Is my 48V LiFePO4 battery with problem?

[tmho]

After reading Aktivator's "How to diagnose 48V LiFePO4 Battery Pack & System" (http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=27902), I guess my 48V LiFePO4 battery is also with problem.

Mine is with 16 cells. The charger output is 58.5V. After the charger stop charging, the battery is only 54.4V. The voltages of each cells are 3.36, 3.36, 3.36, 3.35, 3.35, 3.35, 3.36, 3.36, 3.47, 3.52, 3.48, 3.47, 3.38, 3.46, 3.41 & 3.44V. Is it with problem? What is the cause? The battery, the charger or the BMS? Could someone please suggest some ways for me to fix the problem?

So far my e-bike still can run with the battery. It also got problem (http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=24265) but not as series as Aktivator. I am not sure if the problem is related to the battery.

Below please the photo of my battery and BMS for your reference.
View attachment 1

 

[FMB42]

LifePo4 cells are usually fully charged at 3.65-3.70 volts. Cells that are "hot off the charger" might indicate as much as 3.9 or so volts but, will drop back down to ~ 3.65v once the "surface charge drains off (often in a few hours or less).

Anyway, I'd replace the battery or batteries in you meter with a brand new fresh set just to make sure that your meter isn't off a bit. Also make sure that the meter test leads are clean and tight (you can also "sweep" the meter selector through the various ranges and selections a number of times in order to "clean the internal contacts"). You might also consider using another meter just to be sure.

Other than that, I'd suspect a charger or BMS problem.

Meanwhile, can you give us the brand name and model #s of your battery/BMS and charger?

 

[dogman dan]

I'm going to guess that you remove the battery from the charger as soon as the light turns green. Start leaving it on the charger longer, like overnight regularly. The bms should bring down the high cells, allowing the charger to turn back on and bring up the low ones. But it can take a loooong time.

If it's an old battery, it's likely that it will need more time to balance than it used to. But I wouldn't say it's toast just yet. It may be done for though, if the voltage on any one cell drops a lot more than the others under load. That would cause the bms to shut it off much earlier than before.

 

[dogman dan]

Reading your other thread, I think I know what you are having happen. The fusin controller is amp limited. So if you are traveling in the H switch position, you have the amp limiter kicking on as you pull a load. Then as the bike gets up to speed the motor draws less amps. Now, drawing less amps, the amp limiter shuts off and the amps flow again. So you would often feel an unintended acceleration if the throttle had been held in the full on position.

 

[OlderThanDirt]

Are you using a 360W KP charger?

I had a similar situation with my 38V LIFePO4 batteries. They seemed to slowly degrade after 6-8 months and were no longer capable of delivering their full rated capacity, even though the balance looked reasonable (not exactly equal, but close). With some searching on the forum, I solved my problem. Look for the "Ping modification" thread.

Last year, I had upgraded my King Power charger from the 4A model to the 360W 8A model. This model has a small daughter board mounted near the end of the charger by the fuse. Its purpose is to shut off the charger as soon as the maximum voltage is reached. This is to prevent overcharging of Li-ion cells, but it isn't useful for LiFePO4 because it doesn't give the BMS an opportunity to balance the cells. Monitor the charger current while charging; if it turns off at the green light and never goes back on, the BMS cannot balance the cells.

This may sound drastic but if you have this version of the KP charger you need to clip off the transistor on that daughter board. Then when you monitor the charger current during a charge, after the green light goes on you'll see the current pulse in short, small bursts several minutes apart -- that's the balancing going on.

As Dogman says, leave the charger on overnight. It took a few weeks of use and rechargings before my batteries regained their full capacity.

 

[tmho]

LifePo4 cells are usually fully charged at 3.65-3.70 volts. Cells that are "hot off the charger" might indicate as much as 3.9 or so volts but, will drop back down to ~ 3.65v once the "surface charge drains off (often in a few hours or less).

Anyway, I'd replace the battery or batteries in you meter with a brand new fresh set just to make sure that your meter isn't off a bit. Also make sure that the meter test leads are clean and tight (you can also "sweep" the meter selector through the various ranges and selections a number of times in order to "clean the internal contacts"). You might also consider using another meter just to be sure.

