Battery not holding enough charge

[sefs]

Even more curious, what does that mean?

There is a recalibration command in IDS for the battery. It appears it just strips all GOM data, and resets it to some baseline. I'm not sure that it changes the Ah counting calibration or not.

 

[michael]

As far as I can tell:

The TMS tries (and is generally successful) in preventing the battery from exceeding 98 F, but it makes no effort to maintain some "optimal" temperature lower than that

I live in SoCal and I have never observed my battery cooled to the point (based on what I've read here, 50 F) where the TMS attempts to to warm the battery, but based on how it works at high temperatures, I would expect it to heat to 50 F and then stop TMSing.

So it looks like there is a window between 50 F (I am told) and 98 F (I have observed) where the TMS does nothing, simply allows the battery to go to whatever temperature circumstances cause.

Unless it's quite cool, the battery will generally progressively heat up to 98 F during charging, at which point the TMS system will prevent further temperature increases (perhaps a degree or so, I've never seen more)

Driving will heat the battery but not nearly as fast as does charging. I can go on a 40 mile freeway drive with the battery starting at 70 F, and when I arrive it will have warmed only a few degrees. If I plug in and start charging, and it quickly starts climbing. If I don't plug in, temperatures remain quite stable. Even on a hot day, it will climb slowly until charging begins at which point it will heat quickly.

This design is different than, for example, in the Volt. People have shown that the Volt TMS system keeps the battery between approximately 85 and 70 F when plugged in a not charging. It is what the NREL calls an "agressive" cooling system. The FFE does not work this way as far as I can determine. It simply keeps the battery temperature from exceeding the limits of 50 and 98 F. I don't know how Tesla/Toyota/Mercedes or BMW work.

 

[EVA]

How do you read the temperature of the battery pack?

Thanks so much for the responses. Good to know 10% is the bottom - no harm in that.

 

[michael]

You need an accessory OBD scanner to get the temperatures, not displayed on the dash.

Yes, taking the battery to the lowest level that the system normally permits (actually 8%) is not harmful. For lead-acid and some other types of battery, yes, but lithium perfectly happy at this level.

Lithium batteries will be ruined if taken to EXTREMELY low levels, but the car will not permit this in normal operation.

 

[magudaman]

I had a similar experience. I was down to 17.9 kWh before about 1% battery. It ended up being battery capacity miscalculation. Here is the gold standard for checking capacity: Fully charge the battery. With the car in your garage, turn it on and reset the trip meter. Roll down the windows, and turn the HVAC on max defrost. Turn off the rear window heater. Let the battery go all the way till the contactor opens. This will take a couple hours. This will be when the Ready to Drive green car goes away, not just when it says stop safely now. In my case, stop safely now occurred at 18.1 kWh, the contactor didn't open until 19.4 kWh. It was all battery capacity miscalibration.

I'm not sure that you would generally see that 19.4kwh number while driving or in normal use circumstances. Several factors could have changed the capacity of the pack driving = ~1hr discharge verses a 3 hour discharge.

First off unless the batteries are warming up during discharge, that faster you discharge them the less capacity you will get. This is due to internal losses in heat and chemical inefficiencies. This is known as Peukert's law. While lithium does much better at high discharges than most chemistries when looking at capacity, it will still show losses.

Here is an example showing AH of capacity extracted from the batteries, if we could see watt hours the effects might be even more visible.

Lastly miscalculations can occur while driving due to regen losses or benefits. The battery can be charged at upward of 52,000 watts as you regen to a stop. The losses and actually capacity making back into the cells chemically may be under or over compensated for. I need to try to confirm this recording data on an actual drive and see what my data's kwh number comes out to verses the kwh trip meter on the car.

Lastly I am pretty positive the car goes into balancing pretty much every charge when approaching 100% indicated charge. This of course depending whether you needed the balance or not. Using forscan you can see when balancing function is active or not

 

[michael]

You are right on the money. And I can tell you the battery doesn't heat up very much in operation, some but not a lot compared to the heating during charge.

My best guess is that 98 F is the reference temperature, and with a fairly slow discharge.

