DIY solar setup?

Xeno, I have already tried it and the CCID (Charging Circuit Interrupting Device) doesn't like anything but house power. The Toyota manuals also forbid the use of anything but house power. They specifically mention homemade power systems or something like that. I tried solar before I read some of the manuals. The CCID gave an audible alarm and flashed. It did charge for about a few seconds. I believe the amps were too high but I have decided not to try it again because I don't want to damage my car! Once you find someone who has already used solar successfully for a while it might be worth trying. Even then I wouldn't do it without Toyota giving their blessing. My mobile solar setups are used for powering my tools to work on housing repairs vice having house power turned on, which can be expensive.

 

Update: I purchased a new inverter. Tested it for purity of sine wave on an oscilloscope etc. and I was able to charge my car for 2 minutes without any issues except for running out of battery power. The sine wave was almost perfect but I'm not fully happy with it and I'm working on getting a better pure sine wave inverter. The prime takes up to 1400 watts to recharge. That's like an industrial microwave! I'm still working out the bugs but I think I will be able to fully charge my car off of solar power at home. I'm learning as I go.

 

That's what I am interested too. Off grid solar recharging.
You could put panels on garage roof and take what you can get.
Most conveniently with wireless recharging, but I am not an EE so gotta wait for a leader.

 

[I missed this the first time around. For reference, I'm a retired electrical engineer, with a self-designed & -installed rooftop grid-tied solar PV system, 7kW. Combined with serious conservation upgrades, my home is now a Net Zero Energy home.]

I'm having a difficult time thinking of how this could be done with any reliability without having a fairly big and somewhat expensive system.

The car charger is not designed to trickle along at just the rate of available solar power. The same applies to the common cheap non-PV inverters that you might put between the solar modules and the charger. You will get 'all' or 'nothing', which the great majority of the time means 'nothing'. Except maybe some smoke.

Could you please describe your solar system? Grid-tied or off-grid? How large (E.g. number of PV panels, power each, DC output voltage or cell count)? Serial or parallel? Inverter type? On-site storage or not?

 

Regular, non-engineering people don't understand the complexity of electric power. It is taken for granted. If you are serious about a solar system, contact an engineer and describe what you want to do and have a concept drawn up. That could probably be done for $1000. Engineering a workable solution might cost multiple thousands or tens of thousands of dollars. Don't even think about using Harbor Freight or eBay panels and equipment unless an engineer specifies it.

Typical "hobby" solar power systems are used in a far different manner than what you are trying to achieve. In those systems users find uses for the amount of power generated. The purpose built system, on the other hand, is built to produce enough quality power for a purpose. It can be used for other things, since power is a commodity, of course, but its minimum output is designed to meet an existing need.

 

I'm curious about this too. When I was thinking about it I assumed the minimum requirements for the system would be to consistently output over 8 amps (if you set the prime's charge current to 8 amps instead of 12) with a good sign wave. When I looked at batteries that could achieve this output things got large and expensive. And then the panels for charging the batteries...

It would be great if there were some other way.

 

One of the characteristics of electrical power is effective loss. While the total energy is not lost, the usable energy is, and the loss is in the form of heat. At every step of the way power must be derated. There are losses in generation, transmission, distribution, conditioning, storage, transformation, etc.

With solar there are huge inefficiencies based on the technology currently available, plus weather variation, seasonal and daily sun angle variation, and ambient temperature. Losses and inefficiencies result in added cost and enlarged physical size. I think you are looking at approximately the cost of a base model Prius for a suitable solar charging system for a BEV or PHEV.

 

Obviously the solar Prime does this, we just need Toyota to supply us a solar Prime without the solar panel roof, and give us a socket to tie one in from home. I wonder what that would shave off the price? Probably not enough.

 

Someone ought to look up Toyota's technical manuals for this, to see the wiring diagram and parts needed. Can these be installed in the U.S. version as a hack? Without compromising the HV safety protections and disconnects?

Those windowsill chargers provide 12V charging though old-fashioned cigarette lighters that stay live when the ignition is completely off. That doesn't do squat for your HV battery. On top of that, Prius and most modern cars disconnect the lighter sockets to help prevent dead 12V batteries from modern higher powered accessories (such as those electric coolers), so it won't charge you 12V battery either.

