A Battery Replacement And Maintenance On An Electronic Scale
A restaurant manager brought this scale for repair. He said it works only when the AC line is connected and the display is flickering. It does not charge and when the AC line is disconnected it goes into shut down.
This is the model number and as seen it measures up to 150KG. The customer uses his scale to weight meat and it was urgently needed.
I have worked on this kind of scales before and usually the problem is the main battery; usually it is shorted out causing the display to flicker and of course the charging is not done the way it should be.
It is a heavy duty scale so it is time to open and get it fixed.
When powering on the device it shows the AC light but the display is flicking and I could not get that on camera. It measures fine; it is the charging and the flickering is what was bothering the customer.
Four screws on the back were taken off and I was able to see the inside of this scale.
I measured the voltage going to the battery and it was not steady at all indicating either a shorted battery or bad power supply. The customer supplied a new power supply so I headed directly to that battery and de soldered it off.
The moment these wires were soldered off the battery, the flickering stopped and was showing a normal display.
That is the battery found inside the scale and one of the ways to test it out (other than voltage testing) is shaking the battery and sure enough I heard something rattling inside which is an indicator the battery was dry and needed replacement.
Before replacing the new battery, I checked the main line that goes to the battery and this what I got; Almost 12 DC and that is what needed so soldered the new battery in.( it was a little bit hard to find a replacement but finally found one).
I put everything back together and tested the scaled it was fine. I weight almost 100 kilos so I am ok with that…LOL
Any way I called the customer for pick up and the he was happy that it was repaired that soon.
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 article on How To Fix An Electrical Outlet With Surge Protector Built In Repaired
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Anwar Yunas Shiekh
July 22, 2023 at 8:33 am
Seems like a lot of voltage for a 4.4V battery.
Waleed Rishmawi
July 22, 2023 at 1:34 pm
Anwar: yes it is because that is the factcory charger so I did not bother with it and so far it is up and running. have a blessed day
Parasuraman S
July 22, 2023 at 11:46 am
Excellent fix! Shook the battery? Well, that is news to me! I learnt a new trick too! Hope you are not building up weight just for checking such scales after repair (LOL)! Many thanks for sharing your wonderful experience!
Waleed Rishmawi
July 22, 2023 at 1:35 pm
Parasuraman: thanks man. yes I ususally shake the battery and if sound is heard it is dry and need replacement. you are most welcome my friend. have a blessed day
Albert van Bemmelen
July 22, 2023 at 3:15 pm
The shaking battery trick probably works with this scale. Most bad lithium batteries however never make any sound at all when shaken. In those cases measuring the internal resistance of a battery is doable by finding out the current through the circuit. And dividing the emf of the battery by the current through the circuit.
And we subtract any load resistance from the value obtained from the previous step. And we know the internal resistance of our battery. If that is no longer possible we know the battery is bad. Or just use a charger that measures and shows that important resistance of the battery or each cell. Apparently it also can be measured with a good capacitor ESR meter. (Warning NOT every ESR meter can handle placing external voltages on its probes! Like most Arduino component testers that test all RCL components and semiconductors, including the ESR value of capacitors but won't survive any voltage higher than about 3V or its supply voltage on its inputs). But those ESR meters build without any cpu like the Blue ESR meter from AnaTek Corp will survive measuring any internal resistance of most charged batteries and even when measured on power supplies.
Waleed Rishmawi
July 22, 2023 at 4:23 pm
Albert: totally agree with you. when it is dry on the inside you will hear the ratteling noise but I usually test it with a voltmeter and make sure it is taking a charge. thanks for your comments and have a blessed day
Imoudu.O
July 23, 2023 at 5:27 am
I personally don't like using devices using acid-lead batteries because they easily get shorted within short period of use.Thanks for sharing and have a nice day.
Waleed Rishmawi
July 24, 2023 at 1:52 pm
Imoudu: I do not like them either. the main problem is although there is battery in the device but it is never used (battery power) unless there is no main electricty avialable which put a lot of stress on the battery and end up drying up. have a blessed day
Henrique J. G. Ulbrich
July 24, 2023 at 1:29 am
Good maintenance work, Waleed. I had to deal with this lead-acid 4 V battery in the maintenance report https://jestineyong.com/battery-problem-in-head-lamp-retrofitted/ here at Jestine`s site. This type of 4 V battery is not found here in Brazil, so I had to make some modifications for the gadget to work with NiMh cells. Indeed, I understand well when you say it was a little bit hard to find it.
Waleed Rishmawi
July 24, 2023 at 1:55 pm
Henrique: thanks man. usually the rated batteries here are usually 6 volts which power the LED emergency lights but 4.4 volts batteries are very hard to find. some time if these batteries are not found I use the 6 volts one. I did it once and so far no complain. have a blessed day
Yogesh Panchal
July 24, 2023 at 3:08 pm
Good Job! Waleed,
I come across few batteries which shows proper Voltage but not holding current...better way to check is to use another working battery for testing.
Waleed Rishmawi
July 27, 2023 at 1:54 am
Yogesh. Thanks man. Yes totally agree with that. Have a blessed day.