I actually did a quick test yesterday. Charged the battery and ran the heater full blast. Battery temp was 58 F. The consumption meter on the dash showed almost exactly 6 kW consumption (6 kWh/hour) but the OBD scanner showed the energy to empty (ETE) falling must faster. I didn't take it all the way down, but it wouldn't have delivered anything close to 18 kWh I'm sure.

 

[sefs]

I'm running the test right now. The first time I got 18.1 kWh with the battery starting at 50F. I'm now charging and heating the battery for a higher temperature test.

 

[sefs]

You are right on the money. And I can tell you the battery doesn't heat up very much in operation, some but not a lot compared to the heating during charge.

The reason the battery temperature is rising so much faster during charging is that the charger is in the same coolant loop as the battery. So when the charger is running, it is preheating the coolant into the battery.

 

[michael]

I don't think so. I don't hear any sound of coolant running until the battery temp reaches 98 degrees. What's your basis for saying this?

I would expect the reason for the heating is the efficiency....22 kWh of power in to put 18 kWh into the battery (approx) the other 4 kWh turn into heat.

I wouldn't think Ford would intentionally lower the MPGe of the car by heating the battery (except of course when it's very cold). And it would be a bad thing for battery life.

 

[sefs]

The pump is running the whole time the car is charging. It does run more quickly when it's hot, but it's running all the time none the less. Put your hand on the pump, you can feel it running. At low speed it's nearly silent.

As for the coolant loop being battery and charger, it says it right in the manual.

 

[fbitz777]

Lately (cold here) I have seen around 18.4kwh and the car stops moving... However the strange things I see:

1-if I wait a few minutes then the car can move for a little bit longer....saved from being stranded so close to charger. I never saw that during the summer.

2-Once there is no more moving possible I turn the MAX defrost and I see on the power meter 5KW+ for while!

3-by the time that heat stops,...I am usually at 19.4kwh which is what I routinely get when the weather is warm

I am suspecting the car does not want to push much beyond 18kwh range when it is cold (I get that warning about cold weather) maybe as pre-emptive measure?

I know I can get 19.4kwh easily when warm like a week ago.

 

[hybridbear]

I did an 80 mile round trip today. Arrived home with 0 miles and 0% on the MFT screen. I drove about 1.1 miles after the car switched to 0%. The MFM trio log shows 9.4 & 9.5 kWh used on my two trips. Considering that MFM just truncated and doesn't round I would guess that I used about 19 kWh today.

 

[mchafs]

I think it's a good idea to have a full discharge cycle every once in awhile (few months?) to reset the SOC calculations. SOC is very difficult to determine in Lithium chemistry batteries because the cell voltage is relatively constant over the discharge cycle. To calculate the SOC the controller (usually embedded in each cell string) measures instantaneous voltage, current, charge/discharge rate, and temperature and also adds an aging coefficient based on battery age. There may be other factors as well. The 100% SOC is based on monitoring the cell voltage, current and temperature profile as the battery is charged to determine the 100% point and the 0% point by the dropping cell voltage as when near full discharge and the voltage begins to drop rapidly. While the 100% SOC is re-calibrated every full charge cycle, the current actual capacity SOC is entirely based on a complex algorithm using the physical parameters above. If there are any errors or biases in the calculation then the SOC error will gradually increase with time as energy is moved in and out of the battery. I would suspect that the SOC calculation is designed to slightly bias toward reporting a lower SOC than actual to reduce users experiencing rapidly and unexpectedly hitting 0% and SSN as the battery voltage suddenly starts dropping rapidly when the true SOC gets very low. When the battery is discharged to a very low SOC and then fully charged to 100%, the true battery capacity and therefore the current calculated SOC can be re-calibrated by the SOC algorithm.
All of this is completely internal to the battery pack itself and before the calculations of the GOM, which of course are very dependent on recent driving history and other factors.
BTW it's easy to see the Wh/mile estimate that the GOM is using to estimate range when you first start the car, by looking at the height of the "blue bucket". It will be at the value that the GOM is using for the initial calculation (if you do not have a trip destination entered in the navigation system).

2014 FFE 10,000 miles