Battery Charging

[Funky]

Hello, so i just got myself new 18XL.

But i got question about charging: 

I use about 5-15% of battery everyday. I know it's better to charge 100% +(balancing cells).

But should i charge everyday, or when the battery reaches 40-50%?(Once a week)?

Nothing happens to battery, if i charge it one time per week to 100%?

Edited August 9, 2021 by Funky
Mistake

[div]

Good thing to consider.
The balancing part wears on the cells (even though necessary) so you're better off waiting till it is down to 30-40% (or wherever you need some safety margin) before charging to 100%. There are no hard rule simply because we dont know the status of the cells, however balancing every cycle (0-100% additioned segments) is quite often already.
Best storage voltage is around 50%.

Edited August 9, 2021 by div

[Chriull]

21 minutes ago, Funky said:

I use about 5-15% of battery everyday. I know it's better to charge

!to!

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100%

But not once the app shows 100% but the battery state of charge is 100%. So more or less once the charger led turns green. 

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+(balancing cells).

That's already included in the above procedure.

21 minutes ago, Funky said:

But should i charge everyday, or when the battery reaches 40-50%?(Once a week)?

Depends on your riding style. The lower the battery voltage, the lower the safety margin gets.

Just looked again at https://forum.electricunicycle.org/topic/13209-speed-reduction-graph-rider-info-needed/?do=findComment&comment=225406

. For "not riding at the edge" some roughly 50% could be some nice lower limit?

Or another good measure would be if one already feels differences while accelerating. ("Pedal feeling a bit softer")

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Nothing happens to battery, if i charge it one time per week to 100%?

Li ions do not care if they are charged at once or any fractions therof. Leaving the cells at charge states different from 50% stresses them (a bit, ?~proportional? to the difference).

Burdening batteries at low charge states can seriously degrade some weak cells of the pack (if it is already a bit misbalanced/has some differently degraded cells)

Balancing the cells is about the most important thing to keep the battery fine!

[Funky]

Not speed demon, not going over 22mph(35kph) Most time around 16mph(26kph).

So simply speaking: keep batteries above 40% for safety.

Charge whenever you need to 100% for balancing (My case 1-2 times a week)

Nothing happens if i charge to 100% and don't ride for 2-3 days? Or better charge to 100% before ride?

[div]

Just now, Funky said:

Nothing happens if i charge to 100% and don't ride for 2-3 days? Or better charge to 100% before ride?

I charge before ride because Voltage x temperature x time wears on the cells, however 2-3 days isn't much to worry about.

(As for margin the 18XL has a fairly punchy battery, you should be fine going 35kmh even under 40% for the days you didn't get to charge. There is also a power based TiltBack you can't deactivate which is fairly efficient as long as you dont accelerate like a swine.)

[mrelwood]

Battery charging is one of the things where you can need over every little thing as much as you like. There are 1) facts known well before EUCs came along, then there is 2) a huge range of what-ifs and other theorizings that might, could or should be, but have not been shown in real life. And finally, 3) facts based on experience on EUCs.

1) General facts on Li-ion batteries: Don’t charge when hot or frozen. Charge with a suitable charging current. (Check Batteryuniversity for more.)

2) Batteries wear if stored at 100%, and charging only to 80% extends battery life.

3) Experience on EUC has shown that lack of balancing is easily the most common, if not the only true battery killer.

- Dozens of EUC batteries have been reported dying, and the cause has pointed to insufficient balancing. 80% charging doesn’t allow any balancing to take place. Balancing at every 10th charge may not be enough. Chargers turn green when balancing is still taking place.

- I haven’t seen a single report on decreased range because of battery wear or aging. Not even on my MSX after 14000km, which I left on the charger for several hours after every charge.

 Due to this I’m done nerding over battery care, and only act based on what has been shown to be true and to happen in real life. My batteries may drop to 70% of capacity at 20000 (twenty thousand) km instead of the expected 30000km because of my ruthless balancing, but at least it won’t die at a mere 2000 (two thousand) km.

Actually, it will never affect anybody, since my wheels will never get to 20000km.

[Funky]

If i get 20.000km ill be super happy. 20-30% capacity lose 1-2more charging times

Better charge 100%+30min-1hr balancing after charger goes green each time then. (My case when battery drops around 40%)

Than charging to 80% and some times to 100% risking some cell dying.

 

Edited August 9, 2021 by Funky

[johrhoj]

My wheel usage during the week is about the same: 10km every day. 

I charge for the following reasons:

- need full battery for tomorrow's longer distance 

- need a full battery for today's retour-trip. I even recharge then when battery is less then 50 % used. E.g. roundtrip is 70km

- used up between 60 to 80 percent of battery capacity

After somewhere between 5000km and 10000km (i don't keep track of distance at all) i have no noticable battery capacity loss. I stopped worrying about optimal charging strategy. I think that all euc riders that ride regurly and or frequently do not need worry. Batteries are just that good these days, and every 2-3 years, i will buy my next euc.  

My fifth wheel is on the horizon (waiting for the veteran sherman).

Conclusion: you are doing fine when you charge when you need it. Just do not let battery go below 20% for safety reasons, and if you let it go below that, recharge at the first convenient moment.

