# Solar recharging EV's

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I just ordered myself a vectrix, and I was thinking: there must be a way to recharge this with the power of the sun.
Not directly, but indirectly of course.

I don't know much about solar stuff or electronics, but could the following be realistic somehow?

-Find some old or cheap solar panels
-hook them to recharge (enough) (old car-)batteries
-convert the 12V DC to 220 V AC
-plug in vehicle when needed.

I have no idea how to set this up, but I guess some people here could help me out with the theory?

from here I'm just guessing:

-A car battery gives about 45 - 60 AH? lets take 50.. so that would mean 50amps, 1 hour? or 10 amps 5 hours? 10 amps 12v = 120w
-I believe the vectrix needs 5KW to recharge? spread over 5 hours = 1kw/H
-so if I'd hook 10 full car batteries together, they could deliver 5 hours x 1KW? is that a correct assumption?
-let's assume 200w worth of solar panels.. how long would it take to recharge those batteries?

maybe I'm off somwhere?
It may seem a silly idea, but it would make my vectrix really CO2-free!

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Re: Solar recharging EV's

Hi Turok,

a car battery isnt intended for deep discharge, so will suffer rapid failure when used in a deep cycle application.
50AH usable is a bit rare for cars, its alot more like 25AH.

the vectrix needs a 15A 240V line yes? so thats 3.6kw.
3.6kw = 300A from a 12v battery, and a fairly big inverter.

if you are after a CO2 vectrix, it is easier (and cheaper in the long run) to buy a grid tie solar system.
it is also more convenient (IMO)

Matt

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Re: Solar recharging EV's

Quote:

it is easier (and cheaper in the long run) to buy a grid tie solar system

I thougt of that, but it was that or the Vectrix at this time, and the Vectrix is definitely more fun :)

I just thought: some old 2ndhand solar panels, some old batteries (but then some more than I thought?), would be much cheaper (in purchase) than an official grid tie solar system..

Quote:

3.6kw = 300A from a 12v battery, and a fairly big inverter.

would it exist anyway?

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Re: Solar recharging EV's

If you were going for solar charging, you wouldn't want to charge via storage batteries then an inverter, then the the 220 volt AC onboard charger, unless you have to do it anyway as part of a solar power system for the whole house. The conversion efficiencies are going to make the already large panel area even larger to get a reasonable charging time. Instead, you would charge the pack directly from the panels through a regulated DC-DC converter to regulate the voltage and current.

The size and cost of the required panel has to be appreciated. Assuming ideal sunny conditions, and high quality cells, you would get about 120 watts per sq m and need about 5 m^2 to charge a 80% depleted pack in the five sunniest hours from 10 am to 3 pm. I've seen 125 watt, 1 m^2 panels for about US\$550 to \$750 each.

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Re: Solar recharging EV's

Quote:

the vectrix needs a 15A 240V line yes? so thats 3.6kw.
3.6kw = 300A from a 12v battery, and a fairly big inverter.

It may need a 15A circuit but does it actually use that much? That would make it a one-hour charger. What do they do in 120-volt countries where the maximum normal circuit is 20 amps?

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Re: Solar recharging EV's

PJD wrote:
Quote:

the vectrix needs a 15A 240V line yes? so thats 3.6kw.
3.6kw = 300A from a 12v battery, and a fairly big inverter.

It may need a 15A circuit but does it actually use that much? That would make it a one-hour charger. What do they do in 120-volt countries where the maximum normal circuit is 20 amps?

The charger automatically increases the current if the voltage drops.

On 240V it draws about 7A peak.

The peak wattage is about 1700W, regardless of the supply voltage. This is needed for about 2 hrs if the battery is empty, then it reduces to about 500W, then 300W, then 0.5A wastage once charging is complete.

I have opted with my electricity supplier to pay for "25% Green Power". They supposedly use the extra money to buy / produce "green" electricity. It much more than covers the energy use of my Vectux.

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Re: Solar recharging EV's

Quote:

If you were going for solar charging, you wouldn't want to charge via storage batteries then an inverter, then the the 220 volt AC onboard charger

I thought: I'll probably have to recharge my vectrix only once a week, so I don't think I'll need 5m² of solar panels.
And if i'ts correct what I've read about a total recharge being 5KW, I think there must be a way!
I'm just don't know how to do the maths..

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Re: Solar recharging EV's

Once a week changes the whole equation, cutting the size of the panel you need by 7 times. I would think a set of 6v golf cart batteries would do for the storage, a relatively small inverter, like 1000 watts, or whatever it takes to run the charger, and a moderate size panel set up, like 100 watts might do it.

