I have a simple battery charger circuit that I would like to add an LED to indicate if any part of the circuit is open from Vin to ground instead of looking at the ammeter. The LED can either turn on or off when the circuit is open. This seems like such a simple task but I haven't been able to come up with anything that works. It has to be extremely simple as I have to modify 64 of these circuits.

I initially connected it across the fuse but that will only turn on the LED when just the fuse is open. Plus, although the LED is easily visible if the battery is charging but gradually dims to nothing as the battery reaches its final charge due to the decreasing charge current.

Any ideas?

 

1. What is Vin?
2. What is the maximum current?
3. What is your complexity budget?

 

It would be useful if you attach the schematic of your battery charger (if available) to see if it's rentable to modify it. But the project is something ambiguous. When a open circuit occurs, usually something anormal would happen in the correct operating principle of the charger. I think it couldn't be done as simple as you say. Do you plan to repair the charger after finding out that there is an open circuit? A LED can't simply tell you where the open circuit is if you're not designing for an specific area of the circuit.

You should reformulate your question giving more details.

 

"You should reformulate your question giving more details."

Hmmm, not sure if I can...

Vin is 24 VDC, max current, 8A. An ammeter after the power supply supplies Vin. The ammeter supplies power to 8 separate batteries. I simplified the drawing to show just one battery circuit.

I usually watch the ammeter when I plug each battery in to look for the initial current spike. But with 8 batteries I can't rely on the ammeter to show if one battery stops charging. The only way to do that is disconnect each battery and reconnect to look for the initial spike again.

An LED across/in parallel with the fuse works great if the battery is at a high charge rate. If the fuse opens then the LED turns on. But I need a very simple LED circuit to monitor the entire circuit from Vin to ground without being affected by the charge rate.

Maybe if there are specific questions I can answer those.

 

Vin is 24 VDC, max current, 8A. An ammeter after the power supply supplies Vin. The ammeter supplies power to 8 separate batteries. I simplified the drawing to show just one battery circuit.

Charging batteries in series or parallel is not optimal.

Put a small sense resistor in the ground connection between the batteries and the power source. Use a comparator to drive a LED when the current is below your threshold.

 

?

 

Thanks everybody. Looks like I will have to forget this "little" project. With the number of batteries to monitor it just won't be feasible.