Battery charging

[atcspaul]

Is it ok to leave charger on overnight or should you unplug as soon as you get a green light? Most charger shut down or trickle charge when battery if fully charged, I cannot find much on these chargers though.

 

[deanphoto]

I believe the instruction manual advises not to leave it on for sustained periods.

 

[MattyB]

If the charger is functioning correctly there is no negative to the battery itself of leaving it connected to the charger. However, for a safety perspective I would never leave a large lithium chemistry battery on overnight; if the charger does malfunction for any reason and the battery overcharges you are potentially looking at a serious, self sustaining fire. Instead charge in the bike or on a concrete floor during the day when you can check on it at regular prices intervals.

 

[villho]

(I'm not an electrical engineer - if someone wiser than me notices something wrong in my text, I'd appreciate to be corrected)

First things first: normally the li-ion chargers are stupid. I mean by this that they just provide a certain amount of max. current at some voltage and I assume it is the same thing with the Specialized charger: it gives 4 amps at 42 volts and that's it. The actual charging is managed by the BMS inside the battery. It monitors the current coming in, total voltage of the battery and voltages of individual cells (in case of 500 Wh battery: 4 cells in parallel). The moment, when the BMS thinks that "ok, the battery is now full" (and this depends on the settings in the BMS), it stops drawing current and the charging stops and the charger shows green led. In addition to the actual charging, the BMS takes care of also the balancing. This means that it aims to a situation, where voltages of the individual cells is as close to each other as possible (read: close enough).

So, without knowing the details of the Specialized's BMS inside the battery and how it balances the cells (when the balancing starts, when it ends and what is the balancing current), I would actually charge the battery to 100 % and leave the charger connected for some time. Not each and every time one is charging the battery, but let's say once a month or so. And like others have said, of course it's recommended to do the charging in a safe place, where one can also monitor the battery, even though these 18650 based batteries with quality cells and quality BMSes are quite safe and should not be compared e.g. to cheap LiPo batteries.

So leaving the battery connected would support the way, how many BMSes balance the cells: often they require certain voltage threshold (let's say 40,5 volts) to be exceeded, before the balancing starts. Then, after this the balancing current (not the total charging current) is like tens of milliamps - i.e. it may take some time to get out-of-balance cells back in shape.

So... what I'm trying to say is that: if the cells are in your battery are in a good balance, disconnecting the charger as soon as the led becomes green is fine. The older the battery and the worse its condition (read: balance), I would actually leave the charger connected every now and then (and this does not harm a good battery either). This is just to ensure that there is enough time for the balancing to take place even in that situation, where the balancing would continue even though the led on the charger already shows green.

For Specialized charger/BMS:
I measured that once the led is green, the charger takes only like 1,6-1,8 watts from the socket, i.e. nothing. <speculation> However, it may be that the BMS is doing its balancing magic in the background even when the charging seems to be ready. If this is the case, at some point the BMS wants more juice from the charger and if it's not connected, the balancing stops. On the other hand, it may also be that the led does not become green, until also the balancing has been completed, but it's hard to say without opening the battery up. </speculation> The first option would support leaving the charger connected, where the latter would of course mean that the charger can be disconnected as soon as the led is green, as no charging nor balancing would happen anymore after that.

I've also measured that the BMS in these batteries is quite conservative and it let's the cells to be charged only to 41,6 volts. This is of course a good thing thinking the battery longevity and probably also the basis why Specialized give their warranty to the battery. I haven't measured the 0 % voltage, but I would assume that it's also on the safe side.

 

[atcspaul]

Thank you!

 

[MattyB]

First things first: normally the li-ion chargers are stupid. I mean by this that they just provide a certain amount of max. current at some voltage and I assume it is the same thing with the Specialized charger: it gives 4 amps at 42 volts and that's it. The actual charging is managed by the BMS inside the battery. It monitors the current coming in, total voltage of the battery and voltages of individual cells (in case of 500 Wh battery: 4 cells in parallel). The moment, when the BMS thinks that "ok, the battery is now full" (and this depends on the settings in the BMS), it stops drawing current and the charging stops and the charger shows green led. In addition to the actual charging, the BMS takes care of also the balancing. This means that it aims to a situation, where voltages of the individual cells is as close to each other as possible (read: close enough).

