Weak Battery?

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Chris Shearer Cooper - 30 Oct 2005 16:36 GMT

The guy who sold us our Prius said we should never use it to jump-start
another vehicle, as the Prius electrical system just wouldn't be able to
handle it. Anybody else heard this? Is this the "official" Toyota line?

Also got us wondering, my wife usually leaves her cell phone plugged into
the car's "power port" (what us old folks call the cigarette lighter), but
now we're wondering if that would be a bad idea ...

Thoughts?

Thanks!
Chris

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Bill - 30 Oct 2005 17:27 GMT

> The guy who sold us our Prius said we should never use it to jump-start
> another vehicle, as the Prius electrical system just wouldn't be able to
> handle it. Anybody else heard this? Is this the "official" Toyota line?

The Prius has a small 12V battery. It's in the back on the curb side.
Probably not adequate for jumping a big V6 or V8.

> Also got us wondering, my wife usually leaves her cell phone plugged into
> the car's "power port" (what us old folks call the cigarette lighter), but
> now we're wondering if that would be a bad idea ...
>
> Thoughts?

Won't drain the battery if that is your concern. These outlets are turned
off when the car is shut down.

> Thanks!
> Chris

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Michelle Steiner - 30 Oct 2005 17:31 GMT

> The guy who sold us our Prius said we should never use it to
> jump-start another vehicle, as the Prius electrical system just
> wouldn't be able to handle it. Anybody else heard this? Is this the
> "official" Toyota line?

Pretty much, yes; the 12 volt battery is not as powerful as in a regular
car because it doesn't have to be. For one thing, it doesn't start the
engine.

> Also got us wondering, my wife usually leaves her cell phone plugged
> into the car's "power port" (what us old folks call the cigarette
> lighter), but now we're wondering if that would be a bad idea ...

No problem there; the port is disconnected when the power is off. The
phone doesn't use that much electricity, so there's no problem when the
car is running.

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Mike Rosenberg - 30 Oct 2005 17:44 GMT

It's true, the Prius uses a 12V battery with a lower capacity than
normal cars since it's not used to crank the engine.

Not a problem, since the ports are turned off when the car is turned
off. I also leave my cell phone, as well as an MP3 player, plugged in
all the time.

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Toyota Prius fans: Check out alt.autos.toyota.prius

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G - 31 Oct 2005 00:19 GMT

> > The guy who sold us our Prius said we should never use it to jump-start
> > another vehicle, as the Prius electrical system just wouldn't be able to
> > handle it. Anybody else heard this? Is this the "official" Toyota line?
>
> It's true, the Prius uses a 12V battery with a lower capacity than
> normal cars since it's not used to crank the engine.

It's not ? Does that mean the big battery cranks the engine?

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Earle Jones - 31 Oct 2005 01:11 GMT

> > > The guy who sold us our Prius said we should never use it to jump-start
> > > another vehicle, as the Prius electrical system just wouldn't be able to
[quoted text clipped - 5 lines]
>
> It's not ? Does that mean the big battery cranks the engine?

*
My understanding is this: The Prius internal-combustion engine
(ICE) is not 'cranked' in the usual sense -- that is, started up
from zero rpm. The electric motor/generator delivers power through
the planetary gear system, which spins up the ICE (with no fuel
injection and open valves) up to around 700-800 rpm. Then, when the
computer decides that ICE power is required, fuel injection and
normal valve operation begin. In most cases, you cannot tell when
the ICE starts and stops.

The owners' manual tells us **not** to use the Prius to jump-start a
conventional engine. The reverse is not true. It is OK to
jump-start a Prius from another car.

earle
*

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Michelle Steiner - 31 Oct 2005 01:13 GMT

> > It's true, the Prius uses a 12V battery with a lower capacity than
> > normal cars since it's not used to crank the engine.
>
> It's not ? Does that mean the big battery cranks the engine?

That's right, and it does it directly; there's no separate starter.

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Michael Pardee - 31 Oct 2005 01:33 GMT

>> It's true, the Prius uses a 12V battery with a lower capacity than
>> normal cars since it's not used to crank the engine.
>
> It's not ? Does that mean the big battery cranks the engine?

It does indeed! One of the tech wizards in the Yahoo Prius group has
jump-started his Prius with a portable drill battery and a pair of clip
leads. Once the brake booster gets pumped up, all the 12V battery does is
boot the system and let the hybrid system spin the engine up. Pretty slick!

Mike

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Fred - 30 Oct 2005 22:38 GMT

But the Battery doesn't provide total power for jumping another car - the
entire 12v power system does. I've used my Prius to jump start another car,
with the Prius in Ready mode, with no problem at all.

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Bill - 31 Oct 2005 02:05 GMT

> But the Battery doesn't provide total power for jumping another car - the
> entire 12v power system does. I've used my Prius to jump start another
> car, with the Prius in Ready mode, with no problem at all.

Sure, however the fact that the other car needs to be jump-started is
indicative of a problem. If it simply has a low battery then jumping it
with a Prius could work. If it's battery has a shorted cell, or if it has
bad starting motor, inverter or extremely cold lubricants; anything that
results in an extra-ordinary load, then you could blow the Prius 100 amp
fuse or, worse yet, it's regulator. I wouldn't take the chance.

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Earle Jones - 31 Oct 2005 01:32 GMT

> > But the Battery doesn't provide total power for jumping another car - the
> > entire 12v power system does. I've used my Prius to jump start another
[quoted text clipped - 6 lines]
> results in an extra-ordinary load, then you could blow the Prius 100 amp
> fuse or, worse yet, it's regulator. I wouldn't take the chance.

*
The owners' manual says don't do it.

earle
*

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Jay Hennigan - 31 Oct 2005 00:07 GMT

You can sometimes use the Prius to jump-start another vehicle, but you
should do it somewhat differently than the normal way. The Prius 12-volt
system is protected by a 100-ampere fuse. Starter current through
heavy-gauge jumper cables can exceed this, blowing the fuse and rendering
the Prius 12-volt system inoperative. You can safely use the Prius
12-volt battery and inverter system to charge the other car's battery but
not to crank the starter motor.

The recommended way is to connect the cables with the Prius in READY mode,
but do NOT crank the starter of the other car. Allow the Prius to charge
the dead battery for a few minutes, then disconnect the cables and crank
the other vehicle with the cables disconnected. This may not always work
if the battery of the other car is in very poor condition or deeply
discharged.

Going the other way, if you drain the 12-volt Prius battery, you can
jump-start it with very little current. Even a 12-volt lantern battery or
a pack of eight D-cells will do it. You don't need to "crank" the Prius
to get it up and running. You just need eneough electricity to boot the
computers and energize the high voltage relay (the double-click you hear
when the car goes READY).

No problem, but the phone won't charge when the car is off.

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