I have a 2012 HyCam with 121k KM. Over the past month I've begun to notice my SOC dropping below 39% ocassionally. It might have been happening before but maybe I wasn't paying as much attention. I've noticed it most often at startup if the engine is still in stage S1A/B warmup and I was already at a low SoC from the previous trip. If I start driving immediately it'll dip below 39% until S2 when the engine starts charging it back up especially if the AC is on. Here's an example when I was coming out of a supermarket parking lot. the first couple mins were on battery because we were going very slowly till we got to the gate. It's still a bit surprising though because the engine should still have been warm from our trip to get there. Unfortunately I have no way of knowing what state the system was in. But the engine was relatively warm I think: However , the same day, I saw it happen after an 15 min drive down a steep mountain road. I purposely engaged B mode to reduce the amount going into the battery and keep the temperature low but by the base of the hill I still hit 45C. From there I ran into slower moving traffic and was coasting along from 15-30kph which used some of the extra charge available. Unfortunately it seems the decreased Charge Current Limit due to the 45C temp severely limited the amount of charge the battery would take when SoC reached 39% and the engine turned on. The AC was still running too : As you can see it eventually came back up but it spent about 2 minutes under 39%. I know the system is designed to keep SoC betwen 40-80% for battery durability. Should I be concerned about these dips? Now that I'm paying attention I'm seeing them happen at least once a day. In nearly all cases the AC is on but it's summer here so that's a necessity, esp to keep the battery cool.
it's probably normal, but hard to know without historical data. how long have you been monitoring? no doubt the batteries have to have some degradation, especially in warm climes, but unlikely to be more than an ocd issue.
You may be right. I've been monitoring it for a couple months now. I've been hyper-vigilant recently because I've come to realise that we don't have anywhere near the necessary infrastructure to support hybrids locally and the local Toyota dealer is selling new batteries @ 5 times the rate in the US. On top of that they've stated that once it's a Hybrid , they're refusing to even look at the car, even for something unrelated to the hybrid system. I also personally know 2 HyCam's with failed or failing batteries. This is my first hybrid so I'm using this to figure out what's "normal" with an eye to helping out/advising fellow owners locally.
I think I may have talked to you via email about the batteries. No? As for the dropping of the SOC it is normal for an old battery or hot battery and you probably have both being in Jamaica! The car does its best to keep it higher than that, but in reality it could go to 10% or lower without much effect. This is basically the "out of gas" reserve range of the car anyways. It will let you drive down to that low amount. Enough for the engine to try and start a few times after that. In an ideal world with an ideal battery you'd never see those numbers. I don't think there has ever been enough data to pick out these data points and say "that battery is x months away from complete failure". My guess is it just happens sometimes. The Prius calculations are pretty rough and laggy and when the battery gets weak it will fluctuate more. I may have to check it out next time I am down there.
I'm pretty sure my 2018 will run around 50% SOC all the time while on cruise. The SOC tends to be higher while manually using the gas pedal. The lowest the SOC ever seems to be is when it is coming off of an already low SOC from the last time it was driven. There is that spot in the warm up when the engine is running but the system mostly (maybe entirely) uses the battery for propulsion and that can result in an under 50% SOC. This seems to happen most often after a great MPG run that uses a lot of EV at the end of the trip. You get great MPG one day but you pay for it the next trip.