So, without knowing the details of the Specialized's BMS inside the battery and how it balances the cells (when the balancing starts, when it ends and what is the balancing current), I would actually charge the battery to 100 % and leave the charger connected for some time. Not each and every time one is charging the battery, but let's say once a month or so.

....So leaving the battery connected would support the way, how many BMSes balance the cells: often they require certain voltage threshold (let's say 40,5 volts) to be exceeded, before the balancing starts. Then, after this the balancing current (not the total charging current) is like tens of milliamps - i.e. it may take some time to get out-of-balance cells back in shape.

So... what I'm trying to say is that: if the cells are in your battery are in a good balance, disconnecting the charger as soon as the led becomes green is fine. The older the battery and the worse its condition (read: balance), I would actually leave the charger connected every now and then (and this does not harm a good battery either). This is just to ensure that there is enough time for the balancing to take place even in that situation, where the balancing would continue even though the led on the charger already shows green.

For Specialized charger/BMS:
I measured that once the led is green, the charger takes only like 1,6-1,8 watts from the socket, i.e. nothing. <speculation> However, it may be that the BMS is doing its balancing magic in the background even when the charging seems to be ready. If this is the case, at some point the BMS wants more juice from the charger and if it's not connected, the balancing stops. On the other hand, it may also be that the led does not become green, until also the balancing has been completed, but it's hard to say without opening the battery up. </speculation> The first option would support leaving the charger connected, where the latter would of course mean that the charger can be disconnected as soon as the led is green, as no charging nor balancing would happen anymore after that.

Most of what you say is right, but your assumption that balancing continues after the green light comes on is pretty unlikely. If that were the case many peoples packs would never receive the balance portion of the charge at the end which is crucial for cell longevity/cycle life. It's far more likely that the BMS cuts the charge current right back 15-20 mins before the end and completes the balance portion, then shows the charge cycle is complete as per the text in green. Every multi-cell consumer electronic device I've looked at works that way, as well as all DC lithium chargers for hobby usage (RC etc).

 

[villho]

That might indeed be the case and that would mean that once the led is green, the charger can be unplugged as there is no reason to leave it plugged in (although, nor would it harm to leave it overnight).

I try to remember to use a power meter (not sure of the English word for it) the next time I charge the battery and see how the wattage behaves, when the battery is getting close to full. If the last 15-20 mins is only some 10-15 watts, then I would say that that is the balancing taking place. The "problem" with that is that if my battery is in a good condition (like it is), the balancing is not needed (or it will happen before the charging gets complete) and hence should not take any additional time after the charging and led becomes green right after there is a big drop in wattage.

 

[Donnie797]

Since we can't really know, i hope the @Specialized Rider Care Team will answer this

 

[atcspaul]

Since we can't really know, i hope the @Specialized Rider Care Team will answer this

I have an email sent to them and will post what they say

 

[steve_sordy]

Great stuff guys, I learned a lot there!

 

[MattyB]

That might indeed be the case and that would mean that once the led is green, the charger can be unplugged as there is no reason to leave it plugged in (although, nor would it harm to leave it overnight).

There is no harm if the BMS is functioning correctly and the battery did not start the charge excessively imbalanced, no. However I would still never leave one of these batteries on charge unaccompanied overnight - even if they are unlikely to burst into flames they can still vent if overcharged which could do a lot of damage inside the house. At the very least I would say use a timer plug set to the max charge time of the pack.

...I try to remember to use a power meter (not sure of the English word for it) the next time I charge the battery and see how the wattage behaves, when the battery is getting close to full. If the last 15-20 mins is only some 10-15 watts, then I would say that that is the balancing taking place. The "problem" with that is that if my battery is in a good condition (like it is), the balancing is not needed (or it will happen before the charging gets complete) and hence should not take any additional time after the charging and led becomes green right after there is a big drop in wattage.

Generally power meter or watt meter are the generic terms, either is fine to use . My experience with Lipos and LiFe bateries in RC is that on a decent charger (mine balances to within 0.02V/cell) they will always go through at least 3-5 mins of balancing, especially if a charge rate of 2C or greater was used. Obviously we only charge ebike packs at 0.25-0.5C in general, but I would still expect any battery that has done more than 5 cycles to need a few mins of balancing - because of the way the discharge happens the cells are never at identical voltages after use, and over a few (non-balanced) cycles that imbalance can start to grow.

