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Author Topic: 6S Li Ion 22V (25.2V) Battery Pack with BMS - for 10VDC Voltage reference  (Read 218 times)

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Online Kiriakos GR

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I am about to improvise and make one 22V power pack,  this will serve as Travel pack for my  10V DC reference IC which it is installed at my resistors decade box.

The ingredients are 6x 18650 (I have those).
BMS with passive balancing (Price 3 EUR)
Two of 4x 18650 storage clip box (Price 2 EUR for both).
One Blue LED volt meter, among with one button switch (momentarily contact) so this to connect the voltmeter as check point.
And final addition this will be a DC/DC converter with adjustable voltage and adjustable current among with adjustable Charge Full indicator (Price less than 1.5 EUR if you are careful).

Due this opportunity and because I am waiting for some parts to arrive, for now I will add my thoughts and some pictures of the parts which I selected to use.

Especially about this BMS there is so much misinformation at the Chinese neighborhoods.
And this is no accident, most future buyers of 6S BMS these are kids planning to convert skateboards in to electric transportation gadgets, and as we say in Greece: At the kingdom of blind people the King is the one with a single eye.

In the upcoming days I will post more details about this project.
New visitors of ITTSB Blog they are not aware that when Kiriakos (Me) starts a project, end product this will be a unique product design.

My advice = Place a bookmark and visit us frequently.  ;)
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Online Kiriakos GR

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This is a gift to international visitors of ITTSB Blog.   8)
Original Exclusive BMS HX-6S-A06   electrical specifications’ .
BUT THERE IS MORE ....  :)

Second gift this is Original Exclusive BMS HX-6S-A06 NOTE: From the PCB maker for proper operation.


A)
Description
Protection board for the assembly of six li-ion, li-po batteries in series.
With balancing.
Maximum continuous load current - up to 6.0A.
Maximum impulse load current - up to 8.0A.
The recharge voltage of the overcharge protection is 4.28V ± 0.05V, but in fact the balancing chips stand at 4.20V - so after balancing the voltage on the batteries will be 4.20V.
The return voltage to normal mode is 4.08V ± 0.05V.
The voltage of the protection from the deep discharge - 2.40V ± 0.075V.
Restoration of the operating mode - 3.00V ± 0.075V.
Current balancing - 45mA.
Dimensions - 61 * 41 * 8 mm.
Connection diagram included.
To activate the circuit you need to connect the charger.
The protection circuit is not a charging controller.
The required charger voltage is 25.5V (25.5V).
The charge current depending on the battery is usually 50 --- 100% of the battery capacity.

B)
Note: For the balance of balanced better consistency, try to use 25.6 V switch source to charge (since the power flow is lower than 30 mA).
Because of the equilibrium of the 1C equilibrium current at about 45 ma, and on the market most 25, 2 V li-ion battery charger, charging current is lower than 100 mA will stop, is not balanced, no electric charge came in, the battery voltage imbalance in each group.

As for the problem of voltage drop between the battery voltage and the output voltage, the working principle of this kind of protection plate is negative protection.

When it is just combined, some will have a voltage drop of 0.1 ~ 0.3V. 
Try not to use 25V power supply for the charger.
The full charge of 6 series of lithium batteries is 25.2v, and the 25V power supply will not be fully charged, and the protection plate will not be protected, so it will be charged all the time.
Long-term use will have an impact on battery life, thank you for understanding.

C)  ITTSB BLOG Comments

By truly diving in to HX-6S-A06   circuit details I am now aware that this BMS maker he is more honest that retail sellers them trying to trade this product.

PCB printed code this is very explanatory:
HX = Maker logo,
6S =Battery configuration,
A06 = 6A continues at resistive load (car 24V light bulb).


HX-6S-A06 PCB this using quad AO4406A 30V N-Channel MOSFET SOP8, these are 3.5W Max thermal dissipation its one.
AO4406A FET electrical specifications’ sheet this is very informative.
This deliver 10A when warm (70C) and 13A Max at 25C 

HX-6S-A06 Current handling this is lower when load this is resistive at 6A, another serious limiting factor this is PCB dimensions and cooling surface.
Now constant current handling at pulsing loads this increases to 8A due all four AO4406A FET in use, its one will handle 2A and this a decision for minimizing of stress factor (load sharing).

This translates that a load of 5A this will drive this PCB to 35C that is a thermally accepted value.     
Calculation time:  5A x 22V = 110Watt  
This translates to a single row of 18650, because a double row will not be able to get balanced with 45mA.   

The maker of HX-6S-A06 PCB makes also the assumption of 75A short-circuit Max current.

Personally I am going to test and verify HX-6S-A06 PCB at several operating conditions.
In the positive side of things there is an option for thermal switch at fixed temperature and this is highly important and not an option to me, because this it should be there all ready so to monitor PCB temperature.

Many people attach a BMS over the battery cells and this is most stupid idea EVER …
 
My very own application this is a consumption of 8~20mA and this is not stressful for this BMS PCB.
In a few weeks I will discover the entire truth, but one voice in me this says that I am dealing with BMS this made to handle a 100W LED torch or similar Low Drain devices.
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Online Kiriakos GR

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Transit (11Days) from China and delivery by the postman at my door ... this is a wild dream but it did happen.  ;D

Now I am forced to wait for the special lithium battery holder boxes. 
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Online Kiriakos GR

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Here is few thoughts for the ones thinking to activate temperature protection.
You are going to need a switch thermostat, normally closed contacts.
They are many selections available speaking of temperatures range.
You better consult manufacturer documentation so your choice to really get triggered at your choice of Max temperature.

