Solar Charging a PHEV for a Beginner

krieger82

Greetings all and thanks in advance for any input. I live in Germany and recently bought a PHEV. Here is my issue: We live in a row house and our garages are quite a distance detached. The builders in the 80's were not forward thinking enough to wire the garages with any power for some dumb reason. It is not possible to run a cable to them. This leaves only the option of using solar to charge the vehicle at home. While I have some experience with standard electrical systems, solar and DC systems are alien to me. I am looking at buying a single 350w panel just to at least partially charge the vehicle. The research I have done here seems to indicate that I must use a voltage regulator couple with a battery and inverter. I would like to avoid using a battery if possible since it rather defeats the purpose and increases costs to the point of making the project economically moot. Is there anyway to avoid this? I do not need or want to store power and do not care if the charge is variable since I am not running appliances or anything overnight. I just want to charge the car while the sun is out. It came with 230v standard German cable with an inline inverter for charging from a socket. Is it possible to just hook a solar panel to an inverter and straight to the vehicle? Thanks again!

Here are the specs of the panel I am looking at (translating as best I can):

345w max output

Max Voltage output: 35 volts

Max Power: 10 amps

Open Circuit Voltage: 42.25 volts

Short Circuit Current: 10.5 amps

the car has a 13.2 kWh battery and the cable is a standard type 2 electric charging cable designed to work with our standard sockets here (230v 50hz)

BB.

Welcome to the forum krieger82,

I can only give you some generic answers based on what you have typed...

Your charging connection to 230 VAC @ 50 Hz:

https://en.wikipedia.org/wiki/Type_2_connector

I could not find anything that would let you connect an xxx Watt solar panel directly to your type 2 car charging cable... Which appears to expect, at a minimum, 230 VAC @ 15 amps (or so)...

This looks like it might be interesting for smaller AC power sources/slower charging:

https://www.youtube.com/watch?v=wmeXrdju4Es

I cannot see any way of connecting a solar panel/small array -> small inverter  (no batteries) -> J2 charging

Just to give you an idea... Example harvest from 345 Watt panel, fixed array facing south:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Essen (Germany--Guess)
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 39° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
1.39	2.24	2.93	3.76	4.37	4.19
Jul	Aug	Sep	Oct	Nov	Dec
4.22	4.17	3.23	2.26	1.46	1.13

In December, the average daily harvest would be:

• 345 panel * 0.77 derating for controller/inverter/panels * 1.13 hours of sun per day December = 300 WH = 0.30 kWH per average December day.
• 0.3 kWH per day / 13.2 kWH battery capacity = 0.023 = 2.3% charge per day (morning until evening

That is not very much energy (something like USD$0.06 to $0.12 per day worth of electricity in California).

The example in the above video--Quick link to US version (120/240 VAC):

https://www.amazon.com/Charger-Electric-Vehicle-Charging-Station/dp/B08FM825WX?th=1

It appears, at a minimum, it requires 10 Amps @ 120 or 240 VAC--So, roughly 2.4 kWatts at 240 VAC minimum.

If the Euro version is similar, you would need a 2.5-3.0 kWAtt minimum AC inverter to power that. And a solar array of:

• 3,000 Watts * 1/0.77 panel+inverter deratings = 3,900 Watt solar array minimum (and possibly 2x that amount of you want directly from solar panels and no battery bank--To allow for some clouds, dusty panels, and charging more towards morning and envening times---Otherwise the inverter will shut down if you have 2 kWatts of solar/sun and 2.5 kWatts of load).

Even if you could connect a 345 Watt panel to your car--You it would take 5 days to give it a 10% charge.

And to run with even a relatively low power level charging--You are still talking >2.3 kWatts or a 10-15 Amp @ 240 VAC circuit to charge with any "standard" J2 charger (that I can see).

Have people figured out how to "hot wire" (US term for starting a car and stealing it) your electric vehicle for solar charging--Probably--But I am not into the electric vehicle DIY (do it yourself) scene--So I cannot really help.

Searching forums with your brand/model of PHEV--You might find somebody.

In anycase, I would want to ensure that they have a working solution before buying any solar hardware.

The J2 charging has a communications bus between the charger and the vehicle (it looks like)--So it is, probably, nothing you can simply "wire around" and get it to work.

-Bill

krieger82

Oh thank you so much for your reply. While disappointing It makes sense. However, it would still be a way to save money over some time. Petrol costs about 8 dollars per US gallon here. While the winter would not be the best, the summer might be. What a cool website that is. It seems a battery may be needed. I can talk to my friend who owns a car shop and try and get a deep running lithium battery. I think that is what I would need because charging the car would drain a lead battery completely which I know is bad? So would that mean a panel + load regulator + battery + inverter would work at least a little bit? Sorry, I am completely new to this.

BB.

Your are very welcome.

It is certainly possible to design an off grid solar power system to charge a car... Just need to know how much energy per day you want to charge.