 

[villho]

Yeah, so let's say it once more (and I probably should've been more accurate in my previous message): if all is good in the battery and the BMS works as it should work, it's not a problem (for the battery itself) to leave the it in charger for longer periods of time (ok, then we start to talk about elevated state of charge etc. but let's not go there). HOWEVER, if the things go south, they might go there all the way and you don't want to be elsewhere (or sleeping upstairs) when that happens. This is general rule for all batteries.

With that said: use common sense

 

[Jaygam]

It's worth mentioning that if your battery is going to be left unused for a while it's best left in a cool place and it is important to store it at around 50% to 80% charge to achieve a good open-terminal resting voltage in the cells.

A fully charged battery is not a happy battery but will be ok for a day or two!
Storing it in a hot place or fully charged for an extended amount of time will damage it's lifespan considerably.

 

[atcspaul]

Here is the copy paste of the email from specialized

Sam <[email protected]>
To:xxxxxxxxxxxxx

Mar 26 at 6:04 PM

Hey Paul, thank you for reaching out to us. The charger does have a auto shutoff feature so there is no harm in leaving it plugged in over night! enjoy the sweet new ride.

Have a great day!

-Sam

 

[xcentric]

Here is the copy paste of the email from specialized

Sam <[email protected]>
To:xxxxxxxxxxxxx

Mar 26 at 6:04 PM

Hey Paul, thank you for reaching out to us. The charger does have a auto shutoff feature so there is no harm in leaving it plugged in over night! enjoy the sweet new ride.

Have a great day!

-Sam

Hmmm, hardly a detailed response, is it?!!

 

[atcspaul]

Hmmm, hardly a detailed response, is it?!!

my email to them was not detailed. I just asked if it was ok to leave the charger on over night and the question was answered.

 

[Specialized Rider Care]

For those wanting a more detailed response, the battery management system (BMS) inside the battery indeed manages everything and controls the entire charging process. Inside the BMS are all kinds of temperature, voltage and cell-balancing based controls/safety monitoring systems, the charger itself is relatively simple.

Once the battery is fully charged and balancing is completed, the charging process will stop and the light on the charger will turn from red to green. The battery will then enter standby mode for 2 hours until it fully shuts down, just the same as after every other time you turn the bike off. The charger is not doing anything to the battery in this state and it is completely safe to leave it like this. The battery will not wake up again until you remove it from the charger and either connect it to the charger again or connect it to the bike/turn it on.

It's worth mentioning that if your battery is going to be left unused for a while it's best left in a cool place and it is important to store it at around 50% to 80% charge to achieve a good open-terminal resting voltage in the cells.

A fully charged battery is not a happy battery but will be ok for a day or two!
Storing it in a hot place or fully charged for an extended amount of time will damage it's lifespan considerably.

As this helpful member advises, storing any Lithium Ion battery at 100% charge long-term is not best for battery state of health (SOH) - particularly if the battery then gets really hot (in a van or shed during summer for example). Fully charging your bike the day before a ride is a good habit to prolong battery life - if you can plan that way.

 

[Maastricht]

For those wanting a more detailed response, the battery management system (BMS) inside the battery indeed manages everything and controls the entire charging process. Inside the BMS are all kinds of temperature, voltage and cell-balancing based controls/safety monitoring systems, the charger itself is relatively simple.

Once the battery is fully charged, the charging process will stop and the light on the charger will turn from red to green. The battery will then enter standby mode for 2 hours until it fully shuts down, just the same as after every other time you turn the bike off. The charger is not doing anything to the battery in this state and it is completely safe to leave it like this. The battery will not wake up again until you remove it from the charger and either connect it to the charger again or connect it to the bike/turn it on.



As this helpful member advises, storing any Lithium Ion battery at 100% charge long-term is not best for battery state of health (SOH) - particularly if the battery then gets really hot (in a van or shed during summer for example). Fully charging your bike the day before a ride is a good habit to prolong battery life - if you can plan that way.

Thanks for the additional information!

You wrote: The battery will then enter standby mode for 2 hours until it fully shuts down, just the same as after every other time you turn the bike off.

