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My New ESR Meter Found Bad E-caps

By on February 24, 2020
battery charger repair










A carpenter who lives nearby my shop brought this battery charger for repair. I was out on a repair mission when this customer brought it and gave it to my brother next door. 

battery charger repair

When I came back to the shop, and called this customer about the fault of this charger, he explained that the moment he put the battery on it, the light switches right away from green to flashing red light which according to the manual, it is a fault taking place in the charger.

As I tested the charger in my shop, I saw the same thing the customer said except I could hear a relay clicking and then the red light on the charger comes on. Very Interesting.

battery circuit board repair

As I worked on such chargers before, I can say for sure that some capacitors are faulty and needed to be changed. To confirm that, I tested them with my new ESR meter and look what I found.

silicon chip esr meter

It was 470uf/35 volts and I was supposed to get 0.1 reading on the meter but according to this meter this capacitor was faulty. I tested the other capacitors on that board but all of them were good except this one. So I changed it with a new one and tested it out but the result was the same.

My second suspect with the relay itself since it was still clicking. I noticed when I tap on it with a screw driver; the charger comes on and starts charging indicating a faulty relay.

faulty relay

I replaced these two suspects and then I put everything back and tested the charger and…

how to repair battery charger

As you can see, the battery was charging fine this time. This green light was flashing indicating a good charger.

Mission Accomplished.

This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.

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Note: You can check his previous repair articles in the link below:




  1. Albert van Bemmelen

    February 24, 2020 at 6:27 pm

    Tapping on the relays with a screw driver is exactly what my shopowner friend does when fixing washing machines and dryers. But I also made him a relay tester to be able to test those mostly 12V relays removed from their circuit boards.

    • Waleed Rishmawi

      February 25, 2020 at 2:54 pm

      Albert: yes I usually test the relay by clicking and confirming it by taking it off board and apply power to it and test.. have a blessed day

  2. Parasuraman S

    February 24, 2020 at 7:20 pm

    Vow! Straight to the defective components and replaced it and brought the charger up! Good job there!

    • Waleed Rishmawi

      February 25, 2020 at 2:54 pm

      Parasuraman: thanks man..experience makes all the difference. have a blessed day

  3. Imoudu Onwumah

    February 24, 2020 at 9:47 pm

    I suppose the reading of cap should be same or above it's esr reading on the chart before it can be considered bad .But your cap reading is still below it's esr by .o4.I do not understand why it is considered bad. Please explain. I use blue ring esr meter.

    • Waleed Rishmawi

      February 25, 2020 at 2:58 pm

      Imoudu: the reading on the display was higher the what chart on the meter can refer to the photo with the marks I add it to. have a blessed day

  4. Gassan Ali

    February 25, 2020 at 2:48 am

    Nice repair! From where did you buy that ESR meter?

    • Mike

      February 25, 2020 at 11:46 am

      It's a kit designed by Bob Parker and would havbe been a kit from the Magazine "Silicon Chip". Probably available on ebay as well.

      • Waleed Rishmawi

        February 26, 2020 at 7:09 pm

        Mike: I checked for it on Ebay and could not find it. I could only find it in Australia and it was too expensive to order and to ship to the States.

    • Waleed Rishmawi

      February 25, 2020 at 3:00 pm

      Gassan: thanks
      I bought it from Australia and assembled it myself but you can still buy the blue ESR meter from Jestine Yong web site. you can either buy it ready to go or assemble it yourself. have a blessed day

  5. Don Oser

    February 25, 2020 at 5:06 am

    Good job. Capacitors and relays are a good place to start looking. I enjoy these repair briefs.

    • Waleed Rishmawi

      February 25, 2020 at 3:02 pm

      Don: thanks man. I am glad you are enjoying these short articles. have a blessed day


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