Look on solar panel sale sites to find maps of average insolation time for your area to get an idea how much power to expect out of a certain size panel. watts is voltage x amps so a 100 watt 12 v panel puts out 8 amps. In my area, you'd get that for 6 hours. Real world experiments are priceless, so buying a pair of 6v batteries and an inverter and finding out how long it would run your charger is a good starting point. Then you can buy more battery to get enough if it is too small to start with. Once you know the battery size, you can then see how much panel is needed to charge it in 7 days.

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Re: Solar recharging EV's

I was an electrical and electronics engineer before I became a pilot. Your main problem is going to be one of efficiency as has been noted. I have several large Solar panels and a 3.5kw solid state inverter. The solar panels feed a leisure battery of 100A hour capacity via a regulator to avoid overcharging and gassing of the lead acid battery. I am on my 2nd Vectrix after the first one was written off by a stupid female car driver, but that's another story.

Technical bits: The Vectrix initially takes nearly 11.5 amps from 220 v mains, gradually decreasing until fully charged when it consumes an idle current of 2.2 amps (this is why most of us use a 3-4 hour timer). This is also why they recommend a 15 amp supply. OK that is roughly 3 kw to make the maths easy. To Supply 3 kw from an invertor with a 12v input, assuming 75% efficiency(which is what my invertor is) requires a DC input of nearly 300 amps!! So you need very substantial cables at the very least from the battery to the invertor. My 100AH battery lasted precisely 15 minutes before the low voltage alarm shut the invertor down. It did not even lift the charge indicator on the Vectrix one bar!!

There you have it. Think of the expense of the batteries, invertor, solar panels, regulator, cables and it becomes a law of diminishing returns trying to use solar panels for a Vectrix, in my humble opinion. Any way, its fun trying!!
Regards
Ray

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Re: Solar recharging EV's

I can see on the Vectrix website :"1.5kW on-board battery charger, 110V-220V (50/60Hz)"

So I guess if I'd start out with an inverter that provides (220v) 2000w / 4000w peak, that would be enough? I can find them quite cheap (around 250€) after 1 search on google..

Then, when I look around for (car) batteries I can find several +-50AH batteries for about 50€/piece.
But is this calculation correct? :
12v x 50AH = 600w for 1 hour
I believe I read somewhere a full vectrix charge requires 5KW (can someone confirm this??)
so I think I'll need about 10 batteries (maybe more, so they will not be deep-discharged during a full vectrix charge)

Then, I looked for some solar panels, I found panels with 80w (peak), they cost about 600€ each, but I'll have to find a formula to see hom many I would need.
I'll also need a solar charge controller, but they seem to be quite cheap too (+-135€)

So all in all, It 'll probably cost around 2000€ or so.. It would be worth concidering to me, even if I'll never have a return of investment :-)

Im I far of with these calculations somewhere?

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Re: Solar recharging EV's

raytheham wrote:

Technical bits: The Vectrix initially takes nearly 11.5 amps from 220 v mains, gradually decreasing until fully charged when it consumes an idle current of 2.2 amps (this is why most of us use a 3-4 hour timer).
Ray

Great to hear you got a new Vectrix and you are back in the saddle!

How did you obtain those current numbers? They are very different from my measurements, and so far all other reports I got my hands on had been consistent with my measurements.

Could it have something to do with the "power factor"?

If it were really drawing 2.2A at 220V whilst idling, that would be 484W - I guess the charger would get so hot it would melt the fairings! Mine gets too hot to touch for long at 0.5A .

Maybe your voltage drops significantly during the initial charging stage. If it dropped to 144V it would explain the high current draw.

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Re: Solar recharging EV's

turok wrote:

I can see on the Vectrix website :"1.5kW on-board battery charger, 110V-220V (50/60Hz)"

So I guess if I'd start out with an inverter that provides (220v) 2000w / 4000w peak, that would be enough? I can find them quite cheap (around 250€) after 1 search on google..

I believe I read somewhere a full vectrix charge requires 5KW (can someone confirm this??)

5kWh is about right for a full charge.

But you do not need 4kW peak power, 1800W should do in my experience.

Check out this thread for more details: http://visforvoltage.org/forum/5406-has-anyone-charged-his-vectrix-small-portable-generator-such-honda-eu2000i

The main fault with your idea is something altogether different: You will damage the battery by regularly discharging it deeply. They don't like it, it's much better to top it up frequently!

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Re: Solar recharging EV's

Quote:

The main fault with your idea is something altogether different: You will damage the battery by regularly discharging it deeply. They don't like it, it's much better to top it up frequently!

Do you mean the solar system battery (I could use more batteries), or the Vectrix battery?

