Does the PV cell on the roof of the SL make a difference?

Hi all,
I'm still doing some research about the leaf before I decide to pull the trigger. I'm looking at going SV or SL. I was wondering, does the PV cell on the roof of the SL make a noticeable difference in any way? What situations/scenarios does it really come into play?

cstambaugh said:

I was wondering, does the PV cell on the roof of the SL make a noticeable difference in any way?

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No.

RegGuheert said:

cstambaugh said:

I was wondering, does the PV cell on the roof of the SL make a noticeable difference in any way?

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No.

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haha ok. Why would they put it there if it makes no difference? I understand what it does, but how does that help the overall range and functionality of the leaf? Maybe I'm missing something.

it is possible the 12v battery will lead a slightly less stressful life, due to a slight trickle charge if you happen to park in the sun. I'd hate to calculate the Return on Investment on it though.

^^^
Yep.

If one is curious about solar panels on the roof of a car, see http://www.mynissanleaf.com/viewtopic.php?f=27&t=6316" onclick="window.open(this.href);return false;.

cstambaugh said:

haha ok. Why would they put it there if it makes no difference?

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Marketing. Purely.

cstambaugh said:

I understand what it does, but how does that help the overall range and functionality of the leaf?

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Do you really understand what it does? Because I don't. First of all, you shouldn't link the concept of the solar panel and range in the same thought, since the PV panel supposedly charges the 12V battery, not the 400V battery that propels the car. I use the word "supposedly" because we have reports on this forum of LEAF SLs which were parked outside (exposed to the sunlight) whose 12V batteries died. This matches my experience with similar (but much larger!) thin-film PV panels that I have used to try to keep 12V batteries charged. In fact, I'm not convinced that Nissan even engineered these things properly to prevent the dark current from discharging your 12V battery at night. If they didn't address that issue, it is quite possible that this "feature" discharges the battery over the course of 24 hours rather than charges it. I've been inclined to get in there and disconnect ours, but I just haven't found the time.

cstambaugh said:

Maybe I'm missing something.

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You and me both!

Yep... The 12V panel on my SL is useless and I'd be just as happy if it weren't there at all. I'm sure that would save a little money building the car.

The 3rd gen Prius has a really nice solar panel on its roof. I think it can generate about 60 watts of power in good sunlight. But it just powers the ventilation fan.

I knew it was dedicated for the 12v accessory battery, not the 400v main drive battery. My thinking on helping with range would be that it would help alleviate some of the load from running the AC/heater away from the 400v battery. It seems like that is not the case.

Parked inside, and at night, the PV panel does no good,
but is there a series diode to keep it from drawing current
from the 12v Battery when dark? If there is a diode is its
reverse leakage too much, or was it installed backwards?

Assuming all that ws engineered and done correctly, it should
charge the 12v Battery... but how much? The charging current
might not be enough to offset the other alays-on loads.

I have not heard of anybody really investigating this issue.

Useless

Philip

essaunders said:

it is possible the 12v battery will lead a slightly less stressful life, due to a slight trickle charge if you happen to park in the sun. I'd hate to calculate the Return on Investment on it though.

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we can hope, if it's parked outside enough. I think it's part fashion statement, part leading suggestion. This car, when it hits the mass market sales level, if it ever does, will carry with it an idea that many folks have hardly ever heard of, making electricity directly from the sun, rather than solar energy stored in fossils. While it's actual effect on the car may be negligible, I think the solar panel is awesome as a flag waver for solar. for us, it may have had a slight influence on adding to our resolve to go solar and it has certainly sparked conversations with onlookers.

The PV cell produces about 5W in bright sunlight which is supposed to trickle charge the Aux. battery.

