eBay ebike batteries (new)?

[CreativeSource]

Hi guys I've just purchased a 48v 15ah silverfish battery pack from eBay, 2 questions if I may.
Q 1) it only reads 53.6v hot off the charger, and not 54.6v. is this okay? or does this need to go back?
Q 2) with the battery off the bike and key switched off, the charger stops charging at 53.6v, however, if I then switch the key to the on position, (still off the bike) it continues to charge for a further 45 minutes to an hour, is it safe to charge this way? As seems to be the only way to get it to around 54v

many thanks in advance
Daron

 

[vfr400]

How do you know that that voltage is measured right? Did you validate your meter in any way? Did you measure the voltage on the charger jack?

You should charge with the bike switched off otherwise the charger will be providing the power for it, which is why you see it come back on.

 

[CreativeSource]

How do you know that that voltage is measured right? Did you validate your meter in any way? Did you measure the voltage on the charger jack?

You should charge with the bike switched off otherwise the charger will be providing the power for it, which is why you see it come back on.

Hi there
Yes the KT LCD 3 on the bike reads 53.6v hot off the charger. It also reads 53.6v via 2 different digital multimeters via the battery jacks hot off the charger. The battery is always charged in the office, and not on the bike. The bike is 30 meters away in the shed.
So with that in mind, the charger switches off at 53.6v, but then charges for another hour if I turn the battery key on? (Still off the bike)

A) is this safe for the battery as it's the only way to get the voltage somewhere near 54.6v
B) is 53.6v hot off the charger acceptable for a (new?) Battery?

Many thanks again guys

 

[Nealh]

The 53.6v = a tad over 4.12v per cell group average which is low for balance to occur, it might be that one or two cell groups are hitting 4.2v before the others and then shutting off balance charging. It is likely then that some groups are out of balance, try using it and several normal full charges ( off the bike) to see if the balance improves, this will be noticeable by the full voltage charge increase. Try discharging to near cut off value of around 39 - 40v and then a full long recharge, the BMS may eventually correct the imbalance but If no joy with voltage change one either puts up with it or contacts the seller.

Sometimes the BMS may have a lower top balance final voltage of between 4.15 - 4.2v so a min full charge would be around 54.1v.

 

[CreativeSource]

The 53.6v = a tad over 4.12v per cell group average which is low for balance to occur, it might be that one or two cell groups are hitting 4.2v before the others and then shutting off balance charging. It is likely then that some groups are out of balance, try using it and several normal full charges ( off the bike) to see if the balance improves, this will be noticeable by the full voltage charge increase. Try discharging to near cut off value of around 39 - 40v and then a full long recharge, the BMS may eventually correct the imbalance but If no joy with voltage change one either puts up with it or contacts the seller.

Sometimes the BMS may have a lower top balance final voltage of between 4.15 - 4.2v so a min full charge would be around 54.1v.

Thanks very much for the above information Nealh. I will certainly try that method. Could I just ask you though, when the charger shuts off at 53.6v (key in off position, and off the bike) if I then put key in ON position (still off the bike) it charges to 54.2v. Should I try your method with key switched off? Or key switched ON?

Cheers Nealh

 

[Nealh]

I guess you can try charging with the key in the 'ON' position, some of my batteries have a switch and when charging I always have the switch on.
The on switch with mine is/are hard wired to the BMS, whether the key 'ON' is the same I don't know, though possibly sounds like it.

 

[CreativeSource]

I guess you can try charging with the key in the 'ON' position, some of my batteries have a switch and when charging I always have the switch on.
The on switch with mine is/are hard wired to the BMS, whether the key 'ON' is the same I don't know, though possibly sounds like it.

Thanks Nealh
I Really appreciate your help on this matter.

 

[Nealh]

End of the day it depends on the balance spec of the BMS, I have one albeit made by LG with is set for 4.15v per cell group. Others I have are generic China ones, some at 4.2v and a couple that are set for 4.18v. 54v is tad over 4.15v so is about the bare minimum one should expect to see.

 

[vfr400]

I guess you can try charging with the key in the 'ON' position, some of my batteries have a switch and when charging I always have the switch on.
The on switch with mine is/are hard wired to the BMS, whether the key 'ON' is the same I don't know, though possibly sounds like it.

You can charge with the battery switched on, but not with the controller/bike switched on. Bear in mind that some bikes are switched on from the battery, though not so many these days.

 

[Tony1951]

I'm interested to know when my charger is balance charging. It is a 36 volt Chinese generic, fan cooled system. Does the balance charging happen late in the time when the red light is on the charger, or does it happen when the green light comes on?

I have so far tended to switch off the charger pretty well as soon as the green light comes on - not wanting to over charge and shorten battery life. Is this correct?

Thanks for any advice you can offer.

 

[vfr400]

The charger doesn't do any balancing. The battery does it on its own.

Imagine 10 buckets each with a small hole drilled in the side an inch from the top. The buckets are all about half full of water, but slightly different levels. A big pipe with a single tap splits into 10 equal smaller sized pipes that fill up the 10 buckets. The tap has a red light when on and a green light when off. As soon as the first bucket starts to overflow, you get the green light and the tap switches off.

Now analyse what happens. If the tap is manually switched off before any levels reach the small holes, the level differences stay the same, and whatever caused the differences will add to them in the future.
If the tap stays on until the first overflows, then switches off. All the buckets with levels above the hole will drain down until the level is one inch from the top. Maybe some don't reach that level, but next time, they have a better chance.

After a few cycles, all will be the same level unless the thing that is disturbing the balance, like a small leak in one of them drains down more than an inch during the cycle. In that case, you have to fix the leak.

Your charger is the big pipe with the tap on it. Your buckets are the 10 cells in the battery. The small holes and pipes are the management circuitry in the battery (BMS).

 

[Tony1951]

The charger doesn't do any balancing. The battery does it on its own.

Imagine 10 buckets each with a small hole drilled in the side an inch from the top. The buckets are all about half full of water, but slightly different levels. A big pipe with a single tap splits into 10 equal smaller sized pipes that fill up the 10 buckets. As soon as the first bucket starts to overflow, you get the red light and the tap switches off.

Now analyse what happens. If the tap is manually switched off before any levels reach the small holes, the level differences stay the same, and whatever caused the differences will add to them in the future.
If the tap stays on until the first overflows, then switches off. All the buckets with levels above the hole will drain down until the level is one inch from the top. maybe some don't reachh that level, but next time, they have a better chance.

After a few cycles, all will be the same level unless the thing that is disturbing the balance, like a small leak in one of them drains down more than an inch during the cycle. In that case, you have to fix the leak.

Your charger is the big pipe with the tap on it. Your buckets are the 10 cells in the battery. The small holes and pipes are the management circuitry in the battery (BMS).

Great explanation. EDITED OUT MISTAKE HERE.

It is a new battery, so I have no reason to suspect low cell groups yet.

 

[vfr400]

Sorry, I meant the reverse. The charger shows red while charging until the first cell reaches the top, then it goes green and switches off. I've edited above.

Different chargers have different light systems on them, some have one light and some have two. Most of the basic Chinese ones show green when not connected, red when charging and green when finished.

 

[Tony1951]

Sorry, I meant the reverse. The charger shows red while charging until the first cell reaches the top, then it goes green and switches off. I've edited above.

Different chargers have different light systems on them, some have one light and some have two. Most of the basic Chinese ones show green when not connected, red when charging and green when finished.

Thanks. I edited my summary based on the misunderstanding, so we won't inadvertently misinform later followers of the thread.

Cheers and thanks for your time.