Battery gauge bars - misleading?

KMO · 02-22-2005, 08:57 AM

Okay, I've seen lots of posts about the fuel gauge and its non-linearity - I've got a European, non-bladder car, and mine seems fine.

But I am doubtful about the battery charge indicator. If I switch to EV mode, as I watch the Energy screen, it always seems to take a long time to go from 6/8 to 5/8, but then the next 3 bars vanish quite rapidly (EV deactivates the instant the indicator shows 2/8).

So if I start at 6/8, I get the impression that at the moment the gauge moves moves to 5/8, I've exhausted more than half my EV range.

Am I imagining things?

**efusco** · 02-22-2005, 02:55 PM

There is definately some non-linearity, particularly with higher drain or charge rates.

DaveinOlyWA · 02-22-2005, 03:31 PM

the entire charge display only represents a small range in the SOC of the battery.

there are too many variables on how fast you will use the charge. many dont realize how much of a difference the volume of the stereo can impact the charge. then throw in lights, air conditioning, speed of vehicle, running time of ICE, etc...

**Tideland Prius** · 02-22-2005, 05:52 PM

but I notice the bottom half of the battery recharges faster than the top half or is it just that the computers are sending a lot of the engine's power towards the battery pack when it's low?

KMO · 02-24-2005, 04:51 AM

Okay, I've got confirmation of my suspicions from Attila Vass, who's been working hard on a CAN analyser.

He reports that the battery bar has some hysteresis, so the transitions between bars are different depending on whether it's going up or down. But the CAN numbers are:

Going down:
8->7 @ 150 (75%)
7->6 @ 128 (64%)
6->5 @ 110 (55%)
5->4 @ 104 (52%)
4->3 @ 98 (49%)
3->2 @ 90 (45%)

When going up, the charge has to reach 5 (2.5%) above the downward transition threshold before changing.

Thus, going up:
2->3 @ 95 (47.5%)
3->4 @ 103 (51.5%)
4->5 @ 109 (54.5%)
5->6 @ 115 (57.5%)
6->7 @ 133 (66.5%)
7->8 @ 155 (77.5%)

Looking at it another way, the bar sizes are:

8 = 10 (5%)
7 = 22 (11%)
6 = 18 (9%)
5 = 6 (3%)
4 = 6 (3%)
3 = 8 (4%)
2+1 = 10 (5%)

So that matches my suspicions. Running in EV mode, if the gauge starts at 6, then the charge is probably around 60%, but it could be as high as 66%. It won't go to 5 until it reaches 55%, and it'll reach 2 at 45%.

So maybe I was seeing the gauge start at 65% (=6), halfway it went to 5 @ 55%, then later it went to 2 @ 45%. 6->5 is the halfway point.

And this is why you see it mainly at 6 or 7 bars - between them they cover half the usable charge range.

All this is assuming that the CAN readings are linear - they're believed to be.

**efusco** · 02-24-2005, 10:10 AM

Realize too that that range of SOC/voltage shifts with temperture...I think that's part of the reason we see a higher SOC indicated in colder weather than in warm weather.

Below are a couple SOC diagrams that Wayne Brown determined using a voltmeter.

This first one shows the voltages measured for each bar:

This one is the percentage of SOC:

Frank Hudon · 02-24-2005, 10:24 AM

Thanks Evan for posting that. This should help people get their head around the charge/discharge display of the Prius.

DaveinOlyWA · 02-24-2005, 11:03 AM

very good info on this thread, definitely bookmark quality

thanks all

rbartels · 04-01-2005, 07:50 PM

PriusChat.com
I've had a 2005 Prius for about 6 weeks and have a question about the battery gauge bars. I've read the posts that I could find but none directly answered my question. My gauge goes up to the 6/8 bar position but usually goes no higher. A handful of times it's BRIEFLY gone to 7/8 [and the display turned green], but I've NEVER seen it go the top 8/8 bar. Two times I've driven it for about 8 hours in one day at mostly highway speeds.
My question: Is this normal?

rbartels in San antonio, TX

Frank Hudon · 04-01-2005, 08:11 PM

yes it's probably nomal. I've only see the 2k4 BSOC at all green a very few times. Mainly in the winter when the ICE runs more often and at at bottom of a long hill. Start off from the bottom and it quickly goes down a bar or two. Very sensitive. You can't hurt it so just drive it.

02-22-2005, 08:57 AM	#1
KMO Senior Member Join Date: Apr 2004 Location: Cambridge, UK Posts: 936 My Car: 2009 Prius Model: Package: T Spirit Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	Battery gauge bars - misleading? Okay, I've seen lots of posts about the fuel gauge and its non-linearity - I've got a European, non-bladder car, and mine seems fine. But I am doubtful about the battery charge indicator. If I switch to EV mode, as I watch the Energy screen, it always seems to take a long time to go from 6/8 to 5/8, but then the next 3 bars vanish quite rapidly (EV deactivates the instant the indicator shows 2/8). So if I start at 6/8, I get the impression that at the moment the gauge moves moves to 5/8, I've exhausted more than half my EV range. Am I imagining things?

