calibration error - I charge B6 (Clone)

[Josef Melvald]

Can anyone shed some light on this error "Calibration error I charge" on B6 (I think clone), please?
I have three of these chargers and only one is doing it every-time I try to charge or even discharge.
I have tried calibration three times still with the same result
fw I use is cheali-charger-imaxB6-clone_1.99-20150917_atmega32
I have tried cheali-charger-imaxB6-original_1.99-20150917_atmega32
same result.

[Josef Melvald]

Anyone any idea?? at lease description of this error.

thanks

[Samuel Lang]

Does the charger respond to value changes in I discharge current? Can you measure something reasonable?

See my post, my charger burned the discharge mosfet and the shunt at calibration attemp.

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[Josef Melvald]

as far as I think calibration worked ok. I think the value was bit hight to get 100mA the value is 1239 and to get 300mA 4649.

I am not sure what value range is acceptable.

Ill check your post. Thank you

[Paweł Si]

2015-09-19 10:06 GMT+02:00 Josef Melvald <josefm...@gmail.com>:

as far as I think calibration worked ok. I think the value was bit hight to get 100mA the value is 1239 and to get 300mA 4649.

I am not sure what value range is acceptable.

Ill check your post. Thank you

what values do You get on "I charge"  calibration?

[Josef Melvald]

1049 = 100mA

13542 = 1A

[Paweł Si]

2015-09-19 11:15 GMT+02:00 Josef Melvald <josefm...@gmail.com>:

1049 = 100mA

13542 = 1A

 hm... there are two possible reasons for your issue:

1. You are doing something wrong during "I charge" measurement (the charger may also be broken)

or

2. Your charger is not a 5A charger (very likely)

roughly speaking if a 5A current would flow through the charger (based on your data)

you should see a "value" equal to ~= 5*13542 = 67710

and this is beyond the ADC capabilities 

(max. possible value is 65472)

so, if it's the second case please try this version:

cheali-charger-imaxB6-clone-50W-4.5A_1.99

[Josef Melvald]

Well I have three of these chargers (this one is the only copy actually) and I do the same calibration on all three and two work fine.

ruling out #1. Broken anything is possible but it worked fine with I think I had v0.33 in it and after update stopped working.

#2. I see as the most likely problem after all it is a Chinese copy :-)

Could you tell me what converts it from 4.5 to 5A?

I do charge a lot of 6.9Ah batteries so every little bit helps:-)

Thanks for your help

[Josef Melvald]

So I have burned cheali-charger-imaxB6-clone-50W-4.5A_1.99 done the calibration and it is working fine.

Now what do I have to do to increase current output again? Some hardware change is it?

[Paweł Si]

2015-09-19 15:47 GMT+02:00 Josef Melvald <josefm...@gmail.com>:

So I have burned cheali-charger-imaxB6-clone-50W-4.5A_1.99 done the calibration and it is working fine.

Now what do I have to do to increase current output again? Some hardware change is it?

sorry, I'm quite busy  right now :/ , that's why you get only a short answer

parts: R53-R54; R70,R77, DA2:1 (LM2904) are responsible for the charging current measurement

see:

http://www.rcgroups.com/forums/showatt.php?s=df7049bcbafdb5d7d06765c264e5c4bb&attachmentid=3693125&d=1293732709

[JagiChan Sir]

Very true, the parts R53 and R54 are the current sense resistors. The parts R70 and R77 are the feedback resistors for the LM2904.

In the case of B6 clone the gain is set to 6.66 (R77/R70) (it is a simple non inverting amp). I don't know the ADC vref that is being used, but I believe it is 5V, and the shunt resistance is 0.05 ohms (0.1 || 0.1) so this will give us a measuring capability of 15 Amps. Of course if ADC Vref is 3.3V then, the measurement capability is reduced to 9.9 Amps.

On the question of increasing the current output, I believe there are two aspects to it, one is hardware and the other is software.

For the hardware part, I can say, that the FET's are able to handle the power, but again, I don't know if enough cooling has been provided to them to dissipate the heat generated. Additionally, are the tracks able to handle the extra current you are looking for??

For the software some where in the code I saw "ENABLE_DYNAMIC_MAX_POWER". But i is commented, so I don't know if that works.

Also you may want to look into the SMPS.cpp and its associated components, because that is where the Max current is being set.

Hope this helps.

--JagiChan--

[Josef Melvald]

Ok guys all done changed R77 and burned 5A clone firmware and just charging/ discharging one pack and it seems ok so far.

Thank you

[JagiChan Sir]

Good to know that you got it working. What is the value you put in for R77?

