Nowadays there are some calculators that are power of from the heat of the sun. It is actually a solar power calculator has a set of solar panels built into it. This panels help extend the life of the calculator by slowly recharging the original battery. This calculator has a long lasting this may not weak because it is powered by solar energy.
Use of solar power calculators like you would any other calculator. Recharge the battery powered calculator by leaving under the sunlight. Recognize when you have a true solar energy calculator. Keep cleaning the panels for you able to keep them working well. You can usually used the solar power calculator under the heat of the sun. It works well, you need to buy more battery that is not solar battery. For you have to save your money, you may buy the battery that is solar that is rechargeable under the heat of the sun.