Cold weather

[prebson]

In all this talk about whether warming the battery before driving helps with range, I haven't noticed a discussion about warming the battery before charging. The owner's manual states

When the ambient temperature is 32F
(0C) or less, charging time may be
longer than normal and the level to
which the Li-ion battery can be charged
may be less than at higher temperatures.

That statement would seem to indicate that the temperature of the battery at the time of charging is also a factor with the range one can expect. It seems that the battery can hold more charge with warmer ambient temperatures. Can anyone verify that?

Thanks,
Mark

 

[TonyWilliams]

battery pack temperature info, during charging and while driving, could be very useful.
Anyone have suggestions on that subject?

My thoughts are to drop the battery (relatively easy for me to do), and put a generic temp probe. Any suggestions to a suitable probe / display assembly would be appreciated.

Even if we get CAN bus data to suggest temperatures, I suspect like any LEAF processed data, it will have to have an asterisk next to it until such time as it can be correlated to a separately measured source.

 

[TonyWilliams]

In all this talk about whether warming the battery before driving helps with range, I haven't noticed a discussion about warming the battery before charging. The owner's manual states

When the ambient temperature is 32F
(0C) or less, charging time may be
longer than normal and the level to
which the Li-ion battery can be charged
may be less than at higher temperatures.

That statement would seem to indicate that the temperature of the battery at the time of charging is also a factor with the range one can expect. It seems that the battery can hold more charge with warmer ambient temperatures. Can anyone verify that?

Thanks,
Mark

One thought is that the heated, then charged battery, while sitting at 100% charge in much cooler temperatures, would eventually become "overcharged" as the battery pack cooled.

You would need to drive the car.

But, I also believe Nissan had the pack spec'd at 4.2v per cell originally, over the 4.1v we have on production cars. I think there's a safe top threshold for those situations, but to what range of temperature delta, I don't know.

 

[TonyWilliams]

I believe you may be confused, because, both reduced available battery capacity, and separately, lower m/kWh performance, seem to correlate to lower temperatures, as I believe that I have stated...repeatedly.

I am confused by your posts, of how (or if) you are trying to determine these two distinct cold-weather effects.

I'm working on cold temperature effects on battery capacity now.

To measure the effects on miles/kWh, my next experiment will probably be:

1. Make a cold temperature data run to collect battery capacity and miles/kWh. There's a baseline.

2. Heat battery in heated garage, and/or maintain temperature with electric resistance heat (from external power source), and drive same circuit at same speed, with same density altitude, weight, etc.

Observe difference in battery capacity between two temperatures (ok, that's easy enough so far) and observe different miles/kWh for same speed.

 

[Herm]

I would think an external temp probe on the battery case would be better than the dash gage.. in the centerline of the pack you would not be near any cells but the internal air should be equalized enough for a rough measure of all the cells.. the cells are cooled by conduction thru nearby cells to the steel battery case.

 

[edatoakrun]

"derkraut"I've been out of town for a couple weeks; so I charged the Leaf (for storage purposes) to 50% before I departed. At that time, the temperature in my garage was 70deg., and the battery temperature showed 6 bars.

A few days later, I remotely checked the SOC, and it showed 42%, with the battery temp @ 5 bars. Next day, it showed 50% again, with 6 bars. So, as the temperature in my garage went up & down, so did the SOC, commensurate with the battery temperature. In my case, a single bar difference in battery temperature resulted in about 20% change in SOC. I'm a bit surprised, because I didn't think it would be so significant.
Geez! I'm happy I live in San Diego.

Recently I charged from 80% to 100%. Several days later, I charged to 100% in the Early am off-peak, at about 30 degrees ambient. 5 hours later, at about 40 degrees ambient, still showing 12 bars, I hit "start charging", and it started. CW notified me it stopped after about 20 minutes.

