Battery Profiling - 4 Wire mode

Support
1

Hi,
I have a question regarding the battery profiling toolbox and if it is recommended to connect the battery with the 4-wire method to avoid the resistance of the leads.

Thanks in advance

2

Hi and welcome to the forum,

This greatly depends on the battery internal resistance and the current you are profiling the battery with.
If the battery has ohms in internal resistance, then most likely the resistance in the cables and connections will not impact that much.
If you are in the order of hundreds of milliohm then you should at least consider using 4-wire.

Best regards,
Björn

3

Ok, thank for your the fast response.

Regards

4

@bjorn.rosqvist how do you enable 4-wire battery profiling in the Otii 3 interface?

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5

I see it now:

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So the expectation is that the Ace needs to be in “Power Box” mode when using the Battery Profiler. Got it.

6

Yes, correct!

Best regards,
Björn

7

I am glad I found your post, I about to ask same question. Thanks for the help and also for asking.

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For accurate profiling, especially in 4-wire mode, consistency and precision in the power path are crucial. That’s where stable, high-performance transistors like the MRF454 come in handy—ideal for building reliable test setups or improving custom battery analysis rigs.

8

Hello everyone, im currently trying to profile a nickel–metal hydride battery (NiMH) the voltage itself and discharge model after the Otii profiling looks normal, but my Otii Ace Pro is having problems measuring the internal resistance, i even get a notification message “Invalid internal resistance. check profiling settings”. I should be looking at something like 300mOhm

Any idea why this might be?

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Thanks!

9

Hi and welcome to the forum!

The internal resistance warning is a warning, so the profiling continues regardless.
The warning is that the internal resistance calculation ended up with a negative resistance.
To understand this, the theory behind the internal resistance calculation needs to be understood.

Battery profiler discharges the battery with a high discharge pulse and a low discharge pulse.
When the switch from high to low happens, the voltage (VH) and current (IH) is measured . Then when the switch back from low to high happens, the voltage (VL) and current (IL) is measured.
The internal resistance is then calculated by Ohms law
Rint = (VL-VH)/(IL-IH)
The currents are negative.
If the battery has a lower voltage in the end of the low discharge, than the voltage at the end of the high discharge, Rin will be negative.

To avoid this do the following:

  • Have a shorter cycle time
  • Have a higher difference between high and low current

Best regards,
Björn

10

Hi Bjorn, thanks this solves my problem