How many amps drawn when stopped with light foot on brake?

theorist · 07-27-2006, 12:19 AM

I've noticed that when completely stopped at a red light, the MFD shows current flowing from the battery to the wheels if I don't have a really firm foot on the brake pedal. Can someone with CAN-view tell us how many amps are flowing from the battery or to the motors when stopped and how this depends on the amount of pressure applied to the brake pedal?

**efusco** · 07-27-2006, 09:47 AM

<div class='quotetop'>QUOTE(theorist @ Jul 26 2006, 11:19 PM) [snapback]292992[/snapback]</div>

Quote:

I've noticed that when completely stopped at a red light, the MFD shows current flowing from the battery to the wheels if I don't have a really firm foot on the brake pedal. Can someone with CAN-view tell us how many amps are flowing from the battery or to the motors when stopped and how this depends on the amount of pressure applied to the brake pedal? [/b]

My recollection is that it's about one additional amp.

ScottY · 07-27-2006, 10:14 AM

I noticed that if I have everything off, no AC, no headlights, and car stopped, current draw is below 2 Amp. If I don't press on brake hard enough, but not till the point that the car's moving, current draw went up to around 5 Amp.

hobbit · 07-27-2006, 11:09 AM

5 amps sounds like a lot. I see almost nothing until I actually
start *moving*. Yes, there's a little bit of torque applied from
MG2 as hill-holding and creep force, but at locked-rotor if it was
any more than an amp or two you would have much more trouble holding
the car still. The way to think about it is this:
__ power = torque * rpm
__ power = volts * amps
if RPM is zero, then power is zero [other than maybe a teeny bit of
heat dissipated in the windings], and thus amps must be close to
zero too. Current starts to rise as you begin moving, and when it
reaches a certain threshold the ICE starts to make up for it. This
gives rise to the common but incorrect notion that the "engine starts
above a certain speed" that is less than 42. With steady foot
demand, it simply starts when battery current goes above 50A [at
nominal SOC].
.
_H*

ScottY · 07-27-2006, 11:39 AM

5 amps is what CAN-View is showing at the condition mention above. How about other CAN-View users, what you guys get?

tomdeimos · 07-27-2006, 12:25 PM

I see only 1 amp on my canview with brake on too lightly. Maybe peaks of 2, as it seemed to jump around a bit.

This was at a draw of 3 amps when stopped with brake on normally. This varies mostly with ac and fan speed.

This all might vary with battery charge as in creep mode the battery might try to charge a bit too, but in full stop it should not.
Grade of the road might affect the current needed to hold the car too.

ScottY · 07-27-2006, 12:49 PM

wow... am I the only one with this high of current draw? The readings are pretty consistent since day one I got CAN-View.

tomdeimos · 07-28-2006, 10:52 AM

<div class='quotetop'>QUOTE(ScottY @ Jul 27 2006, 11:39 AM) [snapback]293194[/snapback]</div>

Quote:

5 amps is what CAN-View is showing at the condition mention above. How about other CAN-View users, what you guys get?
[/b]

OK last night I measured this again and I got 5 amps this time.

This was at night with headlights on and AC working hard.
Maybe the current varies due to charging the 12 volt battery and givine more power to the AC?

Mostly I just see the 1 amp change between brake full on and on lightly at a stop.

ken1784 · 07-28-2006, 11:23 AM

<div class='quotetop'>QUOTE(hobbit @ Jul 28 2006, 12:09 AM) [snapback]293176[/snapback]</div>

Quote:

5 amps sounds like a lot. I see almost nothing until I actually
start *moving*. Yes, there's a little bit of torque applied from
MG2 as hill-holding and creep force, but at locked-rotor if it was
any more than an amp or two you would have much more trouble holding
the car still. The way to think about it is this:
__ power = torque * rpm
__ power = volts * amps
if RPM is zero, then power is zero [other than maybe a teeny bit of
heat dissipated in the windings], and thus amps must be close to
zero too.
[/b]

Yes, the power output is zero, but the input is not.

