Bridging the Gap between Solar Power and Batteries

In 2016, Solar Impulse 2 made history by being the first solar powered plane to fly around the world. The plane would fly between 30 and 60 mph and took 16 months to complete, although the actual air time was substantially less. This single passenger plane would climb to 29,000 feet during the day to charge the batteries and slowly glide to about 5000 feet during the night to conserve battery power. The Solar Impulse 2 had 17,000 solar cells and wing span longer than a Boeing 747. The batteries made up roughly quarter of the planes weight. 1

Commercial solar powered airlines are still a long way off, but solar power is gaining traction as a source of energy for industrial, commercial, and residential applications. There is a growing need for power management integrated circuits (PMICs) designed to connect solar panels to batteries. Traditionally, the simple way “is to connect a battery to the solar panel through a diode.” 2 This method has a number of limitations mainly dealing with a very narrow voltage band. With solar power, power will greatly vary from sunny days to cloudy days, from the start of the day to the end. There is a lot of variation here that a diode is not equipped to deal with. If power levels increase or the load increases beyond the ability of the diode, the system is at risk of catastrophic failure.

Now there are better solutions available. Power by Linear™ / Analog Devices has a wide range of products to complement solar power especially when it comes to charging and maintaining batteries. “The LTC4015 is a versatile synchronous step-down charger capable of supporting a variety of battery chemistries including lead-acid, Li-ion and LiFePO4.” 3

The LTC4015 is a controller that can regulate input voltage, input current, battery charge voltage, and battery charge current, which makes it ideal for battery storage solutions found in solar power applications. The way that this is done is by using the Maximum Power Point Tracking (MPPT) algorithm. With the MPPT algorithm the system can distinguish between multiple peak power levels, which is ideal for various power levels produced by solar power. The LTC4015 can handle voltage inputs up to 35 V. Most solar panels have a peak output voltage of 17 V. The charging input voltage range is from 4.5 V to 35 V.

The LTC4015 is a multi-chemistry buck controller and charger ideal for a battery power solution that requires wide input ranges, charging batteries, and supporting loads from power sources such as solar power.

Solar Impulse 2 was quite the accomplishment. I wonder if there will be a Solar Impulse 3?



1 – Solar Plane makes history after completing round-the-world trip.

2 – Techniques to Maximize Solar Panel Power Output.

3 – Multi-Chemistry Battery charger Supports Maximum Power Point Tracking for Solar Panels

About this author

Image of Stephen Wegscheid Stephen Wegscheid, Senior Product Manager-Semiconductors at Digi-Key Electronics, specializes in analog/linear electronics, connectivity products, and single-board computers. He has a Master of Science degree from Bemidji State University and over 25 years of experience in design, manufacturing, and distribution. Additionally, he is the holder of a US patent.
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