Those of you with the ability to meter "at the wall", and/or other charge monitoring capabilities, might find some interesting Battery capacity/temp info by charging to 100% at low temps, and seeing how many more kWh the LEAF would use/receive (charge inefficiency?) at significantly higher temps.

Anyone tried it?

 

[edatoakrun]

I believe you may be confused, because, both reduced available battery capacity, and separately, lower m/kWh performance, seem to correlate to lower temperatures, as I believe that I have stated...repeatedly.

I am confused by your posts, of how (or if) you are trying to determine these two distinct cold-weather effects.

I'm working on cold temperature effects on battery capacity now...

Yes, but, I believe you (currently) propose identical percentage corrections, for both capacity and range, when discussing the two subjects.

"5. Temperature Decrease: Subtract 1% loss from range for each 4F/2C below 70F/20C"

http://www.mynissanleaf.com/viewtopic.php?f=31&t=4295&start=270" onclick="window.open(this.href);return false;

The 1% loss per 4F/2C below 70F/20C rule-of-thumb is for battery capacity...

http://www.mynissanleaf.com/viewtopic.php?f=9&t=7612&start=10" onclick="window.open(this.href);return false;

To measure the effects on miles/kWh, my next experiment will probably be:

1. Make a cold temperature data run to collect battery capacity and miles/kWh. There's a baseline.

2. Heat battery in heated garage, and/or maintain temperature with electric resistance heat (from external power source), and drive same circuit at same speed, with same density altitude, weight, etc.

Observe difference in battery capacity between two temperatures (ok, that's easy enough so far) and observe different miles/kWh for same speed.

This is what I tried to do between my September and November range/capacity tests, though I didn't try to control battery temperature, of course, and used CW-derived battery capacity. I think the greatest uncertainty will be in replicating both weather, route, speed, and driver inputs for these tests, absent having a level course/constant speed opportunity.

An accurate battery temperature control/measurement system might be difficult also.

On a tangential question, wouldn't you expect the different battery location within the pack, to result in different warming/cooling rates and temperatures, due to varied ambient temperatures? Couldn't this effect cell balancing operations, and also temperature-related battery capacity?

 

[GaslessInSeattle]

until we have good battery temp figures I can only try and surmise what is happening when I preheat/charge from 80% to 100%. there is greater resistance in charging the upper 20% and thus maybe more potential to generate heat during charging. the preheat/charging could be warming the battery internally some, while also warming it with heat radiating from the cab, both working together to raise the temp enough to increase the charge it is accepting. It's also possible that the preheat mechanism allows for a little over charging. How well this works in extreme cold, I have no idea. but in moderate cold like we have here, it seems to make a good difference. I also have been experimenting with driving the car a bit more aggressively before charging it up, which also seems to warm the battery internally, presumably improving the uptake... previous trip driving style, yet another potential factor in charging and subsequent trip range. since efficiency, not just range seems to be effected by cold, it could be that other influential parts of the car, not just the battery, are getting warmed during prewarming that also improve the efficiency... I just don't know but I'm not going to let it obscure the observation that efficiency seems to improves with moderate increase in battery temperature... I'll take what I can get. prewarming seems to be a key tool in winter time range extension for a variety of reasons.

because I'm prewarming and charging at the same time, I can not track the kW used, at least not from the wall. another side note, I do wonder if driving more moderately has an even greater effect on efficiency with a cold battery than a warm one. moderate warming above some temp threshold may more dramatically improve efficiency/range at more moderate speeds only... if I switched to an aggressive driving technique, I may watch the numbers fall more dramatically, more along the lines that some are experiencing.

the more I try and wrap my head around this, the more I appreciate the design of the Leaf efficiency tools. Extensive prewarming combined with focusing on the power meter to stay within 2-3 bubbles, keeping a close eye on the MPkW for a given trip and staying in the 4's and adding miles driven to the GOM, staying within the trip target distance, really is a remarkably doable way to average out all these effects and get where you need to go as quickly as the range allows. Assuming you are not going up or down hill for prolonged periods, like up or down a mountain pass, one can learn to sharpen these skills and get to your destination reaching very low battery warning with precision.

