Best way of charging the battery

I make every day short trips of about 10 km. When I return home the batery indicator has still 5 out of 5 stripes, Nevertheless I connect the battery to the charger untill the red indicator on the charger switches from red to green and than I disconnect the charger immediately. Once every 2 weeks I charge the battery when only 2 out of 5 battery indicator stripes are visible and than recharge the battery. I now notice that when i have a full battery after disconnecting the charger and leaving the battery over night from the battery, connect the battery to the charger the red indicator of the charger lights up for about 15 minutes. So the battery decharged overnight a little which not happened when the battery was new. With this battery I drove 1100 km so the battery fairly new. My question is :

1. What is the correct procedure in terms of life time to charge the battery ?
2. Is my battery already failing more than it should after driving 1100 kn with it using my charging procedure ?

Depends on the charger relative to the chemistry and the Ah / xPyS layout.

Really need to track the volts and amps output resulting from the automated process. Clamp style ammeter, shunt based, cheap Ah counter all can be used for that.

If you disconnect the cahrger immediately, it doesnt' get the chance to balance the battery, making all the cells equal.

When cells aren't equal, they don't all have the same amount of charge, so when you recharge, some get full faster, and BMS shuts charging off when they do.

Once BMS lowers those cells enough, charging can restart to keep filling up the low cells.

This cycle can go on for minutes to an hour on a mostly balanced pack.

It can go on for hours on a not-so-well balanced pack.

It can go on for days or longer on a poorly balanced pack.

While it's balancing, you'll usually see the charger shut off, then turn back on, and cycle back and forth until it's done balancing.

Thanks for the replies. I will try to keep the charger connected longer (will start with 2 hours) once the green indicator on the charger is on.

If the balancings is finished after 1 hour but you keep the charger connected does it hurt the battery ?

By the way it is a 48V/12A battery and the charger is 54,6 Volt/2A?

Odessadream said:

Thanks for the replies. I will try to keep the charger connected longer (will start with 2 hours) once the green indicator on the charger is on.

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Better to keep it connected until you see that it is no longer cycling on and off. This means sitting nearby and keeping an eye / ear out for it's changes. Without opening the battery and measuring individual cell group voltages at the BMS wires, there's no other simple way to "know" that it's done balancing. :/

If the balancings is finished after 1 hour but you keep the charger connected does it hurt the battery ?

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It shouldn't, because the charger should shutoff current internally once it drops to a certain amount (that's what makes it go "green"), *and* the BMS in teh battery will stop allowing charge once it's full, too.

By the way it is a 48V/12A battery and the charger is 54,6 Volt/2A?

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"48v" is just the average voltage.

48v packs are usually 13 cells in series, average of 3.7v. Full at 4.2v, which is 13 x 4.2 = 54.6.


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The best time to fully charge and equalize a lithium pack is before you ride, not after. Lithium batteries don't like sitting at 100% charge, so it's best to get them there right before you use the pack. There shouldn't be a need to EQ after every ride, so your best bet is to store the pack at 60-75% charge and then top it off before use if you need more juice.

Odessadream said:

Thanks for the replies. I will try to keep the charger connected longer (will start with 2 hours) once the green indicator on the charger is on.

If the balancings is finished after 1 hour but you keep the charger connected does it hurt the battery ?

By the way it is a 48V/12A battery and the charger is 54,6 Volt/2A?

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Ideally you are verifying the state of balance pretty regularly, looking at each cell's voltage with an accurate instrument independent of the BMS.

The less frequently you do a full balance charge, the farther out of balance the cells are allowed to get, and some BMS are so slow it takes days, especially as your new cells start to age.

So some banks really should be balanced-charged every cycle to keep the time required reasonable, since as mentioned keeping the bank at 100% SoC for long periods is not healthy.

There are also dedicated balancer gadgets (non-BMS, no protections) that are much faster, but they cost more than regular cheapo BMS of course.

