway.

Absolutely. It has everything to do with familiarity. I didn't start doing this until about a year after owning the vehicle(s).

But I always find out on purpose before I find out accidentally. Doing it on purpose means I'm in control and understand the consequences. Having it happen to me accidentally likely means I didn't want to spend the time waiting for a tow truck or a friend to come give me a roadside charge.

 

[RodorW]

For me, it's more to do with how familiar you are with the vehicle whether it's ICE or EV. For an ICE vehicle, you tend to know if the "needle" can go past the "E" and sometimes even how far past. I tend to get anxiety even with my ICE vehicle when it approaches empty since it gets around 12 MPG. There's not a lot of margin and I start looking to fuel up.

I'm not familiar enough with my EV to go too low yet. Is there any "margin" after 0%? I'm not tempted to find out just yet. Not on purpose anyway.

You could always look up your car with out of spec reviews and see if they’ve range tested it, they usually run them dead for that exact reaso

 

[SpaceEVDriver]

You could always look up your car with out of spec reviews and see if they’ve range tested it, they usually run them dead for that exact reaso

But knowing it hypothetically and knowing it personally from experience are often very different.

 

[RodorW]

But knowing it hypothetically and knowing it personally from experience are often very different.

No doubt, but if you see it can go past the screen saying zero, or if you know the range estimator is close to accurate it can remove some anxiety and that’s just one small step closer to never really feeling it again. I’ve brought my car home on 0% the issue in Chevy is it stops giving me range estimates under 8%

 

[speedrye]

General EV question: Is it more efficient to slowly increase your speed to the speed limit, or make a mad dash to your desired speed? Of my ICE vehicles, about 2/3s of them were actually more efficient to accelerate 100% to your intended speed while the other 1/3 are much more efficient to slowly get yourself up to speed. In those where it was more efficient to max out acceleration, it was even more efficient to push past your desired speed and coast for a bit back down to your desired speed. It's counterintuitive for most, but I'm generally a numbers guy and enjoy playing with variables. So, in an EV, quick burst of electrons, or slow release?

 

[SpaceEVDriver]

General EV question: Is it more efficient to slowly increase your speed to the speed limit, or make a mad dash to your desired speed? Of my ICE vehicles, about 2/3s of them were actually more efficient to accelerate 100% to your intended speed while the other 1/3 are much more efficient to slowly get yourself up to speed. In those where it was more efficient to max out acceleration, it was even more efficient to push past your desired speed and coast for a bit back down to your desired speed. It's counterintuitive for most, but I'm generally a numbers guy and enjoy playing with variables. So, in an EV, quick burst of electrons, or slow release?

This is a great question that’s still being researched.

In general, higher acceleration means higher current. Higher current means higher losses through waste heat (Joule heating).
This is one reason we prefer higher voltage batteries to get higher power to charge and discharge.

However. There’s a lot of nuance to all of this. If you compare acceleration from 0-60 at 12 seconds, 6 seconds, and 3 seconds, most of the time you’re probably better off with the 6 second acceleration. You’ll generate less waste heat. You’ll be less likely to tear up your tires. You’ll be more likely to safely hit your target speed (don’t go over—there’s no benefit to accelerating past your target speed).

That said, it’s been seen in the lab that low frequency (occasional) hard acceleration can help the battery maintain a longer life. This is especially true when on the freeway—breaking up long stretches of nearly constant current is good for the battery. Accelerate hard to pass and then let regen put energy back into the battery to recharge it a bit and return you to your cruise control speed. Repeat from time-to-time.

In sum:
Don’t floor the accelerator every single time you drive.
Don’t never hit the accelerator hard.
Try not to stay at a perfectly constant speed for long stretches of driving. Break it up by sometimes accelerating and then decelerating.

 

[speedrye]

This is a great question that’s still being researched.

In general, higher acceleration means higher current. Higher current means higher losses through waste heat (Joule heating).
This is one reason we prefer higher voltage batteries to get higher power to charge and discharge.

