The component that decides cost and life.
WHAT TYPES ARE COMMONLY USED
Flooded lead-acid Sealed lead-acid, including gel and absorbed glass mat Lithium, typically lithium iron phosphate
WHAT LEAD-ACID PROVIDES
Lower purchase price Wide availability
WHAT IT COSTS
Shorter life Limited usable capacity Weight Maintenance, for flooded types
WHAT DEPTH OF DISCHARGE MEANS
How much of the battery's capacity you may use before recharging.
WHY IT MATTERS ENORMOUSLY
Lead-acid batteries are damaged by deep discharge, so only part of the rated capacity is usable.
WHAT THAT IMPLIES
A lead-acid bank must be substantially larger than the energy you need.
WHAT LITHIUM PROVIDES
Far more usable capacity Many more cycles Less weight Little maintenance
WHAT IT COSTS
A higher purchase price.
WHAT TO COMPARE
Cost per usable unit, across the expected life.
WHY THAT COMPARISON
On that basis lithium is frequently cheaper despite the purchase price.
HOW TO CALCULATE IT
Usable capacity, multiplied by expected cycles, divided by price.
WHAT SHORTENS BATTERY LIFE
Deep discharge Heat Overcharging Poor ventilation Mismatched batteries in one bank
WHAT TO NEVER DO
Mix old and new batteries, or different types, in one bank.
WHAT TO PROVIDE
Ventilation and shade.
