Cold weather battery drain.

[WIZARD]

I ride daily in temps as low as 10f (-10c). Short fun or errand trips of a few miles. I hear everywhere how low and little the battery will put out in Cold. Yet I have yet to find any noticeable effect Cold has had. I'm guessing its because of my shorter time and distances.

Question: Can a rider starting out rely on the light bar or phone app as to the ACCURATE battery level of charge and continue to rely on it AS the ride progresses? Thereby avoiding getting stranded.

My fear is that although these Indicators show 70% or 60% or 50% etc left, the cold skews the reading and a rider actually has less battery than Indicated? I think not and the level indicated IS accurate at that moment. It is just that COLD deteriorates the available power at a higher RATE than it would on a warm day.

The lesson being... simply watch and monitor the Battery more closely/frequently. Correct? It's not just going to drop to zero in a couple minutes inspite of Indicating an acceptable level?

Nb1c+  2200miles and loving it!

 

[esaj]

https://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures

 

Quote

The performance of all batteries drops drastically at low temperatures; however, the elevated internal resistance will cause some warming effect by efficiency loss caused by voltage drop when applying a load current. At –20°C (–4°F) most batteries are at about 50 percent performance level. ... Specialty Li-ion can operate to a temperature of –40°C but only at a reduced discharge rate; charging at this temperature is out of the question.

Figure 1 illustrates the discharge voltage of an 18650 Li-ion under various temperatures. A 3A discharge of a 2.8Ah cell represents a C-rate of 1.07C. The reduced capacity at low temperature only applies while the cell is in that condition and will recover in room temperature.
 

Figure 1: Discharge voltage of an 18650 Li-ion cell at 3A and various temperatures.
Cell type: Panasonic NRC18650PD, 2.8Ah nominal, LiNiCoAlO2 (NCA)
^{Source: Technische Universität München (TUM)}

Matched cells with identical capacities play an important role when discharging at low temperature and under heavy load. Since the cells in a battery pack can never be perfectly matched, a negative voltage potential can occur across a weaker cell in a multi-cell pack if the discharge is allowed to continue beyond a safe cut-off point. Known as cell reversal, the weak cell gets stressed to the point of developing a permanent electrical short. The larger the cell-count, the greater is the likelihood of cell-reversal under load. Over-discharge at a low temperature and heavy load is a large contributor to battery failure of cordless power tools. (See BU-803a: Cell Matching and Balancing.)

The driving range of an electric vehicle between charges is calculated at ambient temperature. EV drivers are being made aware that frigid temperature reduces the available mileage. This loss is not only caused by heating the cabin electrically but by the inherent slowing of the battery’s electrochemical reaction, which reduces the capacity while cold.

 

[Cutiyo]

Speaking of which, my riding group and I took a 90 mile ride during 30/40 degree temps with wind gusts about 30 mph., not as cold as the temps you do your short rides of late, but I'm here to tell you with the temps we were dealing with, we noticed anywhere from 15% to 20% decrease in battery life depending on the rider's weight, elevation, wind, speed and of course the current temp. We all were riding KS 18xls with one rider on a KS 16x. We did reference the app to see where our battery level were and found it to be accurate, especially when one of the riders (220 lbs) who had 80% battery life that drained to 39% battery life after about 15 miles of riding. We were shy 17 miles to the half way point. He wound up swapping wheels with a rider (140lbs) who had roughly 50% battery life and they slow crawled (below 12 mph) the 17 miles to the half way point with 5%-8% battery life left on his wheel. The rider (220 lbs) normally averages 60 miles from his wheel, during summer months, but was averaging a good 45 miles if that. Now, I don't know about the cold skewing the percentages, as much as it will zap the crap out of the available volts a battery have.

As far as a wheel just cutting off when it gets to zero., truth be told before it gets to that point your wheel will beep to high heaven because you can't ride it faster than 4/5 miles and the tilt back will be so, that you'd hop off. What would be the point, you could walk faster than the wheel will take you. To boot, balancing a wheel that slow is an art in and of itself.

[WIZARD]

Thanks to you guys for your input.

My rides are so short that I can see that makes a big difference too.

Very informative.

My bigger worry or project is riding through various concentrations of patchy soft snow, packed snow and shear ice. 16" street tire.

Woops, off subject.

Thanks everyone.

 

[meepmeepmayer]

The cold affects the battery, but not the reading itself.

You get lower range from a cold battery. And the voltage drop under load (drop of battery % when you accelerate) may be worse than at higher temps. This means you might get low battery warning beeps on acceleration earlier than in summer.

But the reading of the battery percentage/voltage (same thing) itself is correct. You won't suddenly be stranded at 50% battery or so. The 50% battery will just appear a bit earlier than usual

[Aneta]

9 hours ago, esaj said:

https://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures

 

 

So, at -20 Celcius discharge at 1C brings the voltage almost to typical "zero %" voltage of 3.3V, which means the wheel, even if it's working, can sporadically shut down completely, esp. if more than 1C per series is demanded. 0 Celcius is more or less OK, but anywhere colder than -10C seems to be very sketchy.

[mrelwood]

A physically large battery pack takes a bit of time to drop in temperature, especially while being used as it warms itself up. Not that I recommend fast accelerations to keep the battery a bit warmer, but the performance drop will just take a little time to materialize.

[Planemo]

Yep we are averaging a 20~25% drop in range from our summer rides at around 25 deg C to our recent ones at 8~9 deg C. A staggering difference really.

[WIZARD]

Thank you guys for keeping it simple. I pretty much knew these things at least from a non-enginer point. I was concerned that the drop could be more sudden than I would anticipate.

Speaking of Drops.

As I am becoming a Seasoned Rider, I am paying more important attention to Lower Battery and sudden inputs, acceleration, potholes (one of my biggest and HIGHEST unscheduled dismounts, literally. I was launched Up Up and away).

I would encourage newer riders to consider Hotdogging and Aggressive riding not be practiced.

Maybe with a Death Wish and full body armor.

Perhaps a few Face Plants are always required to get our attention.

A low battery does not give the same buffer or safety reserve that is inherently required by the euc.

I know many need their euc for transportation. But I ride slow and easy. Like flying. I do it for pure pleasure.

The travel, the trip, the destination is nothing to me. It's the Pure pleasure of the motion, banking, carving my way through the air.

Slow down. Ignor the hotshot videos. Breath the air and put a smile on your face.

We are the secret envy of everyone we pass. Every euc rider knows what I'm talking about! 🙂🙃🙂🙃

Edited December 20, 2019 by WIZARD
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[Aneta]

10 hours ago, WIZARD said:

Slow down. Ignor the hotshot videos. Breath the air and put a smile on your face.

THIS