MagicPie4 , array of 16 lifepo4 battery 40152S 3.2V 15AH

[Abe]

Alan,
I want to wish you Merry Christmas and Happy New Year.
It's been a long time since our last conversation.

General description:
First it's a MagicPie4 motor.
I purchased the battery two years ago.
I use the bike 4 days a week for a maximum of 20 minutes per day.
At the end of the day the bike is stored , I charge the battery for at least 5 hours.
The battery pack recently makes me trouble.
This is an array of 16 batteries LiFePO4 Battery Cell 3.2V 15AH
 (Blue and 190X40 mm including a suitable controller).

I would like to ask or get assistance / idea how I can locate the problem.
It is clear to me that there are several options such as:
1. Charger
2. Battery controller
3. One or more batteries
4. And more ...

** How do you think the problem can be attacked?

Thanks,
Abe

[Bikemad]

Hi Abe, and Merry Christmas and Happy New Year to you too.

Presumably, this is the battery that you built yourself, but what exactly is the problem that you are now experiencing?

What are the symptoms, is it low power, cutting out, or excessive voltage drop etc.?

What checks (if any) have you carried out already?

Which make of LiFePO₄ cells did you use?

What is the voltage measured at the battery after it has just been fully charged?

Alan
 

[Abe]

Alan Happy New Year.
General description:
First it's a MagicPie4 motor.
I purchased the battery two years ago, lifepo4 battery 40152S 3.2V 15AH 16 cells .
I live in the mountains with lots of Steep hills up to 25 degrees.
I must note that the voltage I measure by voltmeter in the connection of the battery charger.
1. When the battery is fully charged, the battery voltage is about 53-55 V.
2. After riding the bike for 15 minutes in the hills of 20 degrees the voltage drops to 51 volts.
3. Then, another trip in the planar flat area of 20 minutes at a reasonable speed and battery voltage drops 48.6 volts.
Recently I felt low power after a relatively short ride, in the not so distant past I never felt the loss of power of the engine.
Alan, there is a possibility that only a few battery cells are not working, how can I check which battery compartment is malfunctioning or defective.
Could it be the BMS battery controller?
** I very much hope that the information answers your questions.
** From your broad experience, what do you think?
Thanks,
Abe

[Bikemad]

Hi Abe,

55V seems a bit low for a fully charged battery, as 16 cells @3.65±0.05V each is 58.4V±0.8V.

If your charger's output is less than 58.4V, it is possible that the cells could be out of balance, and perhaps some/many of them are not being charged to 100% of their available capacity.

You can usually check the open circuit output voltage of the charger by measuring across the two output terminals on the charger's connector plug, but be very careful not to short the two terminals together! 
If your charging plug has a central pin and an outer cylindrical collar similar to this:



then I recommend using a short piece of drinking straw over the centre pin to ensure the meter probes cannot touch each other or accidentally short circuit the two contacts together. One probe goes inside the straw (usually the positive probe) and the other goes outside of it.

If you can access the balance lead connector on the BMS board, you should be able to measure the individual cell voltages to see if they're all the same or whether some are different to others.



If they are all reading the same voltage when fully charged, it is worth rechecking the voltages at the end of a ride where the battery has been placed under load high load (steep hills etc.) to see if any of the cells are then noticeably different to the others, which might help to identify any weak or failing cells.

The best way to check the cells is to monitor their voltages while they are being used under load, but this can be difficult to do without suitable equipment.

Alan
 

[Abe]

Hi Alan,
First thank you,
Is there a dedicated device to check my battery (lifepo4 battery 40152S 3.2V 15AH) or battery pack?
If so, what kind of device is there at a reasonable price that you know and recommend?

** (You say: If your charger's output is less than 58.4V, it is possible that the cells could be out of balance).

** Voltage charger port you specify it when the charger is plugged in and charging the batteries OR when the charger is working but not connected to batteries?

** Tomorrow I will conduct the tests you ask me to perform.
Thanks,
Abe

[Bikemad]

Hi Abe,

I use a Celllog 8s (not the Celllog 8m) for monitoring and recording the data from up to 8 cells at a time.

