48V battery is charging to 53.3V only

[Kyokushin]

Dears,

I have a question - got my new bike (Eshion with Bafang M500) and its working fine but when i am charging the battery (2A 54.6V charger) its charging the battery only to 53.3V (checked on voltometer), and after pluging battery to the bike the charge level is 92% instead of 100%.

After fully charge the charger is blinking green light and is going to idle. After disconnection and connection again its still green.

What do you thing about it? Battery have an issue or charger? Battery is 48V 17.5Ah on samsung cells.

 

[Neeko DeVinchi]

Hi KyoKushin,
Your battery and charger are fine.

If I may take 2min to explain charger to battery amp charging and bafang products in terms of their protocols, it'll all make sense.

Charger-battery amp charging
In order for cells within a battery to charge, more current needs to be introduced. Otherwise, by applying the same voltage, the cells would simply remain active (unable to discharge, regulate or recharge). A 52v charger is common to supply with a 48v battery. Just like a 42v charger would be supplied with a 36v charger.
As for the charger being 2amp, this is usually supplied to ensure safety. Granted from flat to full, it would take roughly 8hrs 40m. But manufacturers do this in case the user forgets to turn off the charger once the battery is fully charged. Their is a debate on whether higher amp chargers reducing the lifespan of a battery pack. However, multiple variables makes this impossible to truly quantify (baring in mind that not all batteries are built equally) and the main anomaly which usually throws the argument into a point of contention is the BMS (Battery Management System). Which brings us nicely to the second point.

Bafang Protocols
Contrary to popular belief, Bafang (like Bosch) actually have their own dedicated batteries which their BMS' specifically interface with the display. Allowing (depending on which display you have) to individually see each cell banks state of charge and to identify any irregularities. Sadly, I know of a couple of emtb's which use Bafang's specific batteries but usually, the manufacturer will 'attempt' to program the motor to recognize near what a true Bafang specific battery would show in terms of % of battery. To that end, Samsung cells (especially for 48v batteries) are used as Bafang would ordinarily use those cells for their packs.

To summarise, your ebike is fine and it is not broken. 92% shown on the display is what the motor is predicting as it cannot interact with each cell bank to check. In addition, I imagine that the way the motor has been programmed, you'll never truly drain the battery as the motor has probably been programmed to assume that 34v is the lowest current it it'll use before assuming that the battery is dead.

I could go into more detail about the specifics of the BMS but I think my 2min are up.

Your bike is fine and unless you are competent at reprogramming the motor (for fear that you may void your warranty), I'd leave it as ??

How much mileage are you getting so far?

 

[Kyokushin]

I think its not Bafang dedicated battery - Bike is with the Eshion engine, but batter is rather something produced for this bike manufacturer.
I have been checked the battery by external voltometer. Charger is also not the 'bafang' but its universal ebike charger only with 2 pins (5.1/2.1).
I have been not drainded battery full, only to around 50%. So from the starting point i made over 40km with 35-40km/h speed on max assist/throttle.

 

[Neeko DeVinchi]

I think its not Bafang dedicated battery - Bike is with the Eshion engine, but batter is rather something produced for this bike manufacturer.
I have been checked the battery by external voltometer. Charger is also not the 'bafang' but its universal ebike charger only with 2 pins (5.1/2.1).
I have been not drainded battery full, only to around 50%. So from the starting point i made over 40km with 35-40km/h speed on max assist/throttle.

I see.
Are you able to take a picture or direct me to where I can study the battery please?

I understand that your volt meter is showing less when fully charged so the BMS is doing something in the background which may explain this.

 

[Kyokushin]

I took below photo after fully charged battery.
To charge it i am not using the socket where i am holding the multimeter.

A plug for charging.

 

[Neeko DeVinchi]

Is this the bike @Kyokushin?

If so, bare with me as I examine it??

 

[apac]

Dears,

I have a question - got my new bike (Eshion with Bafang M500) and its working fine but when i am charging the battery (2A 54.6V charger) its charging the battery only to 53.3V (checked on voltometer), and after pluging battery to the bike the charge level is 92% instead of 100%.

After fully charge the charger is blinking green light and is going to idle. After disconnection and connection again its still green.

What do you thing about it? Battery have an issue or charger? Battery is 48V 17.5Ah on samsung cells.

have you got a photo of your charger? Some chargers have a small dial inside (a potentiometer) so you can fine tune the cut-off voltage. It sounds like your charger may need it turned up a little. It is very easy to do.

 

[apac]

Hi KyoKushin,
Your battery and charger are fine.

If I may take 2min to explain charger to battery amp charging and bafang products in terms of their protocols, it'll all make sense.

