Featured Prius Prime Drain

0% loss on the dash SOC display, if you are talking about traction battery. I have parked my car for a week at a time but did not change the SOC level. I have been keeping my traction battery SOC at a 35-45% level lately with a prolonged period undriven during COVID-19 stay home.

If you are talking about 12v battery. That's a different story. I am testing the self-discharge on almost brand new PRIME 12v battery. It seems to lose ~0.1v/day. So, from a full 100% 2.7v, it will be about ~2.0v or 50% in one week.

 

That's a good point. I don't know which for sure. Surely, if I put the car into Ready mode and start driving EV, the SOC does decrease immediately. Even without driving, if the HVAC is on, it will drain the SOC very quickly. But, I think the phantom drain of the traction battery is pretty small even if it exist at least in my experience with 2017 PRIME. With the Hybrid Assistant reading of SOC, I don't think I saw any decrease in SOC after overnight (~14 hours) parking. The Hybrid Assistant reads the SOC to 0.01%.

 

Mine was electrically isolated so any loss of traction battery SOC was normal, self-discharge.

Bob Wilson

 

Prime battery can't ignore physics/chemistry so yes it does lose SOC over time; it's just a matter of how much.

That's my experience with other PHEV's and even the Prius HEV can sometimes lose a bar or two overnight. Another example why they are called guess o' meters.

 

What I am saying is that SOC on the dash decrease after car starts using charge, but not before. I certainly have not seen any substantial phantom loss of SOC on my PRIME so far. I will try to check the SOC before and after during week of parking using Hybrid Assistant to make sure what I am seeing is the actual State of Charge. I am now driving only once a week.

 

Yup, a limitation of the Toyota/manufacturer software. IOW, you can't see monitor vampire drain, etc.

 

Guess-O-Meter is correct. I've been using the Spark while the sequester is going on 'cause I know the Volt ICE will start up as soon as I hit the button. Last night, when I pulled it into the driveway, there were 10 miles left on the Spark GOM. This morning, there are now 12 miles on the GOM.

This thread reminded me that it's time for 12V battery maintenance and to charge them up.

 

12v battery discharge seems to be mighty common in the last year or so. Rav4 hybrid and ICE in 2020, Honda CRV, and now Prime reporting parasitic looking drain. Did they make some change in battery chemistry or is some common electronic part and its firmware doing it? Toyota doesn't seem to know or care.

 

I drove my 2020 PRIME yesterday after sitting for 1 week. I used up the traction battery on this run and replenished the traction battery to 43% SOC. I do not want the car to sit full SOC or empty SOC for the whole week. After the charge, I did read the real SOC with HA. It is now at 48.24% SOC (which is 43% on the dash). The car is going to sit for 1 week, until next Sat. I will report if there is any traction battery drain by then.

 

When the car is just sitting the HV battery pack is not connected to anything.
The HV contactor is open until boot up. There is no electrical drain.

But there is a very, very slight 'self-discharge' that Li-Ion batteries have, but less than any other battery chemistry.

 

Yes, that's what I referring too in this instance. So many threads by folks who notice the discrepancy in SOC from shutdown to next startup that it could be labeled a hybrid FAQ. I've "lost" up to 3 miles on my Energi from lunch to 5pm during extreme hot weather.

 

Li-ion 'Self Discharge' would not be anywhere what is stated above. It is measured in months of storage.

I suspect that the 'SOC displayed' might be effected by ambient temp and will change with outside conditions,
similar to how the 'GOM range' is calculated.

 

Temperature definitely seems to be a factor. I don't think it's the car's measurement of temperature, but the effect of temperature on the voltage of the battery. I've seen the Hybrid Assistant SOC go up as much as 3-4% a couple times after parking overnight. I've always noticed it when the EV range was depleted before parking, but it might happen other times too and I just haven't noticed.

 

Yap, I have seen the SOC slightly higher than day before when I parked, but I can't remember the temperature relationship.

 

Usually everything is colder the next morning.

Also, the only time I saw the SOC indicated by the car change significantly was, after a short drive in the morning (cool battery) I had 97% remaining, but then when I left in the afternoon and the car had been sitting in the sun all day, the car showed 93% remaining. It's possible that it didn't drop until I started rolling, I can't remember, but if so it was down to 93% before I left my neighborhood.

 

So, here is after 1 full week after a partial charge (up to 43%).

SOC on the dash on 4/25 after partial charge: 43%
SOC on the dash on 5/2 after the start and waiting for ~30sec at park: 44%

Yes, it went up 1%, but I think this is just within a margin of error on the SOC display.

I also took HA reading right after the partial charge was finished, and right before driving the car.

SOC by HA on the dash on 4/25 after partial charge: 48.24%
SOC by HA on the dash on 5/2 after the start and waiting for ~30sec at park: 45.49%

So, with HA reading, 1 week of just being parked (no opening door or fob near the car) drained 2.75% of SOC.

 

I bet if you went for a short drive the SOC on the dash would drop faster than expected to catch up to the real change in SOC. It would be hard to notice 3%, but maybe do a 1 mile loop around your neighborhood, and then do the same thing immediately after charging.