By the way, I made a mistake in the calculation that I showed in my previous post. The configuration is a non-inverting amp, the equation for the gain is (1+Rf/Ri). I forgot the 1 :(

So the gain of the opamp would be 7.66.

A quick question: The I_ERR is being fed into VT4, which will be turned on when the base of VT4 reaches 0.7V (and it will in turn switch off the PWM). But my question more specifically is "Is this I_ERR not limiting the output current to 2A?? because at 2A, there will be a drop of 0.1V across R53 || R54. This will result in output of the opamp reaching 0.76V and hence turning off the PWM and the SMPS. How is the system achieving 5A or 80W output? Am I over looking something trivial.

--JagiChan--

[Josef Melvald]

I actually forgot what I put in I think it was something stupid just to try, 4K7 I think.

I think it starts doing something stupid over 3.2A for 4S 6.9Ah pack.

This might be another good thread to beef up B6, I would not mind getting this charger to charge and discharge with higher current eventually.

[JagiChan Sir]

Okay, then it means you have increased the span of current measurement from 13A to 24A effectively. But then you have also reduced the least count of system. In the original setup with 10K, the minimum "strom" resolution was 12mA and now it is going to be 24mA.

Beefing up the B6 is not just software magic, you need to change the inductor and the flyback diodes to handle the xtra current output. The PTC resettable fuse is rated at 2A hold current and 4A trip, which means even that needs to be changed. Additionally, you may want to look if those PCB tracks can take the extra current.

[Paweł Si]

2015-09-20 17:53 GMT+02:00 JagiChan Sir <jaganna...@gmail.com>:

Okay, then it means you have increased the span of current measurement from 13A to 24A effectively. But then you have also reduced the least count of system. In the original setup with 10K, the minimum "strom" resolution was 12mA and now it is going to be 24mA.

Beefing up the B6 is not just software magic, you need to change the inductor and the flyback diodes to handle the xtra current output. 

The PTC resettable fuse is rated at 2A hold current and 4A trip,

 

do You know what purpose has this PTC fuse?

(fuse near the balance port)

[JagiChan Sir]

Here is my understanding of the PTC function looking at the hardware and doing some tests, the PTC fuse performs the current limiting of 1A into the cells (during balance charging, more especially during discharging to maintain the cell balance). It trips at 2A. Maybe it is used to protect against over current into/from the battery. The datasheet of the PTC is attached for your reference.

[Paweł Si]

2015-11-04 11:02 GMT+01:00 JagiChan Sir <jaganna...@gmail.com>:

Here is my understanding of the PTC function looking at the hardware and doing some tests, the PTC fuse performs the current limiting of 1A into the cells (during balance charging, more especially during discharging to maintain the cell balance).

it's interesting that you can remove this fuse and the charger will still work perfectly (balancing works too)

I do sometimes even advice people to remove it since the fuse has a negative impact for the cell voltage measurement.

[JagiChan Sir]

Hmm....I'm looking at the PTC and the board opened in front of me. The PTC is connected to the +ve terminal of the battery and the other one is going to some resistor network. Is it some kind of pacifier for the troubled minds about safety. Now, I'm confused, with your experiment. I'll also try the experiment and post my results.

[Paweł Si]

2015-11-09 14:33 GMT+01:00 JagiChan Sir <jaganna...@gmail.com>:

Hmm....I'm looking at the PTC and the board opened in front of me. The PTC is connected to the +ve terminal of the battery and the other one is going to some resistor network. Is it some kind of pacifier for the troubled minds about safety. Now, I'm confused, with your experiment.

I'm confused too :)

I even asked somebody for imaxRC (probably the wrong person)

what for is this fuse, but never got an answer.

My current theory is that this fuse is for cell  balancing when the main leads are not connected,

this way there is a GND connection with the batter.

(cheali-charger forces users to always connect the main leads, since there are chargers without the fuse)

[JagiChan Sir]

Ok, I removed the PTC and one of my B6 still has the original firmware. Now I did a charge and discharge. The charger works as expected, there is no deviation of the voltage or current with or without the PTC. So I tried to trace the path of the PTC. The PTC seems to be connected to BATT+, to the drain of the FET on the backside and then it goes into a track and small via and finally vanishes into a complex resistor network, near to the CPU. Unfortunately, my eyesight is getting weak (I'm 45 years young and my eyes are no longer happy help me with small objects). Nevertheless, I tried to check the path with a multimeter but again got lost in the whole bunch of SMD resistors. So finally, I don't understand the reason for having the PTC. By the way, if you look at the pictures of the clone, they don't have the PTC, and the charger still works. Maybe the PTC is only a pacifier and it is just there to fill the PCB ;)