What Do the Numbers Next to "100Ah" on a LiFePO4 Battery Spec Sheet Tell You?
Summary
How capacity shrinks in the cold, the temperatures at which the battery can be charged, the maximum and recommended currents, and the conditions behind the cycle-life figure. Victron's Lithium Battery Smart 12.8 V/100 Ah holds 100 Ah (1,280 Wh) at 25°C, 80 Ah at 0°C, and 50 Ah at −20°C. It can discharge from −20°C but will only charge at +5°C and above.
One 100 Ah battery, several capacities
From the technical data in Victron's manual, the 12.8 V and 25.6 V 100 Ah models. Capacity figures assume a discharge current of 1C or less.
| 12.8 V/100 Ah | 25.6 V/100 Ah | |
|---|---|---|
| Capacity at 25°C | 100 Ah, 1,280 Wh | 100 Ah, 2,560 Wh |
| Capacity at 0°C | 80 Ah | 80 Ah |
| Capacity at −20°C | 50 Ah | 50 Ah |
| Max charge current | 200 A | 200 A |
| Recommended charge current | 50 A or less | 50 A or less |
| Operating temperature | Discharge −20 to +50°C, charge +5 to +50°C | Same |
| Weight | 14 kg | 28 kg |
Same Ah at twice the voltage is twice the watt-hours. And the maximum charge current of 200 A sits four times above the recommended 50 A.
Cycle life comes with a depth
The cycle-life rows count cycles until capacity falls to 80% of nominal: 2,500 cycles at 80% depth of discharge, 3,000 at 70%, and 5,000 at 50%. Going from 80% to 50% depth doubles the count, so a single cycle figure from another brand cannot be compared without its depth.
The battery calls for a charge voltage of 14.0 to 14.4 V (14.2 V recommended) and a float of 13.5 V. Victron's own SmartSolar MPPT 100/30 ships with defaults of 14.4 V absorption and 13.8 V float, so the float value differs from what the battery specifies.
How many can be connected, and the external BMS
The battery supports series and parallel connection, and the product page says it requires an external BMS such as the Smart BMS CL 12/100 or Lynx Smart BMS. A system can use up to 20 of these batteries in total, for up to 84 kWh at 12 V and up to 102 kWh at 24 V or 48 V. When the battery gets too cold, the BMS raises a low-temperature alarm and turns the chargers off.
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Sources
- Victron Energy — Lithium Smart Battery Manual, 7. Technical data
- Victron Energy — Lithium Smart Battery Manual, 3. System design and BMS selection guide
- Victron Energy — Lithium Battery Smart 12,8V & 25,6V
- Victron Energy — SmartSolar charge controller MPPT 100/30 & 100/50 datasheet
We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.