48V12Ah Battery problem

[GM Brazil]

Now... my turn

My battery can not handle more than 8km now, suddently. And the recharger does not detects the battery when the bms cuts - I need to plug the recharger annd spin the motor mannualy, use the regen brake then the back voltage turns on the controller and BMS back and the recharge cycle starts.

Also the battery lost a lot of energy while stand still.

I sent this e-mail to tom:

Hello Tom,
Tom, I'm having problems with my battery.
About the product:
Magic Pie rear kit with LFP48V12S battery
Bought as a sample product  to test for this dealer contract
Received 18/01/2010
Use:
At the city, some bad asphalt, rain
650km of use
4 months of use
10km/day most rides
Symptoms
The bikes no longer achieves 40hm/h. The maximum speed is 35km/h
The battery lost a lot of charge while resting
The range was 25km, then 20km, and now only 7km on controlled tests (I do them every 15 days)
When the BMS shuts the battery down the recharger is not able to detect that the battery is connected - I needed to spin the wheel and use the regenerative brakes to have enough voltage to the recharger be able to detects that the battery is connected and starts the charging process.

Photos of the recharger annexed.

Please, answer me with any tests needed to confirm that this is a quality problem of the battery.

Thank you!

Bruno F. Porto
Golden Motor Brazil

[GM Brazil]

Hello Bruno F.Porto
 
Remove the battery end cover containing the charger socket. You will find a printed circuit board (PCB).
It is a battery management system (BMS) which equalizes the charge in each of the cells.
The wire B1 is the one attached to the battery anode. Connecting his professional quality voltmeter to the battery anode and to the other twelve wires in succession.

There is one 13-Pin connector on this PCB. (B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1)

Measure the voltage between
the  green wire and other nine wires as below:
 
B1 green wire   to:                              Specification
B2 yellow wire(the second wire)   3.6V  ~   4.15V
B3 yellow wire(the third wire)        7.2V   ~  8.30V
B4 yellow wire(the fourth wire)     10.8V  ~ 12.45V
B5 yellow wire(the fifth wire)         14.4V ~  16.60V
B6 yellow wire(the sixth wire)       18.0V  ~ 20.75V
B7 yellow wire(the seventh wire) 21.6V ~  24.90V
B8 yellow wire(the eighth wire)    25.2V  ~ 29.05V
B9 yellow wire(the ninth wire)      28.8V  ~ 33.20V
B10  yellow wire (the tenth wire)   32.4V ~  37.35V
B11 yellow wire(the eleven wire)  36.0V ~  41.5V
B12 yellow wire(the twelve wire)  39.6V ~  45.65V
B13 black wire(the thirteen wire)  43.2V ~  49.8V
 If the voltages are normal,
then the cells are okay.

Incidentally, 43.2~49.8V   +  3.6V~4.15V   =  46.8V~53.95V
Then, measure voltage of the battery
without BMS (B- and battery anode)  46.8V~53.95V
with BMS (D- and battery anode)  46.8V~53.95V
If these two voltages are the same, then the battery pack is okay.
 
Note:If the voltage of any cell is more than 4.15V.I think the cell is overcharger.It can stop BMS and battery work.So you should find out which cell is overcharged.
 
Best Regards
Tom

I tested the battery and had these results:

B1 green wire   to:                             
B2 yellow wire(the second wire)  4.1V Cell=4.1V
B3 yellow wire(the third wire)        8.2V  Cell=4.1V
B4 yellow wire(the fourth wire)     12.3V Cell=4.2V
B5 yellow wire(the fifth wire)         16.5V Cell=3.9V
B6 yellow wire(the sixth wire)       20.4V Cell=4.3V <-Bad?
B7 yellow wire(the seventh wire) 24.7V Cell=4.2V
B8 yellow wire(the eighth wire)    28.9V Cell=4.1V
B9 yellow wire(the ninth wire)      33V Cell=4.1V
B10  yellow wire (the tenth wire)   37.1V Cell=4,2V
B11 yellow wire(the eleven wire)  41.3V Cell=4.0V
B12 yellow wire(the twelve wire)  45.3V Cell=4.1V
B13 black wire(the thirteen wire)  49.4V Cell=4.0V

without BMS (B- and battery anode)
53.4V
with BMS (D- and battery anode)
53.4V

So, the battery seems ok, the problem could be the charger? Why does it still not capable of doing more than 7km instead of 25km when it was new?

ps.: The epoxy at the sides of the PCB I put to hold the pack in place as it was loose inside the casing.

