Chevy Bolt EV Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
605 Posts
Discussion Starter · #1 · (Edited)
I found a video where some guys compared the Tesla, Bolt and Leaf against some custom job EV in range (spoiler, the custom job has the longest range which is no surprise, you can compromise in that kind of build). Anyhow interestingly was the range, the Bolt went longer than the Tesla S, but the test they did was to fully charge up then drive the car until the battery was at zero.

https://youtu.be/InWSsghejdE?t=4m18s

It used 54.3 kWh and went 271 miles.

This is curious. First it's great that it went 271 miles, that's impressive but we already know actual range is usually greater than the spec range of 230. The interesting thing is that it only burned 54.3 kWh total - where's the extra 5.7 kWh? That's almost an even 10%. Now we don't know exactly what usage the car is reporting, but the most likely answer is the raw output from the battery before conversion and motor losses because that's easy to measure and the obvious answer*. So either the battery didn't charge up to the full 60 kWh that it reports, or it won't discharge to zero, or they reserve about 5kWh at both the top and bottom. Any of these is effectively the same thing, but would indicate that there is a hidden reserve of about 10%, either on the top side, the bottom or split the difference.

*Further, the motor is at least 7%-10% inefficient and the DC-AC power conversion is somewhere there too, which wouldn't account for the difference. Also, it's easy to measure DC current delivery to the inverter, but it's difficult to measure the post inverter 3 phase AC current and you can't measure the power delivered to the drive train. Therefore, the measurement is very likely the power delivery from the battery and thus shows us the total available capacity of the battery
 

·
Registered
Joined
·
134 Posts
Is it coincidence that 10% is also almost exactly hilltop reserve?

I found a video where some guys compared the Tesla, Bolt and Leaf against some custom job EV in range (spoiler, the custom job has the longest range which is no surprise, you can compromise in that kind of build). Anyhow interestingly was the range, the Bolt went longer than the Tesla S, but the test they did was to fully charge up then drive the car until the battery was at zero.

https://youtu.be/InWSsghejdE?t=4m18s

It used 54.3 kWh and went 271 miles.

This is curious. First it's great that it went 271 miles, that's impressive but we already know actual range is usually greater than the spec range of 230. The interesting thing is that it only burned 54.3 kWh total - where's the extra 5.7 kWh? That's almost an even 10%. Now we don't know exactly what usage the car is reporting, but the most likely answer is the raw output from the battery before conversion and motor losses because that's easy to measure and the obvious answer. So either the battery didn't charge up to the full 60 kWh that it reports, or it won't discharge to zero, or they reserve about 5kWh at both the top and bottom. Any of these is effectively the same thing, but would indicate that there is a hidden reserve of about 10%, either on the top side, the bottom or split the difference.
 

·
Registered
Joined
·
1,087 Posts
I've been able to get over 300 plus miles on a single charge. IIRC it was 347 miles with 28 left.
 

·
Registered
Joined
·
605 Posts
Discussion Starter · #5 ·
I've been able to get over 300 plus miles on a single charge. IIRC it was 347 miles with 28 left.
Right, that's great, but the key is the total energy used. I've said before the only way to really tell what the battery capacity is would be to do this test, fully charge then drive it to zero. Now they could fool us by not telling us the actual kWh used but the actual - reserve, but that's cheating and engineers would have a hard time lying about the numbers in that way, just to hide the fact there is a reserve. The other possibility would be that the 60 kWh is just the specification, not the actual which is larger due to the reserve. That possibility seems low because they'd have to lie about the actual battery capacity, which is something companies don't like to do (lying about specs is a bad idea, as Volkswagen found out).

So this test I believe shows us that the wonderfully long range we are getting is on 54 kWh of battery not 60 kWh, and they keep 10% back on the top, bottom or both.
 

·
Registered
Joined
·
220 Posts
This gentleman used 59.2kWh on his range test and and I believe there are more examples on YouTube. Bjorn did a hypermile of 387 miles on one charge in the Opel Ampera-e badged version, he didn't show a final kWh reading, but at ~3km from his destination he showed 57.2kWh used.

There is a term used by these hypermiling folks called driving at "zero mile" - that is how much range and usable energy is left after the range indicator goes to '0' or when the low battery conditions start hiding the range estimate - how much range over and above the last displayed range remaining is possible before motor cut.

I've seen it mentioned on several videos that at low battery, how you drive makes a big difference in when the motor will cut. The more gentle you drive, the longer it will go and the closer you will get to the maximum usable pack energy available. If you romp on it, the BMS will cut off when it sees a deep enough voltage sag. So a 70mph test will cut out before a 25 mph city test when you're on the last legs of the battery.
 

·
Registered
Joined
·
862 Posts
An important consideration is that battery capacity is derived from cell specifications at 25º C and a 0.3 C rate. In addition to temperature and discharge rate, the usable capacity is influenced by many other factors and SOC (and hence the guess-o-meter) can only be an approximation.



Any "reserve" is not "hidden", the 60 kWh capacity spec is based on a set of laboratory conditions unlikely to be recreated precisely in real world use.

Driving habits, environmental conditions and other factors will affect not only consumption rates but also the capacity available from the battery.
 

·
Registered
Joined
·
196 Posts
I've been able to get over 300 plus miles on a single charge. IIRC it was 347 miles with 28 left.
:)I consistently get 260 miles plus per each 100% charge. That's driving normally for me, neither conservatively or excessively. I know 300 miles is doable, but there's no incentive for me. Plug it in, and go another 260 plus miles.
 
1 - 8 of 8 Posts
Top