Quote:

But you do not need 4kW peak power, 1800W should do in my experience

I'd probably over-engineer :) but you're saying e.g. a 1500w (3000w peak) inverter would do?

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Re: Solar recharging EV's

I am not sure what type of charger you have for the V, but I wonder if it will run from an inverter. There are different types, True Sine Wave and Modified Sine Wave Inverters. Some devices will only work using a True Sine Wave Inverter. You may want to learn about the differences at this link; Power Inverters: True Sine Wave versus Modified Sine Wave. I hope this helps you understand there is much to learn for what you are attempting. My house uses True Sine Wave inverters running from a large battery bank and I have done lots of research on placing solar panels on my roof to charge the batteries. Right not my system is used as a whole house backup as I live in the country where a simple storm causes power loss often. My system will run the house for 12 hours before the batteries need recharging.

Grandpa Chas S.

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Re: Solar recharging EV's

I am no expert, but here is my 2 cents worth.

I have an EVT Z-20a and use it for a 10 mile round trip to work (weather permitting in Chicago, of course!). It takes about 1.0 to 1.2 kilowatt-hours to recharge for this range. My charger pulls about 450 watts at peak and tapers down as full charge is approached.

I have been able to successfully fully recharge my scooter with a days worth of sunshine doing the following.

1. I have 5 - 85 watt (at 17 volts) solar panels, so on a good summer day they put out a maximum of about 425 watts (\$450 per panel).
2. I use the panels to charge 5 deep cycle 105 amp-hour batteries wired in parallel. That is roughly an equivalent 525 amp-hours battery (about \$80 per battery).
3. The batteries are charged during the day with a 25 amp solar charge controller (about \$100).
4. The scooter (and other household devices) are run off of a 600 watt pure sine wave inverter (about \$120).

In theory, it sounds like there is more than power to handle the job, but several things come into play. The first of which is the fact that the faster you pull power out of a battery, the less power it will give you. Batteries are rated assuming a 20 hour discharge rate. So that 105 amp-hour battery will only give you 105 amps (assuming fully charged, new and perfect) if you are pulling 5.25 amps (x 12 volts = 63 watts per hour). If you pull it any faster than that, the effective capacity rapidly goes down.

You also don't want to discharge your batteries below about 11.5 volts if you want them to last any length of time. So, in my application, I am just able to get the 1.2 kilowatt-hours I need during the summer months, even though the numbers without any losses look like they should give you about 6.3 kilowatt-hours.

Adding batteries in parallel helps to improve efficiency by reducing the percent of the pack capacity being removed (i.e. pulling 50 amps from a 105 amp-hour battery is far less efficient than pulling 50 amps from a 525 amp-hour battery).

Adding batteries in series to increase the voltage also improves conversion efficiencies and wiring losses. My solar charger is 12 volts which I purchased because it is easier and cheaper to find 12 volt inverters and other hardware. But solar chargers are commonly available for 24 volts.

I like the independence of my off-grid system, but if you are really looking to use every ounce of power coming from your panels, a grid-tie system is more efficient. This is both because they typically run at higher voltages and all of the power will be sent into the grid. But if the utility company power goes out, your solar panels are useless unless you also have a backup off-grid configuration (gets pricy to do both).

Hope that helps. I definitely would not discourage you from trying, but it will probably take more batteries and panels than you are thinking right now. When you work the numbers, you cannot really justify the cost given the current cost of electricty. But when you compute the solar cost compared to \$4/gallon gasoline, you get a much better payback.

Scott...

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Re: Solar recharging EV's

I asked the same question to a solar panel specialist.
He said it would be possible to do with these components:

-190Wp monochristaline solar panels: 1.240 Euro

-solar charge controller 12A: 60 Euro

-2 x gel-battery 200Ah: 380 Euro/pc
or 2 x gel-battery 250Ah: 445 Euro/pc

-converter 125€

So let's count 2500€.. hmmmm....
The guy also says maybe better to connect to the grid..

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Re: Solar recharging EV's

Look into connecting to the grid, since then the e company, in a way, will store the power till you need it. Also then you have the potential to add more panels later, and "bank" even more green energy. As long as you are a producer, you can cosider your vehicle to be run on green power. The minimun practical size may be bigger than you plan now though, so you might be ok with less panel and more battery.

Another option, a smaller battery and inverter could run some item in your house, like the computer, or tv. Consider the power not used to be the ammount you can take from the grid and put in the vehicle and still call it running on green electricity. The main thing is to gather as much power as the vehicle uses, not actually putting that power in the vehicle. Who cares where the power actually goes?

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