i recently received this battery in the mail ;
it's a three cell lithium ion battery ; i built one like it before .
this one though has 2 pins only ; supposedly + and - . not fit to be connected to the balance charger
i usually use for these batteries ; the apparent solution seems to just connect it to a 3amp 12V DC line .
however i wanted to ask here just to make sure that's safe .
one other quick simple question : i have an electromyograhy module (the MyoWare muscle sensor) when i use it on battery and just read the signal with a battery operated volt-meter ; it seems to work very well and with very little noise .
however when i connect it to an Arduino that is hooked to my computer (the power jack being connected the the computer) to monitor the signal through Serial . there is alot of Noise ; i am wondering why : only the ground line of the module is connected to the arduino for reference and an analog pin to the A0 input of the arduino . how is noise propagating to the module i wonder .
It's not even close to being safe trying to charge a Li-ion battery from a DC source unless it has current and voltage limiting and you really know what you're doing. If you're good with a soldering iron perhaps you can fit a balance connector to it. JST- XH connectors are easy enough to find.
amine2:
the apparent solution seems to just connect it to a 3amp 12V DC line .
however i wanted to ask here just to make sure that's safe .
I too would be surprised if that is safe.
When charging Lithium batteries you really do need to do it right and the datasheet for the battery ought to give you some idea as to the charging possibilities of the battery.
Some packs have a built-in charge management and balancing controller. If there's a datasheet for it, check it out. If its just 3 cells in series without any protection you are taking a risk.
USB power from computers is about the noisiest power you will ever see(*), not surprisingly you fell foul of that.
(*) Over a vast range of frequencies from audio to microwave.
Hello : thank you very much guys for your attention and i am very sorry for responding late it's because of my work schedule .
the datasheet (as brief as it is) does indicate that there is a "safety board" on ; which probably is just a
BMS (battery management system) ; limits charge and discharge currents and protects against over-voltage .
pert:
Noise doesn't need to get to the module. It only needs to get to the Arduino board's analog to digital converter (ADC).
Hello ; thank you for your attention .
it's just that when i measure any other signal ; it would be relatively stable even while using the serial monitor .
only when i use the Emg module does real fluctuation start to happen .
for example : when the output of the module is 2v ; on the voltmeter i get values between 1.8 and 2.2v .
on the serial monitor the variance is between 1 and 4v .
You should be aware that it is safer to use 18650 individual batteries with a BMS because it allows monitoring
of individual battery levels and current and prevents overcharging of individual batteries. The pack you purchased may only have two wires but in this case less is less and more is more, meaning you would be
better off having access to each battery in the pack and a BMS that can control the charging .
