Astonman2
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Joined: Tue Oct 13, 2015 8:01 am

Solar panel charging

Wed Oct 14, 2015 12:05 am

Hi all, This is my first post. I take delivery of my 2009 model with 10000 miles on clock on Saturday 17/10/2015. Noticed the speedo reads mph but the distance recorder reads km. Strange :? I have been experimenting at home with solar panels and wondered if it is possible to fix some flexible panels like used on trailers/ boats etc to the roof of the car and use a 1kw converter to charge the car ? Presumably this would only work when the car is parked & not moving. 100w panels are getting cheap now but don't want to blow anything on the car :evil: Anyone had any experience of doing this successfully ?

jsantala
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Re: Solar panel charging

Wed Oct 14, 2015 2:02 am

Technically, yes, you could charge the car with solar panels, but if we assume 100 W output per square meter you'd need 10 square meters (or 12 square yards) to produce 1 kW of power. The i-MiEV's roof space is considerably smaller. :)
kWsaki.com / EVs: Nissan Leaf 2012, Citroën Xsara 1997 (conv. 81V & 8" Series DC) and Kawasaki GPX750R 1987 (conv. 87V & ME1003 PMDC) / Used to have a Citroën C-Zero 2011

jsantala
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Re: Solar panel charging

Wed Oct 14, 2015 2:39 am

You'd then have to convert the output from the panels into something you could use. The best solution would be a DC/DC-converter, which would take panel input and convert it to 360 VDC, which you could feed directly into the car battery, but it's not actually supported by the vehicle so you would need to hack it quite a bit. Not to mention locating such a DC/DC converter (I haven't been able to).

Easier solution would be to get an inverter to convert the DC input from the panels to AC and then use that AC output with the integrated charger, which you can ask to only take in for example 6 A, but you will lose around 10% in each conversion. Practically you would put around 700 W of that 1 kW panel setup into the battery this way.
kWsaki.com / EVs: Nissan Leaf 2012, Citroën Xsara 1997 (conv. 81V & 8" Series DC) and Kawasaki GPX750R 1987 (conv. 87V & ME1003 PMDC) / Used to have a Citroën C-Zero 2011

Astonman2
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Re: Solar panel charging

Wed Oct 14, 2015 6:12 am

Yes, that's what I was thinking of doing. The 1KW invertor I have left over from my experiments with home solar panels takes 24 volts DC from the panels and converts it to 240 volts AC to plug straight to your household socket to supliment your mains power usage. I only managed about 200-300w max with 4 working panels but we don't get many sunny days here in UK ! I just wondered if trickle charging the batteries with this low level of AC power into the car AC charger would be worth doing. If you were parked at work for 9 hours on a sunny day it might add a few miles to your range. I seem to remember reading some where that the latest generation Prius had a solar panel option, maybe just to charge the backup 12 volt accessory battery ?

jsantala
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Re: Solar panel charging

Wed Oct 14, 2015 10:45 am

The problem is that the least you can set the car's charger is 6 amps. It's a little conservative, so it tries to draw 5.5 amps. At 230 volts that's 1265 watts. You can't make it draw any less. So your inverter should be able to put out that much continuous and it's DC source should be able to provide something like 1400 watts, which is about 60 amps at 24 volts DC. So you'd need a bigger inverter and most likely some batteries to store the solar energy into. In any case, it's a good project, even if the actual solar energy to miles on the road might be quite little.

I'm not aware of any OEM vehicle which would charge a traction battery directly from solar. Mostly they just charge the 12 V aux battery.
kWsaki.com / EVs: Nissan Leaf 2012, Citroën Xsara 1997 (conv. 81V & 8" Series DC) and Kawasaki GPX750R 1987 (conv. 87V & ME1003 PMDC) / Used to have a Citroën C-Zero 2011

wmcbrine
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Re: Solar panel charging

Wed Oct 14, 2015 10:55 am

Astonman2 wrote:I seem to remember reading some where that the latest generation Prius had a solar panel option, maybe just to charge the backup 12 volt accessory battery ?

From what I've read, the solar panel on the Prius only drives a fan, to keep the interior from overheating. Which is nice, but sadly it does NOT charge the 12V, which IMHO would be even nicer. Much less the main battery. :)

PV1
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Re: Solar panel charging

Wed Oct 14, 2015 12:33 pm

jsantala wrote:I'm not aware of any OEM vehicle which would charge a traction battery directly from solar. Mostly they just charge the 12 V aux battery.

I though the Fisker Karma did this, but the roof on that car is so small it only added 1-2 miles a day at the best. The Nissan LEAF SL has a small solar panel in the rear spoiler that keeps the 12 volt battery up. The Prius solar option only runs the cabin fan.

