Low Battery engine behaviour

That's normal. If you press the brake, the engine revs down... as long as you are moving. If you aren't moving it's the same as if you don't have your foot on the brake.

 

It can be normal...if I start the car cold with a low-ish battery to begin with, and I just take off, the battery drains down to 2 bars pretty quick. (Don't worry, 2 bars does not mean less than 25% charge, it's actually a bit more than 25%...) Anyway, the engine kicks in to keep the battery from going below 2 bars, but that also means your fuel economy goes down a bit.

I usually try to pull in for the night with 5-6 bars.

 

Sounds perfectly normal from a Prius hatchback point of view.

Most of the car's strategy has a reason.

Would you really find it less annoying to have the engine run at high speed for a longer time in stopped traffic? The car can't predict the future. Heck, I can't predict the future.

Most of the time I'm stuck in traffic, after a while the traffic clears and then the engine gets to charge the battery while I'm driving at a normal speed. Much more efficient (and, to me, less annoying) than what you've asked for.

 

With the ScanGauge I can see mine charge the battery up to 45.0% SoC and I think it gets defensive around 38.0 SoC, depending on circumstances. As others have noted - 2/8 on the dash battery display does not mean 25% - the car will never let you go so low. I can't remember if mine reads 2/8 or 3/8 at 45% SoC but it's certainly down around that level.

In short: normal.

 

Yes, it is normal. I always try to stay in EV drive as long as possible so my SOC is often down to 2 bars. I have SGII to monitor the SOC as it provides more information than the bar graph.



The power management control ECU set the Lower SOC control limit at 40.0%. Once it drops to 39.6%, it will automatically start the engine to charge the battery to 45.0%. Once it reach 45.0%, it will stop the engine. This SOC is different from the Target SOC control shown above. The Target SOC shown above is for speed above 46 mph and is around 60% whereas 45.0% is for the controlled SOC once it drops below 40.0%.

The HV battery is smaller than the hatchback so it only need a short time to charge to 45.0%. Similarly, it also looses charge faster than the hatchback. That is why this start/stop cycle is more frequent than the hatchback.

Vincent

 

Yaris Hybrid (I assume the same construction as Prius C) uses more battery range. I've pushed it recently to it's limit while recording data on Torque App. I don't have graphs yet but looking into Excel Yaris managed to get top speed of 173 kmh (108 mph) despite that maximum declared speed is 165 kmh (103 mph). There is no speed limit as in Prius.
It took about 50 seconds to deplete battery from 60% SoC to 33,3%. Then car slowed down a bit. ICE RPM was steady at 4800 RPM. So the lower battery limit is much lower than in Prius. Battery Current was at steady level of about 120 A for all 50 seconds. MFD was showing 2 bars. Never dropped to 1 bar. When car slowed down HSD indicator dropped from top of the power scale to eco/power intersection.

Back to the main topic. Yaris Hybrid behaves the same in traffic jam. It turns on ICE, runs it for a (quite short) while, then shuts off. It pushes about 30A to the battery at this time. In Prius it works much longer (from 2 to 3 full bars) and pushes about 10 to 20A. Technology in Yaris/PriusC is harder for the battery but much more effective in terms of fuel usage, because smaller ICE works near it's full efficiency.

Both cars does not charge battery when car is moving and brakes are engaged (on high speed regen braking loads the battery, but below 10 kmh / 7 mph recharging operation is paused until car stops or accelerates). That's why engine sound is different while braking than while standing still. You can also feel a bit of vibration while engine switches from idling to 90% load and charging operation.

 

What about engine battery low when it's sitting outside (OFF) while I'm at work and come out to it to go home?

 

What about it?

 

Why is it low?

SCH-R530M ?

 

Lower than it was when you parked it? How much lower, and how big of an outside temperature change from morning to evening commute?

 

Much lower, almost full when I parked it and on the opposite end when I got end. Maybe 10 degree change during the day at the most.

 

It shouldn't discharge that much without using it. Do you have the solar sunroof vent? I wonder if maybe that quit working and your battery is powering everything... although, those solar cells don't produce a lot of power so the fan can't use a lot... hmm... do you have a light that stays on? I've got nothing. Sorry.

 

No solar roof and no lights that I know of

SCH-R530M ?

 

Are you absolutely sure that the car is completely OFF when you leave it ??

If you are talking about the main propulsion battery (as opposed to the 12 V one), then about the only things that would cause that much of a drop is the battery going bad, the car still being ON or a major fault in the electrical system somewhere.
In any case, it probably needs dealer attention to figure out.

 

Definitely off, yes main propulsion battery

SCH-R530M ?

 

If you are completly sure that the car is completly OFF then visit your service as soon as possible.
Hybrid battery is disconnected from the system completly as soon as you turn it off (you can hear characteristic click from the rear of the car) and reconnected just before "READY" indicator is back on.

You can have one bar change between startups due to recallibration but nothing more. Battery should keep it's charge for few months.

 

Got clean bill of health despite the battery's continued behavior