ISSUE: NE555 LED is ON only for 2 seconds.

Thread Starter


Joined May 28, 2024
Please help me fix this issue

My ordered XH M601 just received today in sealed packed condition.

I want to start charging at 11V and stop at 13V. So, I set the min voltage at 11V, and adjusted the RP1 to turn on the LED. Yes, the LED turn on, but for only about 3 seconds.

Actually, it should still remain ON until I set the max value and adjust the RP2 to turn the LED off. Why the LED is only on for momentarily only??? Please help me fixed this issue.

Every components on the PCB looks fine. No breaking or burning anything.



Joined Sep 17, 2013
Welcome to AAC!
According to the product specification:

Item Type: Battery Charging Control Board
Material: Copper Clad Laminate
Model: XH-M601
Power Supply Voltage: 13.8V-14.8V
Relay Closing Voltage: 12.4V
Relay Disconnect Voltage: 14.8V
Voltage Difference: ±0.1V
Voltage Detection Method: DC Voltmeter
Charging Type: 12V Battery
Potentiometer Adjustment: RP1 RP2 (Adjust Carefully)

Perhaps 11V is below the voltage at which the module is intended to function, even with the adjustment provided.
A lead-acid battery which has dropped to 11V on standby is probably damaged. The module may recognise that and refuse to continue charging.

Thread Starter


Joined May 28, 2024
thanks for the reply.

Please watch here...
He is making 9V as min, and 12.5V as max.
So, still the module works.

Thread Starter


Joined May 28, 2024
12.5V isn't enough to fully charge a 12V lead-acid battery.
Don't take it too seriously. I'm just making an assumption only. Hence, the mentioned voltages.

I already told you...... The LED is ON only for about 2 seconds after the RP1 is set. In fact, it has to be ON continuously until I set the max value after adjusting the RP2.

How do I check the 555 with multimeter for any defects??? What are the readings I have to get on each pins?


Joined Sep 17, 2013
I already told you...... The LED is ON only for about 2 seconds
1) Indeed, but I was asking about the relay.
2) Can you upload a sharply focussed pic of the under-side of that module?
3) What is the power supply voltage?
4) Do you have a schematic of the module?

The 555 can be used in various ways, so there is no definitive set of pin readings. However, it is likely that pins 4 and 8 should be at the +ve supply potential, pin 1 at the -ve supply potential, with pins 2 and 6 being used as the inputs to the two comparators inside the IC.
Last edited:


Joined Jan 23, 2018
How about monitoring the actual battery voltage? What is supposed to control when the device switches off?? It is entirely possible that the battery voltage rapidly rises when the charger is connected.
In addition, it is also possible that there is some unknown resistance in the battery charge connection that is allowing the sensed voltage to rise as current flows.
So the TS needs to monitor the battery voltage ON THE BATTERY TERMINALS and see if it is rising. I know that on a standard car battery that is connected to a charger that the voltage rises before the battery is charged. Then it drops rapidly when the charger is disconnected, untilafter the battery is finally charged.