Charging Volt directly from a solar panel
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Thread: Charging Volt directly from a solar panel

  1. #1
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    Default Charging Volt directly from a solar panel

    Hi I am a newbie to the volt and also aim to be one of the first Volt owners in the UK.

    During the summer months I only use my car occasionally as I try to keep fit by riding my bycycle to work. This leaves me thinking that it may be a good idea to leave the volt plugged into some solar panels to charge up the car when not in use.

    OK so nows the technical bit:-

    I realise that there are various issues that need to be addressed, but for simplicity lets say that I have a 250w 12v panel plugged into an inverter and the inverter's 240v outlet is then plugged into the volt.

    Now you may think that this would, in ideal conditions, work however I am unsure about how much power the volt needs for battery management purposes in order to keep the battery cool and to transform the current from 240VAC to the high voltage DC etc.

    What concerns me is that I did hear that the volt takes 10kw of charge plus 2kw of extra power, which I assume may be for battery mangement.

    Can someone provide me with the technical answer as to whether the volt will take a charge form 240w power input or whether it will just end up powering the battery cooling system?

  2. #2
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    I have a 10 KW PV system.. 43 panels @ 240 KW .. only for a brief period of time could I charge the Volt.. The rest comes from power company. I may get between the hours of 10am - 2pm 5kw to 7kw of power.. just about enough to keep the charger running.. if the sun stays constant.. no clouds in between. If power drops below about 4kw.. then the power company has to provide the difference.

    But if I produce more than I use at any time my meter rolls backwards so I actually produce more then I use most days.

    This week here in NJ I have had 60 KWH produced in a day.. about 11 hours of usable sun light. Volt will use.. if empty about 13kwh .. we usually use less more like 5-10 kwh to fully charge.

    One 250 watt panel will not even start the charger up... plus I have heard if power is not constant or fluctuates.. Volt throughs an error.
    Jack Phillips
    Hamilton, NJ
    Volt 2011( White) and Volt 2013 (Black)

  3. #3
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    Scroll down here and some similar threads have happened before regarding Solar and EV charging.
    Basically, the idea is if you want solar, don't buy it for car-charging. Buy it to "supplement" your electric usage from the home.

    You would want a "grid tie" solar system which is tied into your home breaker box. It acts as a supplemental power source to your home and if you are not using all of it, it feeds to the grid. Hence the name, "grid tie".

    Once you learn more about the solar grid technology, you'll see what is meant by grid tie and the whole idea of this. Also, www.homepower.com is a good resource (for $10 subscription, you can read 2+ years of issues).

    Solar is getting cheaper by the minute due to cut-rates on modules. Watch out for "bad" installers, though - and I see you are in the UK and there have been stories of people being "taken" by installers who do a bad job. You must have a good southern exposure roof and very little shading issues (or none) to really make solar work.

    There are a lot of solar PV homeowners here on this forum who can add to this - but read through the other threads where they have offered quite a wealth of input already. Your example of the inverter and such isn't going to work as the Volt draws much more power. But, you can actually use a 700W 3 or 4 module array with a 700W grid-tie inverter and some of that solar energy will be used by the home and Volt during charging when wired up properly. That's called a small "hobby" system but indeed offers solar power to your daytime use.

    >> What concerns me is that I did hear that the volt takes 10kw of charge plus 2kw of extra power, which I assume may be for battery mangement.
    <<
    Not exactly. It takes a total of 13.3 kWh (kilowatt hours) which is a measure of power over time. This is the billable unit from the power company. The battery charge usable when driving is about 10.4kWh so you have some "charging losses" which make up the 2.9kWh difference. Nothing quoted has to do with battery management "directly" but sure, during charging "some" energy may be used for battery temperature management during cold nights.
    Last edited by bonaire; 04-11-2012 at 07:03 AM.

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  5. #4
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    As the others say your 250W panel isn't going to do anything useful. If you want to run your Volt from solar energy then you will need to put in a proper installation on your house, and even then it's just going to assist with the charging; it won't replace it.

    I'm a bit north of you in the UK and I have solar panels rated at 2.8kW peak. That means I get up to about 2.5kW output but most of the time it is quite a bit lower than that. For the last sunny week of March I was getting just over 13kWh every day (the panels were only installed in January so I don't yet know how much I'll get in the summer) so that's enough in theory to recharge my Volt (when it arrives!), but in practice what will happen is that most of the electricity goes out onto the grid. A grid connection is much more convenient anyway as most of the time I'm at work during the day so I'll want to charge overnight - I expect most people will be the same.

    In case you haven't looked at the tariffs involved for solar power in the UK, here's a quick summary:

    Feed-in-tariff: 45.4p per kWh for installations under 4kW installed prior to 1st April this year, 21p for new installations. You get that money whether you use the electricity yourself or feed it back to the grid.
    Export tariff: 3p per kWh for energy fed out to the grid. You can choose whether to have this metered or just have the electricity company assume it is 50% of what you generate.