Is this also valid for the new 2019 Levo battery? I thought to have understood that this feature is only related to the older battery design as you can still find it via bluetooth for several hours after switching the battery off. With the 2019 version this is not possible according to my experience.

 

[Specialized Rider Care]

Thanks for the additional information!

You wrote: The battery will then enter standby mode for 2 hours until it fully shuts down, just the same as after every other time you turn the bike off.

Is this also valid for the new 2019 Levo battery? I thought to have understood that this feature is only related to the older battery design as you can still find it via bluetooth for several hours after switching the battery off. With the 2019 version this is not possible according to my experience.

Yes - the 2hr standby mode is common across our batteries - however with the 2019 Levo the Bluetooth connectivity is inside the TCU on the top-tube and this requires the bike to be fully powered on to connect. (With earlier Levos the Bluetooth was built into the battery)

 

[MattyB]

Here is the copy paste of the email from specialized

Sam <[email protected]>
To:xxxxxxxxxxxxx

Mar 26 at 6:04 PM

Hey Paul, thank you for reaching out to us. The charger does have a auto shutoff feature so there is no harm in leaving it plugged in over night! enjoy the sweet new ride.

Have a great day!

-Sam

So in other words they have no idea at what point the balancing stops (before or after the green light). To be fair I doubt any CS rep would; it is only likely to be documented in the technical design docs for the charger and BMS which they are unlikely to have access to.

 

[Specialized Rider Care]

So in other words they have no idea at what point the balancing stops (before or after the green light). To be fair I doubt any CS rep would; it is only likely to be documented in the technical design docs for the charger and BMS which they are unlikely to have access to.

See my comments above, charge and balancing is completed before red light changes to green, hence you can turn charger off with confidence that everything is done when the green light shows. BMS is in standby mode at that point for 2 hrs before sleeping. You are correct, we don't train most service team members to this level of detail but will consider working charging/charger behaviour more deeply into training modules - these are fair questions.

 

[Ross1137]

Is it ok to leave charger on overnight or should you unplug as soon as you get a green light? Most charger shut down or trickle charge when battery if fully charged, I cannot find much on these chargers though.

I plug my in of an evening if it's pretty low it takes around 3 hours, then when I get up the next morning I turn it off, this is my second levo and have done this from day one and have never had any issues it cuts out automatically so there is no point worrying about it hope this helps.

 

[Chubba]

Anyone have issues with their spesh charger? I charged my bike 2 days ago and plugged the charger in tonight and there is no power to the charger, no green light. Tried in different plugs, still nothing. It’s 6 weeks old.

 

[lolp]

Hi.
I have a 2018 levo with a new 504wh battery thats done about 20 charges. I noticed that its now showing only 91% health (i.e. will only charge to about 460wh). I think the last couple of charges ended by me accidentally knocking the charger plug from the battery just before the green light came on. My question is whether this possible lack of balancing time at the end of a charge might be responsible for the loss of health and whether it can be recovered by leaving the charger on for say an hour after the green light appears.
I hope this isnt hijacking the original question but it does seem very related.
Thanks.

 

[Jeffw]

Anyone have issues with their spesh charger? I charged my bike 2 days ago and plugged the charger in tonight and there is no power to the charger, no green light. Tried in different plugs, still nothing. It’s 6 weeks old.

I had the same issue on my 2018 Kenevo 3 weeks ago. Took it to my LBS, they put a new charger on and still no green light. The problem was that the battery was dead. Replaced under warranty. The Kenevo has since been handed back and my new Levo Expert is sitting in the garage, just dying to get out

 

[MattyB]

Hi.
I have a 2018 levo with a new 504wh battery thats done about 20 charges. I noticed that its now showing only 91% health (i.e. will only charge to about 460wh). I think the last couple of charges ended by me accidentally knocking the charger plug from the battery just before the green light came on. My question is whether this possible lack of balancing time at the end of a charge might be responsible for the loss of health and whether it can be recovered by leaving the charger on for say an hour after the green light appears.
I hope this isnt hijacking the original question but it does seem very related.
Thanks.

By all means do a full cycle (empty to flat then charge to full including balancing) as that may recalibrate the battery health if it’s got out of kilter during a number of partial, non balance phase charges. However, Li-ion packs cannot be “recovered” from abuse like the old nicads could so don’t expect any real world capacity increase from the battery.

 

[lolp]

Cheers Matty B