YCF 50E dirt bike question

[nez_fer]

Hi All,
I'm looking for help as I'm new to the Lithium and Electric Moto world. I bought a YCF 50E dirt bike for my son. It uses a 48V 10ah battery with 1200W motor. I really like everything about the bike, but suspect there might be an issue with either the battery, BMS or the controller.

At full charge the Battery Voltage reads 58.8V. The bike runs great until the battery goes down to about 50V with no load. With a load the Voltage can drop down to 47V and all power will shut off. The lights on the throttle turn off then turn back on showing a dead battery (single orange light) even though the battery voltage shows 49V or 50V. If I unplug the battery from the controller and plug it back, the bike seems to reset with the throttle lights showing all green, Battery voltage showing 49V or 50V and the bike will run again until the load draws the battery down to 47V and it will shut off again.

Is it normal to shutdown at 47V? If not, is the problem the battery or the controller?

Thank you and my apologies if I'm asking obvious questions.

Nez.

 

[amberwolf]

If it actually powers off, the BMS in the battery is doing it's job and protecting it from potential damage.

The most likely thing is that the cells in the battery are not very good, and are not really capable of the load being placed on them (so they sag in voltage a lot under load), and not matched to each other in characteristics.

The first part is likely because you have a 10Ah battery that *might* be only capable of 10A-20A loads, and a 40A controller that's placing loads on it probably twice as much as it was meant to handle, and possibly four times as much. ****

The last part means that their voltages vary from each other (unbalanced), especially under load, and one or more of them is dropping below the cell-level LVC of the BMS, so the BMS turns the output off to protect them from damage.

You can verify this by opening the battery and measuring the voltages between each pair of wires on the multiwire BMS-to-cell connector. If they are balanced (matched cells) they will all be exactly the same regardless of how charged or discharged the battery is. If they are not, then the differences are probalby causing the problem.

Replacing the pack with one made of matched cells (hard to find one though) that are significantly more capable than you need them to be is the "best" option. More capable meaning able to handle higher currents than you need, with more capacity than you need, so that as it ages it will still be capable of what you need.

Replacing it with a cheap one (and doing that again whenever the replacement begins to fail) is a more common choice.

Repairing the pack usually costs more than replacing it, because of the cost of parts and of the downtime while you learn how to safely do so, and buying all the test and repair equipment.

If the BMS has a balancing function, you can leave it on the charger until the charger stops turning on and off (hours, days or longer) to rebalance it, but htat doens't fix the problem, only helps you use a bit more of the remaining capacity.



See some of the "similar threads" at the bottom of your thread here for other situations like yours and their solutions, as well.


**** Searching for the BTRX5019 on the battery label finds other examples of battery problems with this kind of bike, such as th is one

https://www.reddit.com/r/diybattery/comments/18d4x0e

this page

BtrPower Ebike Battery 48V 10AH, Li- ion Battery Pack with 3A Charger

Parameter. 48v 10ah battery suitable for 250w-1000w motor. 54.6V 3A charger. 20A BMS(Battery Management System). Range is about 20-30 mils without pedaling Longer Service Life. lithium battery still has more than 80% capacity after 1000cylces. life expectancy of our Ebike Battery up to 5 years...

www.btrpower.com

might be for a similar pack from the same manufacturer, that only has a 20A BMS, and it's almost cerrtainly newer technology than whatever you've got there. Doesn't say what cells are in it or it's configuration, or if they are new cells or recycled scrap garbage cells, so can't say what it is physically capable of.

 

[nez_fer]

If it actually powers off, the BMS in the battery is doing it's job and protecting it from potential damage.

The most likely thing is that the cells in the battery are not very good, and are not really capable of the load being placed on them (so they sag in voltage a lot under load), and not matched to each other in characteristics.

The first part is likely because you have a 10Ah battery that *might* be only capable of 10A-20A loads, and a 40A controller that's placing loads on it probably twice as much as it was meant to handle, and possibly four times as much. ****

The last part means that their voltages vary from each other (unbalanced), especially under load, and one or more of them is dropping below the cell-level LVC of the BMS, so the BMS turns the output off to protect them from damage.

You can verify this by opening the battery and measuring the voltages between each pair of wires on the multiwire BMS-to-cell connector. If they are balanced (matched cells) they will all be exactly the same regardless of how charged or discharged the battery is. If they are not, then the differences are probalby causing the problem.

Replacing the pack with one made of matched cells (hard to find one though) that are significantly more capable than you need them to be is the "best" option. More capable meaning able to handle higher currents than you need, with more capacity than you need, so that as it ages it will still be capable of what you need.

Replacing it with a cheap one (and doing that again whenever the replacement begins to fail) is a more common choice.

Repairing the pack usually costs more than replacing it, because of the cost of parts and of the downtime while you learn how to safely do so, and buying all the test and repair equipment.

If the BMS has a balancing function, you can leave it on the charger until the charger stops turning on and off (hours, days or longer) to rebalance it, but htat doens't fix the problem, only helps you use a bit more of the remaining capacity.



See some of the "similar threads" at the bottom of your thread here for other situations like yours and their solutions, as well.


**** Searching for the BTRX5019 on the battery label finds other examples of battery problems with this kind of bike, such as th is one

https://www.reddit.com/r/diybattery/comments/18d4x0e

this page

BtrPower Ebike Battery 48V 10AH, Li- ion Battery Pack with 3A Charger

Parameter. 48v 10ah battery suitable for 250w-1000w motor. 54.6V 3A charger. 20A BMS(Battery Management System). Range is about 20-30 mils without pedaling Longer Service Life. lithium battery still has more than 80% capacity after 1000cylces. life expectancy of our Ebike Battery up to 5 years...

www.btrpower.com

might be for a similar pack from the same manufacturer, that only has a 20A BMS, and it's almost cerrtainly newer technology than whatever you've got there. Doesn't say what cells are in it or it's configuration, or if they are new cells or recycled scrap garbage cells, so can't say what it is physically capable of.

Thank you for the info. This helps me a lot. Currently the ride time is sufficient for the little guy, but I'll have to get a second battery. I agree it is most likely that I will just get a cheapo battery.