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surfingslovak
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Re: Kudos to the CANbus SOC meter team!

Thu Aug 11, 2011 6:48 pm

TonyWilliams wrote:At 281 SOC data points, that's only 20 kWh of battery.
Yes, absolutely. We don't have a large enough data sample to determine what the multiplier is. I would hope that it's 75Wh/SOC, but that's based entirely on nothing but speculation.

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garygid
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Re: Kudos to the CANbus SOC meter team!

Thu Aug 11, 2011 9:29 pm

1. mike means miles/kWh, not kWh/mile

2. the multiplier is not constant over the SOC range, being lower (moderately predictably) at the high end and UNpredictably and significantly lower at the low end of the SOC scale.

3. Throughout the center range the multiplier might be meaningful, but it will depend upon temperature and it will decrease with "age/use".
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surfingslovak
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Re: Kudos to the CANbus SOC meter team!

Thu Aug 11, 2011 11:12 pm

garygid wrote:1. mike means miles/kWh, not kWh/mile

2. the multiplier is not constant over the SOC range, being lower (moderately predictably) at the high end and UNpredictably and significantly lower at the low end of the SOC scale.

3. Throughout the center range the multiplier might be meaningful, but it will depend upon temperature and it will decrease with "age/use".
Yes, thank you for catching that Gary! I corrected this mistake. If I understand you correctly, the SOC number likely correlates to a certain pack voltage. This in turn correlates to a certain amount of available energy, but exactly how much depends on several factors.

The reason why I'm looking to confirm the 75Wh/SOC multiplier is simple. If this number was correct, at least on paper, it would validate a few aspects of the following battery model: 21kWh of available energy, roughly 1.5kWh per bar, and 6% unavailable capacity on each end of the range. I apologize if this looked crude or otherwise inadequate, and I appreciate your comments.

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Re: Kudos to the CANbus SOC meter team!

Fri Aug 12, 2011 6:36 am

Unfortunately, your WattHour per SOC-tick estimate will not tell you any of those THREE things, other than as approximate "averages", thus still just guesses.
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Re: Kudos to the CANbus SOC meter team!

Fri Aug 12, 2011 9:47 am

My commute is almost identical to Mike's so, for comparison:
I received the SOC gauge on Wednesday night by UPS. I had driven 30.7 miles in the morning and 31.4 at night (slightly different, but faster route after 6:45PM). I used cruise control to keep speed at 60 MPH. After running the meter through its checks, I read 34.1% remaining and I always charge to 100%

Yesterday, pretty much a repeat of Wednesday with the exception of 1 slow patch coming home. Drive in 30.7 miles and using only 31% of charge, drive home for total RT of 62.1 miles left me with 36% charge remaining. Both days I was right at 4.8 m/kWh according to the energy meter on the dashboard.

The SOC meter might give me the confidence to try 80% charge for commute and/or Mike's approach, which is to go at 65 MPH (which does make the drive more bearable, believe it or not).
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DaveEV
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Re: Kudos to the CANbus SOC meter team!

Fri Aug 12, 2011 11:58 am

gascant wrote:Both days I was right at 4.8 m/kWh according to the energy meter on the dashboard.
Interesting - that's very good efficiency for 60 mph. You should be able to do 90+ miles easily on a full charge. Any AC usage?

Tony's Range-Speed-Bars table has 60 mph at 3.9 mi/kWh - how are you getting 20% better range?
gascant wrote:The SOC meter might give me the confidence to try 80% charge for commute and/or Mike's approach, which is to go at 65 MPH (which does make the drive more bearable, believe it or not).
65 mph should be no problem on a full charge - estimate about a 10% reduction in range going from 60 to 65 mph.

Does a 80% charge read 80% on the SOC meter?

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Re: Kudos to the CANbus SOC meter team!

Fri Aug 12, 2011 12:05 pm

surfingslovak wrote:
garygid wrote:1. mike means miles/kWh, not kWh/mile

2. the multiplier is not constant over the SOC range, being lower (moderately predictably) at the high end and UNpredictably and significantly lower at the low end of the SOC scale.

3. Throughout the center range the multiplier might be meaningful, but it will depend upon temperature and it will decrease with "age/use".
Yes, thank you for catching that Gary! I corrected this mistake. If I understand you correctly, the SOC number likely correlates to a certain pack voltage. This in turn correlates to a certain amount of available energy, but exactly how much depends on several factors.

The reason why I'm looking to confirm the 75Wh/SOC multiplier is simple. If this number was correct, at least on paper, it would validate a few aspects of the following battery model: 21kWh of available energy, roughly 1.5kWh per bar, and 6% unavailable capacity on each end of the range. I apologize if this looked crude or otherwise inadequate, and I appreciate your comments.
this is very interesting... in your mind, what are your take-aways? The battery will hold up better than expected? They will be able to increase the car range via SW updates?

tks so much,

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Re: Kudos to the CANbus SOC meter team!

Fri Aug 12, 2011 5:07 pm

drees wrote:Does an 80% charge read 80% on the SOC meter?
On the SOC meter, 10 bars is actually 82.9% and in CarWings, it's 83%. I see that the bars that CarWings shows and their percentage are pretty close to the SOC meter (within 1% or so), at least at the 35%/4 bars and higher mark.
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Re: Kudos to the CANbus SOC meter team!

Mon Aug 22, 2011 11:57 am

Just popping in to say that I came || close to hitting 100% / 281 on last night's charge - I was at 99.6%/280 this morning.

Now, how did I manage that last night, when my numbers before have been all over the map, but never that high? I have no clue, but one thing that was not typical from last night is that I was charging from just over 50% charged. Normally when I charge, I'm down to around 30% remaining. However, I did also noticed that my battery pack was cooler this morning (5 bars rather than 6). So maybe less heat is able to build up with the shorter charging time and, therefore, the pack is able to charge more? Just a theory.

But you know what else I've noticed....is that it doesn't matter what I've got charge-wise when I leave home (and I've started out with only 92% before today), I seem to loose that first 10% or so with about the same speed no matter what.

Starting out with almost 100% also blows my first bar reduced mileage theory out of the water too, because I didn't do any better today that I would any other. But I haven't seen the restorative action of pre-conditioning the cabin of my car since winter. Maybe it takes pre-conditioning via heater to work, or maybe my pack isn't capable of being restored in this fashion anymore? Hard to say.
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Re: Kudos to the CANbus SOC meter team!

Mon Aug 22, 2011 12:20 pm

mwalsh wrote:So maybe less heat is able to build up with the shorter charging time and, therefore, the pack is able to charge more? Just a theory.
Or maybe the car will let the battery charge a bit more thanks to the lower temps - and in warmer temps it cuts off charging sooner to help preserve battery life also knowing that a warmer battery is also a bit more efficient than a colder battery.

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