However. There’s a lot of nuance to all of this. If you compare acceleration from 0-60 at 12 seconds, 6 seconds, and 3 seconds, most of the time you’re probably better off with the 6 second acceleration. You’ll generate less waste heat. You’ll be less likely to tear up your tires. You’ll be more likely to safely hit your target speed (don’t go over—there’s no benefit to accelerating past your target speed).

That said, it’s been seen in the lab that low frequency (occasional) hard acceleration can help the battery maintain a longer life. This is especially true when on the freeway—breaking up long stretches of nearly constant current is good for the battery. Accelerate hard to pass and then let regen put energy back into the battery to recharge it a bit and return you to your cruise control speed. Repeat from time-to-time.

In sum:
Don’t floor the accelerator every single time you drive.
Don’t never hit the accelerator hard.
Try not to stay at a perfectly constant speed for long stretches of driving. Break it up by sometimes accelerating and then decelerating.

Aside from heat generated, any idea how the efficiency changes at the inverter on low-load vs high-load situations? Obviously, this will vary per manufacturer, but are there any general rules?

I'd love to know the delta in heat generated at the battery, motors, etc in your different scenarios.

 

[SpaceEVDriver]

Aside from heat generated, any idea how the efficiency changes at the inverter on low-load vs high-load situations? Obviously, this will vary per manufacturer, but are there any general rules?

I'd love to know the delta in heat generated at the battery, motors, etc in your different scenarios.

I’ll answer in several comments.

One general rule is that the cost to run the inverter, onboard charger (for AC—L1 and L2—charging), and other electronics is essentially constant. Lower current through those usually means longer run-time, which means that constant power draw by the electronics leads to lower efficiency.

Example:
Using an L1 EVSE vs a low-amperage L2 EVSE vs a mid-amperage L2 EVSE vs a max-amperage L2 EVSE. Assume the onboard charger (AC to DC converter) requires 200 watts. This will be different for different brands, etc.; this is just illustrative.

• L1 = 1.4 kW draw from the wall. 200 watts goes to the onboard charger, 50 watts goes to the EVSE. That means, discounting any heat generated, only 1.15 kW goes to the battery. So you get an 82% efficiency.
• L2 @ 15 A = 3.6 kW draw from the wall. 200 Watts to onboard charger, 50 Watts to EVSE, ignore heat generated. 93% efficiency
• L2 @ 25 A = 6 kW: 96% efficiency
• L2 @ 48 A = 11.5 kW: 98% efficiency
• L2 @ 80A = 19.2 kW: 99% efficiency
• L2 @ 80A = 19.2 kW: 97% efficiency

There are other losses, so these numbers are inaccurate as you go to higher currents, mostly because of joule heating. So you won’t see much better energy efficiency above about 48 A. And this isn’t the efficiency of the entire system, just that one component. You’re going to see around 95-97% efficiency maximum.

 

[SpaceEVDriver]

Aside from heat generated, any idea how the efficiency changes at the inverter on low-load vs high-load situations? Obviously, this will vary per manufacturer, but are there any general rules?

I'd love to know the delta in heat generated at the battery, motors, etc in your different scenarios.

For motors, the general rule is that for highest efficiency, you want to run around 75% to 100% of the maximum power of the motor.

I get my best efficiency in the Lighting and the Mustang at about 35 mph. Not 20 mph. Not 55 mph. This is because I’m utilizing the best efficiency of the motor without encountering enough drag from air resistance to matter. So very low speeds means a less efficient motor. Very high speeds means higher drag.

 

[SpaceEVDriver]

Aside from heat generated, any idea how the efficiency changes at the inverter on low-load vs high-load situations? Obviously, this will vary per manufacturer, but are there any general rules?

I'd love to know the delta in heat generated at the battery, motors, etc in your different scenarios.

For the DC to AC inverter, this is similar to the onboard chargers: There’s a baseline energy use in the inverter no matter the load.

I don’t have the numbers for that, though. I believe some of that may be discoverable from the spec sheets of individual inverters, but that’s too much work this early.