    So in my case every unit I generate pays me 46.9 pence and I pay about 13p per unit that I use from the grid. If I can charge during the day then I'll be saving the 13p but I don't lose out on the 3p export as I haven't bothered to meter it.

    Of course all that assumes you have a suitable roof which you may not.

    The other question I need to look at is what happens if I switch to Economy 7. That will make the overnight tariff cheaper and the daytime more expensive but I haven't yet figured out whether solar panels plus overnight car charging will make it worthwhile.

  6. #5
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    He does bring up an interesting point though regarding the 12v PV panel. You can't of course, directly connect a PV panel to the battery terminals of the 12v auxiliary (SLI) battery. It would need a maximum power point tracker (MPPT) to properly adjust the load resistance to gain maximum power generation. However say, you had the output the MPPT which is typically combined with a unidirectional DC-DC converter, it could theoretically reduce the load from the main charger if the SLI battery required significant charging during the process.

    According to others, the inverter can provide up to 1.2-1.5 kW to the SLI battery, so if your panel was supplementing the power to the battery, it would reduce the load from the inverter.

    All this is a lot of work of course and I'm not sure if it is even wise. Still, its sounds like a possibility...

    If you were asking about directly charging the main traction battery, then that is not going to happen.
    My Baby Jane: Volt Stats
    Leased: 2012 Viridian Joule / Black Accents + Leather + Ceramic White / Navi+Bose / Park-Assist / Polished Wheels / D8191
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  7. #6
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    From what I've read on these forms the lowest you can set the volts internal charger is to take six Amps a 120 volts.
    The included charge cord only goes as low as eight.

    I'm with you I just wanted to do it
    I have three things I want to do with my volt.

    1. Direct connect to a wind generator.
    2. Charge up the car at Comanche peak nuclear power generating plant
    3. 10 people on bicycles at the local YMCA charging my car.
    2012 RED Volt VIN:#C-8860 - Premium Leather Seats Jet Black with Dark Trim, Rear Camera & Park Assist, Nav
    09/29/2011 Ordered -- 11/15/2011 took it home

  8. #7
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    Hmm Ok then if you guys are right then how do you explain this.....
    http://cleantechnica.com/2010/10/19/...-in-san-diego/

    1.8kw array charging a Chevy volt in 6hrs and off grid!

  9. #8
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    Quote Originally Posted by sphhants View Post
    Hmm Ok then if you guys are right then how do you explain this.....
    http://cleantechnica.com/2010/10/19/...-in-san-diego/

    1.8kw array charging a Chevy volt in 6hrs and off grid!
    They are being a bit loose with the numbers, it takes 13.4 kWh to fully charge a Volt. It has to have a battery some place to provide a buffer for the charging system, otherwise cloud events will impact the charger disconnect alarm. Trackers do improve the output but getting enough out of. 1.8 Kw array is pretty optimistic.

    In a great solar location like Phoenix this is what you get with a one axis tracker , on average on the best day of the year you get 10.42 kWh out of a array that size.
    Last edited by solar_dave; 04-14-2012 at 04:14 PM.
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  10. #9
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    Over here, we have a 2 kW array built about 4 years ago, (Sanyo 16.7% efficienct rated panels), and I've seen as much as 13 kWh in a day. That 13.4 kWh figure to charge a volt is using 120v, if it was 240v, it'll be closer to 12.5 kWh.
    My Baby Jane: Volt Stats
    Leased: 2012 Viridian Joule / Black Accents + Leather + Ceramic White / Navi+Bose / Park-Assist / Polished Wheels / D8191
    Electric. Unlimited.

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  12. #10
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    Quote Originally Posted by Jedi2155 View Post
    Over here, we have a 2 kW array built about 4 years ago, (Sanyo 16.7% efficienct rated panels), and I've seen as much as 13 kWh in a day. That 13.4 kWh figure to charge a volt is using 120v, if it was 240v, it'll be closer to 12.5 kWh.
    I use 240 and it is about the same, maybe only slightly less. My point is that a 1.8 Kw array is going to have trouble producing those kind of numbers in general. Google the pvwatts sight and plug in the numbers and location, alter the derate to 0.80 and you will see that most of the year it doesn't even come close for most places. Even ideal conditions, time of year and location is a stretch.

    So your panels are some of the most efficent, now lower your array size 10% and see what it produces in Jan or Feb or March.
    Last edited by solar_dave; 04-15-2012 at 03:37 AM.
    Diamond White #B2140 ecosister plate=SLRRYDER
    Crystal Red #C8885, Red-Rider plate=NO2OPEC
    Only 50 gallons purchased, fully charged off Solar , Keeping the utilities at bay.
    DRIVING for FREE! NO OPEC FEE!

    My TED 5000 power monitoring

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