Help! [Newbie] Batteries in Autumn/Winter

FatBob

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Apr 15, 2020
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Greater Manchester
With the cooler and wetter weather approaching, I (a newbie to ebikes) was looking for some help and advice on best practice for caring for batteries.

I have a bike with a Samsung Lithium-Ion 21Ah 36V 756Wh battery. The bike's user manual only says not to charge the battery below 17 °C [edit] 4 °C.

Q1) Presumably though it's perfectly OK to use and store (e.g. at night) the battery below this temperature?
Q2) Is there a temperature (or range) below which most batteries should not be used or kept?
Q3) Is there a level of charge that the battery should be kept at in cold conditions (or just in general)?
Q4) Is it OK to use in rainy/wet conditions? As far as I can tell the battery looks waterproof but obviously has metallic connections. It sits under the seat.
Q5) If I wasn't going to ride the bike for a number of months (e.g. because the roads are too dangerous) how best to look after the battery to maintain optimal 'health', i.e. frequency and level of charging, storage temperature?

Thanks in advance.
 
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sjpt

Esteemed Pedelecer
Jun 8, 2018
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Q1) yes, store and use it below 17 degrees (and most advice has quite a bit lower safe charging temperature)
Q2) probably don't use or store it much below 0. Range will be lower at these temperatures.
Q3) storage charge: around 80% for shortish periods (weeks), around 50-60% for months
Q4) rainy, yes, fine. The display is often the weakest point in rain
Q5) Keep it around 50-60%, probably charge a little once a month just be sure. Room temperature should be fine.
 
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Nealh

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Aug 7, 2014
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Don't charge below 17c what a load of cods, you will fine charging at lower temps just avoid freezing to about 10c.
1. Lithium stores best at low temps (remember to bring in doors for a day or so to acclimatise to ambient rom temp before charging). Low temps reduce the ability of lithium to maintain full capacity.
2. Degradation is slower at freezing air temp, using in freezing weather then one can expect less range. I have ridden in freezing weather with no major issues except cold toes.
3. Storage charge 38.5v .
4. Ok, just don't leave out in standing rain for hours on end.
5. As for #3. Wake it up once a month if you wish with a 10 min charge.
I simply just monito voltage.
 
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vfr400

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Jun 12, 2011
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With the cooler and wetter weather approaching, I (a newbie to ebikes) was looking for some help and advice on best practice for caring for batteries.

I have a bike with a Samsung Lithium-Ion 21Ah 36V 756Wh battery. The bike's user manual only says not to charge the battery below 17 °C.

Q1) Presumably though it's perfectly OK to use and store (e.g. at night) the battery below this temperature?
Q2) Is there a temperature (or range) below which most batteries should not be used or kept?
Q3) Is there a level of charge that the battery should be kept at in cold conditions (or just in general)?
Q4) Is it OK to use in rainy/wet conditions? As far as I can tell the battery looks waterproof but obviously has metallic connections. It sits under the seat.
Q5) If I wasn't going to ride the bike for a number of months (e.g. because the roads are too dangerous) how best to look after the battery to maintain optimal 'health', i.e. frequency and level of charging, storage temperature?

Thanks in advance.
You've misunderstood something. I can guarantee that they don't say to not charge below 17 deg. It's either a typo or yoou didn't read it right. Can you show us exactly what the instruction says?

To save a lot of words, you don't need to care about temperature. Just use the battery the same as you always do. Charge it until you get the green light, then ride your bike.
 

FatBob

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Apr 15, 2020
134
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Greater Manchester
You've misunderstood something. I can guarantee that they don't say to not charge below 17 deg. It's either a typo or yoou didn't read it right. Can you show us exactly what the instruction says?

To save a lot of words, you don't need to care about temperature. Just use the battery the same as you always do. Charge it until you get the green light, then ride your bike.
I have checked and you are all quite correct. I now have absolutely no idea whatsoever where I got the figure of 17 °C from (possibly something to do with work), but I would have sworn that's what I read! It does in fact say not to charge below 4 °C (40 °F).
 

vfr400

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Jun 12, 2011
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There's no harm in charging at 4 degrees C or any other temperature. In theory, you can get a bit more capacity if you warm your battery up before charging, but if your journeys are not long enough to run it right down, that's not worth it. Also, the battery warms itself up when you charge it, so it won't be 4deg for very long unless the outside temperature is minus 15 with a strong wind blowing.
 
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Gringo

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Jun 18, 2013
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I always change indoors at room temperature.
In my early days of lithium battery use I read about “lithium dendrite growth” and the damage it causes. It’s still an issue !