Other than that, I'd suspect a charger or BMS problem.

Meanwhile, can you give us the brand name and model #s of your battery/BMS and charger?

Hi, FMB42, thank you for your reply.
I have used another meter to confirm that my measurements are correct.
The battery/BMS and charger came with the e-bike conversion kit I bought from a china manufacturer called Fusin Motor. On the battery cover, there is a lable with the name of "Worldwide Electric Bikes". I think Fusin supplies the same battery and/or e-bike kits to Worldwide Electric Bikes. But it seems that Worldwide Electric Bikes is no longer in business anymore. From the BMS inside the battery, there is only the chinese name of the supplier. It is called 上海博強微電子有限公司which is in Shanghai of China. The model no. is RPO1620-F-6012008 and the serial no. is 092024-GX-00016.
For the charger, there is a label showing the manufacturer/supply name is Fuyuang and the model no. is FY5802000.
Hope this information may help.

 

[tmho]

I'm going to guess that you remove the battery from the charger as soon as the light turns green. Start leaving it on the charger longer, like overnight regularly. The bms should bring down the high cells, allowing the charger to turn back on and bring up the low ones. But it can take a loooong time.

If it's an old battery, it's likely that it will need more time to balance than it used to. But I wouldn't say it's toast just yet. It may be done for though, if the voltage on any one cell drops a lot more than the others under load. That would cause the bms to shut it off much earlier than before.

Hi dogman, thank you for your kind reply.
I will follow your suggestion to leave the charger on for a longer time to see if it will balance the cells.
Actually I got the battery in late 2009. I use it no more than 20 times and mostly for testing and each time no more than half an hour. And usually I charge it before and/or after each use and I believe I have never discharge it lower than the limit.

 

[tmho]

Reading your other thread, I think I know what you are having happen. The fusin controller is amp limited. So if you are traveling in the H switch position, you have the amp limiter kicking on as you pull a load. Then as the bike gets up to speed the motor draws less amps. Now, drawing less amps, the amp limiter shuts off and the amps flow again. So you would often feel an unintended acceleration if the throttle had been held in the full on position.

Hi dogman, thanks for reading my other thread. Sorry that I do not quite understand what you said. Also, I still have not tried your suggestion that when there is load (someone riding on the bike), there will not be a sudden jump in speed in the H switch position. I am just a occasional rider. I am really scared going so fast especially because that is just an DIY e-bike. Also, the position of the battery is so high making the center of gravity quite high and I feel the bike is not is stable in high speed. Anyway, I will try it later or find a skillful rider to test it for me. But for the time being, let solve the problem of the battery first.

 

[tmho]

Are you using a 360W KP charger?

I had a similar situation with my 38V LIFePO4 batteries. They seemed to slowly degrade after 6-8 months and were no longer capable of delivering their full rated capacity, even though the balance looked reasonable (not exactly equal, but close). With some searching on the forum, I solved my problem. Look for the "Ping modification" thread.

Last year, I had upgraded my King Power charger from the 4A model to the 360W 8A model. This model has a small daughter board mounted near the end of the charger by the fuse. Its purpose is to shut off the charger as soon as the maximum voltage is reached. This is to prevent overcharging of Li-ion cells, but it isn't useful for LiFePO4 because it doesn't give the BMS an opportunity to balance the cells. Monitor the charger current while charging; if it turns off at the green light and never goes back on, the BMS cannot balance the cells.

This may sound drastic but if you have this version of the KP charger you need to clip off the transistor on that daughter board. Then when you monitor the charger current during a charge, after the green light goes on you'll see the current pulse in short, small bursts several minutes apart -- that's the balancing going on.

As Dogman says, leave the charger on overnight. It took a few weeks of use and rechargings before my batteries regained their full capacity.

Hi OlderThanDirt, thanks for your reply.
I am not sure if my charger is 360W KP charger. I could not find similar information on the charger. I can find the name of Fuyuang and model no. FY580200. Also I can find that its output is 58VDC 2A. There is no screw on the charger and so it is not easy to open up the charger to see if my charger has the similar problem of what you mentioned.