02-24-2005, 04:51 AM	#5
KMO Senior Member Join Date: Apr 2004 Location: Cambridge, UK Posts: 936 My Car: 2009 Prius Model: Package: T Spirit Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	Re: Battery gauge bars - misleading? Okay, I've got confirmation of my suspicions from Attila Vass, who's been working hard on a CAN analyser. He reports that the battery bar has some hysteresis, so the transitions between bars are different depending on whether it's going up or down. But the CAN numbers are: Going down: 8->7 @ 150 (75%) 7->6 @ 128 (64%) 6->5 @ 110 (55%) 5->4 @ 104 (52%) 4->3 @ 98 (49%) 3->2 @ 90 (45%) When going up, the charge has to reach 5 (2.5%) above the downward transition threshold before changing. Thus, going up: 2->3 @ 95 (47.5%) 3->4 @ 103 (51.5%) 4->5 @ 109 (54.5%) 5->6 @ 115 (57.5%) 6->7 @ 133 (66.5%) 7->8 @ 155 (77.5%) Looking at it another way, the bar sizes are: 8 = 10 (5%) 7 = 22 (11%) 6 = 18 (9%) 5 = 6 (3%) 4 = 6 (3%) 3 = 8 (4%) 2+1 = 10 (5%) So that matches my suspicions. Running in EV mode, if the gauge starts at 6, then the charge is probably around 60%, but it could be as high as 66%. It won't go to 5 until it reaches 55%, and it'll reach 2 at 45%. So maybe I was seeing the gauge start at 65% (=6), halfway it went to 5 @ 55%, then later it went to 2 @ 45%. 6->5 is the halfway point. And this is why you see it mainly at 6 or 7 bars - between them they cover half the usable charge range. All this is assuming that the CAN readings are linear - they're believed to be.

02-24-2005, 10:10 AM	#6
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,228 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	Re: Battery gauge bars - misleading? Realize too that that range of SOC/voltage shifts with temperture...I think that's part of the reason we see a higher SOC indicated in colder weather than in warm weather. Below are a couple SOC diagrams that Wayne Brown determined using a voltmeter. This first one shows the voltages measured for each bar: This one is the percentage of SOC:

04-01-2005, 07:50 PM	#9
rbartels Join Date: Mar 2005 Location: San Antonio, TX Posts: 1 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Re: Battery gauge bars - misleading? PriusChat.com I've had a 2005 Prius for about 6 weeks and have a question about the battery gauge bars. I've read the posts that I could find but none directly answered my question. My gauge goes up to the 6/8 bar position but usually goes no higher. A handful of times it's BRIEFLY gone to 7/8 [and the display turned green], but I've NEVER seen it go the top 8/8 bar. Two times I've driven it for about 8 hours in one day at mostly highway speeds. My question: Is this normal? rbartels in San antonio, TX

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02-22-2005, 02:55 PM	#2
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,228 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	There is definately some non-linearity, particularly with higher drain or charge rates.

02-22-2005, 03:31 PM	#3
DaveinOlyWA 3rd Time was Solariffic!! Join Date: Apr 2004 Location: South Puget Sound, WA Posts: 12,375 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 24 Thanked 121 Times in 103 Posts Friends: 10	the entire charge display only represents a small range in the SOC of the battery. there are too many variables on how fast you will use the charge. many dont realize how much of a difference the volume of the stereo can impact the charge. then throw in lights, air conditioning, speed of vehicle, running time of ICE, etc...

02-22-2005, 05:52 PM	#4
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 19,606 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 227 Thanked 343 Times in 242 Posts Friends: 23	but I notice the bottom half of the battery recharges faster than the top half or is it just that the computers are sending a lot of the engine's power towards the battery pack when it's low?

02-24-2005, 10:24 AM	#7
Frank Hudon Senior Member Join Date: Jan 2004 Posts: 4,144 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Thanks Evan for posting that. This should help people get their head around the charge/discharge display of the Prius.

02-24-2005, 11:03 AM	#8
DaveinOlyWA 3rd Time was Solariffic!! Join Date: Apr 2004 Location: South Puget Sound, WA Posts: 12,375 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 24 Thanked 121 Times in 103 Posts Friends: 10	very good info on this thread, definitely bookmark quality thanks all

04-01-2005, 08:11 PM	#10
Frank Hudon Senior Member Join Date: Jan 2004 Posts: 4,144 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	yes it's probably nomal. I've only see the 2k4 BSOC at all green a very few times. Mainly in the winter when the ICE runs more often and at at bottom of a long hill. Start off from the bottom and it quickly goes down a bar or two. Very sensitive. You can't hurt it so just drive it.