There are two major (reasonable) off grid solar battery types... One are variants of Lead Acid (flooded cell, AGM, etc.) which tend to be cheaper and last between 5-10 years (you can get industrial forklift/traction Lead Acid which may last ~15+ years). And there are Li Ion types (typically LiFePO4--Lithium Iron Phosphate for off grid--The "safer" type of Li Ion battery chemistry).

We can do some quick estimates to size your system and you can see if it makes (typically economic) sense for your needs. Also, for solar, the panels cannot be shaded--They must be exposed to direct sunlight--Any shading on panels reduces the harvest by 50% to 100% (buildings, trees, etc.)...

Note that Lead Acid batteries are good for cold climates (below freezing). Li Ion are good for warm to hot climates, and cannot charge below ~5C/40F (would you need to insulate/heat your garage battery bank?).

Just to give you an idea of the math and sizing... Lets make up some numbers (these are very rough estimates, but will give you a good starting point for your costing).

• estimated car Watt*Hours per mile/km: 400 WH per mile * 0.62 km/mile = 248 WH per km
• 248 WH per km * 25 km per day driving = 6,200 WH per day (about 1/2 your PHEV battery capacity)
• 6,200 WH per day daily load (6.2 kWH)

For Lead Acid batteries, typically design battery bank for 2 days of usage (no sun) and 50% discharge--Or 4x daily loads (for various reasons):

• 6,200 WH per day * 1/0.85 AC inverter eff * 2 days * 1/0.50 max discharge * 1/48 volt battery bank = 608 AH @ 48 volt battery bank

Note that this is not a small bank. And could be enough to power a pretty energy efficient home (~186 kWH per month).

Sizing the solar array. One is based on battery bank size--5%/10%.13%+--5% for weekend/summer usage. 10%+ for full time off grid minimum rate of charge for Flooded Cell Lead Acid:

• 608 AH * 58 volts charging * 1/0.77 panel+controller eff * 0.05 rate of charge = 2,290 Watt array minimum
• 608 AH * 58 volts charging * 1/0.77 panel+controller eff * 0.10 rate of charge = 4,570 Watt array nominal
• 608 AH * 58 volts charging * 1/0.77 panel+controller eff * 0.13 rate of charge = 5,954 Watt array "typical" cost effective maximum

And size the array based on your daily loads and amount of sun... Lets just pick "3 hours of sun" per day as "break even" (in winter, use utility power to help charge car). You can use the solar energy harvest website and pick other months if you wish (other than 3 hours per day):

• 6,200 WH per day * 1/0.52 off grid lead acid system eff * 1/3.0 hours of sun per day = 3,974 Watt array for 3 hour of sun "break even"

You may have issues trying to fit a ~4 kWatt array on your garage (something like a 51 degree from horizontal panel tilt, etc.). Might not have enough roof space for full array.

The above is based on Lead Acid battery capacity of 25% discharge per day using our rules of thumbs for a reliable system:

•  608 AH * 48 volts = 29,184 WH = ~29 kWH lead acid battery bank capacity

For Li Ion, you could use as minimum capacity battery bank of (Li Ion batteries are much better at charging, so you could get away with 1 day solar charging cycle--I.e., a large array with small battery bank is practical. For FLA batteries, need larger bank to "recharge" 25% in a day's worth of sun):

• 90% - 20% Li Ion bank capacity usage = 70% daily usage of Li Ion bank (1 day discharge--Different rules for Li Ion needed)
• 6,200 WH per day * 1/0.61 off grid Li Ion eff * 1/0.70 Li Ion capacity usage * 1/48 volts = 302 AH @ 48 volt battery bank minimum suggested

Say you need a 3,000 Watt minimum AC inverter (10 amps @ 230 VAC with a bit of "head room". For lead acid batteries you would need a minimum battery bank capacity of ~300 AH @ 48 volts to supply a 3,000 Watt inverter (lead acid batteries cannot supply as much current as a Li Ion bank). But this is just a quick check--Suggest a 608 AH @ 48 volt battery bank (based on 25 km per day drive). If you drive less than 1/2 that--Then your minimum FLA (flooded cell lead acid) battery bank is needed to supply the charging Wattage/current.

In the USA, a very rough cost of electricity for an off grid system is around $1.00 to $2+ per kWH (all costs--New installation, replacement batteries every 5+ years, electronics every 10+ years--system life 20+ years). Vs $0.10 to $0.40 per kWH (California is currently around $0.20 to $0.40 per kWH and gas is around $4-$5+ per gallon--The "California Cost of Living").

You might want to revisit setting up charging station in your garage... Right now, there are "government" incentives to encourage PHEV purchase/usage... You might be able to get permits to add power to your place (perhaps work with others in your block of homes) to bring power from your homes or have the utility make a drop to the block of garages (others want PVEV too)?

Of course, the above is all academic until you know your actual energy needs. The above is pure guesswork to at least get you started.

-Bill