Solar Storage Batteries

Solar batteries are designed for deep daily cycling with slow charge from variable solar input, using thicker tubular plates or other cycle-oriented designs. Inverter batteries are designed for standby with occasional discharge and regular grid charging. Using an inverter battery in daily solar cycling shortens its life.

Gel batteries tolerate deep cycling and high temperature a little better and typically have longer life, while AGM batteries accept higher currents and are often lower in cost. Both are sealed and maintenance-free. For remote sites with daily cycling gel is often preferred, but datasheet cycle-life figures should decide the selection.

It depends on the load criticality and weather at the site. Off-grid systems often design for two to three days of autonomy so they ride through cloudy weather, while grid-connected hybrid systems with a diesel or grid fallback can use less. More days means a larger and more costly bank, so find the balance.

It depends on the battery type and cycle-life datasheet. Lead-acid solar batteries are commonly designed for a daily depth of discharge of around 50 percent or lower to reach their rated cycle life, while lithium can usually be used deeper. Check the cycle-life versus depth-of-discharge curve in the datasheet for your product.

Choose between PWM and MPPT based on array and battery voltage. MPPT controllers extract more energy when the array voltage is well above battery voltage and are common for larger systems. The controller's current rating must match the array, and its charge profile must suit the battery chemistry: flooded, gel, AGM or lithium.