Charger-battery amp charging
In order for cells within a battery to charge, more current needs to be introduced. Otherwise, by applying the same voltage, the cells would simply remain active (unable to discharge, regulate or recharge). A 52v charger is common to supply with a 48v battery. Just like a 42v charger would be supplied with a 36v charger.
As for the charger being 2amp, this is usually supplied to ensure safety. Granted from flat to full, it would take roughly 8hrs 40m. But manufacturers do this in case the user forgets to turn off the charger once the battery is fully charged. Their is a debate on whether higher amp chargers reducing the lifespan of a battery pack. However, multiple variables makes this impossible to truly quantify (baring in mind that not all batteries are built equally) and the main anomaly which usually throws the argument into a point of contention is the BMS (Battery Management System). Which brings us nicely to the second point.

Bafang Protocols
Contrary to popular belief, Bafang (like Bosch) actually have their own dedicated batteries which their BMS' specifically interface with the display. Allowing (depending on which display you have) to individually see each cell banks state of charge and to identify any irregularities. Sadly, I know of a couple of emtb's which use Bafang's specific batteries but usually, the manufacturer will 'attempt' to program the motor to recognize near what a true Bafang specific battery would show in terms of % of battery. To that end, Samsung cells (especially for 48v batteries) are used as Bafang would ordinarily use those cells for their packs.

To summarise, your ebike is fine and it is not broken. 92% shown on the display is what the motor is predicting as it cannot interact with each cell bank to check. In addition, I imagine that the way the motor has been programmed, you'll never truly drain the battery as the motor has probably been programmed to assume that 34v is the lowest current it it'll use before assuming that the battery is dead.

I could go into more detail about the specifics of the BMS but I think my 2min are up.

Your bike is fine and unless you are competent at reprogramming the motor (for fear that you may void your warranty), I'd leave it as ??

How much mileage are you getting so far?

that is a very long winded answer, especially for someone who maybe translating the information. AND many of your facts are incorrect.

 

[Neeko DeVinchi]

that is a very long winded answer, especially for someone who maybe translating the information. AND many of your facts are incorrect.

Lol. Oh this I've gotta hear.

Go ahead @apac, clearly you're more knowledgeable about bafang products puts mine to shame ?

@Kyokushin, I'm aware you have a standard 2amp charger with a 54v output so I'll continue to study battery design itself to determine the reason for the voltage irregularity (which is probably because of the BMS) for fear that apac suddenly disappears from the thread (unable to assist further).

If need be, I can always consult a good friend of mine who has made extensive videos of building ebike batteries ??

 

[Kyokushin]

Is this the bike @Kyokushin?

If so, bare with me as I examine it??

View attachment 67890

Yes.

Photos of charger:

 

[RustyIron]

i am charging the battery (2A 54.6V charger)

its charging the battery only to 53.3V

the charge level is 92% instead of 100%.

charger is blinking green light and is going to idle.

Battery is 48V 17.5Ah on samsung cells.

Oftentimes we accumulate data without the ability to interpret it, and we imagine problems where none exist.

What you've described wouldn't get me excited, but I'm sure we can break it down. You mentioned that the battery is charging "only to 53.3V." The implication is that the battery should charge to a greater voltage. What voltage is that, and why do you think that?

 

[Kyokushin]

Its commonly known it should be rather higher, count the voltage and cells. The topic is about i should worry or rather not.

 

[apac]

Its commonly known it should be rather higher, count the voltage and cells. The topic is about i should worry or rather not.

you are correct that the charger should be charging the pack up to approx 54.6v... maybe a little lower.. 54.4.
13 series cells x 4.2v = 54.6v

it could be that the seller of even the manufacturer has purposely lowered the cut-off voltage.

Are there any screws on your charger that can be unscrewed to see inside the charger? You MAY find there is a small brass screw that can be turned. Though looking at the type of charger I am skeptical. Are you willing to open up the charger and photograph the inside components?

 

[apac]

Lol. Oh this I've gotta hear.

Go ahead @apac, clearly you're more knowledgeable about bafang products puts mine to shame ?

@Kyokushin, I'm aware you have a standard 2amp charger with a 54v output so I'll continue to study battery design itself to determine the reason for the voltage irregularity (which is probably because of the BMS) for fear that apac suddenly disappears from the thread (unable to assist further).

If need be, I can always consult a good friend of mine who has made extensive videos of building ebike batteries ??

Kyle, when you get a moment have a look at this thread....
Some of my builds

 

[Kyokushin]

I have been ordered the charger - different brand from local store, i should have it at evening, we will compare

What do you think - its rather case of battery or charger?

 

[apac]

I have been ordered the charger - different brand from local store, i should have it at evening, we will compare

What do you think - its rather case of battery or charger?

Currently your batteries are charging to 4.1v, which could Be set on purpose. To be honest, I don't know for sure which it will be, but if the battery is new it's unlikely to be out of balance already.

 

[apac]

Currently your batteries are charging to 4.1v, which could Be set on purpose. To be honest, I don't know for sure which it will be, but if the battery is new it's unlikely to be out of balance already.

the BMS could have also been pre-programmed to halt the charging at 53.3, but that depends on the bms being used.