[Cornelius]

I think these cells should be very close to each other volt-wise; a difference of 0.40V are too much. I think 2 decimals should be used when measuring.

Are these voltages after a charge, or when the battery/bms cut?

[GM Brazil]

I think these cells should be very close to each other volt-wise; a difference of 0.40V are too much. I think 2 decimals should be used when measuring.

Are these voltages after a charge, or when the battery/bms cut?

After a charge, I'll try to load the battery with some controllable resistance, as I'm far from my bike now, to test the voltages after the cut.

I did measure the voltages between B1/B2, B2/B3, B3/B4, etc to have more precision (two digits) and all the cells looks ok.. I'll measure like this again tomorrow and post the results here.

[Leslie]

Now... my turn

My battery can not handle more than 8km now, suddently. And the recharger does not detects the battery when the bms cuts - I need to plug the recharger annd spin the motor mannualy, use the regen brake then the back voltage turns on the controller and BMS back and the recharge cycle starts.



Bruno F. Porto
Golden Motor Brazil

[/quote]

Wow how did you figure all that out.  It amazes me the things people fall upon when trying to get something to work.

That test seems to confuse people but I could be wrong.  But these results from ground to pins make me dizzy to work out.

I would try measure the voltages between pins and post.

B13 B12.
B12 B11.
B11 B10.
B10 B9.
B9 B8.
B8 B7..
B7 B6
B6 B5,
B5 B4.
B4 B3.
B3 B2.
B2 B1..

And post the results.

This way it is easy to spot a bad cell block.  And do use the 20v selection not the 200v selection on the meter for individual cell measurements as posted by Cornelius.


Have you checked the 220v 110v selector switch on the charger.  Someone had this problem before.

[GM Brazil]

Wow how did you figure all that out.  It amazes me the things people fall upon when trying to get something to work.

This bike is my prototype. I'm taking notes of every behavior so I can write a good manual One of them was after the BMS shuts down in one of my several "controlled" range tests I saw that during a downhill when I used the brakes the controller turned on again, activated the regenerative braking and then the BMS turned the battery on again.

Also, my charger have a relay that turns on the process when it detects any voltage from the plug - I always hear it. And when testing the voltage of the charger there always zero - it only starts with the battery connected.

I tested the charger plug from the battery with my multimeter and when the BMS kicks off, there was no voltage. I figured out that for some reason the BMS cuts out the charger plug from the circuit too, so, to turn it on again I would need to raise the battery voltage so the BMS let it works and this leads to "simulate a downhill" with my tire in the air

Testing with the 20V settting at the multimeter to have better precision:
B+/B12=4,06 (there is only 12 cables and no B13 at the board, check the attached pic)
B12/B11=4,07
B11/B10=4,06
B10/B9=4,07
B9/B8=4,08
B8/B7=4,07
B7/B6=4,06
B6/B5=4,08
B5/B4=4,08
B4/B3=4,05
B3/B2=4,07
B2/B1=4,08

Pretty ok to me....

Have you checked the 220v 110v selector switch on the charger.  Someone had this problem before.

I checked this after that post

I think I'll need to do some load test.... The problem is that my watt meter is 770km away from here now, with the bike.

Thank you very much for the help!!

I'll try to buy some watt meter here, and create a simple circuit to control correctly the amperage drain and test the battery with some lamps. Any other, simpler, idea that I could use to test the battery?

[vapid2323]

I am glad the solution to my issue in now standard troubleshooting 

[Leslie]

Wow how did you figure all that out.  It amazes me the things people fall upon when trying to get something to work.

This bike is my prototype. I'm taking notes of every behavior so I can write a good manual One of them was after the BMS shuts down in one of my several "controlled" range tests I saw that during a downhill when I used the brakes the controller turned on again, activated the regenerative braking and then the BMS turned the battery on again.

Also, my charger have a relay that turns on the process when it detects any voltage from the plug - I always hear it. And when testing the voltage of the charger there always zero - it only starts with the battery connected.

