Problem with a solar power bank indicator LEDs

ledmicrocontrollerpower supplypower-consumptionsolar cell

I bought a 10000mAh (actual 4000mAh) solar power bank from Victsing few days ago. After having solved a short-circuit problem that affected the solar panel, I noticed that it took an extremely long time to charge from direct sunlight: in six very sunny days just about one quarter. The device presents four blue indicator LEDs that sequentially turn on when the power bank is charging (both from sun or microUSB). The problem is that the LEDs are very brights and seems to consume a lot of energy. From some calculations and measurements, it seems that they consume about 10-30% of the energy harvested by the solar panel, a lot in my opinion. The four LEDs are controlled by an unidentified microcontroller. The question is: is it possible to reduce in someway the consumption of the LEDs, by modifying the circuit, the microcontroller or the LEDs?

Thanks a lot.

Alessio

Best Answer

Most LEDs have a nominal current of 20mA. By choosing a larger resistor, the current can be reduced, but their light becomes dimmer. There are LEDs for just 2mA, saving 90% of current / energy without being too dim. So, changing the LEDs may also be an option, if the device doesn't already use low-currrent LEDs.

However, what's the size of your solar panel? If it's 10cm x 10cm = 0.1m x 0.1m = 0.01 square meters, it catches only 10W of sunlight. (The sun gives us a maximum of 1kW per square meter) The efficiency is as low as 20%, resulting in just 2W electrical power gained. At 5V, that's just 400mA.

So, one to three 20mA LEDs are noticeable consumers, but 2mA LEDs are not.

Now you say your powerbank holds a charge of 4000-10000mAh. It takes 10-25 hours of bright sunlight to collect this charge.

In reality, there are power conversion losses and sunlight isn't always as intense as in the Sahara at 12 o'clock. You can for sure add 20% to the charging time, maybe more.

So, don't expect too much from the solar module.