 

[Waynemarlow]

After fully charge the charger is blinking green light and is going to idle

Are you disconnecting the charger whilst its blinking green ? Usually the charger will go into a mode at the end of the charging cycle to balance the cells by putting a very small charge into the cells at just below the top threshold of the cells, a multiple of times. Only when it reaches approx. 54.4 volts repeatidly on short pulses will it turn itself off fully and the green light will stay fully on. On a new pack that could take a good hour or two.

If its a new pack you may also want to consider that one of the groups of cells is out of kilter with the other groups and the BMS is balancing the other cells downwards in voltage to match the errant group after the charging cycle. Easy enough to check by monitoring the voltage immediately after the charger has done its stuff, if its 54.4v as expected but the next day the voltage is down to 53.3, then the BMS has discharged approx. 0.1V off the other 12 groups, to match the lowest group. Is that a good thing or bad thing, possibly not a bad as you may think as its only 0.1 V its down, but its unusual not to balance the groups before assembly just to prevent this happening.

 

[apac]

Yes, as said above, the charger will go from constant current charging to constant voltage charging right at the end of the charge. The amp input will slowly lower into a kind of trickle charge where it's trying to stuff in the very last amount needed to fully charge. If your charger has a fan inside, the fan usually switches off when the charger goes into this state. However as it's only a 2 amp charger if probably doesn't have a fan to cool it.

 

[Kyokushin]

I got the new charger (different brand, also 2A 54.6V) - effect is same - after connecting the battery the charger is considering this as charged and is showing green light.

 

[Neeko DeVinchi]

Apologies for the delay @Kyokushin, (work commitments).

Anyway, I think I've got to the bottom of it after briefly liaising with a fellow YouTube/ebike builder (why this person doesn't join forum is beyond me but still).

Anyway, we both agree that BMS is the culprit but we'll need your help to verify this. I gladly say, I'm not expecting you to open up the battery or the charger as you have already checked the voltage with a meter.

1, on the bafang display when fully charged, what voltage is shown?

2, if the voltage shown on the display is the same as your voltage meter, then the motor has been programmed to recognize the voltage accurately so we can proceed to phase 3 (if the display shows a different reading, then we'll approach in a different way).

3, you've used a 2amp charger and I believe you have just purchased a second charger of a different manufacturer but remains compatible. This means that the BMS within your pack is similar to that of a dolphin style battery or a shark style battery (a different battery design compared to my Reention Darado style).
I would recommend purchasing a 3amp charger as this will speed up this process. You'll need to 'roughly discharge the battery to get down to near 43v. At that point charge the battery to to near 50v. Then discharge to 44v then charge to 51v and repeat the pattern. The reason for this is because the BMS within your battery works best after each power cycle (it sounds weird but this is an inherent trait for these batteries).

You'll find that the capacity will slowly increase in terms of voltage. Once it begins to show at the correct voltage, continue using the 2amp charger to ensure the packs maximum lifespan and only use the 3amp charger for fast charging.

If you need recommendations for a descent 3amp charger, SANS would be a good choice. As apac mentioned, a fan assisted charger will ensure no accidents through use.

Please kindly keep me posted as to your progress ??

 

[Kyokushin]

Thank you for support gents, i have no the voltage on display (CP241) but i used the bessst tool and it showed 52.6V.
After that i detached battery and check on multimeter and it was 53.1V.
In next steps i will follow discharge battery more and follow @Neeko DeVinchi advices. I will write the feedback from tests.

 

[Calsun]

What is important is the voltage provided by the battery pack when there is a load applied. Without a load the voltage reading is going to be misleading. Batteries by design will deliver the highest possible voltage until the SOC is greatly reduced and the battery charge is depleted. Is not a linear drop in voltage over time as the battery charge is being used.

Faster charging heats the battery more and heat is detrimental to the overall life of the battery. The transformer bricks provided to recharge battery packs and not intelligent lithium battey chargers by any stretch of the imagination.

Marketing hype for the most part to talk about quick charging. How many people take their battery down to 20% and then actually need to get it back to 100% SOC in two hours? My concern is overcharging with the bricks and so I use a $13 Restmo 15 amp rated outdoor timer with two outlets that shuts off the AC power to the battery chargers after a set amount of time.

 

[Kyokushin]

I have been tested by few discharges (to around 51V) and charges - no change. 53.3V is max what i saw.

 

[Neeko DeVinchi]

Are you measuring the voltage via the display or a voltmeter @Kyokushin?
Also, are you using the 2amp charger or a 3amp charger?
Please kindly confirm

 

[Kyokushin]

3 Amp charger and voltometer. I have connected to the motor by besst and got similar values to voltometer.

 

[Neeko DeVinchi]

Bare with me @Kyokushin. Please allow me to quickly consult a colleague.

Additionally when riding/discharging the battery, how low in terms of voltage did you discharge too?

 

[Kyokushin]

I discharged battery once to 10% but i have not measured how much voltages it is. Mostly i am discharging to around 60%.

 

[Neeko DeVinchi]

Gottya. Bare with me. I'll get back to you shortly ??