Questions About Batteries

There are two types of deep cycle solar storage batteries chemistries mainly in use today: Lead Acid and Lithium.

Lead acid is tried-and-true, is not prone to thermal runaway meltdown/fires, and has an established and relatively safe recycling industry.

The lowest LCOE (Levelized Cost Of Energy) of these two types is lead acid, and the lowest LCOE of the lead acids is the wet cell. Wet cells require maintenance, adding water and checking specific gravity of the solution at least every few months.

Sealed lead acid batteries are more expensive (about as much as some lithium’s) but are maintenance free.  AGM (Absorbant Glass Material) is a good choice for general use; Gels are more suitable for extreme cold.  Gels are also more prone to damage from overcharging.

Lithium batteries are generally available in two main chemistries: Lithium ion and Lithium iron phosphate.  Both these chemistries are more energy dense than lead acid but are prone to thermal runaway/uncontrollable meltdown and fire.  Lithium in its raw state is explosively reactive making its viability in the recycling market hazardous.

Lithium ion is more greatly prone to thermal runaway than Lithium iron phosphate and may be less expensive, but they are less tolerable to freezing temperatures and heat.  Its discharge limit is 80%.

Lithium iron phosphate is much more tolerable to colder and hotter temperatures but its energy storage density is less than Lithium ion.   It is considered to be safe enough from thermal runaway problems. Its discharge limit is marketed as 90-100% of its nameplate amp-hour rating.

Lithium titanate. Although not new, these are now available in the solar storage commercial market, but are expensive.  Their energy density is also the lowest of the three main lithium types.  They are marketed as not prone to thermal runaway.