[CaliforniaJed]

Just curious whether anyone has ever seen their hybrid battery charge level at full (all bars lit) on the navigation system screen? I never have on my 2009 TCH. Mine frequently gets to all but one bar (and turns green), but it never gets to full.

Cheers,

Jed

[jdenenberg]

All bars full is rare, but it can happen. One way it occurs is going down a long mountain road. The ECU tries to avoid fully charging the battery (all bars is about 80% charged) or fully discharging it (no bars is about a 40% charge). This is to insure that the traction battery lasts "the life of the car".

JeffD

[FastMover]

There are several reasons that you don't see the battery at a fully charged state. The recharging limit for a charge from the ICE is limited to a lower SOC to permit dynamic braking to work with a (as far as ICE charge) fully charged battery. This provision recovers some energy in the deceleration and braking processes that would otherwise become heat, so it is also easier on the friction brakes.

For maintaining cruise power at or near a constant over even mostly level terrain, the battery is constantly acting as a buffer between charge and power assist. (You can see this on either display. The traction drive assist is constantly switching in and out as power is either demanded or reduced on the pedal, or by the cruise control.) This is done to make use of the small amounts of excess energy that the ICE is putting out that would otherwise be lost if the battery was literally fully charged.

As mentioned in the previous post, one of the most challenging regimes for a hybrid is a long, extended down grade. There is no easy way for the hybrid system to utilize all of the available kinetic energy in a useful manner. (The HSD system does use some of this energy in a dynamic relationship between MG2 and MG1 that creates a sort of "electronic drag" effect by spinning the ICE in fuel cutoff in either "D" or "B" drive selections, but this use of the energy is counter-productive to fuel efficiency. It is done only to reduce the need for the friction brakes, and has the effect of transferring energy dissipation that would be otherwise be producted as heat by the frictioin brake into the drive system to spin the fuel cut ICE.). This saves wear on the friction brakes, but at the expense of some amount of drive train wear.

HYBRID 101 - EXTENDED DOWNHILL GRADES

Hybrid drivers should look for opportunities during any extended travel DOWN a long grade to use energy from the battery (power assist, as opposed to the ICE) on every occasion that presents itself during such down grades. This may actually mean sometimes using a more agressive pedal than in a conventional car during short uphill or even level stretches along the grade. They should understand that this is not wasting energy, but is actually spending, and then recovering some energy that would otherwise be lost as braking heat or drive train resistance during the down grade. The objective on these occasions is to use the traction assist while still in fuel cut (60 MPG on USA cars) if possible, or to make a sufficient petal demand to engage the assist if the ICE comes on.

HYBRID 101 - EXTRA CREDIT

Another tip that I came across recently. In mountainous terrain, turn your air conditioner off when going uphill and turn it on high when going downhill. The first is obvious, more of the battery charge will be availble for traction assist. The latter one is more subtle that just getting cool -- by using your AC on high it creates an electrical load that uses some of the stored energy, and therefore also creates the ability to use more regen braking to replace the energy used by the AC.


RFB