Another thought that it should puzzle your head, this is what you are thinking to protect?
The switch thermostat is rather slow, this is not for measuring the temperature of a single battery cell.
Such a switch thermostat, this is more an fuse with self recovery action, it might help protecting and air-tight battery pack in which the BMS this is stuffed in it.

My own first thought this is that for my application I do not need such a thermostat.
If I was using this battery with a high drain device then I would worry so the power MosFet to never get very hot, because the heat eventually will be shared at the lithium cells, and entire battery pack it would turn to an oven.
     
Soon I will perform a test, so to discover quantity of heat and temperature dissipation according to Load.
This thing has MosFet in the casing of IC, such things brings to me memories from the era that I was placing miniature heatsink over my VGA card so to overclock the speed of RAM chips.  ;D

Here is a picture of such switch thermostat, less than 1 USD on eBay.       
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Online Kiriakos GR

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These are not battery holders ... they are the Green light so this project to move ahead.  8)
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Online Kiriakos GR

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First pictures from my battleground.

While electrical tests demonstrating to me the truth regarding this PCB potentials (over rated specification).
I am now dealing with a new expected problem and this is PCB temperature at the end of the charge, this gets to 50 Celsius with 30C room temperature.

At the end of charge all balancing channels gets at max activity (sinking current) and over all PCB temperature this increases no matter if charging current this is down to 100mA or less (charger input) .
I am now forced to add small heatsink from the era of  486 Intel processors ( this be trimmed in half).

A laptop battery housing this become the nest of this project.  ;)         
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Online Kiriakos GR

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My battleground this is now turned to Playground  :)

I got double-crossed speaking of circuits compatibility and build quality of low-cost buck converter, so I moved to plan B.
Battery pack will be charged exclusively due JK-J5X.
My Olympus digital camera dislikes this Blue-Violet color, even so my project it did pass basic testing, and now I am wasting time to evaluate used 18650 so to create a team of six with equal remaining capacity.

My strategy from the beginning this is reusing parts which I have in stock, so total project cost to be lowest possible.
 
I will simply add few more pictures for now.
Regarding this 6S Li Ion 22V (25.2V) BMS this is not perfect enough for my taste.
I will add my pack of thoughts as soon I will end my testing cycle. 
   
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Online Kiriakos GR

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It is time getting to some conclusions here.

As first I will say that I do trust the small voltmeter on the battery pack more than the JK-J5X which this has larger error.

Now, first discovered fact this is Cut-off voltage of 2.4V per cell,  any cell which will come down to 2.4V under discharge, this BMS will enter to protection mode and will cut off the voltage output.

Second fact this is partial influence of input voltage (charging voltage),  25.20V  VS  25.50 this is does not make dramatic difference speaking of topping up cells voltage.
In my experiment with 6S  (5x 2200mAh) Plus 1X 2000mAh, this BMS refuses topping up any cell at above 4.05 ~ 4.06V.
By monitoring the circuit after been leaved 12 hours connected (charge completed state) this BMS about every hour it does activate to charge mode and stays as that for five seconds, then charge protection activates again.
Naturally passive balancing this is constantly on.   

I am now thinking that I do dislike the electronic design of this BMS but neither I am close to hate it, because this is not perfect according to my expectations.

I do not know how this circuit will perform with bright new and fresh 18650?
But such cells does not require balancing until they start showing their age ...
Therefore I did a reasonable choice using aged 18650 for my electrical testing.


What a BMS balancer can do?  Or does not do ?
Well, such an electronic  circuit it will deliver some of help when the difference of top shape cell versus the second best this is still small.
Passive balance of few mA this is not comparable to dedicated  18650 (charger / discharger) equipment. 
Active balancing this is neither a job for a Low-cost BMS.
 


Topping up to not higher than 4.05V and consequences?
Any Good in shape 18650 it should be charged at 4.2V , in order for us to do that,  charging voltage it should be at 4.3V but no more than that.
Practically when topping up voltage this is not highest possible this translates that we are going to get a percentage of lesser energy under load.
How much this lesser percentage could be ?  I do not know the actual value, but my experiences telling me that it must be lesser than 6% of 18650 energy storage (capacity) or ability (according to manufacturer and product model specification).

Now at 6S (18650) battery chain, sum of internal battery resistance, this it can and it would limit charging voltage from input top value of 25.50V by a percentage.
A new single 18650 this has 20 milliohm or less, by six times this is 120 milliohm in total.
My USED single 18650 this has about 60~70 milliohm, by six times this is 420 milliohm in total (close to half an Ohm).
     
Spesific battery pack this is for low drain project, therefore I can live happily even by not getting top performance.

BMS charging current limit.
Spesific BMS this seems having and another one undocumented specification, circuit protection activates above 2A CC mode.
This is hard evidence that this circuit it is capable to handle a single row of 6S , because with double row of cells, the charging time will dramatically increased, and also the passive balancer will not be able to balance anything.

Good practice for battery internal resistance.
When battery internal resistance this gets double from what was as new, this cell it should not be used any more at critical applications.
When battery internal resistance this gets triple from what was as new, then you may freely use it for hobby/toy/experiments Only in Door:)

About the pictures:
1) This is tiny spikes (of 1V) on-top of 24.433 that is actual battery pack voltage (  U1272A monitoring output of BMS voltage at the batteries side).
2)  Fluke 8846A this does individual cell voltage measuring, by the use of High Impedance,  by doing that the Fluke 8846A this does not influence specific 18650 channel voltage detection.

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