01-14-2017, 09:56 AM
The question to measure the real state of lipos, cell by cell, bothers me a long time ..
Measure the internal resistance is very disappointing, the measure is absolutely no use in real conditions (low measuring current consumption for a short duration)
There is only one thing to do to find out if a cell is in good condition: it must be a serious charge current and voltage measuring needing either directly capacity in mAh.
That's what this assembly: each cell delivers a current in power and its resilience is measured
All necessary equipment comes from Banggood.
The modules used here are limited to 3 Amps, there are up to 10 A (more expensive).
Each module must necessarily be powered by a 5 volt supply galvanically isolated from other.
So you had to use a feeding module.
Fortunately our Chinese friends are here!
As (un) load, I mounted resistance of 1.5 Ohms 5 Watts, and the discharge current is more than 2.5A initially and then decreases to 2.2 at the end A by setting the threshold stop the cycle at 3.3 volts.
The result: very successful ... we see immediately that the capacity is less than the nominal and that the cells are not equivalent.
An example: a 2200 3S gives me 1700/1940/1905 mAh!
And tests were performed at 2.5 amps discharge, in full (un) load 20 or 25 A, on a flying machine for example, it will be worse of course.
In this case, I take it that I could replace the weakest cell, but it does not necessarily worth considering the state of the other two.
By cons, to test a 300mAh lipo, the test would be almost nominal.
Ideal for assembly and tests would be to use the modules 10A but at 18 euros / pièce..bof blah ...
Or measure each cell separately ... but pfffff too long ...
For all of this mounting 3S version, the cost is 17 euros in all, but there is no reason to make a 4S release.
In short, a nice DIY, useful and cheap ... I like what ...
Materials needed for version 3S:
3x unit ZB2L3 Battery capacity test
3x supply 5V 500mA (US model)
Nb: add a unit for each version of the 4S
original article here pimousse.be
Credits: Thierry Kouna Nabakou