Page 17 - PS Battery Guide May 18

Battery guide For PowerSpout

Advantages:

Depth of Discharge.
Lithium batteries can be discharged 80% (or even 100%) of their capacity
and they do not suffer from being left in a discharged state. Lead acid
batteries thrive best on a 50% DoD cycle and need to be kept well
charged, and periodically overcharged to avoid sulphation of the plates.

Cycle Life
Most lithium batteries are warrantied for 10,000 cycles (at 80% or more
DOD) over a ten year period, whereas even the premium brand lead acid
batteries are unlikely to offer more than 3,000 cycles (at 50% DOD).

Efficiency
Lead acid batteries are around 80% efficient at best whereas Lithium
batteries can be 98% efficient.

Relative costs of lead batteries in ($NZ 2018)
To give some indication of relative costs, below is a recent summary that was
done for a client who required 50kWh of cycling capacity for a large NZ home.

Some makers of lead carbon batteries are indicating very high cycle life (20+
years) but are offering only a 3 warranty unless monitoring is connected back to
the makers, then they extend it to 5 years. Nano carbons are a relatively new
technology (they can be considered the lead companies response to lithium), the
life estimates over 20 years have yet to be proven outside of the laboratory. With
only 3-5 years warranty this technology looks higher risk. Check battery
warranty terms closely as after 1-year it is often not full replacement but a pro-
rata payment, for example if your battery bank failed after 2 years and you had a
3-year warranty you would be paid 33% refund. Your battery lasted fine for 2 of
the 3 warrantied years.

FLA at 52% of the cost of tubular gel, can do 3.3 years to 50% DOD so you have
to carefully consider your options. If you have hydro in your system and can keep
to within 20% DOD then your battery bank may last 8-10 years on low cost
FLA’s. A 20% DOD means you can cycle the above battery by 21.6 kWh per day.

© 2018 EcoInnovation Ltd (NZ) Page 17
Last reviewed 19/6/18