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May 23, 2019, 08:35 PM
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kenelder's Avatar
Originally Posted by stevebb
One question though: My two of my 3s 2200's and one 6s 5000's all say "Max current is 39 A" and I measure them on a model and get much more than that. Is this telling me that the voltage will sag too low over this amount of current?
Sounds like maybe you are not setting the pack capacity before testing the 5000??????
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Jul 12, 2019, 08:08 PM
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vollrathd's Avatar
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Builder problem on the BattIR meter

One of the persons that built up this meter had accuracy problems, the BattIR meter showed one cell voltage of 3.437 Volts on a cell with the actual voltage of 4.117 Volts DC. Everything else worked OK, all cells showed up with a low readout voltage.

After a few troubleshooting tips, he found that the two resistors , R27 and R22 had the wrong values on the schematic that he redrew from the schematic published in RCGroups. He had R27 at 2K rather than 1K, and R22 at 10K rather than 47K. Now his BattIR meter is within 0.5% of the correct value.

Here is my response.
"Now that is good news. FYI, the BattIR meter really shines when testing the IR values of those LiFe or A123 receiver battery packs. Since those other IR meters only use the open circuit voltage versus one current test for calculations, they can be way off when checking these types of cells. In fact, all it takes to check the IR value of a 5 cell Nih battery pack is to fool the BattIR meter with a pair of 1K resistors. If interested, I can show you how to do it. (It can only check the total IR of the Nih pack, since they do not have balance wires)

Just a bit of information on the operation principle of the voltage inputs of the BattIR meter. Each cell is connected to the microcontroller, one at a time via the 14 electronic relays. Since the voltage maximum on the microcontroller is 5.7 Volts plus, and - 0.7 Volts minus, these cells could be wired directly to the microcontroller with zero issues.

However, if the battery balance wires under test should be reversed, that would blow the microcontroller A/D input. Or if the balance wire is mis-wired, potentially putting over 5 VDC on the A/D input of the microcontroller. The only function of the 1K R27 is to limit reverse current to the A/D input to a safe value. The same applies to the four 150 Ohm resistor networks. They also are not needed, but if someone has a solder jumper in the electronic relay circuit, those resistor networks can save the day.

If there is no test battery connected, that A/D input winds up floating, with unpredictable voltage levels. The only function of the 47K R23 is to pull the A/D floating voltage down to zero volts DC so the microcontroller can recognize that no battery is connected, allowing the no battery connected alarm to be flashed on the LCD display.

So, basically, the microcontroller is comparing the battery cell voltage directly against that 0.2% precision voltage reference, with the voltage from the cell dropped slightly by the 1K and 47K in series with the battery measuring circuit. That 1K/47K is 2%, which is allowed for in the "C" program in the BattIR project."
Last edited by vollrathd; Jul 12, 2019 at 08:14 PM.
Sep 13, 2019, 12:13 AM
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vollrathd's Avatar
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BattIR meter minor upgrade!

I've purchased several SD card readers for the Arduino Nano, and have had success in writing data to the SD cards via the Arduino Nano's. Next, plan is to incorporate that to the BattIR meters that have the USB port feature. Project will be started in a month or so.

No software changes are involved with the BattIR meter with the USB port. Changes are strictly the Arduino Nano along with a change in the 3D printed front panel. Depending on how the parts go together, the plan is to have both the USB interconnection, along with the SD card reader on the same BattIR meter.
Sep 13, 2019, 08:20 AM
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kenelder's Avatar
Awesome! I am really liking my BattIR meter and this would be a great upgrade....

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