Portable Solar Trickle Charge for Camping

[GZDongles]

I know this seems to be a controversial topic here for some reason, but I'm interested in exploring how it might be possible to use foldable portable solar panels to charge the car. I know there are a lot of reasons that this may be a bad (and certainly a cost and time inefficient) method of charging, but I just want to focus on how I might go about this in theory if I wanted to try.

The (hypothetical) scenario I have in mind is that I'm doing some long term car camping out west in a Model 3 LR AWD. I may be doing long day hikes in an area with pretty much constant sun, and may be sleeping in a campground with no available power at night either in the car or in a tent relatively close by.

I know it would be relatively easy (but not cheap) to fit about 1-1.5 kW DC worth of foldable solar panels into the trunk while still having plenty of room for camping and other gear. This is an example of a folding panel in the right size/power range (assuming two to three of them). I'm sure there may be better ones out there, but it's just for example. At 1.5 kW, you could theoretically charge at 3-5 mph, depending on charging losses. With the summer sun, that could be 30+ miles per day and 60+ over a two day hiking trip.

So, even though it's not really a very practical option, I'm interested in how I might pull this off.

1. What type of inverter would you use?
2. Would the most efficient/simple route be solar panel -> inverter -> 120V outlet -> mobile connector?
3. Will the car handle potential sudden variations in amperage without stopping charging?
4. Will the car be able to automatically start charging again if the power cuts out (due to passing clouds, etc.) and comes back?
5. Are there any other technical roadblocks I'm missing?

Thanks for your input! Again, I know this isn't a practical (or cost effective) method to charge a car on this sort of trip, but it's an interesting thought exercise!

 

[burningchrome]

I don't know much about it. At Harbor Freight, they have solar charging stuff near the RV stuff, so maybe surf the RV community and see what they are doing.

 

[Evbwcaer]

I think you would need a small battery, maybe 2kwh, that the solar charged. The car would charge off the small battery.

The solar fluctuations are too dramatic and unless the sun was peaking, you’d get nothing out of the system, unless it was really huge like 4kw.

Once the small battery was full from solar, the car would charge at 1,200 watts, until the small battery was depleted, rinse/repeat.

 

[GZDongles]

I don't know much about it. At Harbor Freight, they have solar charging stuff near the RV stuff, so maybe surf the RV community and see what they are doing.

Thanks, that's a good idea!

 

[GZDongles]

I think you would need a small battery, maybe 2kwh, that the solar charged. The car would charge off the small battery.

The solar fluctuations are too dramatic and unless the sun was peaking, you’d get nothing out of the system, unless it was really huge like 4kw.

Once the small battery was full from solar, the car would charge at 1,200 watts, until the small battery was depleted, rinse/repeat.

Is this because the onboard charger is not capable of handling a variable input current? It wouldn't be ideal to have battery to battery charging, but I suppose a 1-2kwh battery wouldn't be too excessive to smooth out the variable inputs.

 

[tsh2]

You could charge directly at DC if the car would take it (at 400V), and this could load track, but trying to charge using AC means the car is trying to take a constant power drain from the solar (which won't really work). Don't forget that while the car is charging, its also taking ~200W for the computer, so trickle charging won't work as well as if you could just access the battery directly.

So maybe a smaller buffer storage would be the only possible way, but I think this will be quite inefficient.

 

[Entropy512]

Is this because the onboard charger is not capable of handling a variable input current? It wouldn't be ideal to have battery to battery charging, but I suppose a 1-2kwh battery wouldn't be too excessive to smooth out the variable inputs.

Minimum current for J1772 is 6 amps, not sure what the minimum for Tesla is.

You'd need an EVSE that worked with the solar system to do MPPT to adjust the advertised current - and again, there's the problem that you'd hit that pesky 6A (roughly 700W) minimum.

If you had an EVSE that could tell the the inverter to change output from 120v to 240v it might help for a big array, but who knows how a vehicle would react to the inverter switching from 120 to 240...

 

[outdoors]

Looks like a great idea. I am working currently on converting my airstream to use salvaged Tesla batteries. Will enable me to run most anything and induction cooktop with a much smaller ac set up. I could in theory maybe find a way to reverse it to charge car. I have a buffer using the existing battery and a mppt to smooth.

Someone will have something like the wings or bed cover the that are the talk of the Cyber truck that could have solar as an ad on maybe.

The parasitic drain has got much better since 2017 from my days at leaving it at trailheads. Yet minimal gain would be nice to jump into the car with after driving off the supercharger network for a backpacking trip. Or while camping a fold out set of panels to just keep camper mode going.

 

[JPoldo]

Look at a Yeti Power Station and request its optional solar charger. Yeti is available in different capacities and they are typically used by campers to power appliances. You should be able to use it as a Level 1 charger.

 

[GZDongles]

Look at a Yeti Power Station and request its optional solar charger. Yeti is available in different capacities and they are typically used by campers to power appliances. You should be able to use it as a Level 1 charger.

Thanks for the suggestion, that's really helpful! I'll have to see if the Yeti 1000 could be compatible with a larger solar array than the ones Yeti sells. Maybe if I have a 1000Wh battery with a 1500W solar panel array, that would be enough buffer capacity.

