Hypothetical question - solar charging

[audi321]

Hi all, so I was having a chat with a guy in the office and we were debating whether you could charge a car from solar.

Not sure if it's been discussed on here before, but we talked about 2 options.

Firstly, charging directly from solar panels. We thought this wouldn't work as you would need so many panels to generate the power needed.

Secondly, charging from something like this? i.e. an inverted 12v power pack (which in turn is charged by solar panels). Would this work?

Hypothetical question really as I have absolutely no intention of trying it lol.

[audi321]

sideways sid said:

Or cut out the grid and charge the batteries from solar panels in the bodywork:

https://www.aptera.us/

Probably more suited to California than Cheshire though.

Edited by sideways sid on Thursday 2nd December 14:10

lol I like the idea.........so come on, who's clever enough to work out how many 200w solar chargers it would take to charge a 75kw car? Surely it's not as simple as 75000 / 200? i.e. 375 panels? These solar panels are 12v aren't they so I assume some kind of inverter is needed? What does that do to the watts figure?

Edited by audi321 on Thursday 2nd December 14:21

[audi321]

Fastdruid said:

audi321 said:

sideways sid said:

Or cut out the grid and charge the batteries from solar panels in the bodywork:

https://www.aptera.us/

Probably more suited to California than Cheshire though.

lol I like the idea.........so come on, who's clever enough to work out how many 200w solar chargers it would take to charge a 75kw car? Surely it's not as simple as 75000 / 200? i.e. 375 hours? These solar panels are 12v aren't they so I assume some kind of inverter is needed? What does that do to the watts figure?

Yep, it is that simple. The car is 75kWh which means it'll do 75kW for an hour or less W for more hours.

So 200W Solar for an hour will give 0.2kWh which means to fully charge a 75kWh battery it will take 375 hours. Or 375 200W panels will take an hour.

So what about the voltage? A 12v to 240v inverter doesn't affect things?

[audi321]

Fastdruid said:

Simple answer, no.

The power remains the same even while the voltage changes.

Watts is power and that is voltage multiplied by amps. So 200W at 12V is 16A, 200W at 240V is only 0.83A.

Of course the longer answer is "yes" because there will be losses in conversion.

Wow, so working it backwards, if I bought 10 x 200w chargers (and a suitable inverter) I could get roughly 7 miles of range per hour charge? That's not too bad - similar to a 3 pin plug charger speed

[audi321]

Max_Torque said:

For most of the world, putting solar panels on the actual car is absolutely idiotic


1) it's utterly un-necessary, as a typical passenger car is parked for 98% of it's life

2) It's hugely costly, meaning the £ per kWh is so high as to be none viable (or the for the same cost you could charge many more cars using cheap building roof mounted panels)

3) Cars get dented and crashed, solar panels on the bodywork is going to push insurance costs even higher than they currently are


So whilst the typical insolation at ground level can approach 1.2kW/m^2, a car is

1) not a great shape to fit solar panels
2) realistically, only two sides are going to be pointing at the sun at best
3) Cars get dirty, dirty solar panels have poor efficiency
4) You can't park in the shade of trees or buildings, well anything in fact.

But the biggest issue is the cost, requiring the panels to be engineered into the body work (not cheap) safely wired up (not cheap, esp wrt to HVDC safety), and the power conversion between the panels and battery (which requires a MPPT dcdc converter) must now be born by the manufacturer of the vehicle

A few cars have used panels to trickle charge the LV (12v) battery, helping to maintian that small batteries SoC when parked up for long periods, and a few of the silly start ups like Sono, are claiming to be going to production with integrated panels, but will almost certainly go bust, given how much their (rubbish) product is going to end up costing)

=PARTY POOPER