To be honest I have never seen that once the indicator of the charger turn from red to green it goes back to red again when I leave the charger on. Maybe I have just a very simple battery/charger system which does not balance at all. I oly have a cheap cinese bike from internet so not brand bike.

If you charge the battery not when you get back home again after a ride but only just before you get out for a ride than you first have to wait before you can go since the charging to 100% costs in my case about 30 - 60 minutes. So that is why I immediately charge when arriving home so that the battery will be fully charged henever I want to go. Is it really so bad for the battery to not use it when it is fully charged ???

The problem isn't *using* it at 100% charge, it's leaving it at 100% all the time that ages it faster than leaving it at a lower voltage.

The problem is that the BMS in almost all ebike batteries does not balance it unless you charge to 100%, and many (probably most) ebike batteries are cheaply made of cheap cells and not well-matched, so they wont' stay balanced without doing this frequently, especially as they get older.

So most people don't really have much choice but to just charge to 100%, unless they want to disassemble their pack every ride and check out the state of balance, or solder on wires for an external connector that lets them do this check. That's a lot more than most are willing to do, even if they are able (or willing to learn now)--and honestly they shouldn't have to...but if you want the best performance and max life out of a common / cheap battery, it can take more work. For most people it's not worth that kind of effort.


It's possible your charger is the "latching" type that won't turn back on to balance once it's shut off.

In that case, you can wait say, 10-20 minutes after it's shut off, and power cycle the charger (turn it off, wait a half a minute, and turn it back on). It should then run again for a short time, and stop.

Then repeat that cycle until it doesnt' run anymore when you power cycle it.

Sometiems power cycling doesnt' work unless you also disconnect it from the battery too, but it should for most.

Odessadream said:

If you charge the battery not when you get back home again after a ride but only just before you get out for a ride than you first have to wait before you can go since the charging to 100% costs in my case about 30 - 60 minutes. So that is why I immediately charge when arriving home so that the battery will be fully charged henever I want to go. Is it really so bad for the battery to not use it when it is fully charged ???

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Yes.

Especially if your charger is pushing the finish voltage right up higher than 4.1Vpc.

If the finish point is between 4.0-4.1Vpc, then sitting at that point for a high proportion of its life is a bit less damaging.

The ideal is start charging 70min before you take it out.

Going to a very low SoC every trip is also going to reduce lifespan, best to cut off or swap batteries at say 3.7Vpc, don't go all the way down to 3.0V except unusual / occasional circumstances.

john61ct said:

The ideal is start charging 70min before you take it out.

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That doesn't work if it's a really poorly balanced pack; old, or built out of unmatched or low-quality cells, etc. It won't have time to balance the pack if it's far out of balance, it could take many hours to get it back to where it won't cutout too early on LVC on each ride.

If it really is that unbalanced, it probably has to be left on the charger to balance most or even all of the time it's not being used. :/

Most packs wont' need that, but some will (especially when the owner cant' afford to replace it unless it's nonfunctional).

Yes, I meant for normal usage cycling, not when balancing is required.

If longer time is needed, start earlier.

If people buy stuff where they can't even tell what's what, then yes maybe start hours earlier, but IMO that's no way to run a railroad.

john61ct said:

If people buy stuff where they can't even tell what's what, then yes maybe start hours earlier, but IMO that's no way to run a railroad.

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No, but that's unfortunately the norm.

I don't know many people that do much, if any, looking into the stuff they get to see what it's made of or like, how they should use or maintain it, etc. Especially if it's a new type of thing to them (like someone's first car, first ebike, first celphone, first computer, first house, etc).

Those that do, usually are very very thorough...but if they aren't "experts" in all of the subject matter involved (which can be quite a few disciplines in some things like ebikes) they still leave out significant things that turn out to be important later on.

Long as we keep advancing in the right direction overall, keep learning new things each and every day.

And that includes learning to acknowledge the best can be enemy of good, sometimes good enough is good enough.