battery size options

It’s possible to use a battery that big, as long as the polarization of the JST connector is the same.  However, we rarely have the need for a large battery with our standard stations with sensors like CTD, turbidity, or oxygen, even with cellular telemetry ever 5 minutes.  If you use a really large battery, you have to make sure your solar panel is appropriately sized to fully charge the battery on most sunny days.  If your sensors are drawing a lot of power and your solar panel is undersized (or in a lot of shade), then you might have trouble fully charging a giant battery every day and you’ll end up with a dead battery after awhile.  If you have a really power-hungry sensor or accessory that draws high amounts of current, it is usually a 12-volt sensor or motor or pump, so it would make more sense to use a 12v battery in your enclosure, along with a 12v solar panel and a separate 12v charger for whatever type of battery chemistry your 12v battery is.  The Mayfly logger boards were designed to run on 3.7v lipo batteries, and there are boost converter that generate the switched 5v and 12v supplies for external sensors.   The latest Mayfly v1.1 boards use power directly from the solar panel input connector to power the logger and boost converters, and will only draw power from the battery if there’s not sufficient power from the solar panel.  This means that on sunny days, many stations with simple sensors and a cell board can operate totally from sunlight for a large part of the day, and only draw power from the battery at night, or when it’s cloudy.  This is an improvement over previous Mayfly designs from earlier models where all power is supplied from the battery at all times and it only charges when there’s sufficient light.  This means that stations are more efficient with how they use power.  We also started using the ETFE solar panels a few years ago that offer 5watts out output power, instead of the 3.5watts the older style panels produced with the same size.  So for most people, the new panels coupled with the newest version of the Mayfly board result in sufficient charging and power supply for most deployment configurations.