Dispite all the nay-sayers, here is the theory. Whether or not its practical, I don't know. So, in theory, the solar panel is providing power to the 12V system, including the battery. If this was properly designed, and I have no reason to believe its not, the LEAF is superior in design to any car I've ever owned, then there should be a series diode preventing reverse leakage when the sun is not available. Energy is going into the 12V system, and therefore the 500V system then does not have to provide that same amount of power. So, indirectly, the solar panel is helping out the 500V system keep the 12V system charged. If this is the case, then the solar panel is indeed making a difference and actually helping out with the power bill.

thermon said:

Dispite all the nay-sayers, here is the theory. Whether or not its practical, I don't know. So, in theory, the solar panel is providing power to the 12V system, including the battery. If this was properly designed, and I have no reason to believe its not, the LEAF is superior in design to any car I've ever owned, then there should be a series diode preventing reverse leakage when the sun is not available. Energy is going into the 12V system, and therefore the 500V system then does not have to provide that same amount of power. So, indirectly, the solar panel is helping out the 500V system keep the 12V system charged. If this is the case, then the solar panel is indeed making a difference and actually helping out with the power bill.

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What happens if I leave the car plugged in while out in the sun?

Answer: dead 12 volt battery. That's reality.

tony,
i do that all the time, and never get a dead battery.


only time dead battery happened, the car had its lights on. wasnt even plugged in.

thankyouOB said:

tony,
i do that all the time, and never get a dead battery.


only time dead battery happened, the car had its lights on. wasnt even plugged in.

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You didn't leave it sitting long enough. The point was that the charging of the 12v is inhibited when the car is plugged in, and the teeny solar panel won't help that.

I find the solar panel kind of a silly option (though I am drawn to the SL leather seats). It provides nearly 0 benefit it seems...well unless your android phone is sucking a ton of power through the USB connection.

Why the hesitation from Nissan to have a small PV power the main battery. Even if you got only 1-2 miles after a full day in the sun..it still might be a small but neat feature.

DougWantsALeaf said:

I find the solar panel kind of a silly option (though I am drawn to the SL leather seats). It provides nearly 0 benefit it seems...well unless your android phone is sucking a ton of power through the USB connection.

Why the hesitation from Nissan to have a small PV power the main battery. Even if you got only 1-2 miles after a full day in the sun..it still might be a small but neat feature.

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It makes no sense, too heavy too costly, net loss.

I investigated the output of the panel not too long after I first got my LEAF and found it putting out around 100ma in bright sun (IIRC). It does indeed have a blocking diode to prevent parasitic loading when it's dark.

Disregarding the panel, the LEAF consumes about 300ma when initially stopped, (VCM still awake) and then after about roughly 10 minutes (provided it's NOT connected to an EVSE) it goes to a "deeper" sleep that seems to vary and pulse from 15ma to 100ma. Supposedly after a few weeks the cellular modem is shut down in hopes to prevent a totally dead battery, but in a lot of cases it seems too late by then.

I'm confident that the bulk of the normal idle load is the cellular modem and telematics processor. It has to listen for a possible command from Nissan's carwings data center for all it's various telematic functions to work, such as status updates, remote climate control, etc.

This is why they put the panel on, but it's still too little to stop the little 12v battery from being deep-cycled and eventually going dead.

If you leave an EVSE connected, it seems to keep the VCM awake, which gets the average draw higher than even the panel can compensate for, so this is why cars go dead that are left connected. Your best bet for storage of more than a week is to disconnect the 12V negative lead. If you are going for more than a week, you should also drain the pack to around 40-70% (not critical), then it should store fine like that for the bulk of a year. Anything over 6 months though, and you might want to at least top off the 12V or put it on battery maintainer.

If you get a 2013 S without telematics, the solar panel is probably not needed. All other models definitely benefit, at least somewhat, from it.

It will definitely NOT affect range in any direct way. Though, long-term it could lessen the sulfation of the 12V which will lessen it's charge energy requirement and thus slightly help.

My car is usually parked inside, so it does me almost no good!

-Phil

Is there a problem with leaving the 12 volt connected and putting a float charger on it? I have been doing this with all of my other vehicles for years while in Hawaii for the summer.
The traction battery would be unplugged and at 50-70% charged.