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Safely store EUC during the winter

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Hello,

I live in a cold city in Canada, and I know that in the winter I will not be able to use my EUC.

That way, I´m planning to store it for the whole winter and restart using it in the next year.

My only concern about this is what to do in terms of battery charge before stop using the EUC for a long time.

Should I store it full charged? 80% charged? 50% charged? none of these?

Could you guys give me some advice?

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It's that time of year...

I'm tempted to discharge to 40% and leave it in my basement for 4mos... (MSX 84v 1600wh). I store other lithium ion batteries open-circuit this way for >6mos at a time, and have never had damaging over-discharge from self-discharge.

Who here actually checks the voltage of their EUC when in winter storage?

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Is it yet healthier for batteries to give some excercise once a month or so? Even if it's impossible to ride outside, ride a bit in your house. Then charge it back just enough to compensate for spent energy, and store for another month. Thoughts?

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1 hour ago, Aneta said:

Is it yet healthier for batteries to give some excercise once a month or so?

I haven't yet seen any reliable source suggesting this to be the case.

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7 hours ago, Aneta said:

Is it yet healthier for batteries to give some excercise once a month or so? Even if it's impossible to ride outside, ride a bit in your house. Then charge it back just enough to compensate for spent energy, and store for another month. Thoughts?

its healthier to store them in very cold temps actually.. i have also never heard this to be the case, and as long as they dont discharge fully, should be perfectly good basically indefinitely.. any rechargeable battery will lose some capacity over time with use, so i would tend to think the opposite, that in fact not giving it any "exercise" would be the best way to go..

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But let's imagine this scenario.

One of 18650's in the pack became "mildly sick" - its discharge rate is higher than normal, but since it's sitting in a parallel with several healthy sistren (which equalizes their voltage), and you were using/charging the battery regularly during season, it went unnoticed. Now, you charged the battery to 40-50% and put it away for storage for 4-6 months.

In about a month, not only the sick cell is discharged completely, but the whole parallel (4-6 cells on powerful wheels) is discharged "to the ground" (below 2.5V). The whole parallel is now dead. The BMS will detect this and shut down the battery.

The winter is over, you turn on the wheel... but it doesn't turn on. The battery now needs a replacement or expensive repair.

If you instead discharged a little and charged a little every few weeks or so, the chance of battery going dead would be much less.

Thoughts?

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34 minutes ago, Aneta said:

But let's imagine this scenario.

One of 18650's in the pack became "mildly sick" - its discharge rate is higher than normal, but since it's sitting in a parallel with several healthy sistren (which equalizes their voltage), and you were using/charging the battery regularly during season, it went unnoticed. Now, you charged the battery to 40-50% and put it away for storage for 4-6 months.

In about a month, not only the sick cell is discharged completely, but the whole parallel (4-6 cells on powerful wheels) is discharged "to the ground" (below 2.5V). The whole parallel is now dead. The BMS will detect this and shut down the battery.

The winter is over, you turn on the wheel... but it doesn't turn on. The battery now needs a replacement or expensive repair.

If you instead discharged a little and charged a little every few weeks or so, the chance of battery going dead would be much less.

Thoughts?

be easier to balance the cells before you put it into storage.. its possible, but a highly unlikely scenario seeing as nothing is being actively discharged, especially if stored somewhere fairly cool... unless its a Z10 the battery discharge will be absolutely negligible over a few months

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2 hours ago, Aneta said:

One of 18650's in the pack became "mildly sick" - its discharge rate is higher than normal, but since it's sitting in a parallel with several healthy sistren (which equalizes their voltage), and you were using/charging the battery regularly during season, it went unnoticed

This cell has to be replaced anyhow - such high self discharge won't go unnoticed, also while normal use, too long.

BMS balancing is a very limited feature - "sick" cells get stressed most and degrade fairly fast, so the point where balancing is not helpful anymore comes quite soon.

So, imo there is not too much sense in troubling oneself to caress a sick cell - since there is no way to cure it and it will die relatively soon anyhow, just save nerves and get rid of it.