Check out this post for more details.

I usually check the output voltage of the charger when it is unplugged from the battery, as this should give the maximum set charging voltage (58.4V on my 48V LiFePO₄ charger), but this may not be possible with some chargers that do not allow a trickle balance charge to continue after the pack reaches the maximum voltage.

If your charger has an output of 58.4V when it is disconnected from the battery, try to check the voltage again with the battery connected after a full overnight charge.

Alan
 

[Abe]

Hi Alan,

Towards the end of the week I will carry out the series of tests according to your recommendation.

You can explain to me how to operate the device (in short), plus how do I conduct a series of tests on all my batteries with the CellLog 8S device.
** In short, how does it work and how can it benefit me?
Thanks,

[Bikemad]

The Celllog 8s usually plugs into the battery's balance wire connector to monitor up to 8 individual cells during use.
You have to set the unit to start recording data every few seconds and then place the battery under load (use the bike on a steep hill etc.) and then stop the recording process to save the datafile (refer to the manual that comes with it for more details).

The unit is then unplugged from the battery and connected via USB to a PC or laptop loaded with the supplied LogView software, and you then select the datafile and send it to the PC.
The LogView software allows you to compare the voltages of each of the cells under the same load to hopefully determine which are the weakest cells.

Here is a screenshot of a faulty 5 cell LiPo battery being tested on my 18V grass strimmer:



Cell No 3 is clearly failing dramatically under load in comparison to the other 4 cells.

With a 16 cell pack, you will need to repeat the process twice (first cells 1-8 and then cells 9-16) to check all 16 cells.

Alan
 
EDIT: Added this link to another post which has the CellLog 8s manual attached to it.

[Abe]

Hi Alan,
First of all I'm sorry to bother you...
I understood the general idea of using a device that tests the batteries.
I want to understand how and where I can still connect the device to an array of 8 batteries.
The device has a total of 8 inputs only, in order to connect to the BMS missing additional pins, right?
In addition, where is the most convenient place to connect the device's wires?
Thanks,
Abe

[Bikemad]

Hi Abe,

The CellLog 8s unit has 9 pins which are spaced to fit directly into most balance lead plugs (typically JST-XH connectors are used).

With a 17 pin balance lead connector, you simply plug the CellLog 8s into the first (or last) 9 contacts, making sure the polarity of the device corresponds to the balance lead wires.
The balance plugs usually have a black wire on the negative end (B-) and a red wire on the positive end (B+).

When measuring cells 1-8, the negative pin of the CellLog 8s locates into the B- socket.
When measuring cells 9-16, the positive pin of the CellLog 8s locates into the B+ socket.

Hopefully this will make a bit more sense when you receive your CellLog 8s unit.



Alan
 

[Abe]

Alan, God bless you.

Only to ensure the implementation of the testing process:

During the tests I have to disconnect the connector from the BMS (the BMS along the test is not operationally used at this stage) so that the existing connector is connected permanently to 16 batteries on one side and the other side using a new 9pins Female to Female JST XH Adapter cable to the CellLog 8s  9pins.
Of course the process will be done in two stages cells 1-8 and 9-16.

** In addition, If I disconnect the connector from the BMS still the motor work?
** I need to make sure that the remaining cells not tested at this stage should still be connected to BMS controller.

OR,
That everything is connected normally without any disconnections and only then I connect the CellLog 8s unit with a 9pin JST XH Adapter Cable on one side to the unit and the other side to the battery cells.


Last thing:
1. 1. How do I know that BMS works or that only part works if at all?
2. How do I know that the battery cells are balanced?
3. It is possible that one cell reaches voltage 3.75V and some of the voltage in the other cells is lower, then the BMS stops working, how can I fix this situation?
4. Is it possible to limit battery charger voltage, for example 56V only?
5. To the point: Is there an optimal design of the configuration of the battery array that ensures me balance in all the cells, in addition to allow me to know at any time the status of each cell at any time.

** I have a lot more questions but I feel I exaggerate ....

Thanks,
Abe