“internal short circuits caused by lithium dendrite formation were one of the reasons for battery failure. A Li-ion battery operating under abnormal conditions, such as overcharging or lower temperature charging, can lead to a harmful phenomenon called lithium dendrite growth”

quote from https://www.batterypoweronline.com/news/a-look-inside-your-battery-watching-the-dendrites-grow/
 

FatBob

Pedelecer
Apr 15, 2020
134
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Greater Manchester
Yes, I've read a little and seen microscopy videos about dendrites and the nasty after-effects, i.e. explosive fires. Since I have no option but to charge indoors this is one reason I'm a little nervous about ensuring I'm not doing anything to unnecessarily put my family in danger.
 

vfr400

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Jun 12, 2011
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Yes, I've read a little and seen microscopy videos about dendrites and the nasty after-effects, i.e. explosive fires. Since I have no option but to charge indoors this is one reason I'm a little nervous about ensuring I'm not doing anything to unnecessarily put my family in danger.
Don't take any notice of that stuff. Most of it is hopelessly out of date. You're more likely to kill your battery by frequent removal than by dendrite growth. Those that worry the least have the least problems. Just use your battery and charge it until the charger goes green. That's all you need to do for years of service.
 

vfr400

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Jun 12, 2011
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I always change indoors at room temperature.
In my early days of lithium battery use I read about “lithium dendrite growth” and the damage it causes. It’s still an issue !

“internal short circuits caused by lithium dendrite formation were one of the reasons for battery failure. A Li-ion battery operating under abnormal conditions, such as overcharging or lower temperature charging, can lead to a harmful phenomenon called lithium dendrite growth”

quote from https://www.batterypoweronline.com/news/a-look-inside-your-battery-watching-the-dendrites-grow/
He said dendrites cause short circuits and fires. Use some common sense: How many ebike batteries have you seen spontaneously catch fire? That article is just irrelevant poorly though out research. The cell construction, anode, cathode and electrolyte were nothing like what you find in ebike cells. All he proved was that the more energy you put into a system, the faster things happen, which has been known since the dark ages and proven by every schoolkid doing science and every housewife cooking food.
 
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Gringo

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Jun 18, 2013
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Northampton
From the same article I quoted earlier.
Several Samsung Galaxy Note 7 batteries caught on fire in 2016, and the investigation revealed the mechanism that lithium dendrites caused an internal short circuit
 

vfr400

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Jun 12, 2011
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From the same article I quoted earlier.
Several Samsung Galaxy Note 7 batteries caught on fire in 2016, and the investigation revealed the mechanism that lithium dendrites caused an internal short circuit
and what chemistry was in those Samsung Batteries?

Did they catch fire because they were too warm or cold when charged?

Where's the connection between phones and ebikes? Washing machines and electric bikes both have electric motors. Some Whilpool washing machines caught fire. Does that threfore mean that we should wear asbestos socks when riding our bikes?

I don't know why you guys do this. It happens every couple of months, when someone finds something irrelevant on the internet, then tries to scare everybody to death with it, or persuade everybody to do daft things with their bikes instead of just using them.

Listen everyone! Electric bikes have been around long time and there has been a lot of development effort put into them by the manufacturers to optimise them for reliability, durability and user-friendliness. They're plug-and-play. Just charge them and use them. Don't take any notice of this intellectual masturbation that bored people on internet forums come up with. Use some common sense.
 

FatBob

Pedelecer
Apr 15, 2020
134
36
Greater Manchester
By damaging and/or burning the contacts.
At the very risk of your uncompromising disdain and acid-tongued vitriol, I've never come across the phenomenon of contact burning – I'm just a lay person, not an engineer. What is this in the context of using and charging ebike batteries. Thanks.
 

vfr400

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Jun 12, 2011
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I've never come across the phenomenon of contact burning – I'm just a lay person, not an engineer. What is this in the context of using and charging ebike batteries.
I'm just a person that had to fix all the batteries with burnt contacts! I still keep a box of different ones salvaged from different batteries, specially to repair the burnt ones.

Do you know how a smoothing capacitor works, because there's a big one right across the battery wires? Look at all the threads about "I get a big spark when I connect my battery".
 
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Bikes4two

Pedelecer
Feb 21, 2020
183
82
I've just read that linked to article on dendrites - full of if's, buts, maybes and other unquantified possibilities. Then there's the stuff about charging densities in mA per sq centimetre without any attempt to relate that to real world batteries we use everywhere, let alone in ebikes.

And the writers of the article - no attributions such as professional standards or educational position and more importantly, no peer reviews.

Now, I'm not saying the dendrites thing doesn't exist but that article doesn't lead me to have any concerns about my ebike battery - I'm more 'concerned' that my daisy patch could go into a sink hole (which is where articles like that should go).
 

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