How to Check Battery Capacity, Degradation and Range
Posted: Sun Mar 25, 2012 11:03 am
Reg,RegGuheert wrote:I recently purchased a demo Leaf and just yesterday had a very similar excursion to the one which TickTock described in the OP. GOM was reporting 43 miles and five bars were left after driving only 32 easy miles starting from 80% charge.
Congrats on your new car. I'm not sure how much you've followed along on here prior to your purchase, but nobody puts much thought into what the GoM says. Personally, I cover the thing, since bad data (to me) is worse than no data.
The only true method to determine how far your car will go is to actually drive the car from 100% to Turtle. The important parameters to consider are listed in the notes in the bottom of the range chart (link in my signature line).
If you ever think your battery is experiencing an abnormality, as previously suggested in the thread, try to duplicate a test drive in the same conditions (and preferably course) that you test drove when you bought the car. That means you have to make this run now, and then compare it to that same run in the future when you suspect an abnormality. You should always use climate control off, as there are too many variables there, and I suggest as level highway as can be found in your area.
Temperature is easy to match, but an important note is BATTERY temperature. If you just used a DC quick charger 6 times in a row, and the ambient air is 55F, your battery might be 120F.
Conversely, if your car is left sitting outside in the freezing cold overnight, but it's now 70F in the afternoon, your battery is not at 70F. This is a typical southern California winter weather pattern.
So, the baseline run when your car is new (and record all the data for future use) and a subsequent future run when you suspect a battery abnormality later needs similar battery temperature, ambient temperature (it's important to match up air density at the same elevation), same level terrain if possible (level terrain and steady speed will eliminate the variables of regeneration, because there won't be any), no heater or a/c (for hopefully obvious reasons), the same vehicle weight and dry road conditions. The end result should give you a baseline to compare your performances to consider battery degradation. Some great tools for data collection are Gidmeter or LEAFscan tools !!!
Some more notes to gather your baseline range data; you want a road where you can maintain a steady speed. To compensate for any wind and to compensate for elevation variations (you absolutely will be returning to the same elevation when you pull back in your driveway at the end of the test), I recommend 40-ish miles out, and return of 40-ish miles in the opposite direction, all at 60mph. If you can't travel at 60mph, match whatever speed you use with your estimated range; for example, 50mph steady speed can go about 97 miles per the range chart, so drive outbound about 45-47 miles before turning around for the return.
You need to reset your odometer and miles/kWh economy meter on the dash at the beginning of your run, but don't reset this data until you've collected the data at the end of the test. You should use the Nav economy meter (which reads 0.1 high with the present firmware) to get steady speed data. Get your car at the stable target speed (again, let's choose 60mph) and then reset the Nav economy meter while at that target speed to (hopefully) get the target miles/kWh at that speed. For instance, while on the outbound 40-ish mile leg, at 60mph with cruise control, hit reset on the Nav economy screen reset, and at the end of a continuous 40-ish miles while still at 60mph, expect to see 4.0 miles/kWh on that meter before you start slowing down to reverse course. Then subtract 0.1 to match the console date, to get 3.9 miles/kWh.
Then do the same on the return run. Get to speed, then reset Nav economy gauge, and read the result at the end BEFORE you change the speed. Again, if there's any wind, or elevation changes, or both, you'll get two different numbers for each direction. Again, do not reset the dash economy meter until you've recorded that data for the entire trip, from 100% charge to Turtle mode. Naturally, the dash miles/kWh number won't match your two way averaged 60mph Nav data (even when corrected -0.1), since you weren't driving 60mph the entire trip, like in your driveway, and through the neighborhood to the highway that your test was conducted on.
Its not so important to note fuel bars (but you can) as they are a variable In energy capacity per unit (but not as crazy as the GoM). For instance, the fuel bars will show 12 units at "100%" charge, even if the battery is -20C with 50% degradation. Important "hard data" landmarks are the mileage readings at Low Battery Warning, Very Low Battery, and subsequently Turtle. You don't need to drive the car to dead, just Turtle mode.
Check the tire pressure before a run! 36psi is recommended, many of us run right up to the 44psi limit specified by the tire manufacturer. Reset both economy meters and odometers. Do not attempt this on windy days. Do NOT use the GoM (that's just dumb) or CarWings (current firmware is off 2.5% for mileage). DO NOT USE AVERAGE SPEED.
BALANCE THE BATTERY CELLS FIRST!!! That means, charge to 100% and let the car sit for 4 hours after the car reaches 100% while still plugged in. Or, if you observe a top off charge between one and four hours after reaching 100%, you can then consider the cells balanced (as much as is possible). You don't have to do anything else. The LEAF's automation will take care of all the dirty work.
Checklist before the data collecting run:
1. Any changes to car from stock (different tires, bike rack, Texas cattle horns, etc)
2. Tire pressures set, heater and air conditioning off, car at 100% charge, cells allowed time to balance
3. Gross vehicle weight? 3350 pounds plus operator, passengers, spare tire, bags, concrete, etc
4. Route, length, elevation, hills if any, general conditions (dry, concrete/asphalt, etc)
5. Assumed or measured battery temp (from LEAFscan tool)
6. Ambient air temp
7. Gid count at start, if available
8. SOC, if available (from LEAFscan)
9. Starting total voltage (should be 393.5v from GidMeter or LEAFscan tools)
Data to record:
1. Outbound steady speed (confirm with cruise control on)
2. Outbound observed steady speed miles/kWh from Nav adjusted -0.1
3. Inbound steady speed (confirm with cruise control on)
4. Inbound observed steady speed miles/kWh from Nav adjusted -0.1
5. Miles at Low Battery Warning
6. Miles at Very Low Battery
7. Overall miles covered to Turtle
8. Overall miles/kWh from dash economy display
9. Calculated battery useable energy (miles / miles/kWh = battery kWh)
10.Ending pack voltage, SOC, and Gid (350v-ish from GidMeter or LEAFscan tools)
Post all this data on here for our crack team of LEAFers to decode, but plug the car in to recharge first!