An idea for solar charging without extra batteries

[Nicolas Bourgault]

Hey everyone,I have an idea for charging my Mitsubishi Outlander P-HEV using an MPP Solar charger. This inverter allows for a battery-less setup, meaning it only requires solar panels and household electricity. This setup could potentially be installed directly inside the car, with a solar panel on the roof to charge the car when it's parked outside. Once home, it can be connected to the household electricity to continue charging. This setup is great because it doesn't require any additional external batteries.

However, I have a concern: since this setup won't be working full-time and will only charge when the sun is up, it will repeatedly charge and stop charging. Could this be an issue for battery preservation? If anyone has insights or experience with this, I'd appreciate your input.Additionally, would a 5kW inverter setup be sufficient for this purpose?What do you all think about this approach? Has anyone tried something similar?

 

[AndyInOz]

Hi Nicolas,

I don't think the physics of solar panels will be your friend in this regard.

I have 8 solar panels on the roof, and an inverter. (A 1.5 kW, grid-connected system).

The solar panels generate, on average, 5 kWh per day, and take two days to charge the battery from 'empty'.

One panel isn't really going to help you unless you're prepared to wait approximately 16 days to charge your battery.

Lithium polymer cells are unlikely to care about the daily, tiny charges, you'd generate, unless you are constantly 'topping up' the cells from say 95% to 100%.

I recommend you just buy a standard solar system, and continue to plug your vehicle into the mains.

Andy

 

[HeliNurse]

Solar panel efficiency 20%, energy from sun on a clear day directly overhead 1.5 kw/m2. Panel size 0.4 m2, wind resistance of the panel, weight of the panel.
Do the math.
Why not put a wind turbine up on the roof instead? Faster you go the more energy you'll get. ( this is a joke BTW)

 

[greendwarf]

Hi Nicolas,

I don't think the physics of solar panels will be your friend in this regard.

I have 8 solar panels on the roof, and an inverter. (A 1.5 kW, grid-connected system).

The solar panels generate, on average, 5 kWh per day, and take two days to charge the battery from 'empty'.

One panel isn't really going to help you unless you're prepared to wait approximately 16 days to charge your battery.

Lithium polymer cells are unlikely to care about the daily, tiny charges, you'd generate, unless you are constantly 'topping up' the cells from say 95% to 100%.

I recommend you just buy a standard solar system, and continue to plug your vehicle into the mains.

Andy

Whilst I agree with you about using a standard solar set up (not least because of the free electricity for use other than for the car) I am a bit surprised that you are only getting 5kwh per day, even with only 8 panels. I have 12 and get over 20 in summer in the UK but I also have a 5kwh battery and matching inverter. Is your 1.5kw inverter limiting your output or is that your panels are older (mine installed last year) and so less productive?

My point for the OP is that I can easily recharge my car from my panels as quickly as using the mains during the summer. Admittedly winter is more challenging because I don't have the ideal orientation or angle of elevation plus shadowing from next door's house!

 

[Nicolas Bourgault]

Thanks Andy and HeliNurse for your feedback.

I realise that a solar panel on the roof of the car hasn't a big charging potential.
However in my situation it might make sense as I live offgrid and my car isn't home all day. It means I have to add extra batteries home to recharge the car at night.

Battery technology is changing fast so I thought about using the sun shining on the car to fill it up when parked outside could be a viable option (as I am adding 1 or 2 panels to my solar array without the need of extra batteries).

I was thinking of 2x 500w (bifacial). Not sure of the useable surface of the roof as I do not have the car yet.
They are stacked while on the move, and the bottom one is deployed over the bonnet while parked.
I am estimating I could generate a solid 700w while keeping the car cool (I live in Mauritius).
If it stays on a car park for 6h a day... its between 3 to 4 kWh I could harness every day.
Weight wise, panels are 30kg each, inverter about 5kg... its like having an extra passenger (paying) to carry along.
I would design a wind cover to make it as streamline as possible in the continuity of the windscreen.

I

 

[littlescrote]

You normally just connect solar to the mains to either use it or export it (which you get paid for in the UK). The car doesn't know or care where it comes from.

 

[mountkay]

How would you hook the SCC to the cars traction battery?

And how would you hook your new 5kw inverter to the car traction battery?

You would need a special SCC and inverter to work off the voltage the traction battery puts out.

I lived off-grid in a camper for years, w a 12v system. Now I’m in an off-grid house, w a 48v system.

I did have a solar panel attached to my last car, a van. But it was 12v panel connected to 12v battery.

Edit: I also figure it’s good to mention that an inverter will have a lot of idle draw, depending on what type you get.

A low-frequency inverter uses much less idle draw and is much more expensive.

A high-frequency inverter will be cheap, but it will draw a lot of idle. For example my 6.5KW All-in-one inverter uses 70W idle draw. 1600wh per day.

