Battery life in the cold

[Michael Price]

OK - firstly - by cold I mean normal UK cold weather
and I also mean England/Wales - not serious Scotland stuff

Anyway - I went out today for a ride - Bosch ActivLine with the 300 battery pack

Over the summer I could easily do 2 rides of over 20 miles and still have enough battery left to get home - all in Tour mode (2nd from bottom level - out of 4)

But today I started with a fully charged battery and by the time I got home after 24 miles the power level was down to 1 bar - out of 5

Now - I should say - it was not my normal loop
Normal loop involves a lot of canall paths that I dodged due to mud rain - so more on roads than normal

But also - it is cold and wet and I have noticed before that battery range drops in the cold

But is this normal??

TIA

Mike

 

[sjpt]

Cold will reduce capacity a bit, probably not that much though. You may have more hills on the road than the canal, which would make a significant difference. Also, any significant wind would make a big difference.

The Bosch range assistant is very helpful to give a guide of how different conditions affect range. https://www.bosch-ebike.com/en/service/range-assistant/
Some of the details are a little awkward to guess what they mean (eg the terrain setting), and the season only has summer and (by the picture) fairly extreme winter.

Leaving lots of details to default but with 300w battery the assistant suggests 36 miles summer, 30 winter.

 

[Nealh]

Cold can and will reduce range.

 

[vfr400]

In theory, temperature can affect range, but in practice, the cells are fairly well insulated from the environment and they heat themselves up in use, so the temperature of the battery is completely different to ambient.

My theory is that temperature has more effect on the rider than the battery, which is what accounts for the reduction in range.

 

[Michael Price]

Thanks all

especially like
My theory is that temperature has more effect on the rider than the battery, which is what accounts for the reduction in range.
from @vfr400

 

[Gringo]

Definitely reduced range in the cold,
I have a Bosch ALP at the moment, this is my third ebike over the last 12 years and all 3 have given less range during each winter only to get back to normal each spring/summer. It’s not a lot but definitely noticeable.
you use to be able to buy a neoprene cover for Bosch batteries, the idea was to keep the battery war.
I’m finding the best thing to do is start Your journey with a warm battery, I keep my battery in doors and only put it on the bike just before each ride

 

[vfr400]

Definitely reduced range in the cold,
I have a Bosch ALP at the moment, this is my third ebike over the last 12 years and all 3 have given less range during each winter only to get back to normal each spring/summer. It’s not a lot but definitely noticeable.
you use to be able to buy a neoprene cover for Bosch batteries, the idea was to keep the battery war.
I’m finding the best thing to do is start Your journey with a warm battery, I keep my battery in doors and only put it on the bike just before each ride

I still say this is a myth and I'll tell you why.

Firstly, I can't remember anybody ever coming on here and saying how much further they noticed they could go when it's hot.

Secondly, if you charge the battery in the house, it gets the same charge as normal. You can't destroy that charge, you can only use it. It's true that cold can slow down chemical reactions, so you could notice a loss of power, and you could get more sag, but you would still be able to get all the charge back out of the battery.

Thirdly, experiments were done, where single cells were held at different temperatures, that showed a loss of performance, but as I said in my previous post, those conditions don't apply to an ebike battery. The cells have internal resistance, so they start to warm up as soon as you start to use them. Each cell is surrounded by many others, so, like penguins, only the ones on the outside are in the cold, and even they are pretty well insulated in the thick plastic case with air separating them from the case.

If you allowed your battery to acclimatise in a low temperature, then charged it at the same low temperature, I can see the possibility for lower charge

I don’t doubt that people get less range in the Winter compared with the Summer. I believe that there are other factors involved rather than the battery. Interestingly, I've never noticed any difference in my range between the seasons.

I believe that the neoprene cover is a con. If you look inside a Bosch battery, you'll see that the cells don't come in contact with the case and there's already a significant air gap around them to insulate them from the environment.

It's a well-known fact that the human body can't work so well in lower temperatures. When 50% of the power is coming from the rider, and that power is compromised by the temperature, it's very logical that you would be relying more on the power of your ebike. Only a few degrees makes a significant difference to a human. That's why top athletes have to warm up and use special clothing until they're ready to go. In fact temperature has such a profound effect on the human body that a drop of only 7 deg is likely to render you unconcious., while as your ebike battery wouldn't even notice it.

 

[haggis]

Cold will reduce capacity a bit, probably not that much though. You may have more hills on the road than the canal, which would make a significant difference. Also, any significant wind would make a big difference.