In general, you want to be somewhere in the middle of the power draw so that the baseline overhead of operating the inverter isn’t a large percentage of the total power draw and you don’t want to operate at the maximum because other inefficiencies come into play like joule heating.

 

[speedrye]

Helpful! Home inverters got me wondering about this since the baseline draw when idle was higher than I would've expected, but they're not sucking down much power when they're pushing a lot of amperage.

 

[SpaceEVDriver]

I just realized I got the 80 Amp EVSE efficiency wrong.

As far as I know, there are no single onboard chargers that are capable of 80 Amps. The Lightning used two onboard chargers and split the current between them. I think that’s how the other EVs with 80 Amp L2 charging operate as well.

This means they’re less efficient than they could be because they have twice the power overhead.

• L2 @ 80A = 19.2 kW: 97% efficiency

 

[SpaceEVDriver]

Helpful! Home inverters got me wondering about this since the baseline draw when idle was higher than I would've expected, but they're not sucking down much power when they're pushing a lot of amperage.

Excellent.

And none of this includes what happens to power draw when you start having to cool components like the motors, battery, inverters, etc. If you’re running at 100%, you’re going to quickly run into the need to cool those components, and now you’ve added around 5-7 kW (or more) power for the heat pump(s).

 

[speedrye]

Excellent.

And none of this includes what happens to power draw when you start having to cool components like the motors, battery, inverters, etc. If you’re running at 100%, you’re going to quickly run into the need to cool those components, and now you’ve added around 5-7 kW (or more) power for the heat pump(s).

Yeah, that's why I was curious about the heat delta earlier. Assuming the drivetrain is at operating temperature, does the quick 3-second burst (then back to cruising speed) really put off that much heat that needs to be cooled or does the mass of the battery/motor/inverter or whatever is heating at the time help temper that requirement a bit? (Not directing that question at you as there are too many unknown variables at this point) I'm not thinking track driving, just a quick 0-60 run to pull out of my neighborhood onto the 55-mph highway before cruising along with traffic.

 

[maynard]

Yeah, that's why I was curious about the heat delta earlier. Assuming the drivetrain is at operating temperature, does the quick 3-second burst (then back to cruising speed) really put off that much heat that needs to be cooled or does the mass of the battery/motor/inverter or whatever is heating at the time help temper that requirement a bit? (Not directing that question at you as there are too many unknown variables at this point) I'm not thinking track driving, just a quick 0-60 run to pull out of my neighborhood onto the 55-mph highway before cruising along with traffic.

I won’t pretend to understand all of this but I like to read it anyway and look some stuff up…

I did date a Jules in college and she was hot, but I don’t think that counts here…

 

[speedrye]

I won’t pretend to understand all of this but I like to read it anyway and look some stuff up…

I did date a Jules in college and she was hot, but I don’t think that counts here…

Put her in terms of efficiency, and it counts here. Some people require a LOT of energy usage and create heat (aka being hot) as a byproduct while others have much higher efficiency scores and roll out of bed looking hot, though the latter is more akin to the mythical perpetual motion machine.

 

[SpaceEVDriver]

Yeah, that's why I was curious about the heat delta earlier. Assuming the drivetrain is at operating temperature, does the quick 3-second burst (then back to cruising speed) really put off that much heat that needs to be cooled or does the mass of the battery/motor/inverter or whatever is heating at the time help temper that requirement a bit? (Not directing that question at you as there are too many unknown variables at this point) I'm not thinking track driving, just a quick 0-60 run to pull out of my neighborhood onto the 55-mph highway before cruising along with traffic.

I’m going to have to sit down and do the math. This might require that I adjust or update my earlier statements about efficiency during acceleration—a back-of-the-envelope calculation suggested it’s much more inefficient to accelerate hard than I had previously stated, so I have to sit down and do the physics with accurate estimates for battery resistance, conductor resistance, etc. I can’t work on it right now, but should be able to get back to it later today. A rough estimate is that you lose roughly twice the energy to joule heating while accelerating at twice the power, but that can’t be quite right (there are nonlinear factors at play)…thus the need to sit down with physics and to look at some of my data recordings.