Battery and driving on a long slope downhill

Hi,

I'm going to drive my Prius into the mountains in September for holidays.
I know that there is a B-gear that enables the car to brake on its engine
when driving downhill.
I'm wondering if the battery will fill up all the time when doing so and is
there any danger that the battery will be overloaded?
Kind of expect there to be some overload avoiding mechanism in the Prius but
not sure.

Does anyone have any experiences or knowledge regarding this?

Thanks
Bumperkleber

"king" <axelvanderkruk@telfort.nl> wrote in message
news:48a487f7$0$24394$5fc3050@news.tiscali.nl...
> Hi,
>
> I'm going to drive my Prius into the mountains in September for holidays.
> I know that there is a B-gear that enables the car to brake on its engine
> when driving downhill.
> I'm wondering if the battery will fill up all the time when doing so and
> is there any danger that the battery will be overloaded?
> Kind of expect there to be some overload avoiding mechanism in the Prius
> but not sure.
>
> Does anyone have any experiences or knowledge regarding this?
>
> Thanks
> Bumperkleber
>

When the battery is partially charged the motor/generator combines with the
engine brake effect to keep the car going slowly downhill. Once the battery
is fully charged the control systems in the car prevent any further current
from reaching the battery and the car depends on engine braking alone. The
only thing you will notice is that the engine note on overrun sounds a bit
higher (because it's working alone) and you may have to use your brakes a
little more.

Some Prius owners suggest that it is better to use your regular brakes
rather than the B position anyway - more charging current gets to the
battery under normal braking than engine braking - but this only holds true
until the battery is fully charged, after which the above applies and you
will start to wear out your brakes. That would be the time to engage B.

However, it's best to do whatever you feel most comfortable and safe doing.
Whatever you decide you need have no fears about damaging the car - it is
fully capable of looking after itself.

Enjoy the ride!

Chas

Elmo P. Shagnasty wrote:
> In article <48a487f7$0$24394$5fc3050@news.tiscali.nl>,
> "king" <axelvanderkruk@telfort.nl> wrote:
>
>> I'm going to drive my Prius into the mountains in September for holidays.
>> I know that there is a B-gear that enables the car to brake on its engine
>> when driving downhill.
>> I'm wondering if the battery will fill up all the time when doing so and is
>> there any danger that the battery will be overloaded?
>
> No.
>
> The Prius is a highly sophisticated system, much more sophisticated than
> you're giving it credit for.
>
> Plus, B gear does not charge the battery. Period. End of sentence.
> Stop right there. Do not ask questions. B gear does not charge the
> battery. Period.

Going downhill in B gear with foot off accelerator will definitely
charge the battery. Perhaps you are thinking of going downhill in B
gear with the accelerator floored, something one would do only in
suicide mode.

As others have rightfully pointed out, once the battery is fully charged
(as full as the Prius allows) your only braking will be by engine
braking and the foot pedal(s) brakes.

Tom

Elmo P. Shagnasty <elmop@nastydesigns.com> wrote:
> In article <2vSdnZ06jc8guzvVnZ2dnUVZ_uidnZ2d@>,
> MrTom <NotMyAddress@invalid.net> wrote:
>
>> Going downhill in B gear with foot off accelerator will definitely
>> charge the battery.
>
> Nope.

Mine does. At least it adds bars to the display.

cu
.\\arc

Le 16/08/2008 19:12, Marc Gerges nous fit lire :
> Elmo P. Shagnasty <elmop@nastydesigns.com> wrote:
>> In article <2vSdnZ06jc8guzvVnZ2dnUVZ_uidnZ2d@>,
>> MrTom <NotMyAddress@invalid.net> wrote:
>>
>>> Going downhill in B gear with foot off accelerator will definitely
>>> charge the battery.
>> Nope.
>
> Mine does. At least it adds bars to the display.

The rate of the charge done in B mode is *less* than the charge done
in D with foot on break.
Nevertheless, once charged, D mode rely directly on real break,
whereas B still rely on running the ICE in compressor mode.
When the downhill is long (mountain size), B mode is interesting: it
avoid heating the breaks too early.