I am using lm324 as difference amplifier to measure the string voltages of lithium ion battery pack ( four cells in series). I am using all single package of LM324 that have 4 Op-amp. The Lithium ion battery pack is being charged by the UPS ( uninterruptible Power Supply). The UPS voltage have some noise and you can see in the attached picture. The supply voltage of LM324 is also connected in parallel with UPS and Battery terminal.
The problem is that , whenever the ups start charging battery, the output voltage of LM324 is disturbed. Without charging of UPS, the voltage of each cell in the string is 3.3V as nominal. But when the UPS start charging, the same voltage becomes low as 1.6V.
We have connected decoupling capacitor with LM324 but it didn't work. Can you please recommend any suggestion.
difference amplifier circuit configuration.
Complete circuit of LM324 as difference amplifier.