dwf123
Posts: 100
Joined: Sat Mar 10, 2012 8:04 am

Battery Life

Sun Sep 09, 2012 3:40 am

I want to find a way to keep track of the life of my battery. I received my auto on 5/29/2012 and have clocked 5500 miles. MyFord Mobile and the dashboard information do not seem to provide an accurate indication of the battery charge.

Despite the widespread believe that the electric auto will vastly improve over the next few years, I did not lease, but bought my car, because it meets my needs for the next ten year period. And, I am one of these guys who believes in warranties. The warranty said 8 years or 100,000 miles. My Mulally said, in an interview, that means less then 80% diminishment in capacity. If I can keep track of the capacity and if, for any reason, begin to loose the capacity, too quickly, I would like to have the facts to back up my statements.

I am not an electrical engineer so I do not know how to measure the capacity. Is there any place that tells us what the capacity was at the time of manufacturing. is there a way to measure the current charge? What instrument do you use and where would you attach the instrument?
2012 Ford Focus Electric. Delivered 5/29/2012

mr23
Posts: 9
Joined: Sun Sep 23, 2012 6:47 am

Re: Battery Life

Sun Sep 23, 2012 6:51 am

Have you made any progress on this issue in the past 6 months?

Charged Up
Posts: 59
Joined: Wed Aug 10, 2011 7:13 pm
Location: Virginia

Re: Battery Life

Sun Sep 23, 2012 5:30 pm

I think what the LEAFers have recently done is a very good method. Although they ran till full stop, I think a run till low battery warning over a set course, at set speed and temperature and climate control settings should give you a good benchmark.

felkster
Posts: 25
Joined: Mon May 28, 2012 10:10 pm
Location: Seattle

Re: Battery Life

Mon Sep 24, 2012 11:26 am

I can't remember what the Leafs have, display-wise, but we at least see our kWh usage for every single trip in the left dashboard display. I already use this to gauge how much of my battery is left after each drive, percentage wise (running on the assumption of a 19 kWh "full battery").

So you could certainly add up your daily trips and observe the battery capacity, or just drive a long trip until you hit 0 and see how many kWhs you used for that drive. Then pay attention to that number over time.

dwf123
Posts: 100
Joined: Sat Mar 10, 2012 8:04 am

Re: Battery Life

Mon Sep 24, 2012 3:35 pm

I have made little progress on this topic.

#1) There does not appear to be any instrument that easily measures the capacity of the battery after charging.

#2) The alternative is doing some kind of measurements based upon driving a set distance with set parameters of Temperature, Terrain and Technique.

I have been keeping recordings of my trip log, in enhanced mode. Recording the miles driven, watts per mile, killowatts used and percent remaining in the batttery (as reported by MFMobile). If you do the math you can actually figure out what the actual capacity of the battery was at the point of a full recharge. I will be posting these numbers a little later this week.

The only problem is relying on My Ford Mobile to give an accurate percentable of remaining battery. My experience with MFM is odd swings in the "accuracy" of information which it provides. As a hint of the upcoming numbers my battery capacity fluctuates from a low of 17 kWh to 25 Kwh.

At this point in time, the only way to get an exact number is to "run" the battery from full to dead stop.

I have learned the car will drive many more miles than the battery says it has. I have driven 83+ miles several times and had an ending reserve of 7-10 miles when the battery claims to have only 77 miles of capacity at the start of the drive. There is an odd event that occurs when the battery gets under 30 miles of capacity. It starts to bonus you multiple miles of status. I have literaly had a minus 3-4 miles at 30 and ended up with 10 miles of surplus upon the completion of my trip.

My driving technique is very constant. I drive 60 mph on cruise control, ac on, radio on, multiple telephone and text messages. I am not Mr Zippy, but I do want to get where I want in the style that I want.

I am not complaining about my mileage. I am just looking for a way to track, accurately, the capacity of the battery and be able to document my gradual loss. That way I will know when I cannot "stretch" out the miles and start taking my gasser on longer trips.

I will keep you posted here. Wood
2012 Ford Focus Electric. Delivered 5/29/2012

Charged Up
Posts: 59
Joined: Wed Aug 10, 2011 7:13 pm
Location: Virginia

Re: Battery Life

Mon Sep 24, 2012 6:24 pm

dwf123 wrote: There is an odd event that occurs when the battery gets under 30 miles of capacity. It starts to bonus you multiple miles of status. I have literaly had a minus 3-4 miles at 30 and ended up with 10 miles of surplus upon the completion of my trip.
When the battery showed 30 miles of range left you were -3 or -4 on "surplus" and then you drove how much further and ended up with +10 surplus?