Your car charger is meant to throttle power based only on what should be going into the HV battery, not based on how little power may be available from the wall socket. It assumes that it will always have a full 15 amps available from the wall (or maybe 8-10 amps on the reduced setting). When your cheap HF inverter can't provide that much -- WHICH WILL HAPPEN AS THE SUNS SETS ON A BIG SOLAR PANEL SYSTEM -- things shut down for self protection, or break, or smoke. If you start with a smaller solar system that can't provide the FULL POWER demanded by the car charger, then you are doomed to failure even at the start.

On top of this, beware that the charger may require a true sine wave inverter. Cheap inverters are 'modified sine wave' type, which means a crummy square- or semi-square wave, not sine wave.

Trickle charging based on available power is possible with the right purpose-designed equipment. See above for the parts built into a real solar Prime in certain foreign markets. The normal wall charger, like nearly all appliances meant to be plugged into ordinary home 120V wall sockets, is not designed for this application, and simply won't do it.

 

Yes somewhere on PriusChat we have the solar Prime general design diagram. The Prime is designed with space for the solar components, which includes an extra NiMH battery. I just assume installing those parts later would cost a lot unless it could be a factory option.

Part of the problem with Prime, as I see it, is Toyota use of a chassis with too many options in mind like the solar option, so that precludes hiding the HV battery better as that space is needed for the solar option and things like the 4WD version

 

That's a good idea. I might note that the solar roof option does not look like it has much value on an individual vehicle level. From a review, "Toyota claims the solar roof can add up to 3.7 miles of electric-driving range per day while parked, and can continue to feed electricity to the battery pack while the car is in motion." Note the words, "up to." The true volume of miles on a given day may be zero.

 

To answer the question from fuzzy1, on Sep 9, 2017
My solar setup is:
GP-PSK-120 120W Portable Folding Solar Kit with 10 Amp Solar Controller by Go Power! (Amazon)
Pure Sine Wave Inverter 3000W Power Inverter 12V to 120V Off Grid LED Display by Reliablepower (ebay)
2 EverStart Maxx Lead Acid Automotive Battery, Group Size 24 with 700 CCA (Walmart)
My other battery bank is 2 Harbor Freight 12 Volt, 35 Amp Hour Universal Batteries

My batteries are in two separate banks that don’t interact. They are connected in parallel with the exact same battery type. It’s a very simple system but I didn’t intend it for recharging my car but powering my tools and appliances to prepare rentals for rent. This is completely off grid and mobile. I use the folding solar panels to charge them while actively using them sometimes. My inverter is definitely the device that makes recharging my car even remotely possible. The pure sine wave inverter I used before was from “PowerTech On” and I have two of them. Since buying an oscilloscope I realize their sine wave is not clean enough and that’s why my CCID had a fit.

Now with all that being said, I think the best way to proceed is by using supercaps or ultracaps to recharge my Prius prime. This video from youtube will give you some idea how powerful they can be and how you can use power directly from the sun to run almost anything:

I did want to combine a larger true deep cycle battery bank with supercaps which would cause the battery power to last longer but it’s more complicated than just using straight super or ultracaps. I think I need to crawl before I can walk. After building my own, I may find that I will need to combine it with a battery bank consisting of 6 or more true deep cycle 6 volt paired (run serial for 12 volts DC then parallel) in order to keep the AC power up for hours in direct sunlight using a larger solar array. If I do build this, I will probably use it for more than just my car. I’d probably run a window A/C unit or heater and cut down on my utility bill.

 

this all sounds too expensive to be practical.

 

PV to pure AC will just get easier and cheaper with time. So will battery storage of that solar or wind power. There's been a consistent 15% drop in prices for all components every single year. It's like a Moore's Law of green energy.

Yes, but that's what a lot of people have been saying about hybrid and EV cars for many years, yet the adoption rate has been rising fast.

 

Yes all of this can get expensive. However, I'm interested in all of this for the same reason I have a prime; I like the technology. I've got some super caps on order. I ordered 6 rows on a protection board x 3. They cost me a little over $100 from eBay. I just plan on doing some experiments and learn. They will take about a month to arrive. I'll post my findings, but it may take some time.

 

thanks for sharing your expertise with us, all the best!

 

I received my supercaps and modified one of my solar setups.

