Portable solar trickle charger

[AgingHippie]

I don't know if this exists or not, or could possibly be cobbled together with parts.

Say that you want a solar J1772 trickle charger that doubles as a sun shade. You carry the rolled or folded solar panel in the back, and when you park, pull it out and unfold/unroll it from the roof down over the windshield and the hood. Plug in the J1772 cable in the corner. It should include a cable lock of some sort, and there should be a way to tie it down so it won't blow or slide off.

Does this exist? If so, does anyone know where it's sold?

If it doesn't exist, and you wanted to make one, any ideas on where to get the appropriate parts? Assume for the sake of argument that you don't care how much charge it actually generates as long as it's enough to signal the J1772 and put the car in charging state. Also assume for the sake of argument that you don't care how much it costs, just whether it's possible. And assume that you don't care how much carrying it around would reduce your range (although you do care how difficult it is to roll/unroll or fold/unfold, and it must fit entirely on top of the car, including roof/windshield/hood, and it must fit in the back when rolled/folded).

 

[slorav4]

Assuming best case angled mount full southern summer sun all day in California with a top quality residential roof mount (40 lbs) Panasonic panel you're looking at 2KWh a full day vs 12 minutes on a 40amp LV2. Even before dealing with trying to feed the system enough min amps to even start. You'd probably have to design a system to feed that non standard amount of power through the regenerative braking system like the Jdemo does which requires the RAV to be turned on at the time.

Better off getting a (70 lbs) Yeti portable 3KWh battery system to recharge Rav @12amps 120V using the standard cable. Yeti offers solar panel systems to recharge the battery. Just depends on your purposes. Though that will be a lot of weight and cargo space used.

Flexible solar cells creating reasonable power at a reasonable price are still years away.

 

[TonyWilliams]

The 70 pound trickle charger is ridiculous.

Also, if you’re going to charge the car with it on, you’ll need DC power, not AC.

JdeMO™ does not use regenerative braking, nor does it use the motor at all all.

All the trickle solar charging ideas are extremely slow and very expensive.

 

[AgingHippie]

Assuming best case angled mount full southern summer sun all day in California with a top quality residential roof mount (40 lbs) Panasonic panel you're looking at 2KWh a full day vs 12 minutes on a 40amp LV2. Even before dealing with trying to feed the system enough min amps to even start. You'd probably have to design a system to feed that non standard amount of power through the regenerative braking system like the Jdemo does which requires the RAV to be turned on at the time.

Better off getting a (70 lbs) Yeti portable 3KWh battery system to recharge Rav @12amps 120V using the standard cable. Yeti offers solar panel systems to recharge the battery. Just depends on your purposes. Though that will be a lot of weight and cargo space used.

Flexible solar cells creating reasonable power at a reasonable price are still years away.

Thanks for the reply. The vision would be to haul the thing out of the hatch, lay it over the car like a sun shade or car cover, and keep the car cool while maybe adding a mile or two to the range, if it was left on all day. It wouldn't be very effective, but it could be used anywhere. Sounds like there needs to be some advances in panel technology before it'll be possible.

 

[AgingHippie]

All the trickle solar charging ideas are extremely slow and very expensive.

The idea here is to shade the car from the heat, and possibly gain a mile of range while doing it. I wasn't picturing doing DC->AC->DC using a "system" and an EVSE, I was picturing a cable with a J1772 plug that came directly off the corner of the "shade".

 

[TonyWilliams]

All the trickle solar charging ideas are extremely slow and very expensive.

The idea here is to shade the car from the heat, and possibly gain a mile of range while doing it. I wasn't picturing doing DC->AC->DC using a "system" and an EVSE, I was picturing a cable with a J1772 plug that came directly off the corner of the "shade".

I guess we start with, “How much money do you have to spend?”.

Of course, it can be done. There’s not much that cubic dollars can’t fix.

