Overcharge capacity?

[Sovereign]

So I know that you generally don't want to leave a hybrid's battery charged up to the top. If the state of charge gets too high it can actually reduce the battery's life (or so I was told).

Imagine my shock when, driving home, this happened.


The battery reached charge level 7. Of the 8 "levels," only 4 are used in the Highlander (at least from what I've seen).
1 - Critically low. Never seen this, because...
2 - Engine runs constantly to recharge even if the vehicle is physically stopped (i.e. stuck in traffic). Great way to waste gas and kill fuel economy.
3 - Low
4 - Middle
5 - High
6 - "Full"--engine will not charge battery above here.
7 - Overcharge 1 (shown above). Only achievable with epic regenerative braking--the engine will not charge the battery to this.
8 - Overcharge 2 (theoretical maximum the battery can actually hold).

Do other hybrid drivers (mainly Toyota) frequently see "overcharge" capacities? Does it relate to the weather? (It's 44F or colder--batteries hate heat and love cold to a point.)

I've also discovered that the fastest charge on braking is halfway into the "blue" (not all the way).

[F8L]

8 bars is not the equivalent to a true overcharge condition because the battery does not allow you overcharge the battery. If you reach 80% SOC the system will the rev up the ICE to around 3000 rpm to burn off excess charge but no fuel is used during this process. Are you monitoring the system with a scan guage? If so you will notice that average SOC is between 59% and 65% during normal driving. The ICE in the Prius generally turns on when the SOC has reached 57.5% and does note try and burn off excess charge until SOC reaches approx 78%. So in theory you are never truely reaching 100% SOC.

[Sovereign]

So is there a reason why it won't charge above 6 bars unless I really try (major coast/brake)?

[F8L]

Originally Posted by Sovereign

So is there a reason why it won't charge above 6 bars unless I really try (major coast/brake)?

That is pretty normal. It is rare to charge all the way up to full unless you do a lot of downhill driving.

Do you have a Scangauge? If not you may want to get one. They really help with questions like this.

I believe 6 bars is right around 60% give or take.

[Daox]

Originally Posted by Sovereign

So is there a reason why it won't charge above 6 bars unless I really try (major coast/brake)?

It extends the life of the battery and also leaves plenty of capacity to regen if need be (down a big hill for instance).

[Sovereign]

No scangague, but I have answers now. Thanks!