GM Inside News Forum banner
1 - 4 of 4 Posts

·
Banned
Joined
·
6,653 Posts
Discussion Starter · #1 ·
From Martin Eberhard's blog. He was the founder of Tesla. He unceremoniously left, but he owns a Tesla Roadster that he blogs about.

WASTING ENERGY LIKE TWO REALLY NICE REFRIGERATORS
Soon after I got my car, I noticed a funny thing: the ESS coolant pump seems to run all the time. Even when the car is off. Even if it has been off for a long time. Even when the car is plenty cool. You can hear it run, and many people have commented about the noise of the pump and the noise of coolant gurgling into the overflow reservoir.

The Tesla people tell me that when the battery is half-way discharged, and the car is off, and the ESS is cool, then the pump will shut off. Fine. But my average daily drive is less than 60 miles, and I have only driven far enough to drain half the battery 4 times since I got my car three months ago. So, except a few hours on these four occasions, this poor pump has been running 24 hours per day, 7 days a week for three months solid.

I noticed another funny thing: if I charged the car up and let it sit for a few days without driving, I found that the battery was no longer anywhere near full. I guess that the constantly-running coolant pump, along with its support electronics, is draining the battery.
...
How much power does this coolant pump draw? To find out, I charged the car up and read the meter. Then I unplugged the car and let it sit for 4 days. Then I charged the car back up again, and read the meter once more to see how much energy the car had consumed those four days of sitting in my garage.

Whoa! The car consumed a whopping 14 kilowatt-hours in four days, just sitting there! Doing the math, the pump draws about 146 watts all day long, all night long, every day. This works out to 1,278 kWh per year. To put this in perspective, a really nice 26-cubic foot side-by-side refrigerator with an ice maker uses only 618 kWh per year, so this pump is the energy-equivalent of two huge refrigerators!

Okay, so with this pump running all the time, how much energy is my car really using? Since I installed the meter, I have driven 999 miles, and the meter registered 439 kWh consumed. That works out to 439 Watt-hours per mile, way higher than I ever anticipated.

By subtracting out the time that I was actually driving the car, I can calculate how much energy the pump consumed while the car was parked. This works out to 96 kWh of wasted energy in the month since I installed my meter.

Subtracting this wasted energy, the car’s energy consumption at the meter is only 343 watt-hours per mile. A little high, but in the right ballpark. Here is the kicker: 22 percent of the energy consumed by my car happens while my car is parked! Twenty two percent. Imagine that.
...
Aside from the shame of wasting 1.3 megawatt hours every year to gurgle fluid through my car, this brings two questions to mind: The first is battery life. 22% of the energy cycled through my Tesla’s battery is not used to propel the car, and the cycle life of the battery is 22% shorter than if this pump did not run when the car is off. As much as I have promoted lithium ion batteries for cars, cycle life is still a difficult problem for batteries.
...
Now, let’s run that same pump 24/7 instead of the couple of hours per day it would run in our typical car. Running 24/7, that pump will pass 10,000 hours in only 13 months. That’s all – end of life. Just to make it through Tesla’s 3-year warranty, that pump would need to last 26,280 hours without failure. To last just 5 years, the pump would need to run 43,800 hours. Hopefully, Tesla installed a pump rated for at least 50,000 hours of operation without failure, implying an MTBF of at least 70,000 hours, assuming an exponential failure distribution. Does any automotive parts manufacturer even make such a pump?
 

·
Premium Member
Joined
·
8,886 Posts
Somehow this sounds more like poor design. It appears as though Tesla's founders thought building cars was easy and that GM, Toyota, Honda, BMW, Mercedes, Ford, et al were stupid to spend billions on a new platform and drivetrain.

The oddness of this is that the Roadster is way less efficient than thought and sucks up more power than advertised. Plus, if you don't leave it plugged in for a week it'll be dead. Not good.

And let's not even get started on the transmission.
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top