Electrifying forklift fleets has become a priority for many material handling operations that are catching up on this industry trend. Over half of all lift trucks sold in the United States in 2018 were already electric, and the pace of transitioning to electric motive power has accelerated significantly in recent years. Switching from LPG to electric forklifts delivers tangible benefits to all operations using lift trucks, including lower operational costs, reduced total ownership costs, and safer, cleaner, quieter workplaces. Lithium forklift battery technology has made this switch viable for many heavy applications. Understanding how to correctly calculate battery Ah capacity is essential for a successful transition. For those familiar with sizing calculations in other contexts, principles similar to those used in Septic Tank Capacity How to Calculate the Right sizing apply when determining the right energy storage for your electric forklift fleet.
Understanding the Case for Lithium Electric Forklifts
Internal combustion engine (ICE) lift trucks remain in use at many companies today, partly because of business inertia and partly because older-generation electric trucks could not support the switch in demanding applications. Inefficient lead-acid forklift batteries have inherent limitations and cannot sustain high energy throughput applications such as paper and packaging, lumber, metals, and similar industries, especially in extreme temperatures and outdoor conditions.
Why Lithium Outperforms Lead-Acid
Lithium battery packs can store significantly more energy in the same battery compartment size compared to lead-acid batteries. They can also be opportunity-charged during breaks and lunch periods to run through multiple shifts every day. The key advantages include:
- Higher energy density in the same physical footprint
- Opportunity charging capability without damaging the battery
- Consistent power output regardless of state of charge
- No acid spills, fumes, or watering requirements
- Built-in heating and insulation for extreme temperature operation
- Longer cycle life lasting 8 to 10 years depending on application
Long travel distances, driving up ramps, heavy loads, high lift heights, and powered attachments such as paper clamps all place extra demand on the power source. Lithium batteries remove these barriers to going electric while reducing operational costs and pollution simultaneously.
The Economic Reality of LPG vs. Electric
Liquid petroleum gas (LPG) forklifts are, by and large, comparable to diesel and gasoline powered lift trucks. LPG engines produce lower noise and air pollution levels than other ICE options, and they cost less to refuel than diesel or gas. However, when compared to electric-powered lift trucks, they are much more expensive to operate and maintain. The environmental benefits of electric power are obvious, and timing is already set in some states. California, for example, will not allow sales of new forklifts unless they are zero-emission models starting in 2026.
Total Cost of Ownership: LPG vs. Lithium Electric
The advance of lithium-iron-phosphate (LFP) batteries in the material handling industry followed mass adoption in electric buses and passenger EVs. This technology was already tried and tested by the time it was introduced to material handling equipment. Apart from safety and environmental benefits, lithium batteries offer a significant improvement in forklift performance: faster travel and lift speeds, less downtime, and no acid spills or fumes.
What really made adoption possible is the total cost of ownership (TCO) advantage, which comes with significant savings on energy, labor, and infrastructure costs. Below is a real-world comparison of LPG versus lithium-powered forklifts based on five electric and five LPG lift trucks of the same brand, operating five days a week, three shifts per day, for five years.
| Cost Category | LPG Forklifts (5 trucks, 5 years) | Lithium Electric Forklifts (5 trucks, 5 years) | Savings |
|---|---|---|---|
| Upfront equipment cost | Lower initial investment | Higher initial investment | Electric pays back over time |
| Energy/fuel cost | Baseline (propane) | Approximately 10x less than LPG | Dramatic energy cost reduction |
| Maintenance cost | Baseline (ICE engine maintenance) | One-third of ICE maintenance costs | Substantial labor and parts savings |
| Labor cost (battery changes) | Ongoing (changing, watering, equalizing) | Minimal (opportunity charging) | Eliminates labor-intensive tasks |
| Total 5-year cost | Baseline | Approximately 44% of LPG cost | Approximately 56% or $400K savings |
The upfront cost of equipment is higher with electric lift trucks, but the savings over five years are very substantial. With lithium-powered forklifts, this company saved on labor and maintenance. The rule of thumb is that an electric forklift requires one-third the maintenance of any ICE engine forklift. The real difference, however, is in the cost of electricity compared to propane fuel. The company ended up paying ten times less for electric power than what it would have spent on propane. Electricity and LPG prices vary across states, but the difference is dramatic everywhere. Total savings with lithium-battery electric forklifts in this case amounted to about 56 percent, or $400,000.