Ken@Japan

DaveinOlyWA · 07-28-2006, 11:25 AM

i only see 1-3 amps with no lights on. stereo running. as i put it in park nearly every time i stop. but on places where there are extreme hills, i use the brake and it seems the harder i push, the higher the current pulses. (in any situation, the readings constantly fluctuates.) i have seen it as high as 5-7 amps, but you will notice that if braking just hard enough to keep from moving, the change is very slight

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07-27-2006, 12:19 AM	#1
theorist Senior Member Join Date: Jan 2006 Location: Lexington, MA Posts: 330 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I've noticed that when completely stopped at a red light, the MFD shows current flowing from the battery to the wheels if I don't have a really firm foot on the brake pedal. Can someone with CAN-view tell us how many amps are flowing from the battery or to the motors when stopped and how this depends on the amount of pressure applied to the brake pedal?

07-27-2006, 10:14 AM	#3
ScottY Senior Member Join Date: May 2005 Location: Long Island, NY Posts: 1,249 My Car: 2005 Prius Model: Package: #3 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 1	I noticed that if I have everything off, no AC, no headlights, and car stopped, current draw is below 2 Amp. If I don't press on brake hard enough, but not till the point that the car's moving, current draw went up to around 5 Amp.

07-27-2006, 11:09 AM	#4
hobbit Senior Member Join Date: Mar 2005 Location: Bahstahn Posts: 3,590 My Car: Model: Package: Thanks: 0 Thanked 209 Times in 115 Posts Friends: 0	5 amps sounds like a lot. I see almost nothing until I actually start moving. Yes, there's a little bit of torque applied from MG2 as hill-holding and creep force, but at locked-rotor if it was any more than an amp or two you would have much more trouble holding the car still. The way to think about it is this: __ power = torque * rpm __ power = volts * amps if RPM is zero, then power is zero [other than maybe a teeny bit of heat dissipated in the windings], and thus amps must be close to zero too. Current starts to rise as you begin moving, and when it reaches a certain threshold the ICE starts to make up for it. This gives rise to the common but incorrect notion that the "engine starts above a certain speed" that is less than 42. With steady foot demand, it simply starts when battery current goes above 50A [at nominal SOC]. . _H*

07-27-2006, 11:39 AM	#5
ScottY Senior Member Join Date: May 2005 Location: Long Island, NY Posts: 1,249 My Car: 2005 Prius Model: Package: #3 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 1	5 amps is what CAN-View is showing at the condition mention above. How about other CAN-View users, what you guys get?

07-27-2006, 12:25 PM	#6
tomdeimos Join Date: Feb 2004 Location: Lexington, MA Posts: 995 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I see only 1 amp on my canview with brake on too lightly. Maybe peaks of 2, as it seemed to jump around a bit. This was at a draw of 3 amps when stopped with brake on normally. This varies mostly with ac and fan speed. This all might vary with battery charge as in creep mode the battery might try to charge a bit too, but in full stop it should not. Grade of the road might affect the current needed to hold the car too.

07-27-2006, 12:49 PM	#7
ScottY Senior Member Join Date: May 2005 Location: Long Island, NY Posts: 1,249 My Car: 2005 Prius Model: Package: #3 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 1	wow... am I the only one with this high of current draw? The readings are pretty consistent since day one I got CAN-View.

07-28-2006, 11:25 AM	#10
DaveinOlyWA 3rd Time was Solariffic!! Join Date: Apr 2004 Location: South Puget Sound, WA Posts: 12,321 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 23 Thanked 119 Times in 101 Posts Friends: 10	i only see 1-3 amps with no lights on. stereo running. as i put it in park nearly every time i stop. but on places where there are extreme hills, i use the brake and it seems the harder i push, the higher the current pulses. (in any situation, the readings constantly fluctuates.) i have seen it as high as 5-7 amps, but you will notice that if braking just hard enough to keep from moving, the change is very slight