I tested the charger plug from the battery with my multimeter and when the BMS kicks off, there was no voltage. I figured out that for some reason the BMS cuts out the charger plug from the circuit too, so, to turn it on again I would need to raise the battery voltage so the BMS let it works and this leads to "simulate a downhill" with my tire in the air

Testing with the 20V settting at the multimeter to have better precision:
B+/B12=4,06 (there is only 12 cables and no B13 at the board, check the attached pic)
B12/B11=4,07
B11/B10=4,06
B10/B9=4,07
B9/B8=4,08
B8/B7=4,07
B7/B6=4,06
B6/B5=4,08
B5/B4=4,08
B4/B3=4,05
B3/B2=4,07
B2/B1=4,08

Pretty ok to me....

Have you checked the 220v 110v selector switch on the charger.  Someone had this problem before.

I checked this after that post

I think I'll need to do some load test.... The problem is that my watt meter is 770km away from here now, with the bike.

Thank you very much for the help!!

I'll try to buy some watt meter here, and create a simple circuit to control correctly the amperage drain and test the battery with some lamps. Any other, simpler, idea that I could use to test the battery?

You can see any problesm if you put a load on the pack like 4X12v 50 watt halogen bulbs in series.  Wait for a 5 minutes to strip any surface charge then test the voltages of each block to see if one cell block is suffering.

A bad conection to one or more Pcell in a block will show a faster voltage drop between the pins.

[GM Brazil]

I'll need to do the load test.

O tested today again with the bike and the battery stills dropping the voltage a lot at the first high load uphill - It means, the red empty light is the only one on.

317537 - Could I use normal 50W incandescent 120v lamps? Or some type of heat element? I tried to find some schemes using google but not enough information to do the correct set up.

[GM Brazil]

Ok, I did the load test with my Battery!

It looks like thath the BMS is shutting off to early, look at these results:

19:50 Start 150W-3A Battery load test, just after charge without load: 54v, with load 53v
20:10 1,01Ah and 50,28Vm
20:30 2,05Ah and 49,20Vm
20:45 2,78Ah and 48,39Vm
21:00 3,50Ah and 47,62Vm
21:15 4,22Ah and 46,70Vm
21:30 4,86Ah and 45,49Vm
21:45 Stopped before I got the numbers
Estimated final numbers: 5,64Ah and 44,82Vm

So, it confirms that I have almost half of the capacity, just like my ride tests showed.

As the individual cels looks ok, this leads to the BMS system? Hot to test it to confirm?

Thank you.

[Hardcore]

I think I have the same, I used to be able to do my daily commute but now it's shutting down ater only 5 to 10 km and that's not enough, startoff voltage is 54 v and after the cut off no load it's like 49v is this okay, no I don't think so

please help

[Magneto81]

Sounds like you are having a similar problem to mine. Your system shouldn't cut power until the voltage is at 36-40V for a 48V setup.
Similarly for my own setup, my system (3x12V = 36V system) shuts down at 35V, but shouldn't shut down unless it's at only 27-30V...

I gotta tell you, I would LOVE to be able to recreate that programming interface so the side effects of all the settings are clearly defined for us users... Yao - any chance I can get the API or a copy of the source code for the program? I seriously swear I wont' give any copies out unless I have your permission first!!

[GM Brazil]

Does you battery have a BMS (circuit board that manages the battery pack)? Because it is not my controller that is cutting, is the BMS from the battery. If you do not have a BMS your controller is programmed to a 48v system cut-off... Maybe there is some way to twick that....

In my case still could be a problem of one/some cells our the BMS circuit board. I could do a very controlled load test, by passing the BMS to check if the cells still holding the full capacity... then I cut the load at the 35v, this could damage my battery?

How to isolate the source of the problem? That is my actual question.

The cell voltage measurements shows that they look ok - but the bike still showing a very high voltage drop under 18A load.
The load test showed that the BMS is cutting earlier, but I did not see the actual cut-off voltage, just estimates.

Or the BMS is cutting to early or there is some damaged cell that keeps the voltage with no load but lost a lot under load, leading to the premature cut-off...

This is messing with my head 

I start a new job tomorrow, at 9,5 km from home. Pedalling a lot I can manage to get there..... But I will need to bring the charger....

[GM Brazil]

In fact, I need to create a "Cake recipe" for testing batteries, I will need it for my customers very soon...


What do you think about this: http://www.optimengineering.com/CBA.htm

[Magneto81]

I tested mine with a simple 12V inverter and then simply plugged in a lamp. If one battery can output 160 watts, without dropping the voltage below 10.5V, I gave it a pass. It's a pretty rudimentary test, but it certainly proved that my batteries (except one) were able to output enough power.