In all this talk about whether warming the battery before driving helps with range, I haven't noticed a discussion about warming the battery before charging. The owner's manual states

When the ambient temperature is 32F
(0C) or less, charging time may be
longer than normal and the level to
which the Li-ion battery can be charged
may be less than at higher temperatures.

That statement would seem to indicate that the temperature of the battery at the time of charging is also a factor with the range one can expect. It seems that the battery can hold more charge with warmer ambient temperatures. Can anyone verify that?

Thanks,
Mark

 

[TonyWilliams]

I've got to run, so I didn't study your comments with the focus they deserve....

Of course, if CW kWh burns are accurate, it would make it a bunch easier to then make a chart that would both compensate for battery capacity at a temp, and subsequently adjust miles/kWh for the new lower speed required.

My previous suggestion is flawed in not accurately isolating each.

I believe you may be confused, because, both reduced available battery capacity, and separately, lower m/kWh performance, seem to correlate to lower temperatures, as I believe that I have stated...repeatedly.

I am confused by your posts, of how (or if) you are trying to determine these two distinct cold-weather effects.

I'm working on cold temperature effects on battery capacity now...

Yes, but, I believe you (currently) propose identical percentage corrections, for both capacity and range, when discussing the two subjects.

"5. Temperature Decrease: Subtract 1% loss from range for each 4F/2C below 70F/20C"

http://www.mynissanleaf.com/viewtopic.php?f=31&t=4295&start=270" onclick="window.open(this.href);return false;

The 1% loss per 4F/2C below 70F/20C rule-of-thumb is for battery capacity...

http://www.mynissanleaf.com/viewtopic.php?f=9&t=7612&start=10" onclick="window.open(this.href);return false;

To measure the effects on miles/kWh, my next experiment will probably be:

1. Make a cold temperature data run to collect battery capacity and miles/kWh. There's a baseline.

2. Heat battery in heated garage, and/or maintain temperature with electric resistance heat (from external power source), and drive same circuit at same speed, with same density altitude, weight, etc.

Observe difference in battery capacity between two temperatures (ok, that's easy enough so far) and observe different miles/kWh for same speed.

This is what I tried to do between my September and November range/capacity tests, though I didn't try to control battery temperature, of course, and used CW-derived battery capacity. I think the greatest uncertainty will be in replicating both weather, route, speed, and driver inputs for these tests, absent having a level course/constant speed opportunity.

An accurate battery temperature control/measurement system might be difficult also.

On a tangential question, wouldn't you expect the different battery location within the pack, to result in different warming/cooling rates and temperatures, due to varied ambient temperatures? Couldn't this effect cell balancing operations, and also temperature-related battery capacity?

 

[planet4ever]

I've been out of town for a couple weeks; so I charged the Leaf (for storage purposes) to 50% before I departed. At that time, the temperature in my garage was 70deg., and the battery temperature showed 6 bars.

A few days later, I remotely checked the SOC, and it showed 42%, with the battery temp @ 5 bars. Next day, it showed 50% again, with 6 bars. So, as the temperature in my garage went up & down, so did the SOC, commensurate with the battery temperature. In my case, a single bar difference in battery temperature resulted in about 20% change in SOC. I'm a bit surprised, because I didn't think it would be so significant.

Not significant at all. Carwings has tricked you. That so-called SOC it is showing you is nothing more nor less than the number of available charge bars divided by 12. So all it really said was that you lost, and then regained, one available charge bar. That could have been due to a 1% change down and back up in available charge.

And, of course, "available charge" is calculated as (battery energy) / (maximum energy the battery can hold). So, yes, the garage temp went up a ways, increasing the battery max a bit, and dropping the result of the division just over the edge from 6 available charge bars to 5. Then the garage temp went back down, and the calculation tipped one notch back the other direction. Totally meaningless.