 

[dogman dan]

Sounds a bit like the charger may be shutting off too soon, or not reaching the full voltage. If possible, check with a voltmeter to see if the charger even puts out 58v. It's not so unusual for the battery to charge to 58-60 v, but then drop to the real working voltage of around 56v pretty soon.

You can get another lifepo4 charger in many places, ebay, batteryspace, etc. Pingbattery sells ones that are set around 60v.

The batteries supplied by fusin, and sold by wwelectric did not review so good. Warantee on the battery problems may have had a role in the shop going broke. I liked the motor kit a lot though. Especially the three position switch. In low, it made the bike really efficient.

 

[FMB42]

I'd try Dogman's advice of leaving the charger on for awhile. I have seen battery chargers that indicate a "full charge" (green light) and, if left "on" for awhile, then indicate "charging" (red light) again. I'm not sure why this happens though...

Otherwise, I couldn't find much useful Internet info on your batt/bms. However, your battery charger (Fuyuang model FY5802000) seems to be available (at outrageous minimum order numbers). I did notice that input voltage on this charger seems to be both 110 and 240 volts and, as such, you might want to make sure that the proper input voltage for your region is selected (that is, if an 110/240 input voltage selection switch is provided on the charger itself).

Here's a link to what might be your battery:

http://fusinmotors.com/48v10ah-li-ion-pack.html

Below is couple of "interesting" notes from the link above:

"Disconnect the battery wire from the Controller when not in use"

"Leaving the charger plugged into the battery for extended periods of time is ok"

This would lead me to think that you may want to disconnect the battery from the e-bike and then, as dogman suggests, try leaving it on the charger for awhile (even though the charger indicates a "full charge". Note: I do recommend that you supervise this "extended" charging process for safety reasons.

 

[dnmun]

the voltages you posted are made after you stopped charging?

you need to measure the voltage of each cell during the charging cycle. post them.

that BMS uses the O2 micro processor to control the charge. it will shut off the charge at 3.9V but not restart charging until the high cell drops to 3.65V.

you need to see this happening in order to go forward. what is the open voltage on the output of the charger?

 

[tmho]

Sounds a bit like the charger may be shutting off too soon, or not reaching the full voltage. If possible, check with a voltmeter to see if the charger even puts out 58v. It's not so unusual for the battery to charge to 58-60 v, but then drop to the real working voltage of around 56v pretty soon.

You can get another lifepo4 charger in many places, ebay, batteryspace, etc. Pingbattery sells ones that are set around 60v.

The batteries supplied by fusin, and sold by wwelectric did not review so good. Warantee on the battery problems may have had a role in the shop going broke. I liked the motor kit a lot though. Especially the three position switch. In low, it made the bike really efficient.

The output of the charger is 58.5V. After finished charging (the green light on) and when still hooked up, the voltage of the charger is also 58.5V.

 

[tmho]

I'd try Dogman's advice of leaving the charger on for awhile. I have seen battery chargers that indicate a "full charge" (green light) and, if left "on" for awhile, then indicate "charging" (red light) again. I'm not sure why this happens though...

Otherwise, I couldn't find much useful Internet info on your batt/bms. However, your battery charger (Fuyuang model FY5802000) seems to be available (at outrageous minimum order numbers). I did notice that input voltage on this charger seems to be both 110 and 240 volts and, as such, you might want to make sure that the proper input voltage for your region is selected (that is, if an 110/240 input voltage selection switch is provided on the charger itself).

Here's a link to what might be your battery:

http://fusinmotors.com/48v10ah-li-ion-pack.html

Below is couple of "interesting" notes from the link above:

"Disconnect the battery wire from the Controller when not in use"

"Leaving the charger plugged into the battery for extended periods of time is ok"

This would lead me to think that you may want to disconnect the battery from the e-bike and then, as dogman suggests, try leaving it on the charger for awhile (even though the charger indicates a "full charge". Note: I do recommend that you supervise this "extended" charging process for safety reasons.

