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Mar 17, 2008, 08:29 PM
Stryker Junkie
cjbrazil's Avatar
Dusk,

There has to be a way to reset it back to factory defaults allowing the calibration to be redone.
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Mar 17, 2008, 08:46 PM
Crashing on a budget.
dusk's Avatar
Yes, there has to be a way, since Bantam is able to "recalibrate" the chargers. However, it does not have to be simple.

The charger uses an atmega32 micro-controller. This chip has both flash and eeprom memory. The program for the charger is in the flash, and all the settings are in the eeprom. What's more, the charger circuit has an ISP header built in, which allows the flash/eeprom to be programmed without taking the chip out of the circuit.

So potentially, the recalibration could be reset through the ISP. However, the flash/eeprom on our chips is locked. This means that to reprogram any part of the memory using ISP, we need to first wipe the whole lot. Only then can it be re-flashed/programmed.

To do that, you need a copy of the firmware, which I haven't got. I've looked around the Internet and emailed SkyRC, but with no luck so far.
Mar 19, 2008, 01:05 AM
Stryker Junkie
cjbrazil's Avatar
I calibrated mine last night on a reasonably well balanced pack and now after charge the cells read 4.19 4.19 4.19 4.20 4.20 4.19 which is acceptable. If I did it again though I would charge each cell indivually to 4.21 before i did it as the 2 cells that landed on 4.20 were on 4.21 when i calibrated and the rest were on 4.20. I am however very happy with the outcome. Thanks a heap

Forgot to mention prior to the calibration the cells "balanced" at 4.18 4.18 4.21 4.15 4.16 4.08 (no that's not a typo)
Last edited by cjbrazil; Mar 19, 2008 at 04:36 AM.
Mar 19, 2008, 07:28 AM
Registered User
have you upgraded the resistors in your charger?
Mar 19, 2008, 08:29 AM
Stryker Junkie
cjbrazil's Avatar
No I haven't
Mar 19, 2008, 12:43 PM
Registered User
Upgrading the resistors will improve stability also a lot.
Especially temperature drift will be much lower.

Ben.
Mar 20, 2008, 10:56 AM
Pirouetting flip master
this is ridiculous, when i do power on while holding down the dec+enter button on my bantam e-station BC6, i get the same screen that you guys are describing.

however, i cannot get to the other screen (holding down on stop+inc button gets me nothing).

this led me to think that the copy cat products copied up down to the calibration level.....
i think next time i should just buy a copy cat products.

by the way, reading what you guys are doing, i think the number one thing to do is to make sure your 4.2 is really 4.2

else you are doing harm to your battery on long term charging.
i can't seems to trust any meter now.

my watts up meter reading for fully charge battery is 12.55
my cheapo digital multimeter reads 12.45
this has led me open up my multimeter and adjust a variable resistor to match with the watts up meter reading.

how do i get to calibrate my meter accurately to a real 12.6 volt?
i don't trust
1. my charger
2. watts meter
3. digital multimeter.
Mar 23, 2008, 03:59 AM
Registered User
I think, another good method for calibration would be to make a suitable adapter and connect ONE lipo cell, perfectly charged at 4,2V, to all six balancing ports.
There would be no voltage variations at all (at least if you don't have an adjustable power supply)
Mar 23, 2008, 05:01 AM
Registered User
That's not possible, because all 6 voltage sources have to be connected at the same time. You can't use 1 cell for that (I know exactly what is inside the charger, so believe me, it is not possible).

Ben.
Mar 23, 2008, 06:17 AM
Registered User
Quote:
Originally Posted by bennetje
That's not possible, because all 6 voltage sources have to be connected at the same time. You can't use 1 cell for that (I know exactly what is inside the charger, so believe me, it is not possible).
Ben.
dear Ben
this is what I mean but I'am afraid I didn't make myself clear. I suggest you can take a 6S balancing adapter
like this one for example http://www.hobbycity.com/hobbycity/s...idProduct=6544

The six port adapter side will be connected to the charger.
Then cut/strip/connect all six +wires and ground to make the other side a 2pin connector. Then connect the 2 pin side to a good 4,2V cell in one of your batteries through the battery balancing port.
This way you can feed the charger with a perfectly equal voltage (hopefully 4,2V) to all of the six balancing ports AT THE SAME TIME in order to calibrate it.
I know nothing about what is going on inside the charger and I trust you on this but I just tried to figure out a practical way for calibrating the charger without the use of an expensive adjustable power supply.
Last edited by pnikifor; Mar 23, 2008 at 06:27 AM.
Mar 23, 2008, 07:10 AM
Crashing on a budget.
dusk's Avatar
Maybe a resistor network would be a better way to get the individual voltages?
Six high precision resistors in series, with a tap coming off each junction, connected to a 25.2V pack or power source.

The resistor values would have to be very close. An 0.01V error in 4.2V is only 0.25%
Mar 25, 2008, 10:20 PM
Registered User
Hi dusk,
that is exactly what I had made, but only for 3 cells.
I use 68 ohms 1% 1/4W resistors simply because I happen to have some laying around. Although 1 % resistors, I get very close reading on them when
plug to the battery and measure with multimeter. I got same 3 digits on all.


To charger
Balancing Tab

<------------------+-------------------------< Plug to battery
| and T join to Charger
X Output
X 68 ohms 1%
X
|
<------------------+
X
X 68 ohms 1%
X
|
<------------------+
|
X
X 68 ohms 1%
X
|
<------------------+-------------------------<


I use it to test the balancer voltage readout on my IMAX B6.

I am surprise to see that even in LIPO CHARGE mode the readings jumps up and down as if it is doing balacing. It will stable down after a few seconds for about 1 second and start fluctuating again.
During the stable display my readings are 4.19,4.17,4.13 with a slightly discharge battery pack. Can't plug a full pack for charging right?

This values tallies with what I normally gets after charging. My battery will charge to 4.18 4.20 4.24

I am thinking a similar one for 6 cells will be what we need to calibrate the charger.

Unfortunately my menu 1 is not accessible from the beginning.
Mar 26, 2008, 12:31 AM
Registered User
Now here is a drawing of my resistor network since the text version did not come out well.
Mar 26, 2008, 01:40 PM
Registered User
The resistor devider idea should work well probably.
Pnikifors idea will not work unfortunately.

Ben.
Apr 29, 2008, 08:50 AM
iSlope
Pisaneli's Avatar
Quote:
Originally Posted by opit
-20 to +20 that's correction to value showing on display. If your battery is 12,42V (multimeter) but on B6 display is 12,51V you need correct it by -9.
That's simple and easy.
Not in my case.

My Imax showed: -01 12.53V when connected to a battery. I have measured the true voltage with my calibration instrument Prema and it showed 12.5998V.

To get the same value on my Imax I had to changed to +12.


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