 

[AgingHippie]

Of course, it can be done. There’s not much that cubic dollars can’t fix.

Seems like flexible solar panel technology is an obstacle for now. I have a small folding set of panels that can charge a phone using about 2 SF, but they aren't actually flexible, they're just connected by a fabric frame. Also, there's the question of minimum power levels to trigger the car to enter charging mode. I saw an incomprehensible table about this, and I wasn't able to decipher what the minimum power would be to raise and detect the signals - I know the L1 that comes with the car uses 12A, but does it have to be that high to signal properly? When I plug into a Chargepoint, it starts charging at .01, then jumps after a few seconds to the capacity of the unit; could it have continued charging at .01 or would the onboard charger have detected a failure and stopped?

As an aside, I didn't picture this item as specific to any one model of EV, I was thinking more of a general EV accessory that could provide shade and the tiniest trickle charge to any EV with a standard J1772 plug.

 

[TonyWilliams]

You didn’t mention how much money you had to spend for this.

 

[davewill]

Of course, it can be done. There’s not much that cubic dollars can’t fix.

Seems like flexible solar panel technology is an obstacle for now. I have a small folding set of panels that can charge a phone using about 2 SF, but they aren't actually flexible, they're just connected by a fabric frame. Also, there's the question of minimum power levels to trigger the car to enter charging mode. I saw an incomprehensible table about this, and I wasn't able to decipher what the minimum power would be to raise and detect the signals - I know the L1 that comes with the car uses 12A, but does it have to be that high to signal properly? When I plug into a Chargepoint, it starts charging at .01, then jumps after a few seconds to the capacity of the unit; could it have continued charging at .01 or would the onboard charger have detected a failure and stopped?

As an aside, I didn't picture this item as specific to any one model of EV, I was thinking more of a general EV accessory that could provide shade and the tiniest trickle charge to any EV with a standard J1772 plug.

Yeah, you're not getting it. The minimum the J1772 standard can handle is 6a @ 120v. The on-board charger is completely unable to deal with the tiny amounts of power you would be able to generate from a portable solar panel. You'd have to do a custom charger connected to the battery directly to have any prayer of getting your few miles of charging. It's a complete non-starter, which is why no one has done it.

 

[dstjohn99]

So you would need a minimum of 720 watts AFTER conversion available to the car (so only when sun is high, like 1am to 1pm, or maybe 2 kW of panels so it works most of the day), inverter to convert to 120 VAC, then provide the signal telling the car how much power is available. So at least 3 but probably 6 350 watt panels. I don't think 350 watt panels are flexible yet, and they still cover near 20 square feet each? At least that's how I see it.

 

[AgingHippie]

So you would need a minimum of 720 watts AFTER conversion available to the car (so only when sun is high, like 1am to 1pm, or maybe 2 kW of panels so it works most of the day), inverter to convert to 120 VAC, then provide the signal telling the car how much power is available. So at least 3 but probably 6 350 watt panels. I don't think 350 watt panels are flexible yet, and they still cover near 20 square feet each? At least that's how I see it.

I have 350's on my roof, they're 6x9 cells so almost door sized, and weigh 55 pounds each. Of course, not flexible at all. I don't understand why we have to convert to AC, is the J1772 connector not DC?

720w would be a 2x4 array of 90 watt panels (or a 4x9 array of 20w, or 2x9 array of 40w, whatever) mounted in a canvas frame, lying partly over the roof, partly over the windshield, partly over the hood. This would actually charge at half the rate of the pathetic L1 charger that it comes with, but you're saying it would charge. A 720w inverter (do we need one?) could be mounted at the back end of the array, protecting its ventilation and the car's paint job at the same time could be difficult, and it would need to be the smallest, lightest inverter available.

I wonder how hard it is to contact Elon Musk? Better hurry before he goes to jail...

 

[TonyWilliams]

Again, I think the considerable cost and cumbersome size of this project FAR outweigh any benefit. Maybe for wilderness camping?