Doing some measuring with the i-MiEV roof and Grape Solar's 100 watt semi-flexible panels, you could fit 300 watts of solar on the roof of the i-MiEV. Like others have mentioned, getting from the 12-48 volt range to 360 volts required to charge the i-MiEV battery is the challenge. What complicates things even further is that the i-MiEV completely disconnects the drive battery from the car when the key is turned off and the car is not charging. There is only high voltage present on the bus when the car is in READY mode, charging, or pre-conditioning.

I've been trying to figure this out, too. The easiest way I've figured out is to tote around an extra 2-3 kWh of 48 volt LiFePO4 with a pure sine wave inverter to output 6 amps at 240 volts (having plentiful access to 120 volts is a benefit here in the States). The problem I see, though, is that you have one of the first i-MiEVs sold. The 2009-2010 cars hit the road before the J1772 standard was finalized. They may use that connector, but it simply passes power straight through with no signaling. The car is set at a certain amperage and that's that as far as I know. What you could do is meter the consumption (is there a UK equivalent to the Kill a Watt?) and buy a standalone inverter with a rating equal to or higher than what the car pulls in amps or watts. The inverter you described will not work in this scenario, as those type inverters require voltage to already be present. If you can wire flexible panels together to get 48 volts nominal through a solar charge controller to a 48 volt battery bank, then you could run the inverter from that battery to charge the car the same as if it was plugged into a wall. The question is, how much extra battery do you want to tote and how much extra range will you actually get? Without any losses, I calculated that a 300 watt solar roof would add 3-5 miles of range per sunny day, but that doesn't count the range hit from extra weight, extra aero drag, and efficiency losses through the inverter and charger. You may end up breaking even or not quite, as the UK doesn't get as powerful solar radiation as where I live.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

2017 Bolt EV LT in Orange with QC - 7/31/2017

Driving electric since 2-21-2013.

jsantala
Posts: 296
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Re: Solar panel charging

Wed Oct 14, 2015 11:33 pm

Probably the simplest and cheapest way to get benefit from solar is to get a micro-inverter, which just inserts it's output into existing power line and simply charge only when the solar output is at it's maximum. If you can limit the power intake of the vehicle to a minimum would help in this scenario as well. Keeping in mind of course that lower charging speed is less efficient due to the other equipment which always runs during charging.
kWsaki.com / EVs: Nissan Leaf 2012, Citroën Xsara 1997 (conv. 81V & 8" Series DC) and Kawasaki GPX750R 1987 (conv. 87V & ME1003 PMDC) / Used to have a Citroën C-Zero 2011

genec
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Re: Solar panel charging

Thu Oct 22, 2015 11:59 am

My i-Miev. Notice the decal in the upper left of the photo showing the means of fueling I use.

Image

Astonman2
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Joined: Tue Oct 13, 2015 8:01 am

Re: Solar panel charging

Fri Oct 23, 2015 4:54 am

Nice license plate !

I have a small domestic inverter which I was going to use which takes 12-30 volts dc in and gives up to 1KW AC 240 volts out depending on the dc current input. As ponted out earlier, I didn't think about the "island" protection built in to stop the inverter trying to supply the whole neighborhood in the event of a mains power outage, so it would be useless to connect straight to the car as no mains voltage would be detected hence it would shut down. A simple camping style inverter might work that is available to power mains devices from your 12 volt car battery as they are cheap to buy now. I have a wall mounted 5 KW inverter for a domestic solar systems but I am unable to try it as it needs 100-200 volts dc input to fire up and I don't have enough solar panels yet to use it :cry: Maybe I should stick to trying to supplement my household electricity to cut the bill down when charging the car.

I still don't have my iMiev yet as the vendor had not used it for a while and the batteries were flat. She charged them up and entered the wrong immobiliser code which locked her out :oops: The car has been trailered to the nearest main dealer to be re-programmed ! At least it will have a new 12 volt aux. battery as this was ruined by lack of charge and of course the car won't work if this is no good ?

Another question I have : Is it possible to replace individual failed cells in the main traction battery pack ? I fix devices that use Li-ion batteries and one cell failing can ruin the whole pack.
Can you extend the range of the car by fitting more cells ? Charging stations are not yet popular in the UK unless you live in London so a long journey would have to be planned in advance or carry a 5KW petrol generator in the boot to charge up on the road side :lol: Defeats the object of having a green car a bit. :twisted:

I read a few years ago there were companies in the USA that would convert your Prius to plug in charging with a larger extra battery pack and hack the software to increase the electric mode speed to about 60mph instead of up to 30mph on the standard car. The battery pack had built in fire extinguishers which sounded a bit scarey. Are there any mods like this for the iMiev or maybe I should read other posts in the Forum while waiting for my iMiev to be delivered :geek:

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