Author Topic: Chinese BT189 battery tester  (Read 2456 times)

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Offline DatmanTopic starter

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Chinese BT189 battery tester
« on: May 02, 2023, 10:30:38 am »
Hi all
I bought this battery tester:
https://it.aliexpress.com/item/1005001381541786.html
It reads 1.59V instead of 1,5V and 9,41V instead of 9.00V.
Current drawn is 5.35mA @1,5V (280 ohms) and 2.04mA @9V (4K4).
The internal voltage converter is a XC6385, giving 3.0V at the output. It should work at 0.9V minimum.
The third digit is a bit weird... It shows a number when I attach the power supply, but if I adjust the voltage it doesn't  change anymore... 1.51V, 1.41V, 1,31V... But if I retry, it shows 1.52 or 1.53...

I'll try to adjust it, also adding two resistors to raise current drawn (22 ohms for 1,5V and 470 ohms for 9V). I could also keep only the converter and make a new meter with a ATmega328P and a 0.96" OLED display... :)

Mechanics appear to be good.

Note: on 1.5V contacts it measures also 3.7V (3.2/4.2V) from Li-ion batteries, but they don't fit! :(
« Last Edit: May 02, 2023, 12:19:25 pm by Datman »
 

Offline TERRA Operative

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Where does all this test equipment keep coming from?!?

https://www.youtube.com/NearFarMedia/
 

Offline wasedadoc

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Re: Chinese BT189 battery tester
« Reply #2 on: May 02, 2023, 11:06:58 am »
Hi all
I bought this battery tester:
https://it.aliexpress.com/item/1005001381541786.html
It reads 1.59V instead of 1,5V and 9,41V instead of 9.00V.
Current drawn is 5.35mA @1,5V (280 ohms) and 2.04mA @9V (4K4).
The internal voltage converter is a XC6385, giving 3.0V at the output. It should work at 0.9V minimum.
The third digit is a bit weird... It shows a number when I attach the power supply, but if I adjust the voltage it doesn't  change anymore... 1.51V, 1.41V, 1,31V... But if I retry, it shows 1.52 or 1.53...

I'll try to adjust it, also adding two resistors to raise current drawn (22 ohms for 1,5V and 470 ohms for 9V). I could also keep only the converter and make a new meter with a ATMEGA328P and a 0.96" OLED display... :)

Mechanics appear to be good.

Note: on 1.5V contacts it measures also 3.7V (3.2/4.2V) Li-ion batteries, but they don't fit! :(
Do you believe that a 1.5 volt cell always gives exactly 1.5 volts and a 9 volt battery always gives exactly 9.00 volts?
 

Offline DatmanTopic starter

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Re: Chinese BT189 battery tester
« Reply #3 on: May 02, 2023, 11:57:29 am »
Do you believe that a 1.5 volt cell always gives exactly 1.5 volts and a 9 volt battery always gives exactly 9.00 volts?

Obviously, no. Otherwise, battery testers would be useless!

I wrote:
"It reads 1.59V instead of 1,5V and 9,41V instead of 9.00V."
but I didn't write I measured a battery.
« Last Edit: May 02, 2023, 12:00:25 pm by Datman »
 

Offline tunk

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Re: Chinese BT189 battery tester
« Reply #4 on: May 02, 2023, 12:00:21 pm »
A new alkaline AA is ~1.6V, and a new alkaline 9V battery should be around six times that.
 

Offline DatmanTopic starter

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Re: Chinese BT189 battery tester
« Reply #5 on: May 02, 2023, 12:01:25 pm »
Quote from: Datman
The third digit is a bit weird... It shows a number when I attach the power supply, but if I adjust the voltage it doesn't  change anymore... 1.51V, 1.41V, 1,31V... But if I retry, it shows 1.52 or 1.53...
Quote from: wasedadoc
Do you believe that a 1.5 volt cell always gives exactly 1.5 volts and a 9 volt battery always gives exactly 9.00 volts?
Quote from: tunk
A new alkaline AA is ~1.6V, and a new alkaline 9V battery should be around six times that.

Ok, the nominal 1.5V voltage was 1,4996V. I don't remeber exactly the 9V voltage... About 9.002V?
« Last Edit: May 02, 2023, 12:38:10 pm by Datman »
 

Offline Fungus

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Re: Chinese BT189 battery tester
« Reply #6 on: May 02, 2023, 12:31:08 pm »
What are you trying to achieve?

 

Offline DatmanTopic starter

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Re: Chinese BT189 battery tester
« Reply #7 on: May 02, 2023, 12:32:14 pm »
Sharing with you and...
a working instrument?... :)
« Last Edit: May 02, 2023, 12:34:24 pm by Datman »
 
The following users thanked this post: Fungus

Offline Hexley

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Re: Chinese BT189 battery tester
« Reply #8 on: May 02, 2023, 03:09:47 pm »
That reminds me of something I brought back from Japan in the early '80s -- a Sony battery tester model BC-330D.

Was a great device; finally expired a few years ago after the internal coin cells were replaced for the nth time.

 

Offline TheDefpom

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Re: Chinese BT189 battery tester
« Reply #9 on: May 02, 2023, 09:44:08 pm »
It looks like R2/R3 (9V) and R4/R3 (1.5V) are a voltage divider setup, maybe try changing those values very slightly to see if it corrects the reading error.

Most likely R3 is too high in value.
« Last Edit: May 02, 2023, 09:48:44 pm by TheDefpom »
Cheers Scott

Check out my Electronics Repair, Mailbag, or Review Videos at https://www.youtube.com/TheDefpom
 

Offline DatmanTopic starter

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Re: Chinese BT189 battery tester
« Reply #10 on: May 03, 2023, 08:33:15 am »
I have done some tests: it seemed I had to add 4k7 in series to the two 100k resistors. I cut the traces and added them. Readings were ok.
Then, I had to add the two load resistors: 22 ohms for 1,5V and 470 ohms for 9V but strangely, despite of the resistors soldered on the contacts (with no voltage drops on the wires to the electronics), readings were wrong! (???)
So, I restored the two 100k without addictional resistors and now it is ok! :)
I don't understand, but it works.
The strange behavior of the LCD remains.
 


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