Question-2025 Prius in EV Mode: Reply quickly!

Someone put the Toyota techinfo repair guide into a PDF here.

Got evidence or just supposition? What prevents the car from combining and balancing the solar and DC-DC inputs?

 

You made your first comment without any knowledge, and now, you are doubling down on it.

It is simple EE. The main DC–DC converter runs at 14.1 V or higher when Gen 5 is plugged in. If the auxiliary DC–DC converter in the Gen 4 charger is an example, the solar charger auxiliary DC–DC converter only generates a float voltage around 13.0 V. Besides, they are not going to go through great lengths to design an “electronic power-split device” to splice them together. I have never seen two power supplies connected in parallel.

 

I'm a bit confused by your logic of not charging at work, I get that you like the idea of only having to charge once and using solar power to help make the round trip without having to plug in, but I would reverse how you are doing it and charge at work and try to make it home and back to work without having to charge at home, that way you are maximizing your post tax income and shifting the burden of the cost of charging to your work, giving you a slight added benefit to your work life.

 

Correct. The solar-charger computer likely turns off the solar charger entirely when the car is plugged in. As I replied to @Trollbait above, you simply don’t connect two power supplies in parallel, especially if they are running at different voltages, without going to great lengths to design complicated electronics. Last but not least, there is no need for solar power when the car is plugged in, as there is no vehicle-to-home (V2H) in Gen 5.

However, this could likely change in Gen 6, as the car will feature vehicle-to-home (V2H) as the Gen 6 RAV4 PHEV does. In that case, you can use solar energy to help power your home.

New (Gen 6) RAV4 makes world premiere in Japan | Toyota | Global newsroom | Toyota Motor Corporation official global website

 

Then how does the gen4 solar roof help power the 12V circuit while the car is running?

 

In Gen 3, ity only powered the blower fan using a relay circuit. We need to find the drawings for Gen 4 and Gen 5. For Gen 5, they would be in the new-car features (NCF) manual on Toyota Tech Info, as the system is available in the US models.

Solar Roof Schematic? | PriusChat

 

After reading Toyota’s comment that the solar charger “supplies the auxiliary battery system when driving,” it sounds like they may have included a 12-V power-switch device that switches between the solar charger and DC–DC converter while the car is being driven, with the switch being made according to the solar output, system load, and DC–DC converter voltage.

When someone installs a 12-V-battery monitor in a solar Gen 5 Prius PHEV, we can get a better insight on this, as we will see how the voltage behaves in different scenarios.

 

I also don't know how they chose to do it, but if it were me I might just match the panel output to the 12-volt bus voltage with a buck/boost converter and let it contribute however many amps it's going to, and call it good.

 

Well, the main DC–DC converter voltage varies between 12.86–14.4 V according to the computer that controls it. I am guessing the solar-charger auxiliary DC–DC converter runs around 13.0 V to keep the 12-V battery at float.

Again, a battery monitor would be most helpful to see how the system behaves under different solar-operation scenarios.

 

I'm just thinking about keeping component count and complexity down. In no other Prius is the 12-volt battery isolated from the rest of the 12-volt bus and treated somehow differently. There aren't relays clicking it in and out of the circuit. The voltage the DC/DC converter puts onto the 12-volt bus overall is chosen according to the ECU's idea of how much charging the battery needs.

For that matter, a statement that the panel supplies the auxiliary battery system while driving could be true simply by dumping the power into the HV system ... which is already powering the DC/DC converter while driving, so the panel's contribution is included.

What happens while the car is OFF may be where more cleverness lies.

 

I thought about, too. Perhaps there isn’t even a sub DC–DC converter and the solar charger only charges/powers the high-voltage battery and the main DC–DC converter turns on during solar charging (and driving) to power the 12-V system, with that way the solar charger indirectly contributing to the power. And when the car is plugged in, the solar charger turns off in order to prevent interference with the A/C charger. That could be the easiest way to implement it.

Again, a 12-V battery monitor would give us concrete numbers during various solar operations.