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Fully replacing a bike for commuting? Beginner questions.


LZmiljoona

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I was wondering about one thing, though:

Why can it damage the battery if you leave it in the cold, when electric cars are parked outside in the freezing all year long and work fine? (except for a lower range - but that's no big deal as battery technology gets better)

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20 minutes ago, LZmiljoona said:

I was wondering about one thing, though:

Why can it damage the battery if you leave it in the cold, when electric cars are parked outside in the freezing all year long and work fine? (except for a lower range - but that's no big deal as battery technology gets better)

It shouldn't damage the battery. It will just decrease the capacity on the current charge cycle. 

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10 hours ago, LZmiljoona said:

I was wondering about one thing, though:

Why can it damage the battery if you leave it in the cold, when electric cars are parked outside in the freezing all year long and work fine? (except for a lower range - but that's no big deal as battery technology gets better)

I've not heard or read till now from any damaging of Li Ion Batteries left in the cold (freezing). 

Cars seem to have a battery heater - just googled for "tesla battery heater". There are tons of search results from tesla forums...

EUC's have no heater (except one ?trial?/mod by @EUC Extreme once maybe) and can be driven below freezing. Just with (much) less capacity and "performance".

As stated by @WARPed1701D before recharging the Li Ion needs to reach above freezing temperatures, or they get damaged.

Below you find the links for the previous statements to batteryuniversity.com - a very nice source of information regarding batteries.

10 hours ago, Mono said:

It shouldn't damage the battery. It will just decrease the capacity on the current charge cycle. 

+1

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

4 hours ago, WARPed1701D said:

Just don't charge  the wheel when the cells are below freezing. 

+1

http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

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13 hours ago, LZmiljoona said:

I was wondering about one thing, though:

Why can it damage the battery if you leave it in the cold, when electric cars are parked outside in the freezing all year long and work fine? (except for a lower range - but that's no big deal as battery technology gets better)

The key points in the replies here that everyone is missing is state of charge and ‘C’ rating of discharge.

Firstly State of Charge:

A Lithium Ion battery stored at around 40% charge will have the longest possible shelf life the colder (within reason) it is stored. So, at first glance it is easy to say that cold does no harm whatsoever to the battery. However this is very different if the battery is fully charged. Fully charged to 4.2V per cell and then allowed to go below freezing acts exactly like an overcharge and can do considerable damage to the cells. The solution the car makers take is that they have intelligent charge circuitry and they do not fully charge the cells; although there have been quite a few horror stories where the Nissan Leaf is concerned - I haven’t heard particularly bad things about Tesla so far though. Most EUC chargers are designed to fully charge the cells and some BMS appear to clamp cells at the absolute maximum of 4.25V per cell so as to get the absolute maximum capacity out of them at the cost of cycle life regardless of temperature. This is why a lot of people use charge doctors to better protect the cells.

Secondly ‘C’ rating of discharge.

Very cold batteries, not only have lower energy density they also have increased internal resistance. To an extent this might seem helpful as it will, in itself, heat the battery up if used at a high current when cold, but it does some damage whilst heating up. Again most cars are not pulling anything like the ‘C’ values that some of our wheels do and as @Chriull says many heat the cells automatically in cold conditions ( but only in use, not whilst parked) The tendency towards bigger and bigger batteries is certainly going a long way to reduce this as a problem but if you take a typical entry level wheel with only a single, or perhaps at most two sets of cells in parallel the level of current can do real damage if cold as well as the lower power making the wheel less safe to ride.

It is often the growth of lithium metal ‘fingers’ or ‘dendrites’ within the cell that seems to be a major factor in cell degradation causing partial shorts within the cell. Understanding how and why these form and what can be done in the cell chemistry to prevent them is one area where cell design is slowely being improved. http://jes.ecsdl.org/content/164/1/A6281.full 

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On 04/12/2017 at 5:51 PM, KingSong69 said:

As our voltages ar only DC and not AC the limit for DC voltages to contact/touch is set at about 120Volt! AC is another story...and in fact it is AC , where you can not let go after touching!!!

Actually, I think @Smoother is correct, my parents had 120V d.c. electricity at home and they told me tales of people “sticking” to it if they were electrocuted, the muscles would tighten and stay tightened. A.C. because it reverses polarity is capable of causing the muscles to kick and throw you away from the source. As I understand it, It was the practical advantages of A.C. such as being able to use transformers that caused the changeover rather than any safety concerns.

Ringing in Telephone exchanges, in the UK at least, is 80V a.c. and we certainly didn’t worry about handling that, indeed more than one stroppy apprentice has been tied to the MDF and had a phone line wired to him and every time he complained the number would be rung for a bit! 120V d.c. though was definitely capable of killing so I’d be more than a little careful going anywhere near that sort of voltage or even 100V.

I keep meaning to find out what voltage they use on the F1 cars because they are very cautious of that, to the extent of the drivers jumping off of the cars so as not to complete a circuit to ground.

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1 hour ago, Keith said:

Actually, I think @Smoother is correct, my parents had 120V d.c. electricity at home and they told me tales of people “sticking” to it if they were electrocuted, the muscles would tighten and stay tightened. A.C. because it reverses polarity is capable of causing the muscles to kick and throw you away from the source. As I understand it, It was the practical advantages of A.C. such as being able to use transformers that caused the changeover rather than any safety concerns.

Ringing in Telephone exchanges, in the UK at least, is 80V a.c. and we certainly didn’t worry about handling that, indeed more than one stroppy apprentice has been tied to the MDF and had a phone line wired to him and every time he complained the number would be rung for a bit! 120V d.c. though was definitely capable of killing so I’d be more than a little careful going anywhere near that sort of voltage or even 100V.

 

i am no electrician but especially the ac pulsing leads to muscle contraction and to "not let go": (at least i understand it like this)

https://en.m.wikipedia.org/wiki/Electric_shock

quoted:

The minimum current a human can feel depends on the current type (AC or DC) as well as frequency for AC. A person can feel at least 1 mA (rms) of AC at 60 Hz, while at least 5 mA for DC. At around 10 milliamperes, AC current passing through the arm of a 68-kilogram (150 lb) human can cause powerful muscle contractions; the victim is unable to voluntarily control muscles and cannot release an electrified object.[4] This is known as the "let go threshold" and is a criterion for shock hazard in electrical regulation

 

And to be clear: Sure we all should be carefull!!!...i just wanted to point out that the Dc voltage of our wheels is not "That" dangerous that its lifethreatening.

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