Cheers

[The Brahan Seer]

After doing a bit more research (I'm an industrial chemist by trade) and listening to others experience with EUC batteries I have decided the best compromise for me is:

I have taken a note of how long it takes the battery when new to charge to 100%, from 10 and 30% which is my personal lower limits.  Say roughly 5 hours in my case from 30%. If this time stays the same I will stop charging on the green light. However if this drops significantly I can assume some batteries are not as optimum as they were ie not balanced correctly and would then leave the charger on for an extra hour to help it balance the dodgy cells. My reasoning for this is its not good for the batteries to be charged for longer than necessary- this can cause dendrite formation*.  This is also why I personally won't use fast chargers. But as mrelwood has alluded to previously it probably doesn't matter that much as the batteries will likely outlast the wheel even if you don't do everything perfectly. This is just my take on it but I am sure you would be fine with using fast chargers etc. I just want to minimise the fire risk etc and I'm in no rush.

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

[mrelwood]

 

1 hour ago, The Brahan Seer said:

it probably doesn't matter that much as the batteries will likely outlast the wheel even if you don't do everything perfectly.

They most definitely will! Except if balancing the cells is compromised.

1 hour ago, The Brahan Seer said:

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

In the linked dendrite formation test the cell is brought down to 0.7V!!! I don’t know how to get any useful data from that test, since even the 18XL (which uses the cells further than any other EUC) prevents the user from riding when the voltage averages at 3.0V per cell. If anything, this just further proves the importance of a prudent balancing behavior.

Charging the 18XL at 10A, the highest current the charging connector allows, still charges at under 0.5C per cell. This is already much less than the recommended 0.8C “to extend battery life”. Charging the wheel at lower than 5A offers no benefits at all.

 Manufacturers of these cells recommend charging at 0.8C or less to prolong battery life; however, most Power Cells can take a higher charge C-rate with little stress. 
https://batteryuniversity.com/article/bu-409-charging-lithium-ion

 

[Chriull]

21 minutes ago, mrelwood said:

Manufacturers of these cells recommend charging at 0.8C or less to prolong battery life; however, most Power Cells can take a higher charge C-rate with little stress. 
https://batteryuniversity.com/article/bu-409-charging-lithium-ion

These 0.8C seem to be not anymore applicable for now in EUCs used cells. Afair used cells (?even batches of se cells) got "downrated" by manufacturers "continuously"?

As i thought 18650 are about 0.5C by now, 21700 more like 0.3-0.4C with manufacturer specified charging current.

Have just seen that for example the inr18650-35e has 1020 mA recommended charge current for cycle life.... 

 

Edited August 9, 2021 by Chriull

[The Brahan Seer]

The dendrite formation problem looks more complicated than just current level. I would think that the latest battery tech that we use must take this into account too and as long as we follow the battery specifications for charging it shouldn't occur and we should be ok. 0.5-0.8C is good to know. So my concern for over charging and charging rates have lessened. Maybe good practice, if we want to prolong battery life but since the batteries will last anyway its a mute point.

Anyone who's interested in how they are tackling this check here:  https://cen.acs.org/energy/energy-storage-/Video-Battery-scientists-tackle-dendrite/97/i48

But this is 2 years old so may have changed already. So much to learn about batteries.

Thank you for everyone's input, still learning..

[RagingGrandpa]

1 hour ago, The Brahan Seer said:

dendrite formation problem

https://cen.acs.org/energy/energy-storage-/Video-Battery-scientists-tackle-dendrite/97/i48

No; that's regarding lithium-metal batteries. We don't use those (they're not commercialized yet).

 

8 hours ago, Funky said:

I know it's better to charge 100% (balancing cells).

But should i charge everyday, or when the battery reaches 40-50%?(Once a week)?

I vote "once a week."

But either way, the EUC will likely last 10,000km.
I think you're doing less than 50km a week, so that's more than 4 years of usage. After which time, I think we'll have a completely new generation of toys that will make the 18XL seem boring and undesirable

[duanew]

Check out EUC World's charge control.  I plan on getting it set up after my hs-110 modules come in.  You don't have to worry about over charging because it can automatically cut off the charger.  It Al's allows you to monitor charge current during balancing to make sure there are no problems. 

[RagingGrandpa]

On 8/10/2021 at 2:13 PM, duanew said:

worry about over charging

This thread is not about float charging / overcharging... better to discuss that in an existing topic such as below:
https://forum.electricunicycle.org/topic/18153-charge-completion-and-allowing-time-for-cell-balancing/

 

On 8/10/2021 at 2:13 PM, duanew said:

Check out EUC World's charge control. 
it can automatically cut off the charger.

I use EUC World and HS110 occasionally to record the charging process and confirm healthy response from the pack... but it's not suitable for everyday use. Both your phone and the smartplug need to sustain a wifi connection without interruption, during the entire recharging cycle- there's lots of reasons that can go wrong. If the connection was interrupted, the charger will do its regular charging, and EUC World won't be able to do anything to affect it. Useful; but not reliable.

 

Edited August 12, 2021 by RagingGrandpa