I’m guessing you are talking about a high frequency All-in-one type inverter that also has the SCC built in.

 

[AndyInOz]

Whilst I agree with you about using a standard solar set up (not least because of the free electricity for use other than for the car) I am a bit surprised that you are only getting 5kwh per day, even with only 8 panels. I have 12 and get over 20 in summer in the UK but I also have a 5kwh battery and matching inverter. Is your 1.5kw inverter limiting your output or is that your panels are older (mine installed last year) and so less productive?

My point for the OP is that I can easily recharge my car from my panels as quickly as using the mains during the summer. Admittedly winter is more challenging because I don't have the ideal orientation or angle of elevation plus shadowing from next door's house!

We may be talking about different things.

I'm talking about the average production of the panels, you seem to be comparing that to peak production of a larger set of panels.

My system is a 1.5 kW system, which, is eight 188W panels (if I recall correctly).

The system generates a full 1.5 kW instantaneous exactly once per year, when the sun at solar midday is exactly perpendicular to the panels. (Note that my panels are at the optimum angle for average generation at this latitude.)

It is possible to get more out of a system like this, by having more panels, and relying on the inverter to shut down during periods of maximum generation that exceeds the capabilities of the inverter, but I didn't have sufficient space facing North to try that.

Note that 5 kWh is an approximation, the daily average is probably more like 5.5 or 5.6.

I note, with interest, that the previous member who wanted to put solar panels on his car, didn't ever come back to explain how everyone was wrong and how his project was actually a success.

The bottom line of discussions then, was that the electricity generated would not make up for the loss created by carrying the extra weight and increased wind resistance.

Building a solar carport, which is optimised for power generation (e.g. 8 x 350W panels at the right orientation and tilt) and charging the car while parked, is eminently feasible.

If one were trying to generate power from a panel on the roof of the car, and in this case bonnet, you'd need to park at the right orientation, and have a mechanism that allows you to tilt the panels. Panels that point directly upwards will generate very little power.

The mechanism/frame that allows you to do that will also add weight/drag to the vehicle.

Hauling solar panels on the roof of the car, will be a net loss.

 

[mountkay]

The system generates a full 1.5 kW instantaneous exactly once per year, when the sun at solar midday is exactly perpendicular to the panels

The optimum output of panels is also based on temperature, so there are occasions when you can get even more than a panels rated output. Mostly due to “cloud edging”. In cold and cloudy weather the panels will cool off. Then when the cloud moves and you get full sun, you can get more than their output, but only for a very short period of time before the panels heat up.

 

[mountkay]

@Nicolas Bourgault can you post the specs of the inverter and SCC you plan to use? I am curious how it functions without a battery. Mine can technically do the same, but it doesnt do it well.

And so this inverter would make 120v and the you would plug a regular charge cord into it, and then into the car? Or would you somehow hardwire the 120v from the inverter to the car?



This was the best configuration I came up with for my old gas car.

50W panel
to 12v unbranded charge controller
through switch
to fuse splitter
to “always on” fuse

Panel was $75ish. SCC around $15.

So about $100. And it topped up my 12v battery no problem on sunny days. Winter was an issue. The SCC would drain more than the panel could create, hence the switch where I can disconnect the whole thing from the cars battery.

 

[AndyInOz]

If you only want to charge up the 12V battery, there are panels that plug into the cigarette lighter and act as a trickle charger.

 

[mountkay]

If you only want to charge up the 12V battery, there are panels that plug into the cigarette lighter and act as a trickle charger.

Yes but those can overcharge the battery. Unless they have a charge controller. I started with one like that. It wouldn’t work because my 12v cig sockets were not on an “always on” circuit. So then the key is removed the circuit is closed and it will not charge. And then when I hard wired the panel into an “always on” circuit, it overcharged the battery beyond 14.6v. Into 16v range. Could damage the battery.

 

[Ecological]

Hey everyone,I have an idea for charging my Mitsubishi Outlander P-HEV using an MPP Solar charger. This inverter allows for a battery-less setup, meaning it only requires solar panels and household electricity. This setup could potentially be installed directly inside the car, with a solar panel on the roof to charge the car when it's parked outside. Once home, it can be connected to the household electricity to continue charging. This setup is great because it doesn't require any additional external batteries.

However, I have a concern: since this setup won't be working full-time and will only charge when the sun is up, it will repeatedly charge and stop charging. Could this be an issue for battery preservation? If anyone has insights or experience with this, I'd appreciate your input.Additionally, would a 5kW inverter setup be sufficient for this purpose?What do you all think about this approach? Has anyone tried something similar?