I am now trying Dogman's advice of leaving the charger on for a longer time.
There is no switch on the charger to select the input voltage. It is just automatically selecting the input voltage.
I am from Canada.
Each time after testing/used, I will disconnect the battery from the controller.

 

[tmho]

the voltages you posted are made after you stopped charging?

you need to measure the voltage of each cell during the charging cycle. post them.

that BMS uses the O2 micro processor to control the charge. it will shut off the charge at 3.9V but not restart charging until the high cell drops to 3.65V.

you need to see this happening in order to go forward. what is the open voltage on the output of the charger?

Hi dnmun, thanks for your reply.
Do you mean checking the voltage of each cell when the charger is charging the battery? Will the voltages be changing (increasing) since each cell is being charged? Anyway, I will do that and post the result.
Now when the charger is connected with the battery and the charger green light is on. That means the battery is not charging although the highest cell voltage is just 3.52V. I need to connect the battery to the motor and run the motor for a while before I can get the charger to charge the battery (red light on).
Sorry I am not sure what do you mean by open voltage. Do you mean voltage without load (when the charger is not connected to the battery)? If yes, then it is 58.5V. When the charger is connected to the battery and finish charging with the green light on, the voltage is also 58.5V.

 

[dogman dan]

Even though the green light is on, it may still need to charge longer. The bms will lower the voltage of the highest charged cells, and eventually the charger turns back on briefly. If the battery is pretty out of balance the time required to fully balance it could even be a week or more.

There is another common possibility. The green light also comes on if the battery is not connected. So your charger could be stopping early because you have an intermittent disconnect caused by a bad plug, or a bad wire to the plug. So wiggle stuff and see if you can find out if the plug has a poor connection.

Most likely, charging for a long time will help some. But this battery never got a reputation for being reliable.

 

[dnmun]

if the charger puts out 58V then it should charge up to 58V. since it is not shutting off the charge because of a cell reaching 3.9V then something else is stopping the charging either in the charger or the BMS. can you tell which of the mosfets is the charging FET? measure the gate voltage on that charging FET to determine if the BMS processor is turning it off early in the charge for some reason or else the charger is shutting down during the charge, before it achieves full voltage. that could be a bad op amp on the charger, or the resistor divider bridge that sets the reference for the shunt current voltage drop is off and it shuts down while the charging current is still high. it would help to get an ammeter in line with the charging current to evaluate what is happening.

 

[tmho]

if the charger puts out 58V then it should charge up to 58V. since it is not shutting off the charge because of a cell reaching 3.9V then something else is stopping the charging either in the charger or the BMS. can you tell which of the mosfets is the charging FET? measure the gate voltage on that charging FET to determine if the BMS processor is turning it off early in the charge for some reason or else the charger is shutting down during the charge, before it achieves full voltage. that could be a bad op amp on the charger, or the resistor divider bridge that sets the reference for the shunt current voltage drop is off and it shuts down while the charging current is still high. it would help to get an ammeter in line with the charging current to evaluate what is happening.

Hi dnmun, sorry my electronic knowledge is so limited that I can't tell which is the charging FET. If the charging FET is in the charger, then right now I still could not open the charger as there is no screw on the casing of the charger. If the charging FET is in the BMS, then from the BMS photo I shown on my first post, may be you can point it out to me and I might be able to follow your instructions to test if there is something wrong.

 

[louispower]

invited by Tmho I would like to paste here the reply to his question.
Hello Tmho, the cells voltage is 3.65V when the battery was initially assembled, after using on ebikes for some time (for example 1 year, yours battery was produced in 2008) its capacity will drop a little and each cells's voltage will not have exactly same voltage, its allowed difference is 200mV.

After you use charger to charger the battery fully, and keep hooking the charger with the battery, the battery's voltage will be same as that of the charger's output, after you remove the charger, the battery's voltage will drop a little after about 5 minutes.

As of the problem you you said on the forum we have checked the controller you sent back and its 3 speeds function works well.

You need to know the controller for front wheel kit and rear wheel kit is differently setup although the controllers have same outlook, if you mix them you will see the 3 speeds function donot work.

