xanatos said:
My other values if it helps:
SOC = 87.7%
AHr = 51.36
SOH = 78%
Hx = 59.90%
GIDs = 201
xanatos said:
And to answer the question, yes the GID value I posted was at 100% full charge.
My 2011 SL has very similar numbers to your LEAF: Ah reading is currently at 51.09 (78% SOH) and it just dropped the second capacity bar (down to 10), which I predict you will do any day now. That's the bad news.
Now for the good news: As DaveInOlyWA said, it appears that your battery is not balanced, hence the low SOC at full charge that you reported (bolded). That often occurs if you do not charge to full frequently, such as when you use the 80% mode on the charge timer. Why is this good news? Because there are things you can do to achieve higher SOC at full charge, just like when your LEAF was new. Using some tricks I learned along the way, I was able to charge to 95.1 SOC on Monday in order to drive to a Fourth of July picnic that was 75 miles from home.
More good news is that part (maybe a big part) of the degradation reported by your car is likely a form of pessimism on the part of the instrumentation that you can work around under some conditions.. While this is a hotly-debated topic around here, I will confirm that much more of our LEAF's battery's
capacity is still there than is reported by the vehicle. The difficulty is in being able to access this capacity in order to make longer trips. Here's an anecdote from my Fourth of July trip to help illustrate what I mean:
I drove the 75 miles to the destination and arrived with 19.1 SOC remaining in the battery. If I compare this result with a trip I made under the same weather (overcast and 70F) and driving conditions (hypermiling) to this same destination four years ago when the car was new, I believe that back then I arrived with an SOC of only about 17%! How can that be if the battery has degraded over 20% since then?
Here's my take:
- Capacity, as reported by the instrumentation in the LEAF, is DISCHARGE capacity at a particular discharge rate. This is the capacity which matters when trying to drive a particular distance.
- The discharge rate at which the LEAF estimates remaining capacity is likely rather high: probably a C rate (1-hour discharge).
- The PRIMARY degradation that has occurred in our batteries over time is an increase in the RESISTANCE of the battery. I will guess that the resistance of our batteries has approximately doubled from about 60 mOhms to around 120 mOhms, maybe much more.
- The resistance of some cells increases faster than other cells. This makes it harder for the battery management system (BMS) to keep the cells balanced.
- The LEAF's instrumentation ultimately bases ALL of its estimates of SOC on battery voltages.
- The LEAF's instrumentation seldom has the opportunity to measure the battery voltage under no-load (zero current) conditions. Instead, it mostly measures the battery while it is either discharging OR charging.
The practical result of all of the above is this:
- Our batteries are ABSOLUTELY degraded. They are NOT the same as they were when they were new.
- In normal use, our batteries will typically charge to a lower SOC than they did when they were new and the SOC will drop rapidly when we start driving the car.
- LBW and VLBW occur at significantly higher SOCs than when the vehicle was new. It has been reported that LBW occurred at 17.8% SOC when our cars were new, but I now see it at about 26% SOC. This is quite a bit more of an increase than one would expect from losing 22% of the battery's capacity.
- Under "normal" charging and driving conditions (60 MPH) we likely can only go about 78% as far from full to LBW as we could when the car was new. (Tony Williams has done extensive testing that bears this out.)
- BUT, if we can manage to get the battery well-balanced and charged to a very high SOC AND we drive slowly AND we use LeafSpy to know what the actual SOC is, we can still drive almost as far as we could when the car was new under similar circumstances. But this is only true IN WARM WEATHER.
- Unfortunately, in cold weather (below about 30F), the effects of the degradation are felt much more strongly, even if you try to use all the tricks I have mentioned. This is due to a further multiple increase in the resistance of the battery AND the need to run the heater and/or the defroster in those conditions.
Note that none of what I have discussed above will affect what the instruments in the dash display. You won't see capacity bars return or anything like that.
Now for some notes on charging to a high SOC and achieving a good balance:
- You need to charge to full multiple times over the course of a few days if you want to be able to fully charge the battery.
- If you want to charge to a high SOC in a MY2011/2012 LEAF, you need to charge more slowly at the end of the charge (last hour or more). Here are some ways to do this: A) turn on the air conditioner while charging, B) charge at L1 rates (120V) or C) do both. (If you have a 2014(?) or later EVSEUpgrade, you may have the option to control the charging rate using that, as well.)
The bottom line seems to be that increases in resistance of the LEAF's battery are the most significant form of degradation for many of our vehicles, which means that more of the capacity remains than the instruments let on. The trick is in accessing that capacity when you really need it.
