A variety of battery types can be used with offgrid solar systems. The two most common types are lead acid batteries and lithium ion batteries.
Which battery should you choose Lithium ion or AGM/Gel?
Lithium ion, LiFePO4 batteries:
Battery management system (BMS) is usually included. DO NOT buy a Lithium ion battery without a battery management system.
LiFePO4 batteries should not be discharged completely. A depth of discharge (DOD) lower than 80% is recommended. Simply put, the battery should not be discharged more than 80% of the battery's rated capacity.
Tips for buying batteries
- The weight of a lead acid battery is a good indicator of the battery quality. A heavier battery usually indicates a better quality battery.
- Beware for manufacturers who overestimate their battery cycle life. Batteries with thousands of cycles have likely not been tested. The cycle rating is usually an estimate. Tests to determine the battery life can take years to complete.
Determining battery storage capacity:
To determine the storage capacity of a battery, the power that the battery can supply must be multiplied by the time that the battery can deliver the power:
Energy (Wh) = Power (W) x Time (h)
We don't have a power rating for the battery, but we can approximate it by multiplying the nominal voltage of the cell with the Ah rating.
Energy (Wh) = Nominal voltage (V) x Battery capacity rating (Ah)
For use with offgrid inverters:
Offgrid/hybrid type inverters can be set to:
- limit battery charge rate,
- limit battery discharge amount and
- switch to use the grid as a backup (depending on the inverter).
We do sell inverters that do not require batteries to function.