2017 - 2022 Prius Prime - 8.79 kWh Battery and charging system info

I haven't driven it long distance (for the HV battery to be depleted and engine to kick in) since I installed my 12V battery monitor (eight days ago), and in all the drives I did so far with it installed, I didn't see that happening even once. The voltage stayed at at least 14.5V while driving.

 

So my son took the Prime last week while his car was being fixed. He went to the cottage (about 1h30 drive) so the engine kicked in quite alot. This is the voltage graph during that time. The fluctuations were just between 14.47V and 14.54V.



Temperature stayed above freezing for the last few days and with the car plugged in last night, this is the 12V battery voltage graph since plugged in.



The voltage just dropped from 12.59V to 12.51V in that span of 19 hours. I'll leave it unplug tonight and see if there is any difference.

 

I, for one, never saw the video previously, and I totally enjoyed watching it as a 2020 Prius Prime owner.

 

Here's the graph for the car unplugged since yesterday morning and not driven.



At 11:25am, just after that dip (that's when I unplugged it for this test), the voltage climbed to 12.51V. It was down to 12.44 when I took this screenshot this morning. So for a time span of 21 hours, the voltage dropped 0.07V. There are basically no difference between plugged and unplugged that I can see, unless, of course, the battery heater starts, which charges the battery at a voltage of 13.5V.

The voltage drop when the car is just sitting there (plugged or unplugged) seems to follow a linear regression of around 3 to 4 mV per hour. Keep in mind that this device (and my OBD2 adapter) are also drawing current so obviously it's less than that without those devices sucking in power from the battery.

I guess this concludes my test of the 12V battery voltage under different situations.

 

What was the soc tab saying during the 21 hours start to finish? I haven’t used the expanded interval time screen, only the real time short interval. The charging shuts off and on while driving, sometimes steady around 14.5 v a long time, then not, still haven’t figured out why. There is a “charging” icon on the main screen. The monitor drain is insignificant at .0015 amps. If my battery gets to 70% soc, I try to charge it. Haven’t been stuck with car yet. I want the battery to be near 100% all the time like my alternator equipped truck, but not going to happen.

 

The SoC tab shows a flat line



But I don't rely on it as it can be all over the place as shown in these two graphs. It told me the SoC was at 42% but the voltage at that time was still 12.03V.





I've never manually charged my battery since I got the car last July. It has always started fine.

 

Mine would have started fine, got this one last May. It looks like maybe the charging starts at 13 volts as mine does. It should, they are the same only I live where it rarely gets even frost, never freezing so pvc pipes outside break. Couple days ago I was on fast charging, the plastic around the vent gets warm by the back seat. This is when I go up a hill and the charging stops. I think soc is accurate, but I look at the main screen which is short interval. It stops other times as well.
I don’t want my battery hovering at a lower charge, maybe this was not understood. It’s not a dead battery situation. I never bought a new battery for this car. The dealer where I got it did. On the lot they do all sorts of things. With the monitor it should never be a no start situation as I will have known it is low.
I think SOC is accurate, I can watch it climb to 100 on either car. I see no spikes or rapid changes. I see it on manual charging, and it seems perfect.

I’ve never looked at the chart expanded out over days like that. In a short interval I wonder what the 42 % soc shows.

 

Yeah but if you loot at the 24th, the SoC dropped considerably (85% to 60%) while the voltage dropped just 0.17V (12.58V to 12.41V) during that time frame.

 

I looked. I use the home screen. When I went to 5 day I saw something similar to yours on mine last night. Then went to 1 day. Look at that. Awhile back it was posed why 60% soc is 12.68 volts, or something like that. The monitor isn’t just a volt meter that calculates soc based on volts. During charging a 10% soc battery we could see whatever, 13.5-14,5. Volts unrelated to soc. I don’t know how the monitor determines soc. Maybe I can learn something without running to the internet.
Try using the home screen, where it will say “charging” and see if it stays on all the time when in ready mode. Today mine did all the way on my 3 mile trip and back. Went from 66% to 84% charge. Other days it doesn’t. Charging turns off and on at around 13 volts.

 

Ok, I'll give it a try next time the engine runs. Might takes quite some time though now that's warm enough for the heat pump to suffice.

 

I only was using pure ev mode for my observations, not hybrid or ev auto mode. Yesterday was completely opposite, charging turned off and on while making the exact same trip it stayed on the other day. Anyway problem solved for me as to what I can do to avoid a suddenly dead battery in the morning.

 

Ok, I'll check next time I drive the car.

 

I was just curious if the Prime does anything when using Auto Start while being plugged in. But that sometimes need to be figured out by testing near the car for visual and auditory clues and inside the car watching and listening.
Pre-conditioning has always locked doors for me, if they were unlocked. It's one of the easier ways to tell if the ECU is overriding the feature, ( pressing the fob button many times and not getting a response from the car ).

 

Not me. The car would not precondition if the doors were left unlocks, but pressing the A/C button on the FOB will lock them if unlocked. Go figure why they designed it like that.

Same with the A/C FOB not doing anything for the first 10 minutes after leaving the car but will happily turn on A/C as soon as I get back in the car... I have no clue why they designed it like that.

 

I'm not sue I get exactly what you're describing above, I can infer most of it though.

I think that the Prime (at least from what I've seen in mine) that if the ECU calculates that using pre-conditioning will be sufficiently non efficient for electric usage it just disables pre-conditioning completely.

Another weird one I've found is while driving slowly. if coolant temps are above 60 F (15 C) and switch to HV mode the engine stays off, as long as speed is below 20 mph. Where if the coolant temps are below 60 F / 15 C the engine starts up right away when switching the HV mode.

 

It's me now that don't understand what you're staying lol

 

If running pre-conditioning doesn't provide enough benefit to the system / battery.
Like if the battery temps are higher than ambient temps, say, after the car was driven In HV with HVAC set high enough to warm the battery 15 F / 10 C above ambient . Using pre-conditioning might actually lower the battery temp instead of heating it.
Obviously, (to me anyways) that is for a cold weather scenario.
For battery cooling in the summer an opposite scenario might apply, although I don't get enough of those to have tested that.

 

Ah ok, I see what I mean now. But what I can schedule is the charge end time and if I want the cabin to be preconditionned too. It's not hot enough in the morning to justify the A/C to be on but last fall, when I tried it, it would preheat the cabin for exactly 10 minutes if and only if the car is locked. Forgot to lock it? No preheating for you!

 

Ah, I don't ever notice if I get cabin heat from pre-conditioning, So many owners complained about pre-conditioning not heating the cabin and calling it useless back in 2017 I just couldn't understand what they expected from the silly pump. I was more interested in understanding what other things the pre-conditioning feature was doing to prepare the car besides make it comfortable for me to drive it. Beside, if I want the car to feel like it's summertime when I get in the car in the winter, I've already got a way to do that. And only one other member from Saskatchewan did a similar thing, that I remember.
My main objective was to keep the battery warmer than just the battery heaters would..
So I don't usually have HVAC set to ON, before I actually need it.

 

What way? Because after 10 minutes when it's below freezing (but above -10°C), indeed, not much heat can be felt once inside the car. It's a good thing the steering wheel heater heats up fast. Although I would have liked the top of the wheel to be heated too, not just around the spokes.