Newbie confusion - please help!
 

I'm a new owner of the Nissan Altima Hybrid (3 weeks old). I am trying to learn as much as I can on this forum, but am confused about a couple of items:

1) Use of A/C. Several posts have indicated to try and drive without the A/C on as much as possible - that it is a mileage killer. I've seen other posts where it has been said to turn it on, using the coldest setting possible. I've also seen posts indicating that the NAH runs AC off the battery, so impact on mileage is minimal either way. :confused: Maybe this has to do with temperature of the cabin affecting battery temperature which in turn affects how often the engine kicks in. I have a small brain, I'm confused, and I may be sweating unnecessarily - please help!!

2) I've been assuming that any time I can keep the car at a speed where it is in EV Mode, that this is a good thing. But I've recently seen posts indicating that trying to keep it in EV Mode too much may actually be a BAD thing. Can someone help me understand why that would be the case?

Thanks for your help!

Steve

Re: Newbie confusion - please help!
 

I can't say much about the Nissan but it doesn't matter if it runs off the battery or not... all the power in the battery comes from the engine at one point or another and it WILL TAKE MILEAGE from you.... electric or normal.

Especially on a freeway when the engine is running anyway... the only time the electric would help is if the engine WANTS to be off and can't because it has to power the AC. An electric AC can run off the battery in those times... however the engine will have to work harder to recharge the battery eventually.

Lots of people will say that the power in the battery comes from regenerative braking so its "free"... well some of it does but its NOT free.... even if all of it did come only regen... if you've used it to power your AC its not available the next time you accelerate... so the engine will have to work harder accelerating and there you go... the power is still coming from the engine.

Re: Newbie confusion - please help!
 

Hi,

First let me point out I'm not a Nissan Hybrid expert. I don't have one nor the maintenance manuals that would give me a clue to how it works. My understanding is it uses many of the same systems Toyota uses in their modern Camry so I'll share my speculation. This is not fact and I would strongly recommend you consider getting the maintenance manuals since they really are the 'road map' to the systems. Then consider getting one of the OBD scanners to start capturing what data is available from the car itself. So with these warnings, I'll speculate on your questions.

In the 2001-03 Prius, the first generation sold in the USA, the AC compressor is engine driven. This is not much of a problem above the maximum EV speed, 42 miles per hour, because the engine has to run all the time anyway. But at lower speeds, the engine had to come on to run the compressor and this impacted low speed mileage.

The newer Prius and Camry use an electrically driven compressor that can pull power from the main traction battery. This means the engine only has to run as needed for extra motive power and to recharge the batteries. This is a much more efficient system for vehicle AC.

I do not know if the Nissan hybrid drives the AC compressor from the engine or if it also uses the electrically driven compressor. I hope they use the electrically driven compressor since it minimizes the mileage hit.

In my case, I can go to about 82F without AC, depending upon sun light and humidity. But above 82F, I have the windows up and choose a faster route since I'll have to run the engine anyway.

What you really need is an MPG vs MPH chart like this but for your vehicle:
http://home.hiwaay.net/%7Ebzwilson/prius/epa.jpg
This is not a difficult thing but it takes a couple of weeks to map out the low-speed performance and some cross country trips to get the high speed values. This really is needed for the Nissan hybrids and I'd be happy to offer some suggestions on how to do this.

One of the sad things in life is we've found the manufacturers have not been terribly open about the actual vehicle performance characteristics. One of the beauties of GreenHybrid.com is we can figure out how to make these measurements and then share what we know with others. This is how science and engineering progresses.

GOOD LUCK!
Bob Wilson

Re: Newbie confusion - please help!
 

Welcome Steve,
1. Use the AC for temps above 82f, you will get a small hit to FE but it will keep the battery comfy. Set the temp to 75 and place it on auto.
2. EV is a big bang for the buck. Use it up completely when you know you will be getting on the highway soon to recharge at higher speeds. If your battery has to recharge from empty while you are stopped in traffic, it will be a bigger hit than you like.
Good Luck

Re: Newbie confusion - please help!
 

Thanks everyone - this is very helpful!