lifepo4 16S batt pack problem

[Jokostyle]

Hello,

I have a problem with my battery pack (all stuff from BMS Battery)
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Specs:

Headway 40152S 15Ah 10C LiFePO4 Cylindrical
Battery Cell

16S LiFePO4 BMS - Battery Management
System - Discharge Current : 50-100A

Alloy Shell 900W LiFePo4/Li-Ion/Lead Acid
Battery EV Charger - AC Voltage : 200V~264V

Battery Type: : Headway 40152S 15Ah
10C LiFePO4 Cylindrical Battery Cell
Calls in Series: : 16
AC Plug Type: : Prise mâle de type E/F
(norme CEE 7/7)
DC Connector Type: : T-Shape Brass
Connector
Charge Voltage (Default: Typical value
):: 57.6 Volts
Charge Current (Default: Maximum)::
11.52 Ampères
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I suspect that the battery is not fully load,and for the vendor all is ok and I don't have to take care about these disparate voltages.

Does someone could help me, please ?

the problem explain
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Hi Jack,

here is the results below, and the pictures are attached:



Before charging battery

total voltage = 52.5 Volts

cell 1 = 3.29 Volts (+)
cell 2 = 3.28
cell 3 = 3.29
cell 4 = 3.28
cell 5 = 3.29
cell 6 = 3.28
cell 7 = 3.29
cell 8 = 3.29
cell 9 = 3.29
cell 10 = 3.30
cell 11 = 3.29
cell 12 = 3.29
cell 13 = 3.29
cell 14 = 3.29
cell 15 = 3.29
cell 16 = 3.30 (-)
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Charging process during time = 35 minutes
Voltage during charge 55.4 Volts
First time I hear the charger fan rotating.
the bms was very hot (PCB side) especialy near the white connectors .
the brushed aluminum face wasn 't hot.


--------------------------------------------------------------------------------------------------



After charging battery:

total voltage = 57.4 Volts

cell 1 = 3.42 Volts (+)
cell 2 = 3.58
cell 3 = 3.71
cell 4 = 3.63
cell 5 = 3.66
cell 6 = 3.67
cell 7 = 3.60
cell 8 = 3.68
cell 9 = 3.65
cell 10 = 3.65
cell 11 = 3.67
cell 12 = 3.37
cell 13 = 3.38
cell 14 = 3.42
cell 15 = 3.66
cell 16 = 3.70 (-)

In order to not damaged cells , I unloaded a little battery with the motor and the voltage is very quickly came to 53.7 volts.
Is that a cell that has increased to more than 3.6 Volt is deteriorated ?

It looks like the bms does not play its regulatory role during charge and that it allows a cell to be charged beyond the upper limit.
What do you propose for the future?
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if somebody could give me an advice, or an opinion, it would be great friendly !!

I was planning to open a paypal dispute and return back all the stuff to the supplier, but if I can make an arrangement, why not !

See you later

 

[dnmun]

why? seems to be working fine. have you any knowledge of how a battery and BMS work? is this the first time you have charged a battery for the first time?

 

[Jokostyle]

Hello,

no, this is not the first time I load the LiFePo4 batteries, I have already done it ​​with A123 batteries and a charger balancer .

The values ​​was much better balanced +-0.02 volts difference max

Looking LiFePo4 battery specifications they have a max voltage of 3.6 volts.

So according to my records after charging 35 minutes, the cells should have been 3.6 volts each + -0.05 volts

the cell with the highest value was 3.71 volts and the lowest was 3.37 volts, making it a fairly substantial delta.

Furthermore, after the load I connected the speed controller and the motor wihtout load, with few accelerations, the total voltage collapse to 55 volts and the first cell is measured at 3.34 Volts.

 

[dnmun]

what records are you referring to? did you measure the charging current? did you test the BMS channels to see if they are balancing the pack at the 3.60V level?

what is the demand you expect BMS battery to respond to?

 

[chvidgov.bc.ca]

The BMS you show can give individual cells spikes to 3.9 before draining them back down. I think its balancing the pack normally.

 

[Jokostyle]

As soon as I receive the equipment, I assembled the battery and measured the batteries, all were between 3.33 and 3.34 volts.

Then I wanted to make the first charge .
First 2 red lights was glowing, then after a few minutes (10 - 20 I don't measure) the green light was glowing, indicating that the battery was fully charged.

the charger was not heated and the fan don't rotate.

I 've done charger testing by connecting the battery pack to the charger , and then by plugging the charger with a big Resistance , in order to measure the voltage and current.

the voltage was 57.5 volts, but the current was 0.88 amps only.

while the charger is supposed to deliver 57.6 volts, 11.52 amps.

Resistance was 34.7 ohms.

 

[dnmun]

let us know if they give you a new battery for free, or even respond.

 

[Jokostyle]

Ok, I'll tell you what happened.

I don't think the cells are damaged.

for me, the BMS don't regulate with accuracy (the balancing voltage is 3.60±0.025V)

the charger is not able to deliver the 11.52 Amps as requested

I need to have the BMS and the charger in remplacement.

if the maximum pack voltage is 57.6 volts and mini voltage is 51.2 volts,
can we consider that 54.4 volts indicates a level charge of 50% ?

 

[dogman dan]

To get the charger to put out it's max amps, you have to hook it to a discharged battery. One at 48-49v or so.

That big charger is part of the problem IMO. Though it surely slows down near the end of the charge a lot, it's still plausible to me that jamming in the current at that rate causes the cells to charge up more unevenly.

I may be full of shit once again, but since discharging cells very fast causes uneven discharge, wouldn't a hauling ass charge tend to do the same? My dumb ass idea is to use the 900w charger for a quick recharge to perhaps 55v. But use a smaller charger to do balancing to 58v. The smaller charger will match the bms a lot better I think, for that final set of cycles that balance.

Since near the end of charge, the charger does slow down a lot, there is no need for the fan to turn on.

Nearly impossible to say what 50% is, by voltage with lifepo4. Likely it will be more like 52 or 53v from my experience, but it will hover in that area for about 50% of the ride. A wattmeter is needed to have a fuel gage for lifepo4.

 

[wesnewell]

You didn't leave the battery charging long enough for the bms to balance the pack. Just because the green light comes on doesn't mean the pack is balanced, just that the pack voltage has reached the max charge limit. The bms now will bleed off the higher cells, and when they are down lower, it will start charging again thus bringing up the cell voltages. This cycle will continue until all the cells have been balanced at the max charge voltage.

 

[999zip999]

Headways can have a problem with getting them balance and stay balance.

 

[evoheyax]

Don't mean to dig up an old topic, but I came across this looking for answers as to what a full charged headway cell should really be at.

Just like all other battery technologies, these don't discharge linearly. The first bit really has almost no power (look at the discharge curve in the pdf for these cells).

The problem is the graph is not detailed enough to determine exactly what that voltage would be after bleeding it off.

Personally, I have found it to be 3.40-3.41. And my cells have done a great job of keeping it there. After over 200 full cycles, and no bms, all cells are perfectly balanced still.

If cells did come unbalanced, it's easy enough to use a regulated power supply to fix it.

Just a reference for those looking for this later:

Headway blue 15ah cells max voltage is really around 3.4v. The real range of power is 3.4v down to 3v, with 70% or more of the power being being in the 3.3v to 3.1v range.

At 12a (which is how I charge them), they will go from 3.4v to 3.6v per cell in under a minute, and with a few taps of the throttle, right back down to to 3.4v again. There's really no power there.