J1772 is AC powered in the RAV4 EV. You need 120 volts AC 50-60hz (plus or minus 10%), or 208-240 volts. The RAV4 can actually handle 277 volt AC (one phase of 480 volt three phase).

Even if you had JdeMO on the car (to use DC power), we have it programmed to stop charging at 15 amps or below.

 

[davewill]

... I don't understand why we have to convert to AC, is the J1772 connector not DC?
...

Correct, the J1772 connection is AC. Even if it were DC, you would then need a DC to DC converter that could output the actual voltage range the car's battery needs to charge. You're talking about a complex project no matter how you go at it...for a very marginal utility.

The easiest way to do it would be to use a separate battery charged by the solar panels, something you could probably buy off the shelf. It could charge all day at your campsite. Then when you park the car, you could charge from that battery. Really, the whole idea is pretty hopeless.

 

[AgingHippie]

... I don't understand why we have to convert to AC, is the J1772 connector not DC?
...

Correct, the J1772 connection is AC. Even if it were DC, you would then need a DC to DC converter that could output the actual voltage range the car's battery needs to charge. You're talking about a complex project no matter how you go at it...for a very marginal utility.

The easiest way to do it would be to use a separate battery charged by the solar panels, something you could probably buy off the shelf. It could charge all day at your campsite. Then when you park the car, you could charge from that battery. Really, the whole idea is pretty hopeless.

Precisely, useful for camping. Also useful if you are just a mile or two short of range and there's no charger anywhere (like if you ignore your GOM, like everyone here says to do). Or, if you just want to shade the car, and it would be nice to get a mile or two of range at the same time. Or if society collapses and there's no electricity anymore.

I don't think it's quite as far off as everyone seems to think it is. It's just a bigger version of the portable solar phone charger I already have, with an inverter and a J1772 instead of a micro USB. If you used 4x9 80w panels, that would give you a max output equal to 2x the charging cable the car comes with, and average output probably around half to 3/4 of that. One problem might be that momentary cloud cover could cause a signal that would stop the charging. It looks like smaller panels are about a buck a watt, so an array like this would be about $2880, plus heavy waterproof canvas, a 1500w inverter, parts, labor, etc, right now this would retail for about $4K, a prototype would cost about $5K to cobble together. But prices on solar panels are still dropping, and the weight/output ratio is improving, so in a couple of years this might be practical.

 

[davewill]

... It looks like smaller panels are about a buck a watt, so an array like this would be about $2880, plus heavy waterproof canvas, a 1500w inverter, parts, labor, etc, right now this would retail for about $4K, a prototype would cost about $5K to cobble together. But prices on solar panels are still dropping, and the weight/output ratio is improving, so in a couple of years this might be practical.

I would say the prototype would cost you more like $10-12K (and maybe much, much more) as you have custom electronics to build and software to write. There are going to be dicey interactions with how fast the car can dial down current draw when solar output drops...which is why you may have to have an external battery (HEAVY!) as a buffer. Do you really think anyone going to pay $4K for something like this when even one hour at a real charging station would net many more miles? It's not like electricity is rare, even when camping, and this thing is going to be awkward to store and deploy, at best

 

[AgingHippie]

I would say the prototype would cost you more like $10-12K (and maybe much, much more) as you have custom electronics to build and software to write. There are going to be dicey interactions with how fast the car can dial down current draw when solar output drops...which is why you may have to have an external battery (HEAVY!) as a buffer. Do you really think anyone going to pay $4K for something like this when even one hour at a real charging station would net many more miles? It's not like electricity is rare, even when camping, and this thing is going to be awkward to store and deploy, at best

Well, I think your inflated estimate is just naysaying, but even at my estimate, it's far too high to be a marketable product, and flexible solar panels need reduction in weight and cost for it to be workable as well. And current battery/inverter technology would make either the weight or cost of those impractical also.

