Battery guide
A variety of battery types can be used with off-grid 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:
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Battery management system (BMS) is usually included. DO NOT buy a Lithium ion battery without a battery management system.
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LiFePO4 batteries should not be discharged completely. It is recommended to keep at least 20% capacity left after a discharge cycle, hence up to 80% of the battery capacity can be used to ensure optimal life cycles.
- Battery balancers are compulsory to be installed for 24V or 48V AGM/Gel battery banks.
- AGM/Gel VRLA batteries do not want to be discharged completely. Ensure that the cut off voltages is set correctly for off-grid systems or back-to-utility voltages for hybrid installations.
- AGM/Gel batteries do not have a built-in BMS. Hence, the actual state of charge of the battery can not be accurately be determined with voltage only. To ensure decent use-ability from AGM/Gel batteries without a SoC controller, the load on the batteries needs to be less than the following:
- 100AH: ~ 300W @ 12V, ~600W @ 24V, ~1200W @ 48V
- 150AH: ~ 420W @ 12V, ~840W @ 24V, ~1680W @ 48V
- 200AH: ~ 540W @ 12V,~1080W @ 24V,~2160W @ 48V
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 ideal 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)
4x 100AH Gel batteries in series for 48V Inverter utilized 50% DoD | ||||||||
Time to 50% DoD | 30min | 1h | 3h | 4h | 5h | 8h | 10h | 20h |
Constant Load on inverter display | 1960W | 1140W | 480W | 370W | 310W | 200W | 160W | 60W |
Values above includes the AGM/Gel battery Peukert effect, inverter power consumption (60W) and DC to AC efficiency (90%). |
For values not listed in the table above:
4x 150AH Gel batteries in series for 48V Inverter utilized 50% DoD | |||||||||
Time to 50% DoD | 30min | 1h | 2h | 3h | 4h | 5h | 8h | 10h | 20h |
Constant Load on inverter display | 2960W | 1870W | 1110W | 800W | 630W | 520W | 340W | 270W | 120W |
Values above includes the AGM/Gel battery Peukert effect, inverter power consumption (60W) and DC to AC efficiency (90%). |
For values not listed in the table above:
4x 200AH Gel batteries in series for 48V Inverter utilized 50% DoD | ||||||||
Time to 50% DoD | 30min | 1h | 3h | 4h | 5h | 8h | 10h | 20h |
Constant Load on inverter display | 3690W | 2020W | 910W | 720W | 570W | 370W | 340W | 160W |
Values above includes the AGM/Gel battery Peukert effect, inverter power consumption (60W) and DC to AC efficiency (90%). |
For values not listed in the table above:
1x100AH LiPO4 for 48V Inverter utilized 80% DoD | ||||||||
Time to 80% DoD | 1h | 2h | 4h | 6h | 10h | 14h | 16h | 20h |
Constant Load on inverter display | 2510W | 1270W | 630W | 410W | 230W | 150W | 130W | 90W |
Values above includes the LiFePO4 battery Peukert effect, inverter power consumption (60W) and DC to AC efficiency (90%). |
For values not listed in the table above:
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.
Additional information available at Technical Support.