New method for calibrating your shunt for the CA (iCharger)

methods

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This is awesome...

The iCharger 208b 350W 8 cell balancing lipo charger (best value on the market) has a foam cutting feature.

This foam cutting feature is a constant current source.
You can set the compliance current and the compliance voltage.

All you have to do is set the current for 10A - Constant current source !!!

I did a test where I set the current to 10A and the voltage to 1V. I ran this directly into my current meter (short circuit) and read between 9.96A and 10.04A

Drive this 10A into the ground of your CA and back out of one of the phases (per Justin), read the negative current off of the CA, utilize the "CA Tuning Spreadsheet" found in the technical section, repeat twice, and you are done. YOU DONT EVEN HAVE TO OPEN UP YOUR CONTROLLER.

No more silly loads
No more sketchy operating procedures
No more elaborate methods
No calculations (with cumulative error...)
Simple as pie

Run your trusted Ammeter in series to get the most accurate possible reading - or - if you dont have an ammeter - use the reading on the iCharger for a "close" estimate.

Today is a fine day in ebike controller shunt tuning history.
A constant current source for every man, woman, and child that has an iCharger

-methods
 

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NICE!
I just tried it out with one of my assembled controllers. Worked like a charm!
Here is exactly what I did:

* Set iCharger to Foam cut. 10A 3V (if you set the voltage too low it will go into CV before you hit CC)
* Ran positive output of iCharger through Ammeter (though the iCharger reading was accurate)
* Ran output of ammeter into the ground terminal of the controller
* Hooked negative iCharger output to the blue phase wire (any phase wire will work)
* Attached bike battery (44.4V 10Ah Lipo) to the regular power leads
* Turned on controller
* Pre-Set CA to 250uOhms (apx value of my shunt) in high current mode
* Set CA to display current. Phisically located CA next to Ammeter so that I could read them both at the same time
* Started the foam cut routine.
* Observed 9.0A on the ammeter and 11.1A on the CA 23.3% error - turned off foam cutter
* Entered these values into my spreadsheet - Spreadsheet told me to set the CA to 308uOhms (percent difference formula)
* Set CA to 308uOhms
* Turned current back on, observed 10.0A on Ammeter, 10.1A on CA, turned off current
* Entered into Spreadsheet, 1% error, set CA to 311uOhms
* Tested for the last time -> They both read 10.0A.
* Tested with 1A -> They both read 1.0A (linear relationship over an order of magnitude. Very good sign.)

WOW!

Before I used to open the entire box up and short the high side rail (24S lipo 100V) through the shunt and into a giant inductive oil heater that would throw big blue sparks.
It was totally hazardous :shock:
What was I thinking???

Please notice -> What makes this easy is using the CA to read the voltage off of the shunt.
Trying to drive a current through the shunt and measure the voltage (in order to calculate the resistance) creates cumulative error.
This is the best and most direct / easy way to perform this operation. If the Ammeter and the CA read the same - then you know you did a perfect job.
No chance for calculation error.

Ahhhhh..... A fine day it is!

-methods
 
Nice find Method.. I also did a fake C-A connector and use my 0-10A power supply too. It work fine!

You can also re-adjust the ZERO AMP by supplying the C-A thru the shunt negarive and the normal positive cable.

Doc
 
1010B's also have foam cutting.

That's a damn good idea Methy! That should save many people a lot of time!

Good work!

-Luke
 
Thanks for the info, that's the charger I bought recommended by the good Doctorbass. I really like the charger.
 
* Ran output of ammeter into the ground terminal of the controller
You did this without opening the case? Do you have a wire soldered to the ground? Please post pics of the setup with the CA and bike battery plugged in. I thought the ground wire was the black battery wire.
 
I cant set it up right now - but this is how you do it.

You need to splice into the middle of the ground cable between the battery and the controller
Make a Y cable for Ground using whatever connectors you use.
This will be the point where you tap in and drive the constant current from the iCharger
So the controller ground goes to the battery and to the +output of the iCharger

Plug the ground of the iCharger into one of the three phase wires.

Now when you turn the iCharger on in Constant Current mode it will drive a 10A current into the ground of the controller, through the shunt, through the diodes of your Fets, and out the phase wires. This will be displayed both on the iCharger and on the CA.

Does this make sense or do I need to draw a picture?
Looking at my setup will just look like a bunch of wires :mrgreen:

-methods
 
P.S. Yes - all this can be done with ANY controller and you do not need any sort of special wires soldered in. You do not need to open the controller.

-methods
 
Sorry for being a noob. It sounded like you were driving 10amps through the ground and plugging in the bike battery? WTF!! Your obviously unplugging the foam cutter before running the CA. I thought you devised a way to check the CA while checking you ammeter at the same time. Neat setup, looks very accurate.

Thanks Methy,
 
Yes. I am driving current from the foam cutter into the controller while it is powered up with the battery

Battery is connected
Controller is powered up
Ca is running

You run the foam cutter into the negative of the battery and out of the phase of the controller
The current shows up on the CA and on the foam cutter (and on the Ammeter if you have one)

You dont have to open the controller
You can read the values directly off the CA

I will draw a schematic, make a video, and explain exactly why this works.
In a nut shell, the battery is ** Not in the circuit of the foam cutter ** (well, it is, but the potentials are isolated so they dont affect each other)
If you are not familiar with circuit analysis this can be confusing... But I will explain it - or you can just trust me :mrgreen:
The 10A from the current cutter goes straight through the shunt and out of the phase mosfets without affecting the rest of the circuit.

Picture/Video soon

-methods
 
Hi!

Nice to see this mode working for multiple purposes.
I really was only thinking about foam cutting when I proposed it :wink:
http://www.rcgroups.com/forums/showthread.php?p=9628885#post9628885

Cheers,

Julez
 
I recognize you from the forums. Never go over there anymore...
Nice suggestion!

A constant current source is a very, very useful tool. :wink:

-methods
 
For those from the RC hobby world. If you have a wattmeter, just put it in line with the battery. That's what I ended up doing since it was more convenient for me while in the garage. I just ended up tweaking the values to match the wattmeter.
 
Any reason that this would not work connecting up in the 'correct polarity' ..so the current is pushed through the shunt the other way, so the CA reads a positive value rather than negative.

Simply because I tried this this morning, and on initial powering up the CA..it gives a 'Polarity Reversed error'


I only ask because of the info in the CA v3 UUG does say to to connect the iCharger to the CA the other way around.
In discussion with teklektik about this at the moment, and he says he jsut used info direct from one of these threads, and did not actually try himself.

We were wondering if his version in the UUG specifying iCharger negative to batt negative is merely a transcription error or if it will works just as well.
http://www.endless-sphere.com/forums/viewtopic.php?p=571345#p571345


I am not prepared to try it...with my working No.2 iCharger and risk smoking it...as I may have done this morning with charger No.1

I have two iChargers, and this morning, with the first one, I tried this method, connecting iCharger negative to pack negative, and it did not work. It went through a 'testing connection phase' then gave three beeps and a "Connection Break down " error.
After swapping polarity..it still did not work..iCharger gave a different display with current showing zero voltage showing zero and the word "DOWN" flashing. This maybe because the charge was already faulty (it only balances 6s packs not the 10 s it should be able to do), but I don't wish to risk smoking a working charger just to check the theory that I can connect neg to neg and pos to pos.
 
NeilP said:
We were wondering if his version in the UUG specifying iCharger negative to batt negative is merely a transcription error
Neil-
Various posted incarnations of these instructions are consistent but there was a transcription error going into the Guide:
iCharger +/- are reversed in steps A.4.4 and A.4.5

Will correct Guide.
 
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