Smart eBike. Battery care.

[anotherbob]

It is unlikely that my newly-acquired Smart eBike will see much (if any) use during the winter. I've read the manual on care of the battery and it seems that there is a "protection mode" which will switch in if the bike isn't used for two months. A full charge cycle is required to revive the battery after that.
I'd like to know if it would be best to allow that to happen or to take the battery off the bike, store it indoors and give it a regular charge until I start to use the bike in Spring. The bike is stored in my garage which is attached to the house but not heated.
As far as I can tell the bike has only done around 500 KM (according to the console) but that's the only indication of the battery condition. I did have a quick spin for about 3 miles and the battery indicator came down by one bar (of 8 I think). It quickly charged up again.
My old ebike (a Giant Lafree e-Race) used what's called an Energy Management Kit which discharged and recharged the battery. My e-race was stolen a couple of years ago and if anyone is interested I still have two EMK with leads. The thief would have been disappointed since I had the battery box in the house on charge at the time.

 

[flecc]

I prefer to do a recharge every two months during storage to avoid any risk of the "sleep" mode failing. That mode only switches off the BMS supply. In theory the cells themselves don't discharge but could transfer charge if any cell is a bit down.

So for me it's play safe.
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[Andy-Mat]

It is unlikely that my newly-acquired Smart eBike will see much (if any) use during the winter. I've read the manual on care of the battery and it seems that there is a "protection mode" which will switch in if the bike isn't used for two months. A full charge cycle is required to revive the battery after that.
I'd like to know if it would be best to allow that to happen or to take the battery off the bike, store it indoors and give it a regular charge until I start to use the bike in Spring. The bike is stored in my garage which is attached to the house but not heated.
As far as I can tell the bike has only done around 500 KM (according to the console) but that's the only indication of the battery condition. I did have a quick spin for about 3 miles and the battery indicator came down by one bar (of 8 I think). It quickly charged up again.
My old ebike (a Giant Lafree e-Race) used what's called an Energy Management Kit which discharged and recharged the battery. My e-race was stolen a couple of years ago and if anyone is interested I still have two EMK with leads. The thief would have been disappointed since I had the battery box in the house on charge at the time.

A difficult question, I always charge the battery to about 10-12% for long term storage, using guessing and time, say 20 to 30 minutes. That is against a full charge of around 4 hours for my battery/charger.
Or possibly check that the battery has just exceeded say 30 volts, but do switch the charger off, when measuring, though I have not used this method myself....
For long term storage, charging to full is not recommended by some battery makers, Sony is one of these companies, for example. I always do this for any Li-ion products...
The problem with Li-ion batteries is that if they go below a certain charge level, 28v for a 36v nominal bike battery (mine for example), the charger, unless it is of a special type, will not charge the battery anymore.
This is designed into the battery as a safety feature.
This is simply to prevent damage if too large a charge current causes the battery to heat up and gas!
The charger needed when the battery is low, is called a "Zero Volt Charger" apparently. It charges at a low amperage, till the minimum charge voltage is achieved. Then the full charge is switched on.
I needed one for my bike battery when I first bought my bike, delivery had taken too long, the supplier lent me one, it worked well, and I copied the pamphlet, I will attach it here for you to read.
I am sure many will enjoy reading it too!!
"Pre Charge" is what this method is called, this low current charging.
On this charger, it is always 500 ma no matter what voltage charger/battery, you are using!
The only place I know that you can buy such a charger, is from Stark Bikes, it costs around $100 if I remember correctly. They only sell one for 36 volt batteries.
I actually believe it would be quite easy to do exactly the same with a quality lab power supply and a bit of care!! But still not yet tried it out!! Simply because I have not had/got a dead battery anymore!!
regards
Andy

 

[Nev]

For long term storage, charging to full is not recommended by some battery makers, Sony is one of these companies, for example.
regards
Andy

Yes I have read this several times too. Do you (or anyone else) know why it is recommended not to fully charge a battery for long term storage. I would have thought this would lessen the chance of the battery falling below a certain voltage level and then be unable to charge it back up again with a normal battery charger.

I wonder if it might be something to do with safety. For long term storage its going to be safer to have something with less energy contained within it rather than with its maximum energy capacity.

Or is there some other scientific reason why this is the case?

 

[Nev]

Why does it say under anotherbobs' name that he has just joined and then under that it says joined Feb 27, 2007. Was there another anotherbob?

 

[flecc]

Why does it say under anotherbobs' name that he has just joined and then under that it says joined Feb 27, 2007. Was there another anotherbob?

It's an anomally due to him only posting 7 times over the years. That makes him look like being quite new to the forum.
.

 

[flecc]

Yes I have read this several times too. Do you (or anyone else) know why it is recommended not to fully charge a battery for long term storage. I would have thought this would lessen the chance of the battery falling below a certain voltage level and then be unable to charge it back up again with a normal battery charger.

I wonder if it might be something to do with safety. For long term storage its going to be safer to have something with less energy contained within it rather than with its maximum energy capacity.

Or is there some other scientific reason why this is the case?

It's cell ageing. There's optimum charge content and storage temperatures for minimising loss of cell life over time.

Charge content of around 20 to 40% is usually recommended. For long term storage the least capacity loss results from storing at near to zero degrees C, but never below.

If storing at cool temperatures there's not much difference whatever the charge level though as you'll see from the top of this chart:



Not worth reducing the temperature for shorter terms like two or three weeks though since the gain then is very small.


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[Andy-Mat]

Yes I have read this several times too. Do you (or anyone else) know why it is recommended not to fully charge a battery for long term storage. I would have thought this would lessen the chance of the battery falling below a certain voltage level and then be unable to charge it back up again with a normal battery charger.

I wonder if it might be something to do with safety. For long term storage its going to be safer to have something with less energy contained within it rather than with its maximum energy capacity.

Or is there some other scientific reason why this is the case?

It reduces the "chemical stress" on the internal components, I was once told. It is not a problem to set an alarm in a modern mobile phone to alert you to check and if necessary, add some charge when needed....
The likelihood of the battery exploding is also much reduced I would imagine, less energy to get rid of....See here:-
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

regards

Andy

 

[Laser Man]

For long term storage the least capacity loss results from storing at near to zero degrees C, but never below.
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Could get pretty unpopular with her indoors if you store it in the fridge.

 

[Nev]

For long term storage the least capacity loss results from storing at near to zero degrees C, but never below.

I think you have an electric car flecc. How do the manufacturers of electric cars get over the problems of very low and very high temperatures that their vehicles are likely to be exposed to even in the UK, let alone much hotter and colder countries.

 

[flecc]

I think you have an electric car flecc. How do the manufacturers of electric cars get over the problems of very low and very high temperatures that their vehicles are likely to be exposed to even in the UK, let alone much hotter and colder countries.

They often have either active or passive battery heating and cooling, essential in the more extreme climates. Not so important in moderate climates like the UK, so sometimes omitted. Previous Nissan Leafs had it but my 2018 model doesn't *, using rapid charging limitations instead, a controversial decision. On next year's model the temperature control returns.

* The Leaf battery heating only cuts in at minus 17 degrees C, so you can see not vital in the UK where temperatures don't usually drop that low. I've found no drop in performance with the whole car at 4 degrees C so far.
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[anotherbob]

Well..... as Bernard Bresslaw famously used to say, "I only arsked."

I believe I will bring the battery indoors for the Winter, maybe have an occasional spin on the bike when weather permits, and top up the battery monthly.

Thank you to those who have responded.