Arduino Charging Nimh Batteries Solar Panel

The battery capacity is 2450 mah with a nominal 1 2 v per cell and the datasheet is here.

Arduino charging nimh batteries solar panel.

To get the power right while the panel also powers the arduino the battery will act as a buffer for the. I have a battery holder holding 3 x 1 2 volt rechargeable batteries so 3 6 volts total and i want to be able to charge them with a small solar panel some 100ma 0 5 volt panels ill use 4 to get around 2 volt during full sun and use a converter. The controller uses two stages charging algorithm. The arduino mcu senses the solar panel and battery voltages.

Batteries can typically fully absorb a current equal to 1 10th their capacity without any problem. The slightly lower voltage is not surprising because the solar charger was designed to end the charge cycle 30mv under max voltage. This uses the energy from some solar cells to charge the batteries and boosts the voltage from it to the 5v used by the arduino uno. Solar cells are connected to the input of the lithium battery charger tp4056 whose output is connected to the 18560 lithium battery.

If the batteries are not fully charged then they should absorb all of the current from the solar panels minus whatever your arduino is using. If your batteries are fully charged and you re in full sunlight then the tl431 is going to be conducting the full rated current of the panels. Using the percentages calculated above this means i will have 6 7 hours of sunlight for charging time on the shortest day of the year 67 of 10 hours 6 7 hours. This circuit was based on the awesome tutorial by deba168 solar powered arduino weather station.

Now let s assume our batteries are at 13v charging panels are giving 18v 5 5a at 100 working efficiency not possible to have 100 but let s assume. You now have the complete design for your own solar charger. Calculating solar panel and battery sizes. I actually tested the panel myself and found that in the best case with 90 000 lux full sun the max voltage was 5 2 v corresponding to a max current of 157 ma.

The thumb rule for charging ni mh batteries is 1 10th commonly known as c 10. To charge the battery pack at 1 10th its rated current requires 16 hours of charge time you can see the picture. This might be a very basic question but. Your cells are 350mah and your panels are 35ma so it s a perfect combination.

Now we will calculate the size of the solar panel and battery to power my circuit that draws 23 ma. This project can also solve the efficiency issue of arduino when in sleep. The amount of charging current is determined by the difference between battery voltage and charge setpoint voltages. The solar panel receives optimal sunlight for only four hours per day from 10 a m.

The solar charger batteries had an average voltage of 1274mv and the duracell charger batteries had an average voltage of 1295mv. According to these voltages it decides how to charge the battery and control the load. Sleep saves battery however the sensors and power regulators 7805 will still consume battery in idle mode draining the battery. There are many charge controllers available but ordinary cheap ones are not efficient enough to use with maximum power from solar panels.