Initial tests were just done under non ideal conditions. The day was very cloudy and the sun was also going down. I also used just one 100 watt 18 volt solar panel. However, results were very encouraging. My three 16.2 volt 500 farad capacitor banks were combined with my battery bank and it lasted over twice as long as my initial tests without capacitors (2 minutes). The controller never let the caps get above 12v, which I may adjust later.

After the inverter shut itself off to protect the battery when it drained to 10 volts, the unit (caps and battery) recharged very quickly. Then I could go for another 5 plus minutes. Clearly I need:

1. More ideal conditions.
2. More solar panels. (Possibly up to 400 watts like Lasersaber)
3. More supercaps (I recently ordered enough to be comparable to Lasersaber)
4. Another 12v battery would be nice. (I may add one if needed but it does add about 20 lbs.)

I know I planned to just use supercaps without the battery but it was too easy to combine them using a solar charger. Today is also very cloudy. I don’t expect to be able to run many tests. A nice thing about this setup is I may be able to be more mobile by taking out the batteries and just using the caps if sustained power is not needed. When it is all said and done I hope to be able to generate sustained power for at least an hour without my inverter shutting off.

Today, I might use a buck boost converter coming from the solar panel to keep the voltage up on this cloudy day. I would add more solar panels but don't have the parts right now.

Note: Lasersaber's SOLN1-2000 should be able to recharge an electric vehicle because it generates 2000 watts and the prime takes 1400 watts. The only question is how long can it sustain the power. Logically, the only thing needed to fully recharge the prime from 0 volts should be a system with sufficient batteries, supercaps, solar panels and sunlight.

 

SUCCESS!!!

I was able to recharge my prime for 43.5 minutes using materials I already had on hand. I also had periods of full sun today. My prime’s lithium pack was at 75% full. I was able to recharge it to 90% from just sunlight.

I used bath battery banks even though they were dissimilar. I know that this is never done but I think I took precautions such as ensured the amps were running only in the direction I desired. In the future I plan to eliminate this secondary battery assist or use diodes. I made the primary bank the one with the high amperage car batteries (700amps). I used the harbor freight batteries as an assist (35ah).

I used two solar arrays which were also dissimilar. Bank one was 2 - 100 watt panels with an MPPT charge controller. Bank 2 had my 120 watt folding panels. The supercaps were in bank one’s setup with the larger solar array since they were going to do most all of the work.

My inverter shows the voltage constantly and the batteries started out full. When I switched it (inverter) on the voltage dropped almost immediately from 13 something down to about 11.9 then went down slowly, 11.8, 11.7 etc. I had the batteries in a vehicle jump configuration. Once I noticed that the secondary array/batteries weren’t dropping at all, I moved the jumper cables to run from the 35ah batteries/120 watt panel setup to the back of the inverter. The secondary PWM array readout then began to drop in voltage slowly also. The voltage was at 13 point something and began to drop just like the 700 amp batteries. What was amazing is that the inverter voltage readout slowed significantly!!! This is what I was hoping for. This simple action caused power to be drawn from both battery banks albeit more from the primary bank which had thicker cables connected. The primary array would get down to very low voltage and because of the supercaps would recharge quickly. That voltage would return to about 10 or 11 volts and then decrease slowly again. However, unlike before, no alarms sounded for 43 minutes because the voltage was being kept up by the other power sources.

I wanted the secondary array to only have jumper cables for several reasons. 1. This would increase the resistance and not allow current/damage to flow back to my 35aH batteries from the 700amp batteries. 2. This allows for a quicker connect/disconnect of the dissimilar circuits. I will note that the red jumper cable did get hot, which is not good. I know that I still have work to do on this setup but for now I’m happy. When the rest of my supercaps and a few other items arrive I’m sure I can recharge my car for longer than 43 minutes. Which is caused by the inverter cutting the power to protect the battery dropping below 9.8 volts. My 35ah batteries never got below 12 point something volts.

I just checked and my car has 40 minutes to a full charge. My batteries have partially recharged since writing this. So, I’ve started the inverter again and reconnected the secondary bank/setup. It couldn’t go as long so I’ll let the batteries fully recharge. Then try to recharge my car again if the sun is still out.

Tomorrow I think I’ll drive to work on all electric. In fact I think I will be more likely to use my car in all electric mode more often since I can see the light at the end of the tunnel.