ICE turning on and off

nosliw · 03-29-2008, 11:06 PM

Last night my car did a very funny thing.

I had just gone down a long slope, so the battery was fully charged, and my foot was on the brake at a redlight.

I noticed the engine start and then shut off a few seconds later. I could feel it start and stop every 2 or 3 seconds. I can't remember what the MFD said. It continued doing this for a minute until the light turned green.

My foot was firmly on the brake, and it hasn't done it since.

Anyone else experience this?

**TonyPSchaefer** · 03-29-2008, 11:41 PM

This has never happened to my since my battery is almost never fully charged, but I remember some people talking about that here. Apparently, the ICE will run and burn off some of the extra charge. I can't explain it but I'm sure someone will chime in and be able to explain it.

patsparks · 03-29-2008, 11:58 PM

The electric motor will spin the ICE (internal combustion engine) to dump excess energy if the battery is over 80% charged. If the battery is at full charge regularly at the bottom of a hill this is the only time I would recommend using B mode to slow the car on the hill. Basically this manually dumps some of the energy before it gets to the battery.
This isn't compulsory, the Prius can look after itself.

qbee42 · 03-30-2008, 12:06 AM

In case it wasn't obvious from the previous post, the engine isn't running when it does that, it is just being spun by MG1 to throw away excess charge. The motor spins the engine for a few seconds, then checks the battery. If it is still too high, it spins the engine some more. The cycle continues until the charge is down the the proper level.

Tom

MPGsnob · 03-30-2008, 12:19 AM

Is it ideal to have the battery green?

nosliw · 03-30-2008, 01:18 AM

Interesting. Thanks for the replies.

**efusco** · 03-30-2008, 01:49 AM

Quote:

Originally Posted by MPGsnob

Is it ideal to have the battery green?

No, it is ideal to have 6 blue bars...or about 60% SOC...that's what the car is programmed to shoot for to maximize battery life.

nosliw · 03-30-2008, 11:17 AM

What's wrong with letting the battery charge all the way up (like down that hill) and utilizing the battery more for a while to drain it back down?

Doesn't that not waste the *free* energy from going downhill into something I can use for transport later?

I noticed the ICE didn't kick back on to propel me until I hit about 25MPH after that (it was only very slightly downhill after the stoplight. I used up most the battery on the stop-and-go traffic before I got home.

pewd · 03-30-2008, 11:26 AM

for all the car knows, you're fixin' to go down another hill ; the computer is trying to protect the battery from an overcharged situation.
the computer cant see whats ahead, so it makes assumptions that fit the majority of situations.

nosliw · 03-30-2008, 11:39 AM

It didn't burn off much (not a bar) when it was churning the engine those few times. And on the way home I hardly used the ICE. Great mileage.

In THIS situation do you think it would be best to just let 'er charge?

If I use 'B' and understand it correctly, I'm just wasting that potential power.

Or maybe I'll approach the hill slower and glide down the whole thing.

Or maybe I should drive the thing like any other car and let it do its own thing.

03-29-2008, 11:06 PM	#1
nosliw Member Join Date: Mar 2008 Location: PNW Posts: 67 My Car: 2008 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	ICE turning on and off Last night my car did a very funny thing. I had just gone down a long slope, so the battery was fully charged, and my foot was on the brake at a redlight. I noticed the engine start and then shut off a few seconds later. I could feel it start and stop every 2 or 3 seconds. I can't remember what the MFD said. It continued doing this for a minute until the light turned green. My foot was firmly on the brake, and it hasn't done it since. Anyone else experience this?

03-29-2008, 11:41 PM	#2
TonyPSchaefer Ruler of Omicron Persei 8 Join Date: May 2004 Location: Far-North Chicagoland Posts: 7,698 My Car: 2004 Prius Package: #9 Nominated 4 Times in 2 Posts TOTM Awards: 0 Friends: 14	Re: ICE turning on and off This has never happened to my since my battery is almost never fully charged, but I remember some people talking about that here. Apparently, the ICE will run and burn off some of the extra charge. I can't explain it but I'm sure someone will chime in and be able to explain it.

03-29-2008, 11:58 PM	#3
patsparks Uneducated bird-brain Aussie Join Date: Jul 2007 Location: Adelaide South Australia Posts: 4,438 My Car: 2004 Prius Package: Base Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 12	Re: ICE turning on and off The electric motor will spin the ICE (internal combustion engine) to dump excess energy if the battery is over 80% charged. If the battery is at full charge regularly at the bottom of a hill this is the only time I would recommend using B mode to slow the car on the hill. Basically this manually dumps some of the energy before it gets to the battery. This isn't compulsory, the Prius can look after itself.

03-30-2008, 12:06 AM	#4
qbee42 Senior Member Join Date: Mar 2006 Location: Northern Michigan Posts: 4,870 My Car: 2006 Prius Package: #7 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 5	Re: ICE turning on and off In case it wasn't obvious from the previous post, the engine isn't running when it does that, it is just being spun by MG1 to throw away excess charge. The motor spins the engine for a few seconds, then checks the battery. If it is still too high, it spins the engine some more. The cycle continues until the charge is down the the proper level. Tom

03-30-2008, 12:19 AM	#5
MPGsnob Junior Member Join Date: Mar 2008 Location: Arthur, IL Posts: 16 My Car: 2005 Prius Package: Base Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: ICE turning on and off Is it ideal to have the battery green?

03-30-2008, 01:18 AM	#6
nosliw Member Join Date: Mar 2008 Location: PNW Posts: 67 My Car: 2008 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: ICE turning on and off Interesting. Thanks for the replies.

03-30-2008, 11:17 AM	#8
nosliw Member Join Date: Mar 2008 Location: PNW Posts: 67 My Car: 2008 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: ICE turning on and off What's wrong with letting the battery charge all the way up (like down that hill) and utilizing the battery more for a while to drain it back down? Doesn't that not waste the free energy from going downhill into something I can use for transport later? I noticed the ICE didn't kick back on to propel me until I hit about 25MPH after that (it was only very slightly downhill after the stoplight. I used up most the battery on the stop-and-go traffic before I got home.

03-30-2008, 11:26 AM	#9
pewd Clarinet Dude Join Date: Jan 2007 Location: Dallas, Texas Posts: 299 My Car: 2007 Prius Package: #1 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 1	Re: ICE turning on and off for all the car knows, you're fixin' to go down another hill ; the computer is trying to protect the battery from an overcharged situation. the computer cant see whats ahead, so it makes assumptions that fit the majority of situations.

03-30-2008, 11:39 AM	#10
nosliw Member Join Date: Mar 2008 Location: PNW Posts: 67 My Car: 2008 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: ICE turning on and off It didn't burn off much (not a bar) when it was churning the engine those few times. And on the way home I hardly used the ICE. Great mileage. In THIS situation do you think it would be best to just let 'er charge? If I use 'B' and understand it correctly, I'm just wasting that potential power. Or maybe I'll approach the hill slower and glide down the whole thing. Or maybe I should drive the thing like any other car and let it do its own thing.