11 hours ago, Aneta said:

Is it yet healthier for batteries to give some excercise once a month or so? Even if it's impossible to ride outside, ride a bit in your house

But of course - if you miss the EUC and want to ride a bit in wintertime, there should not be any problem. :) just maybe some skid marks on the floor...

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I have a small place in France up in the mountains which I visit a couple of times a year. My original thought was to get one of those Velosolex petrol driven bicycles and use that for local transport. It turns out French law has changed and you now need to wear a helmet to ride one and that just didn't appeal, they're also quite noisy and require a bit of maintenance to keep running. So I'd recently started to think about keeping an EUC over there but obviously it wouldn't get used for months at a time and, during the winter, the temp can go down to -25C (-13F). I probably wouldn't ride when it's that cold but would probably still ride on the roads if the snow wasn't too deep. Would an EUC and/or the batteries work in this situation? Perhaps when I arrived I could charge to 100% and leave it there over night to balance the battery. Then make sure it's down to 40% when I leave. Obviously it would be stored inside but the temp will still drop well below freezing if no-one is staying there. I'm guessing this is just a pipe dream but any thoughts?

solexindexthumb.jpg vsNineBot-Z10-winter.jpeg

Or just lump it and walk?

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8 hours ago, Aneta said:

One of 18650's in the pack became "mildly sick" - its discharge rate is higher than normal, but since it's sitting in a parallel with several healthy sistren (which equalizes their voltage), and you were using/charging the battery regularly during season, it went unnoticed. Now, you charged the battery to 40-50% and put it away for storage for 4-6 months.

In about a month, not only the sick cell is discharged completely, but the whole parallel (4-6 cells on powerful wheels) is discharged "to the ground" (below 2.5V). The whole parallel is now dead. The BMS will detect this and shut down the battery.

My suggestion: know your discharge rate. This is also useful for healthy batteries, as some wheels discharge the battery when not used much faster than others. How to? Note the voltage when stored away and check the voltage after, say 2 months (or 1 month if you are on the anxious side).

10 hours ago, Rywokast said:

any rechargeable battery will lose some capacity over time with use, so i would tend to think the opposite, that in fact not giving it any "exercise" would be the best way to go..

though this single charge would be rather irrelevant on the big picture of battery degradation

4 hours ago, mike_bike_kite said:

I have a small place in France up in the mountains which I visit a couple of times a year. My original thought was to get one of those Velosolex petrol driven bicycles and use that for local transport. It turns out French law has changed and you now need to wear a helmet to ride one and that just didn't appeal, they're also quite noisy and require a bit of maintenance to keep running. So I'd recently started to think about keeping an EUC over there but obviously it wouldn't get used for months at a time and, during the winter, the temp can go down to -25C (-13F). I probably wouldn't ride when it's that cold but would probably still ride on the roads if the snow wasn't too deep. Would an EUC and/or the batteries work in this situation? Perhaps when I arrived I could charge to 100% and leave it there over night to balance the battery. Then make sure it's down to 40% when I leave. Obviously it would be stored inside but the temp will still drop well below freezing if no-one is staying there. I'm guessing this is just a pipe dream but any thoughts?

IMHO that should work with the same caveat as mentioned above: know your discharge rate, both, with connected and disconnected battery. In case, disconnect the battery from the wheel. I stored away a V8 battery, disconnected from the wheel, for about 6 months and observed a charge drop of less than one percent point per month (a Ninebot Z with connected battery loses allegedly 1% point per day).

Edited by Mono

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I guess this discussion leads us to this thought that it's a good idea to know your battery down to behavior of each parallel cell group, before putting it away for storage. Or else... you can find a perfectly dead battery for the new season!

If only we had this inspection port as I described here:

Then we can periodically inspect voltage on each parallel group and see if there is any trouble developing.

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My last ride I got my battery down to 73%.  Ok to leave it like this a few months?  Or should I drain it a bit more?  What's the best way to drain it if I can't ride it? 

