Sharp EL-8026

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Sharp EL-8026 "Sun Man"

Sharp EL-8026

Distinctive features: The first calculator to employ solar cells, though unusually and uniquely these are mounted on the rear and are used to recharge the batteries.

Technical details:
Display is 8 digits, LCD (it does not have the intense yellow filter to remove damaging ultra-violet rays, but does have a very feint yellow tinge).

4-function, %, square root.

Power supply is a rechargeable pack made of 3 button cells giving 3.6V. The advertising flyer for the calculators gives a power consumption of 0.0007W.

Integrated circuit is a Sharp LI3001, here date coded 1976.

Size 66 x 110 x 10 mm (2.6 x 4.3 x 0.4").

1976.

Made in Japan by Sharp Corporation.

The Sharp EL-8026 was one of a series of similar calculators using the same rechargeable button cell pack. The other models employ AC-powered chargers, but this model has no provision for a charger, instead using the solar cells to recharge the batteries by leaving the calculator in strong light such as sunlight.

In 1976 Sharp had developed the more efficient mono-crystal S-225 silicon Photo-Voltaic module, with cell conversion-efficiency of 10.0%. Solar cells of the S-255 type were installed in the EL-8026 calculator, Seiko's "Quartz" watch, and Citizen's "Solar Cell" watch, which became the world's first solar powered consumer products^[1].

Since the solar cells are on the rear, this model was not designed to be used while solar powered. The solar cells are only for recharging the batteries. Pure solar powered calculators (with no batteries) appeared a little later with calculators such as the Teal Photon.

Although Sharp were pioneers in putting solar cells in calculators, they do not appear to have produced a purely solar-cell powered calculator until the EL-826 of 1980.

The calculator comes with a wallet, similar to other models in the series, but this wallet has a cut-out in the rear to allow light to reach the solar cells for recharging the batteries.

Opening the calculator casing reveals the rechargeable battery pack made of three button cells (at the bottom on the left), which the solar cells (on the right) charge. The LI3001 calculator integrated circuit is mounted in a cut-out in the circuit board.

Sharp advertising flyer for the EL-8026 "Sun Man".

This was not quite the first truly "solar powered" calculator since the calculator is actually powered by batteries and the solar cells are on the rear, being used to recharge the batteries when the calculator is not in use.

Reference