Alternative idea: "branch" the J1772 connector, and put another one on the inside of the car opposite the external one (specific to the RAV, of course, others don't always have the port where the gas cap would have been). Now, if you don't have quite enough range, or you aren't sure if you do, you can bring along a big Yeti battery or two (or keep them at the destination), and charge the car while it's parked, without unlocking the car or providing thieves any opportunity to steal anything. This idea sounds to me like it could be done for less than a thousand (depending on how difficult it is to extend wiring without changing its resistance or carrying capacity), plus the cost of batteries and a short J1772 cable.

 

[slorav4]

Current Technology and Market provide this

https://www.goalzero.com/shop/kits/goal-zero-yeti-3000-lithium-power-station-boulder-200-briefcase-solar-kit/
& this to offset the weight
https://www.andysautosport.com/carbon_fiber_hoods/toyota_rav_4.html

Just a JdeMO to access the regenerative brakes DC Charging system is going to cost as much, need custom programming & still need to sort out the panels issue.
Maybe one of the EV manufacturers will include a DC trickle plug at some point, but right now all the research $$$ is headed to faster charging. Solar is just too slow except for fixed charging stations to recharge their own batteries along with 208V like the ones going to the California Rest Stops.

 

[asavage]

The solar phone charger has an easy conversion to do: The panels output DC and the phone charges via DC. The panels output DC at a higher voltage than the the 5V the phone needs; converting a higher voltage DC to lower voltage is relatively easy & cheap.

OTOH, J1772 charging requires AC, and AC at a much higher voltage than the panels provide. So the panel output has to be converted to AC and the voltage raised. That's expensive and inefficient.

The other route, charging the RAV4EV's battery via DC directly (let's say, via a JDemo-like connection; the RAV4EV's pack runs at around 386v, and to get electrons to flow the charging voltage has to be higher than that) poses a similar problem: the panels' output is DC (guess: 24-96v) but much too low voltage (need ~400v). A DC-DC step-up converter is needed. Also expensive and inefficient.

If your portable solar array was massive and could potentially output 400v DC, the problems to be solved would be different and simpler. But now you're talking about something like twenty panels.

As others have said, not practical today. Charging one, two, or four 12v batteries via portable solar is child's play today, but not the traction battery pack.

 

[AgingHippie]

Current Technology and Market provide this

https://www.goalzero.com/shop/kits/goal-zero-yeti-3000-lithium-power-station-boulder-200-briefcase-solar-kit/
& this to offset the weight
https://www.andysautosport.com/carbon_fiber_hoods/toyota_rav_4.html

Just a JdeMO to access the regenerative brakes DC Charging system is going to cost as much, need custom programming & still need to sort out the panels issue.
Maybe one of the EV manufacturers will include a DC trickle plug at some point, but right now all the research $$$ is headed to faster charging. Solar is just too slow except for fixed charging stations to recharge their own batteries along with 208V like the ones going to the California Rest Stops.

Thanks for info - did not know there were chargers at rest stops here, will have to look up which ones. Range and charging speed of the RAV without a JDemo make it impractical to drive SD->SF or SD->LV, but with a charge along the way SD->LA or SD->TJ might be doable.

I notice the Yetis are lighter than I thought, although manhandling one in and out of the hatch would still be a chore. Problem is, with the only J1772 on the outside, when you got where you were going and hooked it up you'd come out 2 hours later to find it missing. And it's only 120@12A.

 

[davewill]

...

I notice the Yetis are lighter than I thought, although manhandling one in and out of the hatch would still be a chore. Problem is, with the only J1772 on the outside, when you got where you were going and hooked it up you'd come out 2 hours later to find it missing. And it's only 120@12A.

Not to mention that it takes 16-25 hours to charge one, for which effort you'd be lucky to get 1kWh (3 miles) worth of charge into the RAV's battery after overhead and conversion losses.

Besides, it's not THAT hard to find a plug if you really need one.