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36 minutes ago, /Dev/Null said:

My last ride I got my battery down to 73%.  Ok to leave it like this a few months?  Or should I drain it a bit more?  What's the best way to drain it if I can't ride it? 

probably better to drain a little more.. not that it wouldnt be perfectly fine either way.. why cant you ride it? theres no good way to drain the battery besides riding maybe have all the lights on and blast some music for a few hours lol

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On 11/9/2019 at 2:26 PM, Aneta said:

it's a good idea to know your battery down to behavior of each parallel cell group

It's this:
B1m-hQlUbRhJptsSLy1TPr6Q9YuW3ZDSQgYB2iK4

e.g., problems with Cell 2 will drag down Cells 4,5,6 equally, not just cell 5.

You do know the voltage of each parallel group: they're all at Vpack.

 

(Not this)
e2-1NsZdBXGT9PPktBN6vS13govFXEFLGEatvlT3

 

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1 hour ago, RagingGrandpa said:

It's this:
...

e.g., problems with Cell 2 will drag down Cells 4,5,6 equally, not just cell 5.

You do know the voltage of each parallel group: they're all at Vpack.

 

(Not this)
 

....

Within each pack it is like you've drawn itin "not this" - each separate cell is paralleled.

Once looking at the battery packs it looks like your first drawing "it's this" with the individual cells beeing in reality pairs of cells...

At least for wheels with capacities above 5/600Wh its like this - 2 or more 2p packs in parallel.

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you guys here tried to find a way to store the wheel for few months.

while I'm thinking when the snow will be clear out a little bit, so I can continue to ride my wheel =))

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1 hour ago, Aneta said:

Battery packs are always built as "not this":

https://www.electricbike.com/introduction-battery-design-1/

We've both committed the sin of speaking in absolutes. It's never "always" ;)

My MSX is 84v 1600wh, built as 2x 800wh packs in parallel. Each of the two packs is 20s3p, likely in the 'bridged' configuration you suggest, because it then requires only a 20-cell BMS to balance the 60 internal cells. The two packs are not bridged. Design tradeoffs.

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4 hours ago, Marty Backe said:

Both KingSong and Gotway wheel batteries last forever.

I understand why you leave Ninebot off that list due to the well-documented Z10 vampire discharge issue, but two questions:

  1. Do other Ninebots (the One S1/S2) have that issue or is it just limited to the Z10?
  2. Is there any evidence of InMotion being any different from King Song or Gotway in this regard? (Or do you just leave them off your list simply because you don't own/ride InMotion wheels?)

If the answer to both of these happens to be 'no' then your original statement could be simplified/broadened (and simultaneously lose the loaded brand implications) to: "Pretty much all modern EUC batteries (except for the Z10) last forever."

Edited by AtlasP

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1 hour ago, AtlasP said:

I understand why you leave Ninebot off that list due to the well-documented Z10 vampire discharge issue, but two questions:

  1. Do other Ninebots (the One S1/S2) have that issue or is it just limited to the Z10?
  2. Is there any evidence of InMotion being any different from King Song or Gotway in this regard? (Or do you just leave them off your list simply because you don't own/ride InMotion wheels?)

If the answer to both of those is 'no' then your original statement could be simplified/broadened (and simultaneously lose the loaded brand implications) to: "Pretty much all modern EUC batteries (except for the Z10) last forever."

I can only speak for wheels that I have personal experience. I try never to speculate or theorize based on specifications.

The only Ninebot wheel that I own is the Z10 and we all know how horrible that is regarding the battery.

I do not own Inmotion, Rockwheel, etc. wheels.

So I think my statement that you are referring to can be left alone. Other people can chime in on their brands if they want to.

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19 hours ago, Rywokast said:

probably better to drain a little more.. not that it wouldnt be perfectly fine either way.. why cant you ride it? theres no good way to drain the battery besides riding maybe have all the lights on and blast some music for a few hours lol

It's -13C....and I"m about to go out of town.

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