iCharger R5 resistor replacement

Yesterday I was out flying and after I got back home I have started charging my batt packs, as usual, to have them ready for the next day.
I’m using my old and trusty iCharger 106B+ for charging for the past 3-4 years and haven’t had any problems with it, but not this time 🙂
Tha charger seemed to be working OK, it was displaying that the batteries were charging and the amount of mAh that were inputted but the battery voltage wasn’t changing and after I have stopped the charging process after an hour or so and measured the batteries I was certain that something is wrong with it since there was no change in the voltage.

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After removing the cover I saw that one M-shaped electronic element was burned, and fortunately, it was marked on the board as R5 so I knew that it was some kind of resistor, but I haven’t seen this kind.
I have decided to contact a friend of mine Marjan that is an expert in this field and sent him some photos of the burned element. He said that it is a shunt resistor that is used for measuring the current and he also mentioned that these are very hard to find.

I have tried googling R5 and iCharger just to find that a lot of people have had a similar problem with several other iCharger models, but I wasn’t able to find any info regarding the mysterious R5 resistor. I have also tried contacting some of the shops that are selling iCharger equipment, but I haven’t got any response.

A bit disappointed that I would not be able to repair my charger I was getting ready to order some of the newer and also cheaper models like ISDT Q6 Plus 300W 14A or ISDT SC-608 150W 8A

Meanwhile, I was able to find one functional 106B+ so I could measure the R5 resistance but unfortunately, my multimeter wasn’t precise enough so I have measured something between 100 and 200 mΩ, closer to 100 and I have tried to find similar in the nearby electronics shop, but I wasn’t able to find shunt, just regular 5W 100mΩ ceramic ones, so I have called my friend again and he told be to drop by in his repair shop so we could try to replace she burned one with a ceramic and see if that will work.

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After soldering the ceramic one the charger continued to misbehave and Marjan decided to try with 10mΩ, 200mΩ and several other resistors without any luck, lastly, he decided to try and make one from a steel spring wire. It was a lucky guess but it worked and the measurement was as precise as it was previously. For anyone having the same trouble here is a photo of the steel spring substitute shunt resistor

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And the be more precise the measurements are the following:

Wire diameter: 1mm
Coil diameter:
10mm
The number of coils:
4
Coil to board distance: 7mm

Hope this helps everyone that have broken iCharger because of the R5 resistor, mine is perfectly normal now.

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