Possible to buy a Prime with the Solar Charging Roof?

edit - I thought I found 8 within 500 miles, but I see now there's something wrong with the search function. It's returning results for cars it shouldn't be. I'm going to do a little playing around to see if I can trick it into giving correct results.


edit2: Okay, there's a weird bug in the Search Inventory software that shows you the wrong results if you select both Adv Tech and Solar Roof. So just choose Solar Roof. It looks like the vast majority of cars that have the Solar Roof option also are XSE+ with the Adv Tech Package.

There's only 5 within 250 miles of you that are not sale pending, but if you expand to 500 miles that number becomes 33.

Toyota Inventory | New Toyota Inventory Search

 

From my browser history:

https://www.puentehillstoyota.com/auto/new-2025-toyota-priusplug-inhybrid-city-of-industry-ca/106354045/

Details/installed options/ Solar Charging Roof

 

I’m assuming the Solar Roof also trickle charges or maintain the small 12v Battery if the car sits idle for days or weeks on end without plugging in.

If it prevents a dead 12v battery then it might be a good option for some.

 

I wouldn't assume that. I think it's for charging the hybrid battery.

But it would be much more useful for that purpose.

 

Typically when the Drive Battery on a PHEV (Prime) Prius charges, it does the same to the 12v battery.

You are right, never assume.

A good way to know for sure is to measure the 12v battery on a Solar Roof equipped Prius in the sun and compare difference in measured value to in the shade.

I don’t have access to Solar Roof equipped Prius, Maybe someone who does can determine if it’s is so.

 

It wouldn't help you if your battery went flat while your car was parked inside. If I didn't know better, I'd say Toyota has contrived to drive the customer to the dealers with this 12V battery nonsense.

 

It probably does not charge the 12-V battery; however, it keeps it from discharging, that is it keeps at a float voltage.

You need at least about 14.0 V to charge the 12-V battery. Gen 4 sub DC–DC converter in the AC charger produces about 13.0 V during AC charging, which keeps the 12-V battery at float and prevents discharging it but doesn’t charge it.

Gen 5 does not have a sub DC–DC converter in the AC charger but turns on the main DC–DC converter in the inverter and keeps at 14.1 V, which charges the 12-V battery during AC charging.

My guess is that during solar charging, the main DC–DC converter does not turn on but there is a sub DC–DC converter in the solar charger that keeps the 12-V battery at float but doesn’t charge it.

If someone has a solar Prius PHEV, this is easy to find out, as all you need to do is to measure the 12-V-battery voltage during solar charging: 14.1 V = charge, 13.0 V = float.

 

I haven't found any evidence that the solar roof charges the 12V battery. That means the 12V battery can drop in voltage to a level that disables the car, which will not start without a boost or a service call.

 

Gokhan in #27 outlined what a person could do to find evidence, but it seems no one has done so yet.

The factory solar roof in gen 3 didn't charge the 12 volt battery, but I'm one of several owners who have modded it so it does, and I've been very pleased with that mod.

If the one in the Prime doesn't do that already, it would probably be easy to mod in a similar way, given it has about three times the panel capacity that gen 3 had.

 

It is a 99% chance that the solar charger only keeps the 12-V battery at float (13.0 V), preventing draining of it but not charging it. Charging the 12-V battery would require up to 40 W (14 V × 3 A = 42 W) or so and substantially reduce the traction-battery charging power; so, it’s very unlikely for the Toyota engineers to output 14.0 V. In any case, it needs to be verified with a voltmeter on the 12-V battery during solar charging.

 

I'm not sure about 99%—I also would not be surprised if it does nothing at all for the 12V, as Paul suspects.

But I agree that measuring the voltage, or reading about it in the New Car Features manual, would be the two ways of finding out.

Toyota Service Information and Where To Find It | PriusChat

 

It's not up to chance how it works.

 

Doesn't look like anyone ever suggested it was—not even Gokhan, whose "99% chance" above could be misinterpreted that way, but the misinterpretation would have to be awfully willful.

 

You can't charge the traction battery without turning on the 12-V system. If the solar charger didn't supply power to the 12-V system, the 12-V battery would certainly drain and die as a result. It would be like letting the headlights and radio run for a long time in the ACC mode.

So, the solar charger will keep the 12-V battery at least around 12.9 V to float and prevent draining it, as the 12-V system will be on. This is exactly what the Gen 4 charger does during AC charging, as there is a 12-V output on it. (Gen 5 turns on the main DC converter, as the charger has no 12-V output.) I gave it a 1% chance that the solar charger would actually charge the 12-V battery, which requires 14.0 V and about 40 W. If you like, you can say a 10% chance. Do you know that Gen 4/Gen 5 doesn't even charge the 12-V battery while the car is being driven (for more than 90% of the time) in order to save fuel (only keeps it at a 12.89-V float to save fuel)? It would make little sense for it to charge it during solar charging. But it must certainly keep it at float as I explained. As we agreed, a battery monitor or voltmeter would put the bottom line on it.

 

I don't see how the solar charging system would need to drain the 12V system. The solar panel likely feeds into the hybrid battery charging system directly. It wouldn't be efficient engineering to do otherwise.

 

The gen4 solar system supplied energy to the 12V circuit while the car was in Ready. I would be surprised if none of the panel output went to the 12V circuit during charging. That circuit powers the monitoring electronics. That doesn't mean it can charge up a weak 12V though. The system priority for output would be to the traction battery; any charge going to the 12V battery is just in support of that.

 

Just my 2-cents; the reason for 12V DC-DC converter activation on a gen4 is to ensure traction battery cooling fan operations during charging - The 12V battery receiving a change at the same time is simply a by-product of that.
I understand the gen5 has switched to Freon heating/cooling - so "all bets are off". Though most solar array controllers do have a 12VDC output port; if that's the way Toyota decided to do it.

Again, Just my 2-cents....

 

The 12V circuit and battery gets power while the battery charging to power the computers monitoring and controlling everything, regardless of cooling source.

 

None of which describes maintaining the charge level of the 12V battery with the solar roof.

 

IMHO; the car's multiple ECU systems DO NOT draw enough power to warrant a 12V DC-DC converter 'wake-up'/activation. That's why the automotive battery is there and why random self-diagnostic is running off of the 12V battery ALONE.

Again, Just my 2-cents....

FWIW; modern computer chips usually run on 3-5VDC, the 12VDC line is for the disk drives and fans. If you ever built PCs, that's how the power supplies are laid out. I believe the old 8080 8-bit microprocessors required five volts.