 

[JPoldo]

Read some reviews on Portable Power Stations because there's a variety of features. Some use lithium batteries which are lighter and more expensive than lead-acid. You can purchase spare plug-in batteries too, but it gets expensive. I'm impressed with bluetooth models that allow control & monitoring from your cellphone.

 

[Bucfan11]

I believe you could charge the 12 volt battery easily. It would at least save you some energy.

 

[mspohr]

I know this seems to be a controversial topic here for some reason, but I'm interested in exploring how it might be possible to use foldable portable solar panels to charge the car. I know there are a lot of reasons that this may be a bad (and certainly a cost and time inefficient) method of charging, but I just want to focus on how I might go about this in theory if I wanted to try.

The (hypothetical) scenario I have in mind is that I'm doing some long term car camping out west in a Model 3 LR AWD. I may be doing long day hikes in an area with pretty much constant sun, and may be sleeping in a campground with no available power at night either in the car or in a tent relatively close by.

I know it would be relatively easy (but not cheap) to fit about 1-1.5 kW DC worth of foldable solar panels into the trunk while still having plenty of room for camping and other gear. This is an example of a folding panel in the right size/power range (assuming two to three of them). I'm sure there may be better ones out there, but it's just for example. At 1.5 kW, you could theoretically charge at 3-5 mph, depending on charging losses. With the summer sun, that could be 30+ miles per day and 60+ over a two day hiking trip.

So, even though it's not really a very practical option, I'm interested in how I might pull this off.

1. What type of inverter would you use?
2. Would the most efficient/simple route be solar panel -> inverter -> 120V outlet -> mobile connector?
3. Will the car handle potential sudden variations in amperage without stopping charging?
4. Will the car be able to automatically start charging again if the power cuts out (due to passing clouds, etc.) and comes back?
5. Are there any other technical roadblocks I'm missing?

Thanks for your input! Again, I know this isn't a practical (or cost effective) method to charge a car on this sort of trip, but it's an interesting thought exercise!

Going direct from solar to inverter would not work well because of too much variability in power output. It would be better to have a "buffer" battery charged by the solar. This would even out solar variability.
As far as sizing goes. You'll need at least a 2000 watt inverter. This would allow the Tesla mobile charger to charge at 12 amps/120volts = 1440 W giving you up to 5 mi/hr. Your 12 volt battery would need to be able to provide up to 100 amps. LiFe batteries are capable of large current output. You could probably get by with a 500 Wh battery since it would be discharging for only short periods. Similarly, you would need at least 1500 W of solar panels. This would be 15 of the common 12v 100W flexible panels.
Alternatively, it might be better to switch to a higher voltage 24 or 48 volt system which would be more efficient. It could use larger solar panels which have a higher voltage and there would be less loss due to lower current in the wiring.

 

[phantasms]

FWIW I got the new Jackery 1000 with a couple panels with this very idea in mind. Even with the Jackery full it it wouldn’t start the car chart at all. :/

 

[runawaymonkey]

@GZDongles did you ever find the info you need? Did you end up with a solution? Found this post in while researching about camping charging.

I'm not affiliated with them but here's an interesting Kickstarter project that looks like it can power a Model X. Considering if I should back it or not.

Reliable Solar Generator Designed for the Modern Home

Affordable Backup Power for Every Household: High Power + Ultra-Fast Recharge; 7 Days of Essential Power for 99% of Home Appliances.

kck.st

 

[mspohr]

Very expensive duplicate of many existing solar generators..

Amazon.com : solar generator

Not enough power to be useful to charge your car.

 

[GZDongles]

@GZDongles did you ever find the info you need? Did you end up with a solution? Found this post in while researching about camping charging.

I'm not affiliated with them but here's an interesting Kickstarter project that looks like it can power a Model X. Considering if I should back it or not.

Reliable Solar Generator Designed for the Modern Home

Affordable Backup Power for Every Household: High Power + Ultra-Fast Recharge; 7 Days of Essential Power for 99% of Home Appliances.

kck.st

@GZDongles did you ever find the info you need? Did you end up with a solution? Found this post in while researching about camping charging.

I'm not affiliated with them but here's an interesting Kickstarter project that looks like it can power a Model X. Considering if I should back it or not.

Reliable Solar Generator Designed for the Modern Home

Affordable Backup Power for Every Household: High Power + Ultra-Fast Recharge; 7 Days of Essential Power for 99% of Home Appliances.

kck.st

I didn't end up doing this! It was an interesting thought experiment but I didn't find a practical need for it, and I was looking at a minimum of $1-2k to get panels plus inverter plus buffer battery needed to make it all work.

I'll check out the kickstarter! Thanks for the recommendation.

 

[Evbwcaer]

I've been off this site for a while but I thought I should mention that there are 12v Lithium batteries, around 500wh, direct replacement for SLA, for around $140. They are made by Valence, model U-Charge, and are sometimes available on Ebay or batteryhookup.com. These could serve as practical base for a project like this. A voltage sensing relay could complete the "brain" of the system, available from Blue Sea.

 

[halans]

FWIW I got the new Jackery 1000 with a couple panels with this very idea in mind. Even with the Jackery full it it wouldn’t start the car chart at all. :/

This guy got it to work

 

[mspohr]

This guy got it to work

The key is to have a large enough battery and inverter as a buffer to store and smooth out the low and variable solar panel output. Probably a minimum of 1500
W inverter.