You are doing the right thing. No it will not damage your car in any way,shape or form. Solar as it is with wind power is quite unreliable. That was why it never caught on for many decades, as the energy in petrol was the easier and more efficient way to move the car. We would have continued doing so until we run out had it not been for the invasion of Ukraine, and massive gloval warming and global disasters. I have 16 panels x 0.8 meters square, and if the sun were intense I would only get about 3kWh, which means that I can only use a 3kWh charger and not a 7kWh charger. If you studied the chemistry of unleaded petrol, the concentration of energy is what is 40 litres of liquid is amazing. To get the same amount of sotred energy from the equivalent in quantity in other things eg wood chips, rapeseed oil, charcoal, you would have to be carrying a lot more than the equivalent of 40 litres- 1700 kWh=35 imperial gallons- most cars in UK can take 45-50 imperial gallons. From our 16 solar panels, the sun would have to be intense for 566.66666666 hours at 3kWh...and in the UK with roughly an average of 3 hours of intense sunshine [Allowing for very dark days with little or no sun of much energy worth], that would be 188.88888888888 days, and that is just for less than one full tank of unleaded petrol!

Energy Content of Fuels (in Joules)​

UW Homepage
https://www.ocean.washington.edu › envir215


PDF

1,700 kWh. One "Petroleum barrel" is a liquid measure equal to 42 U.S. gallons (35 Imperial gallons or 159 liters); about 7.2 barrels oil are equivalent ...
10 pages

 

[littlescrote]

You are doing the right thing. No it will not damage your car in any way,shape or form. Solar as it is with wind power is quite unreliable. That was why it never caught on for many decades, as the energy in petrol was the easier and more efficient way to move the car. We would have continued doing so until we run out had it not been for the invasion of Ukraine, and massive gloval warming and global disasters. I have 16 panels x 0.8 meters square, and if the sun were intense I would only get about 3kWh, which means that I can only use a 3kWh charger and not a 7kWh charger. If you studied the chemistry of unleaded petrol, the concentration of energy is what is 40 litres of liquid is amazing. To get the same amount of sotred energy from the equivalent in quantity in other things eg wood chips, rapeseed oil, charcoal, you would have to be carrying a lot more than the equivalent of 40 litres- 1700 kWh=35 imperial gallons- most cars in UK can take 45-50 imperial gallons. From our 16 solar panels, the sun would have to be intense for 566.66666666 hours at 3kWh...and in the UK with roughly an average of 3 hours of intense sunshine [Allowing for very dark days with little or no sun of much energy worth], that would be 188.88888888888 days, and that is just for less than one full tank of unleaded petrol!

Energy Content of Fuels (in Joules)​

UW Homepage
https://www.ocean.washington.edu › envir215


PDF

1,700 kWh. One "Petroleum barrel" is a liquid measure equal to 42 U.S. gallons (35 Imperial gallons or 159 liters); about 7.2 barrels oil are equivalent ...
10 pages

You're going to have to get your units of power and energy correct if you want to even approach credibility.

 

[greendwarf]

You are doing the right thing. No it will not damage your car in any way,shape or form. Solar as it is with wind power is quite unreliable. That was why it never caught on for many decades, as the energy in petrol was the easier and more efficient way to move the car. We would have continued doing so until we run out had it not been for the invasion of Ukraine, and massive gloval warming and global disasters. I have 16 panels x 0.8 meters square, and if the sun were intense I would only get about 3kWh, which means that I can only use a 3kWh charger and not a 7kWh charger. If you studied the chemistry of unleaded petrol, the concentration of energy is what is 40 litres of liquid is amazing. To get the same amount of sotred energy from the equivalent in quantity in other things eg wood chips, rapeseed oil, charcoal, you would have to be carrying a lot more than the equivalent of 40 litres- 1700 kWh=35 imperial gallons- most cars in UK can take 45-50 imperial gallons. From our 16 solar panels, the sun would have to be intense for 566.66666666 hours at 3kWh...and in the UK with roughly an average of 3 hours of intense sunshine [Allowing for very dark days with little or no sun of much energy worth], that would be 188.88888888888 days, and that is just for less than one full tank of unleaded petrol!

Energy Content of Fuels (in Joules)​

UW Homepage
https://www.ocean.washington.edu › envir215


PDF

1,700 kWh. One "Petroleum barrel" is a liquid measure equal to 42 U.S. gallons (35 Imperial gallons or 159 liters); about 7.2 barrels oil are equivalent ...
10 pages

Hmm seems like Andy you have older panels with a lower output that currently on the market and certainly having a 5KWH battery with mine helps compensate with the fluctuation in sunshine and storing the excess at peak output. However, I would take issue with you over why the switch, as someone who bought their PHEV 10 years ago (i.e. before both the invasion of Ukraine AND me getting solar panels) - in those days the incentive was needing a new large car which I could drive at a fraction of the cost of petrol - simples!