The Bosch range assistant is very helpful to give a guide of how different conditions affect range. https://www.bosch-ebike.com/en/service/range-assistant/
Some of the details are a little awkward to guess what they mean (eg the terrain setting), and the season only has summer and (by the picture) fairly extreme winter.

Leaving lots of details to default but with 300w battery the assistant suggests 36 miles summer, 30 winter.

One of the problems with electric bikes is that you don't get the instant feedback you get from a standard bike when your tyres are under pressure
That makes a huge difference to range .

 

[sjpt]

Secondly, if you charge the battery in the house, it gets the same charge as normal. You can't destroy that charge, you can only use it.

You can't destroy charge, but you can turn it to heat instead of mechanical energy.

Most of the charge will go into driving the motor, but some of the charge will go into heating the battery and keeping it warm. I don't know how significant that will be. If you charge inside and only put the battery on immediately before use the heating it part will be low. If it is well insulated the keeping it warm part ill be low.

There may be other parts of the system that lose more heat in the cold, thus consuming charge.

I still agree that it is almost certainly other cold/winter related factors that are the major contributor to lost range. For example, rolling resistance apparently increases significantly at lower temperatures.

 

[sjpt]

One of the problems with electric bikes is that you don't get the instant feedback you get from a standard bike when your tyres are under pressure
That makes a huge difference to range .

Good point. Also badly adjusted brakes with a little rubbing can similarly get ignored.

 

[vfr400]

You can't destroy charge, but you can turn it to heat instead of mechanical energy.

Most of the charge will go into driving the motor, but some of the charge will go into heating the battery and keeping it warm. I don't know how significant that will be. If you charge inside and only put the battery on immediately before use the heating it part will be low. If it is well insulated the keeping it warm part ill be low.

There may be other parts of the system that lose more heat in the cold, thus consuming charge.

I still agree that it is almost certainly other cold/winter related factors that are the major contributor to lost range.

Surely, if that were the case, the battery would become warmer.

 

[sjpt]

Surely, if that were the case, the battery would become warmer.

The battery does get warmer, as you noted. And because it is warm the energy is dissipated into the atmosphere. As I said, if it is well insulated the 'keeping it warm' won't use much energy; the internals will be significantly warmer with a temperature gradient to the case so the dissipation will be low. Insulated or not it will reach an equilibrium temperature. If well insulated and prewarmed to house temperature the equilibrium temperature may be similar to house temperature. If well insulated the internal temperature will be higher and the case temperature lower than if it is badly insulated.

 

[vfr400]

I think minute amounts of alcohol in the air has more effect on battery range than temperature. I've noticed that I use about 7wh/mile from the battery on a normal ride, but if I stop off at a pub and have a few drinks, afterwards, my consumption goes up to around 12 wh/mile. The more drinks I have, the higher the battery consumption afterwards. That doesn't happen if I have only soft drinks, so I conclude that it must be the alcohol that I breathe out while riding. Obviously, the more I drank, the more alcohol in my breath. Try it for yourselves and see if I'm right.

 

[sjpt]

Some vey rough calculations indicate a few watt-hours for warming up a battery, and a watt or so continuous extra power to keep warm. So probably only a percent or so of total charge. My assumptions could easily have been wrong, as could my calculations. Does anyone know the 'typical' (or even ballpark) temperature of the internals and surface of a battery when the ambient temperature is around freezing; typical riding on medium assist levels? I guess it would be noticeably but mildly warm to the touch; but maybe anything that wasn't actually freezing would be.

 

[WheezyRider]

Not done any range experiments, but I have certainly noticed the power output go down from lithium battery packs when used below 10 Deg C.

In the colder months when getting the charged up bike out of the garage in the morning and riding it to work it is sluggish and the voltage drops low quite quickly for a modest load.

Recharging at the office (which is usually warm) and then riding home again is a different story, power output is normal again.

This is with no human input.

You would think that the battery warms up in use and then gives its normal output, but I think by the time it gets warm, capacity has already been lost somehow. Perhaps it's a case of charging when cold doesn't charge the battery to it's normal capacity.

Now I keep the battery indoors once the weather gets cold and charge indoors, but not overnight if in the house.

 

[georgehenry]

More wind in the winter that definitely effects range.

You mention riding on a tow path, when I ride on the tow path of my local river/canal I do not find I need the motor due to the speed and level gradient.

