ElectricVehicle
Well-known member
- Joined
- Jul 15, 2010
- Messages
- 631
Let's not forget the uncertainty in this procedure. How closely calibrated are the heater coils in the Nissan LEAF? Is EVERY cars heater within 1% of a nominal value? 5%? 10%? I know if I want a 1% tolerance resistor, it's a different part and I pay more for it. I doubt Nissan went to the unnecessary expense of 1% tolerance heater coils. Resistance elements tend to have their resistance change over time ad their resistance is dependent on the temperatures of the hot element wire. Typical elements draw much more energy when they are cold than hot, like the inrush resistance of a light bulb. Changes in air flow due to dirty air filters, lint or dirt in the fan bearings or on the blades slowing down the fan and reducing air flow will affect the resistance. The fan motor itself will draw different amounts of power depending on the condition of the fan and the filter... The heater full blast has many internal variables also that aren't completely controlled or measured. I doubt they are more than 5% accurate across the fleet. The question is whether this test is even 10 or 20% accurate across the entire Nissan LEAF fleet. It's not a calibrated test - the heater elements fan condition, air filter cleanliness etc. are not calibrated.ericsf said:Effective range is what matters to owners : I agree.
That said, Nissan has devised a test described in the LEAF's service manual which consists in running down the battery using the AC and the heater running at full blast and checking how long it takes to drain the battery for a battery with nominal capacity according to Nissan. I would suspect they have done a similar test to determine the capacity of the packs of the cars they took. They know as much as we do that a driving range test has many external variables which are difficult to control (difficult, not impossible).
I've been asking a few days ago if anyone amongst the owners who have lost bars have attempted to perform this battery test as described by Nissan. Tony answered me with links to all the road tests that he and other people have conducted and I did not see any mention of that test beeing done. I am not sure if he misunderstood my question or if I missed this in the pages of discussion he pointed me to.
If you do know how accurate this test is, that would be great information. If it's accurate to within 5%, it sounds like a good tool we should use. I would add the windows should be fully down and the test performed where 20+ kWh of heat can safely escape. If you do it in a closed garage, you'll heat up the entire garage and cook your battery pack that you're trying to test! The ambient temperature probably needs to be controlled within a reasonable range as it will affect both the LEAF's battery performance and the level of power load presented by the heater. I imagine such a test run at 32deg F ambient will have radically different results than one run at 105 deg F ambient.
I'm interested in the heater method, but let's not overlook it's limitations and real world accuracy. The heater method is also a much slower discharge rate than a drive test - 4 or 5 times less power, so the capacity will be a little more than you'll get from an actual drive and it may not expose weak modules that fail only at higher power - though that's not a problem we have at the moment.
Any test method is subject to critique, we need to work cooperatively to refine and develop better test methods within our capabilities that are practical to apply to multiple vehicles and as repeatable as reasonably possible within our means. I'm sure an offer to use Nissan's dynamometer to perform accurate tests will be warmly received! Until then, we work with what we have and not be too critical of a method unless you have a better method that can be practically used. Helpful, constructive criticism with suggestions for improvements and resource donations to support it is a good healthy thing to improve the process.
The drive tests were very well done. Maybe we can further improve in the future. Thanks to all for carefully orchestrated and controlled the drive tests!