Ray

 

[GaslessInSeattle]

has anyone experienced this on the digital soc meter. seems like the greater granularity would be quite helpful. it seems impossible to say if it's insignificant or not until we can tell if it's a simple matter of being at the tipping point at the edge of a bar or something greater. I have seen this happen to.

I've been out of town for a couple weeks; so I charged the Leaf (for storage purposes) to 50% before I departed. At that time, the temperature in my garage was 70deg., and the battery temperature showed 6 bars.

A few days later, I remotely checked the SOC, and it showed 42%, with the battery temp @ 5 bars. Next day, it showed 50% again, with 6 bars. So, as the temperature in my garage went up & down, so did the SOC, commensurate with the battery temperature. In my case, a single bar difference in battery temperature resulted in about 20% change in SOC. I'm a bit surprised, because I didn't think it would be so significant.

Not significant at all. Carwings has tricked you. That so-called SOC it is showing you is nothing more nor less than the number of available charge bars divided by 12. So all it really said was that you lost, and then regained, one available charge bar. That could have been due to a 1% change down and back up in available charge.

And, of course, "available charge" is calculated as (battery energy) / (maximum energy the battery can hold). So, yes, the garage temp went up a ways, increasing the battery max a bit, and dropping the result of the division just over the edge from 6 available charge bars to 5. Then the garage temp went back down, and the calculation tipped one notch back the other direction. Totally meaningless.

Ray

 

[edatoakrun]

Rephrasing my earlier comment, on determining temperature effects on available battery capacity.

A warmer battery should accept additional charge- correct?

Those of you with the ability to meter "at the wall", and/or have other charge monitoring capabilities, might find some useful battery capacity/temp info, by first charging to 100% at low temperature, in several steps, to avoid battery heat increase during the final charge.

Then begin charging again, after warming the battery pack significantly (such as by heating the garage) to see how many more kWh the charger would consume (and the battery would charge, as reduced by charge inefficiency) at significantly higher temps. Shouldn't a 40 degree F temperature differential likely produce a 1-2 kWh increase in available battery capacity, that could be estimated fairly accurately?

You could then calculate the total ABC in a subsequent trip, using the method you choose.

Anyone tried it?

Did it work?

 

[DaveinOlyWA]

has anyone experienced this on the digital soc meter. seems like the greater granularity would be quite helpful. it seems impossible to say if it's insignificant or not until we can tell if it's a simple matter of being at the tipping point at the edge of a bar or something greater. I have seen this happen to.

yes and that only illustrates how difficult charge measurement on batteries can be. unless you are counting coulombs you are really on extrapolating charge and that is what the Leaf does.

other day, i am driving during my 100.1 mile cold weather test. olympia/lacey area. during the day when i was driving around (started at 9 AM) temps ran from 37 to 45º. it was in the 30's until about 12:30 when the Sun came out in full force. (rare for this area to have that much Sun)

because of the test, i was tracking when i lost my battery bars in both GID and SOC. we were going to Sushi place for Lunch. on the way, i lost a bar at 102 GID this was probably less than 10 minutes after the Sun started to shine.

we get there, GID is 98. park, eat, come out just over an hour later or so and GID is at 103!!. Solar radiation made the car very warm to the point where no heat was needed at all. car thermometer went from 40 when we parked to 44º

now, heat does not create the power. it only allows batteries to work better which in turn stores more power but that is only during the charging process. right?

 

[Herm]

now, heat does not create the power. it only allows batteries to work better which in turn stores more power but that is only during the charging process. right?

also works better during the discharge process, lower IR losses.

 

[DaveinOlyWA]

now, heat does not create the power. it only allows batteries to work better which in turn stores more power but that is only during the charging process. right?

also works better during the discharge process, lower IR losses.

right so basically the real time readings on the SOC meter have a bit of sag while moving or when powered on.

Over the next few Weeks I will be checking this inn relation to DOC and account of time between power of and power on