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alarm buzzer

#1
Hi all
I just bought this voltage alarm buzzer : https://www.banggood.com/Wholesale-...r-Monitor-Buzzer-Alarm-p-26049.html?rmmds=buy .
It arrieved today and I went trying it out immediatly. So, I plugged it into my 3S tattu 1300 mAh battery that also just arrieved today and I expected it to say 3 S and than go trough each individual cell and show the voltage. But, it displays 2S5 , and than only 2 cells. Is that normal? How can I know the voltage of the 3rd cell? Thanks!
 

Hoomi

Well-known member
#6
I ordered a 5 pack of those from Amazon. All 5 worked fine, when connected so that the red wire of the balance plug is towards the center, and the opposite black wire is at the left edge of the pins, looking down at the display. If the connector is offset to the right, you will get no display at all. The far-left pin must be connected for correct return. If, however, the connector is offset one to the left, you will get the display for a 2S instead of a 3S.
If you're connecting it correctly as in these photos for a 3S battery, and it's showing 2S, then it appears you have a defective unit, likely an open on the fourth pin from the left.

P9041734.JPG

P9041735.JPG
 

Hoomi

Well-known member
#7
One other possibility is that you have an open wire on the balance connector from the battery, which for the indication you're getting, would be the red wire. Do you have access to, and know how to use a digital multimeter?
 

Hoomi

Well-known member
#8
How to check your battery manually with a digital multimeter:
1: Select VDC on the meter. This will be indicated by either VDC or the V with the straight line over the dashed lines on the meter, as shown.
P9041736.JPG
2: With the negative (usually black) lead and positive (usually red) lead as shown, you should read the full battery voltage.
P9041738.JPG
3: Any two adjacent pins will give you the voltage on a single cell.
P9041739.JPG
4: Close up detail of probing the balance connector manually:
P9041740.JPG
This works best with fine-pointed probe leads, as some probe leads may be a bit large to easily contact the metal in the balance connector. Your voltage will vary a bit, depending on whether you're looking at a full charge, or a battery needing to be charged, but should be around 3.7 - 4.0 volts per cell. With LiPo batteries, you don't want to overcharge them, or over-discharge them, and you don't want to store them at full charge.