Agree it would be reassuring to verify capacity. Would be great to have some method other than running to empty.

Have you triggered the very low battery warning Wood? What do you typically show for range at that point?

dwf123
Posts: 100
Joined: Sat Mar 10, 2012 8:04 am

Re: Battery Life

Tue Sep 25, 2012 4:00 pm

When the battery was at 30 miles and -3 surplus I had approximently 40 more miles to go. This is the only time I ended up in the very low battery range (10 miles or less). I ended up at my destination with 7 miles on the battery and it showed +5 surplus. (Remember the battery shows how many estimated miles you have left and includes the surplus.) In that 40 miles of driving I ended up with a total of 13 surplus miles. I want to let you know I do not change my driving habits very much. Typically it is 60 mph, cruise control, AC on, radio and sync active.

One other thing to keep in mind is the difference between "Battery Gauge" miles and "actual" miles driven. The gauge sets the budget, at the beginning of the trip, lets say 77 miles. When you finish your trip and look at the battery gauge and subtract your original budget amount from the remaining battery balance, 77 miles - 7 miles = 70 miles, it rarely equals the number of miles driven according to the trip odometer. In this case I drove 83 miles and had a remaining balance of 7 so I should have been able to drive a total of 90 miles.

This whole system is a "guesstimation". I understand why it is done and it actually makes sense, however, when you test the logarithm, you can get some different results. This is no different than the warning light on your gas gauge. There is always a couple more gallons buried in there somewhere. You just have to figure out how many.....

The variable we have in the electric car is "degradation" over time. That is one of the things I am trying to get a handle on. Right now I feel very safe driving 85 miles on my battery. But at what point will degradation, and it will occur, shrink that to 83 or 81 or 77 miles?
2012 Ford Focus Electric. Delivered 5/29/2012

felkster
Posts: 25
Joined: Mon May 28, 2012 10:10 pm
Location: Seattle

Re: Battery Life

Fri Sep 28, 2012 12:50 pm

I don't think we can really use miles to measure degredation, especially in the display. The calculation of mileage range happens too often to be able to use that as a measure, unless someone was driving 100% identically, every single day, for many years.

I think we have a great gift here with the kWh display - which is a direct measure of capacity. A much more direct way of measuring than looking at capacity bars (in the Leaf) or mileage (which varies based on driving).

dwf123
Posts: 100
Joined: Sat Mar 10, 2012 8:04 am

Re: Battery Life

Fri Sep 28, 2012 6:26 pm

I think we have a great gift here with the kWh display - which is a direct measure of capacity
Where??? I do not see a kwh display when the battery is freshly charged. Do you mean the kWh hours used when you look at the trip meter after traveling a specific distance? I wish it did have a kWh display you could see when you get in the car, all I see is a battery gauge which tells me XX number of miles capacity on the battery. That is one of the things we keep trying to determine - how many kwh available after a new charge. You can do the math and figure it out by reversing the process and driving a set distance then getting a % of battery left after so many miles. But, that is a variable relationship.

If you have discovered a way to see kWh hours after a fresh charge please let me know.....
2012 Ford Focus Electric. Delivered 5/29/2012

Evocus
Posts: 39
Joined: Thu Jul 19, 2012 12:53 pm
Location: Southern California

Re: Battery Life

Sun Sep 30, 2012 8:13 am

If you use the trip meter for kWh used and MFM for Used Battery Capacity in percent, I believe you can estimate the capacity fairly well. Just reset the counter after each charge and assume 100% as your starting point. Just before you plug in, scan MFM to get your remaining capacity and subtract that from 100%. The more miles you can go with each charge the more accurate this estimation should be because we only get a whole integer for battery percentage. By doing this once per month, we should be able to track the reduction in capacity over time and notice changes in the 5-10% range pretty easily.

Used Energy = 58 miles * 243 Wh/mile = 14.1 kWh used
Used Capacity = 100% - 28% = 72%
Estimated Capacity = 14.1 kWh / 0.72 = 19.6 kWh


Date: 24-Sep-12
Mileage: 3615
Miles This Charge: 58.0
Average Efficiency (Wh/mile): 243
Total Energy (kWh): 14.1
Used Capacity (%): 72%
Estimated Capacity (kWh): 19.6

Date: 25-Sep-12
Mileage: 3670.8
Miles This Charge: 55.3
Average Efficiency (Wh/mile): 259
Total Energy (kWh): 14.3
Used Capacity (%): 74%
Estimated Capacity (kWh): 19.3


Tim

P.S. Sorry for the cross-post in the Estimated Range thread.
2012 Ford Focus Electric White Platinum Tricoat Metallic (4 July 2012)
Schneider EV2430WS Level 2 EVSE

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