I have 12v strip lights in various places like under the stairs. They run off a solar charged battery with a cheap PWM controller. When the panel is charging the battery or just keeping it topped up the LEDs flicker. What can I do to the light circuit to prevent this? At night the lights behave normally.

 

Welcome to AAC! First thing comes to mind is a smoothing capacitor on the DC feed to the LEDs. Posting a circuit diagram of what you have would be much better than trying to guess. Then maybe a much better answer.

 

How does the charger know how much charge is going into the battery when a lot of the charge current is lighting the LEDs?
You might fry the battery since the charger is supposed to turn off when the charging current drops but it never drops when the LEDs are using current. Then the charger circuit is being confused by the LEDs current.

 

How does the charger know how much charge is going into the battery when a lot of the charge current is lighting the LEDs?
You might fry the battery since the charger is supposed to turn off when the charging current drops but it never drops when the LEDs are using current. Then the charger circuit is being confused by the LEDs current.

Welcome to AAC! First thing comes to mind is a smoothing capacitor on the DC feed to the LEDs. Posting a circuit diagram of what you have would be much better than trying to guess. Then maybe a much better answer.

 

Thanks to you both, the current to the LEDs would be under 5 watts as each strip is less than one metre in length, 50-50 LEDs . The strips are only used intermittently so not a great load really.
Not sure why the controller would be confused as it is connected directly to the 70ah battery. The battery only drops below 12.8v after 2 days without sun. Solar panel is one side of a 220w house panel. Other side runs a 12v fan directly. Shall I just try a few capacitors until I find a size which does the job?

 

70Ah is a huge car lead-acid battery. If your wiring is good then the battery itself is a huge capacitor. I guess your car battery is old and needs replacement. You must never let it run down below about 11V.

The charger (controller?) cannot understand why the current is still high when the battery voltage is almost fully charged and is also high. Some chargers have one output for the battery and another separate output for the load.

 

70Ah is a huge car lead-acid battery. If your wiring is good then the battery itself is a huge capacitor. I guess your car battery is old and needs replacement. You must never let it run down below about 11V.

The charger (controller?) cannot understand why the current is still high when the battery voltage is almost fully charged and is also high. Some chargers have one output for the battery and another separate output for the load.

That may be it. I don’t know how old the battery is, it is an ex mobility scooter battery which I got for free, and I’ve had it for about 4 years. It’s a gel battery. I does the job but I haven’t tried testing the capacity of it. It may be nowhere near 70Ah . What is an easy way to test it?

 

I have never tested a huge powerful battery like that.

 

Testing a car battery involves loading it down with 1/2 the CCA rating for 10 to 15 seconds, and if stays above 9.6V it is healthy. See the comments after the article here: https://batteryuniversity.com/learn/article/how_to_measure_capacity
You can measure internal resistance by briefly applying a load and measuring how the voltage drops. If you know the load current or resistance, then it's possible to calculate the internal resistance.
https://www.electronicdesign.com/te...e/21128843/measuring-dcir-of-lithiumion-cells
As for the flickering... a PWM controller manages the charging by periodically switching a power MOSFET on and off, which would cause battery voltage to fluctuate at the switching frequency. You could eliminate the flickering by running the LED strings at a lower voltage, using a buck switching converter. Or change the solar controller for one that uses a switching converter to produce a steady charging voltage, which should also be more efficient. Here's a DIY version:
https://web.archive.org/web/20130523145842/https://www.freewebs.com/acselectronics/buildppt.html