I commute to work and back throughout the year and see the lowest level my battery goes to from full at some point in the winter but that could be a number of variables including sub zero temperatures, wind and wet roads, and of course my own ability to pedal hard. You are also wearing more stuff in the winter which will produce more wind drag.

So in the summer I use about 35% of my 400Wh battery travelling 10 miles quite quickly, and in the winter when conditions combine to be unfavorable I will use up to 10% more battery for the same journey.

 

[artsyhonker]

Just as a data point: twice I've had trouble with battery cut out and inconsistent power readings while coming home from the allotment when the temperature is below 7°C and the bike has been stationary outdoors a few hours. I'm not talking about "gosh, this hill seems harder to get up, I must be tired", I'm talking about the motor cutting out on the flat, low battery symbol flashing when I had three bars left on arrival at the plot, stuff like that.

I'm not using a Bosch system and I have only had my conversion a few weeks, but I'm pretty sure the battery behaves poorly when it gets cold. It's pretty dramatic. I'm not sure what the temperature threshold is, it's only happened twice yet, or whether it's a combination of low temperature and partial charge.

I purposely didn't charge it after it did this last night -- I want to try riding it today after keeping it in the warm overnight, to see if this is "cold will hose the battery" or "the battery needs warming up to work right". In either case, my next step will be removing the battery and keeping it in the greenhouse while I do allotment work, at least in winter. It's a few degrees warmer in there. At least, being winter, I don't have a huge amount of stuff to haul home, but it's pretty annoying since the hill on the way home from the allotment is one of the reasons I got the conversion in the first place, and yes I'm going to be working there a bunch in winter.

 

[Nealh]

I have never had a cutting out issue with battery in the cold but do notice range/mileage to be less (10% or so). Batteries when cold do offer less capacity and possibly could lead to voltage sag, this could be the explanation for the problem being encountered.
Let us know how the battery fairs having been not charged but left indoors to see if the issue is better.

 

[Michael Price]

You could also try having a cover for the battery to keep it warm - some manufacturers sell ready made ones - but making one yourself would also work

I was wondering - if you have to go up a hill on the way home - does that mean you have whizzed down one before stopping - hence possibly extra coldness due to wind chill?
if so then a cover would be even more likely to work if it is wind proof

I do know that my wife's bike (not Bosch) is less sophisticated than mine and will go from only one light down from max - to no lights left at all if you demand lots of work going up a hill.
then magically the battery lights come back once you are on the flat
If the battery is low anyway it can cut out in this situation - add in lower capacity in the cold and this could be the same as your problem

 

[artsyhonker]

You could also try having a cover for the battery to keep it warm - some manufacturers sell ready made ones - but making one yourself would also work

I was wondering - if you have to go up a hill on the way home - does that mean you have whizzed down one before stopping - hence possibly extra coldness due to wind chill?
if so then a cover would be even more likely to work if it is wind proof

I do know that my wife's bike (not Bosch) is less sophisticated than mine and will go from only one light down from max - to no lights left at all if you demand lots of work going up a hill.
then magically the battery lights come back once you are on the flat
If the battery is low anyway it can cut out in this situation - add in lower capacity in the cold and this could be the same as your problem

I really don't think wind chill is the problem: the hill takes a minute or two to go down and I take it slow (especially if I have the trailer, which I have on both occasions). I think it's sitting in the cold for a few hours while I do allotment chores that's the issue.

A cover might help a bit, but it's hard to say if it would be enough. A bit like using a tea cosy but it would be starting a lot cooler.

Anyway -- having not charged the battery when I got in last night after having problems, sure enough I had the same issue today. I do think it might be a voltage issue, as it was worse going uphill than on the flat, and not really a problem at all when I set the assistance to the lowest level. Unfortunately that isn't enough assist to make up for the extra weight of the battery and motor!

It could well be simply that my battery has dodgy overall capacity, but it's frustrating to see it display three lights (of five) and then give up on me.

Next experiment: full charge, cycle to allotment, leave battery outside in cold all day, cycle home. I know in very slightly warmer weather (say, 11°C) this isn't a problem, even with the trailer, so it will be interesting to see what happens. If that's fine, then the cold probably isn't the biggest problem. If it is a problem then I might need a spare battery or a cover or a hot water bottle or something --ugh. The whole point of the conversion was to get me up that hill (both ways!) without killing my knees, if I'm going to walk up it then I may as well use a normal bike.

I won't be able to try it until the weekend though, tomorrow and Friday I have errands taking me a little further and I will want to start both days with a good charge.