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

The disconnect between battery and the rest of the car when shut down was a safety precaution for hybrids. Plus, it could have helped with the NiMH standby discharging. Good to continue the precaution with plug ins, though i don't know of any hard rules that says charging is the same as shut down for this.

Toyota could have always used the main DC-DC converter during charging; I believe others do. I'm guessing they didn't want to muck too much in the hybrid software. The behavior seen here could the result of updating the software after field data showed their initial approach wasn't keeping 12Vs charged.

 

In the youtube comments, Professor Kelly said there is a "software update to address the 12V battery drain". Perhaps this software update has already been mentioned in this forum .

 

Yes it has. Only applies to Primes.

 

is there any way to check if my software is updated?

 

It's been linked already:

Gen 5 Low Voltage Charging System YouTube Video | PriusChat

 

Same question. Is there any way to check if my software is updated ?

 

This was already posted elsewhere. There is not much info in the video than we already didn’t know.

Gen 5 Low Voltage Charging System YouTube Video | PriusChat

 

There is no DC–DC converter in the charger. The charger is an AC–DC adapter—120/240 V AC input, high-voltage DC output. There seems to be also a DC–AC inverter in it to supply the 120 V AC sockets from the high-voltage battery.

Yes, the DC–DC converter, which converts high voltage DC to 12.89–14.4 V DC, turns on both in Gen 4 and Gen 5 during active charging and turns off when the traction battery reaches 100% SOC. The difference between Gen 4 and Gen 5 is that in Gen 4, the voltage is kept at a float voltage (about 13.0 V), whereas in Gen 5, it is about 14.1 V and charges the 12-V battery.

As for the causes of the 12-V-battery problems, the main cause is the miserly battery-management system (BMS), which likes to keep the 12-V battery at a lower SOC (~75%) most of the time. An AGM-battery upgrade seems to somewhat help, as it charges faster. Other than that, the best thing you could do is to occasionally hook up a battery maintainer to bring the SOC to 100% to reduce sulfation. It is not mention that if you don’t drive the car every few days for at least one hour each time, the parasitic drain will keep lowering the SOC and add to the sulfation.

 

Good idea. Perhaps @Tideland Prius can clean this up (and then delete my post?).

 

I think the professor is mistaken. I don’t think there is a “sub DC–DC converter” in the AC–DC charger. I do not see any such wiring in his video.

As far as I know, there is only one DC–DC converter, and there is only one 12-V system. There is not a second 12-V system or a second DC–DC converter. Again, I think the professor was mistaken. The DC–DC converter also turns on in Gen 4 during AC charging, but the voltage stays around 13.0 V (float voltage) instead of 14.1 (charge voltage) as I explained.

The AC–DC charger also seems to have a small DC–AC inverter for the my-room mode. That is all. See the three wirings: 120/240 V AC input, high-voltage DC output (AC–DC adapter), and 120 V AC output (a small DC–AC inverter for the electric outlets). There is no 14.1 V DC output as the professor claimed.

 

Hah, you’re right.

 

Come on, that is a trivial statement saying that the current the DC–DC converter draws comes from the traction battery, which increases the charging time by reducing the total current going into the traction battery. If you are drawing 15 A at 14.1 V, that is about 0.2 kW, which reduces the charging power from 3.5 kW to 3.3 kW, increasing the charging time by about 10%. (Again, there is only one DC–DC converter—no such thing as a sub DC–DC converter as the professor mistakenly claimed.)

@Roy Peterson has done much better experiments than the professor on this. In Gen 5, the DC–DC converter turns on at 14.1 V while the traction battery is charging. It turns off when the charging is complete. It is the same thing in Gen 4, except the voltage is kept at about 13.0 V instead of 14.1 V.

 

If you watched the whole video, the professor corect his statement after his tests.

 

Ah, @KMO, see the very end of the video where he admits he was wrong and there was no such thing as a sub DC–DC converter.

I mean—this is such a trivial observation for us owners with technical knowledge, but I guess even professors can reach silly conclusions by not doing a careful observation. Why so trivial? Because the 12-V charging system works through a battery-management system (BMS), which controls the DC–DC-converter output voltage. It behaves similarly when the car is in the ready mode or the traction battery is charging—controlling the voltage as needed. To add more to the obvious, there was clearly no 14.1 V DC output terminal on the AC charger.

 

i thought perhaps the previous generation has 2 DC-DC converters.