Hi to the comunitee,

I am a mechanically trained tech with alittle electrical knowledge, and very little electronics knowledge.

I have got a small project here which I need alittle help from an expert if you could please assist with it.

Project is to monitor a lifopo4 hobby battery with the battery voltage monitor, this has the ability to program the battery voltage max and min voltage values, and alarm when the battery is above or below the set values, and when alarmin will audibl beep and also trigger a signal through the alarm port, which is an open collector output signal.

I want to connect this alarm signal to the relay pcb circuit to operate a relay to stop the battery charge process to try to stop the battery from overcharging, which is very harmful to the battery life.

I have purchased the relay pcb thinking it would work with the battery voltage monitor device, but have found out that it does not work. Is there anything i can add, or do to the pcb to make this little system work properly.

I have done alot of reading about the darlington transistors, and npn and pnp types of transistors, i thoiught what i have would work, but i have obviously made erros with what i have purchased, but am lookingto make it good. I can desolder the transistor out of the pcb and replace it with another type if required, can do this ok, just need to know what i need to do.

I have the circuits drawn below along with the pictures of both the battery voltage device and relay pcb.

many thanks for the help with this project.

Best regards, Anthony.

 

You need to add an extra resistor from the "open collector" terminal to the relay 12v supply and common both the ground terminals together like this..

An open collector means there is no load resistor, so you have to supply one,

you may find when the alarm is activated the collector is either pulled low or open, so the relay will click in or drop out.

 

Hi Dodgydave,

Many thanks for your time and input. I am for sure thankful and grateful that I can get this to work with a cheap and simple resistor add solution. I shall go out thisafternoon and locate a few resistors and fit them.

I shall eport back when i get it working.

Again, thank you very much.

Love the avatar by the way, you will for sure never walk alone from a fellow lfc supporter.

Anthony.

 

Hi again,

will 1k 1/4w resistor do the same job, I happen to have 2 of them at my home.

Thanks.

 

Hi again,

will 1k 1/4w resistor do the same job, I happen to have 2 of them at my home.

Thanks.

yes, any value over 1k is ok

 

Thank you again

Anthony.

 

yes, any value over 1k is ok

Hi Dave,

fitted a 10k resistor as advised, works like a charm.

Hallelulia (not sure if i`ve spelt that right) but i am singing.

Thank you very much for that support.

Best regards, Anthony.