Hybrid battery gets really low in slick conditions because I'm not braking

B mode does not regenerate more energy. It uses energy from the HV battery to run the engine. So that's not your answer.
I don't know why freezing rain causes you to uses friction braking more than electric braking? Braking lightly will give you 100% electric braking and I would guess that in freezing rain, you are doing that a lot (heavy breaking in slippery situations is a bad idea). Breaking hard will not necessarily generate more energy. When you start using friction brakes (which only happens when braking harder), you will lose some recharge.
Or do you mean you don't brake at all and only slow down by not pressing the accelerator? That will recharge also. As soon as you get the foot off the accelerator, the car starts regenerating.

Heater on does not impact HV battery. In fact: it will cause the ICE to run more often, generating a charge for the battery. Lights come from the 12V battery and that needs to be recharged by the HV battery.

And ultimately: what is the problem? The car wil start the ICE when the HV battery level is too low. It will not break of fail.

 

Your Pri's fine and is working just the way it should. My guess is at those low speeds, it didn't have a need to fire up the Engine until the battery required it to do so. I may be wrong here, but you are aware that braking isn't the only way the Prius puts electricity back into that battery...?

 

Don't worry about it. Drive safe.
In reality the battery is not really low, when it says it's low.

Again, drive safe!

 

welcome!
heat comes from the engine, not battery.

lights don't use much juice.

regen works when gas pedal is let up, notjust when pressing brake pedal.

unless you get warning lights or a message on the screen, everything is fine and operating correctly.

the computers manage everything for you.

 

Quit thinking about it and drive! Toyota did a beautiful job automating everything related to underway battery state-of-charge maintenance. It's time to trust them and pay attention to traffic and road conditions instead.

Overthinking your car can be every bit as distracting as texting behind the wheel.

 

Dubit got it right, this happened because you were driving slower.

Normally, most of traction battery charging comes from the ICE, not from regenerative braking. But when you drove slower due to slick conditions, your propulsion shifted away from ICE power and instead using more EV-only power that drains the battery. And the ICE didn't get run enough to refill it.

Don't worry about it. The ICE will automatically kick in to prevent it from getting too low. The car's computers have you covered.

 

I just rolled into the garage with only 2 bars displayed, due to lowish/steady speeds and level roads. Not worried; it'll bounce back.

And yeah, B is for reducing charging, uses engine braking, most applicable during long hill descents.

 

I'm going to say your Hybrid Battery reading on the lower side of charge probably has little or nothing to do with you "not braking".
Probably has a LOT more to do with cold freezing rain temperatures, and the slower, careful driving we all do when in that type of environment.

Pure personal feeling, but I always looked at the regenerative braking system of the Prius as being a brilliant part of the HSD package. But the key word is "part". I'm guessing..yes guessing, that HSD isn't designed to depend on the particular aspect..braking..as being primary to how the system charges or maintains the Hybrid Battery. It almost can't be, because braking IS affected by personal driving habits, and also environment.

So also IMO, I would actually just ignore the lower state of charge. As long as the system is working, you're getting good MPG, and no battery failure codes, I would chalk up the reality of a generally lower state of charge being displayed, as simply being part of driving in the winter in harsh conditions.

And in that environment, the priority in HOW you drive, has to be SAFETY, not in maintaining a comforting graphic of green bars.

If it's anything else? Failure of the Hybrid Battery, 12 volt, speculative etc, etc, etc,...you'll get codes, and you'll know. But IMO as presented, I don't think there really is a problem.

 

Do you have the p0A80 code?

 

No codes.... He/She was driving in bad weather & at extremely slow speeds. While at those speeds, the vehicle operated in EV mode bringing down the charge in the battery. We "believe" that he/she may be thinking the only way a Prius puts energy back into that battery is by braking.

 

Have your 12 volt battery checked with an electronic load tester. Or you can DIY with something like Solar BA9.

 

I would just replace the 12 volt battery.

 

The battery indicator should be 2 bars or higher. So don't worry unless you see just 1 bar.

As far as the car is concerned in slick conditions, the mode doesn't matter. Use whatever feels best for you.

 

Does car the have any signs of 12v overheating?

 

I don't mean to hijack the thread, but I'm really curious. Does a 3rd generation Prius (like OP's 2010) always show the hybrid battery charge on the dash display?

Our Prius c will show it if we select that display out of the 5 or 6 available, but we never actually do that in ours apart from maybe 20 minutes on the first day we had the car.

 

I think it does actually show thee battery on the dash

 

Gen3 Liftbacks have a permanent SOC (state of charge) gauge, separate from the user selectable displays.