WeberAuto: 2024 Prius Prime PHEV Low-Voltage Charging System Testing

You also cannot conclude that the professor was wrong at the beginning of the video then. People here have been basking him and his expertise.

 

This is from the Gen 4 NCF. They show a sub DC–DC converter inside the charger in this figure, but then they also say that it is inside the inverter assembly. Go figure. All I can say is that the voltage never goes over about 13.0 V in Gen 4 during traction-battery charger. In the video for Gen 5, there is clearly no 14.1 V output on the charger.

 

Yeah. thanks for the idea. Much less clutter now after blocking them.

 

Here is the Gen 4 video. There seems to be indeed a ~ 13.0–14.0 V DC output from the charger (a sub DC–DC converter inside the charger) in Gen 4. However, in my observations, the 12-V battery stays at a float voltage of about 13.0 V during traction-battery charging in Gen 4—enough to keep the system running but not enough to charge the 12-V battery. Therefore, the current capability of this output is very low.

So, the elimination of this sub DC–DC converter in Gen 5 is a most welcome thing, as it does more harm than good in Gen 4 by not charging the 12-V battery during traction-battery charging.

 

At the end, the lack or existence of a small (sub) DC–DC converter in the charger is a moot issue. Toyota is not known to make the best engineering decisions when it comes to electrical systems one way or the other.

The end result is that:

• Gen 4 keeps the 12-V battery at a float voltage of about 13.0 V during traction-battery charging but does not charge it.
• Gen 5 charges the 12-V battery at 14.1 V during traction-battery charging through the (main) DC–DC converter.

Other than that, the behavior of the 12-V-battery-management system (12-V BMS) in Gen 4 and Gen 5 seems to be identical.

 

While these videos are fun to watch as you can see the guts of the system, they have little value in helping understand how the 12-V-battery-management system (12-V-BMS) works.

Get a BM2 Bluetooth battery monitor as some of us have, and you will have a much better understanding of how the 12-V-BMS works. You will be surprised to find out when the BMS charges the battery and when it doesn't. Last but not least, you can connect a battery maintainer before you end up with sulfation if you see that the battery SOC has gone too low.

 

If you ever get a battery monitor or something as simple as a cigarette-lighter voltmeter, which tracks the battery voltage closely, what you will find out is that you are driving the Gen 4 or Gen 5 does not mean that the battery is charging. The voltage will stay at a low float voltage of 12.89 V for most of the time unless the SOC has fallen below 75%. At other times, it will briefly charge at 14.1 V to make up for some of the parasitic drain.

It is good that the Gen 5 PHEV now charges the 12-V battery during traction-battery charging, which doesn’t happen in Gen 4, which is apparently because in Gen 4, only a low-current “sub” DC–DC converter turns on during traction-battery charging. Also, reportedly, both Gen 4 and Gen 5 charge aggressively when it is very cold, which I cannot see in the warmer Southern California. However, these will still not change the fact that the 12-V battery is not charged for most of the time when you are driving the Gen 4 or Gen 5.

So, don’t expect your 12-V-battery SOC to hover close to 100% as in your grandfather’s car. The Gen 4 and Gen 5 BMS does not do that. You will be lucky if it does not fall below 75%. Occasional use of a battery maintainer such as Noco Genius to bring the SOC to 100% to reduce sulfation is a good idea.

 

If this can help: when I park my car in the box, and I want to plug it, I need to lock it, so that the mirrors fold and there is room to move around: then i need to unlock it in order for the plug door to unlock. So what happens is that i lock -> reach for the plug -> unlock -> plug -> lock again. So I have the mirrors folding twice, first with the car unplugged and then with the car plugged and charging. The noise of the mirror motor is quite different in the two cases, suggesting a different input voltage.

 

sorry my bad english may have made my message misleading: I'm not annoyed by such fold/unfold behavior: I described my experience since it seems to support the idea that the whole 12V systems (which feeds the mirrors motors) is stepped upa bit while charging from AC.

 

It was very clear to me what you said.

 

No worries.
Your English is MUCH better than my (non-existent) Italian.