Thanks.

the link is here http://fusinmotors.com/distribution/post248.html#p248

 

[tmho]

invited by Tmho I would like to paste here the reply to his question.
Hello Tmho, the cells voltage is 3.65V when the battery was initially assembled, after using on ebikes for some time (for example 1 year, yours battery was produced in 2008) its capacity will drop a little and each cells's voltage will not have exactly same voltage, its allowed difference is 200mV.

After you use charger to charger the battery fully, and keep hooking the charger with the battery, the battery's voltage will be same as that of the charger's output, after you remove the charger, the battery's voltage will drop a little after about 5 minutes.

As of the problem you you said on the forum we have checked the controller you sent back and its 3 speeds function works well.

You need to know the controller for front wheel kit and rear wheel kit is differently setup although the controllers have same outlook, if you mix them you will see the 3 speeds function donot work.

Thanks.

the link is here http://fusinmotors.com/distribution/post248.html#p248

Hi Louispower, please confirm if you mean there is no problem in my battery system.

 

[louispower]

Hi Tmho,

honestly we didnot see any problem since this battery has been 3 years old, the fact that the cells capacity drops a little is normal.

thanks.

 

[dogman dan]

Louis is correct, as the battery ages it will stop holding the full voltage it is charged to. My year and a half old pingbattery drops to 3.55 per cell pretty quickly. But it does, if only for a few minuites, charge to 60v.

Perhaps we are miscomunicating just a bit. I was under the impression that the battery never quite reached your top of charge voltage of 58v. That's why we said charge it longer so the bms can work and the battery get better balanced. Louis says your battery is normal. It's true, an older battery has a much more pronounced tendency to get out of balance. The voltages you posted show exactly that. So more time on the charger, or bringing the charge on the individual cells manualy is the first step. Try just charging longer first, since you seem to be less electronicly experienced.

A more serious problem with the battery would be shown by a marked lack of range, such as one or more set of cells dropping to 3v when used, while the others remain much higher. So you'd be seeing a huge drop in capacity, not just a few miliamphours of capacity loss that is normal for an old battery.

Your controler has checked out normal, so you suspected the battery? Does that mean you have a problem where the bike won't run? There is a ton of wiring on those fusin kits. Are you positive the key switch or other connectors work?

 

[tmho]

Louis is correct, as the battery ages it will stop holding the full voltage it is charged to. My year and a half old pingbattery drops to 3.55 per cell pretty quickly. But it does, if only for a few minuites, charge to 60v.

Perhaps we are miscomunicating just a bit. I was under the impression that the battery never quite reached your top of charge voltage of 58v. That's why we said charge it longer so the bms can work and the battery get better balanced. Louis says your battery is normal. It's true, an older battery has a much more pronounced tendency to get out of balance. The voltages you posted show exactly that. So more time on the charger, or bringing the charge on the individual cells manualy is the first step. Try just charging longer first, since you seem to be less electronicly experienced.

A more serious problem with the battery would be shown by a marked lack of range, such as one or more set of cells dropping to 3v when used, while the others remain much higher. So you'd be seeing a huge drop in capacity, not just a few miliamphours of capacity loss that is normal for an old battery.

Your controler has checked out normal, so you suspected the battery? Does that mean you have a problem where the bike won't run? There is a ton of wiring on those fusin kits. Are you positive the key switch or other connectors work?

Hi, my big query is why my battery is just 54.4V after freshly recharged off the charger which has an output voltage of 58.5V. I admit that I have limited electronic knowledge, but I really doubt if this is true for a 3 years old battery which I used it no more than 20 times and mostly for testing and each time no more than half an hour.

 

[dnmun]

there doesn't appear to be anything wrong.

 

[tmho]

I have just read another post from this forum that it is okay to charge a LiFePo4 battery without a BMS so long as you monitor the voltage of each cell closely that it won't be higher than a certain value. I am planning to try it on my battery. If the result is my battery voltage can go up to 58V and stay there for a certain period of time, then can I say that my current battery system (the charger and/or the BMS) is with problem (because it cannot go up to 58V)? Your comment on this is highly appreciated.