How to Calculate the Battery Ah Capacity for Switching to Electric
When calculating the correct battery Ah capacity for converting an LPG forklift to lithium electric, engineers must compare comparable specifications. This means matching forklift models of the same brand and comparing engines that are similar in terms of energy and power output. The calculation methodology parallels approaches used in structural engineering, similar to how a Plate Load Test to Calculate Bearing Capacity and settlement of soil follows standardized testing procedures.
The Step-by-Step Calculation Process
Follow these steps to determine the correct lithium battery capacity for your forklift conversion:
- Determine the forklift power requirement – Identify the motor power rating in kilowatts (kW) for the electric equivalent of your LPG model. Reference the OEM specifications for similar electric models.
- Calculate the daily energy consumption – Multiply the motor power rating by the expected operating hours per shift and number of daily shifts. Use the formula: Energy (kWh) = Power (kW) x Operating Hours.
- Apply the voltage factor – For a given voltage platform (48V, 80V, or higher), divide the daily energy requirement by the system voltage to determine the Ah capacity needed. The formula is: Ah Capacity = Energy (kWh) x 1000 / Voltage (V).
- Add a safety buffer – OneCharge engineers typically recommend choosing a higher voltage battery option to maintain reserve capacity for unexpected extra operating hours or missed charging events. It is good practice to keep the battery state of charge above 50 percent to prolong cycle life, so extra Ah capacity always helps.
Sample Calculation
Consider a forklift that requires 15 kW of continuous power and operates for 8 hours per shift across two shifts (16 hours total).
| Parameter | Value |
|---|---|
| Motor power requirement | 15 kW |
| Operating hours per day | 16 hours (2 shifts) |
| Daily energy required | 15 kW x 16 h = 240 kWh |
| System voltage | 80V |
| Minimum Ah capacity | 240,000 Wh / 80V = 3,000 Ah |
| Recommended capacity (with 20% buffer) | 3,000 Ah x 1.2 = 3,600 Ah |
In this example, selecting a 3,600 Ah lithium battery at 80V ensures the forklift can handle full two-shift operations with reserve capacity. The same systematic approach used in foundation engineering, such as when engineers Calculate Capacity of Pile Group and Efficiency, ensures the final specification matches real-world demands.
Key Factors That Affect Ah Requirements
- Application intensity – Paper, lumber, and metal handling consume more energy than lighter loads
- Travel distance and ramp grades – Longer distances and steeper ramps increase power draw
- Lift height and load weight – Higher lifts and heavier loads require more energy per cycle
- Attachment usage – Powered attachments like paper clamps or rotators add to the energy load
- Temperature extremes – Cold environments reduce battery efficiency; factor in heating requirements
- Charging opportunities – Planned breaks and lunch periods enable opportunity charging, reducing total Ah needed
Addressing the Transition: Why Some Operations Still Use LPG
Many companies today still rely on their old propane lifts because of inertia, long-standing business relationships with local material handling equipment dealers, and limited familiarity with new lithium technology. LPG forklifts are typically found in outdoor operations in the lumber, paper, and recycling industries. Traditional business and financing terms for leasing equipment may also prevent customers from transitioning. For example, if a third-party logistics company has a three-year contract, the utilization of higher-priced electric forklifts may not reach full value by lease end, and the market has not yet standardized a way to recover the high residual value of lithium batteries after just three years.
These issues will be resolved in the near future. Even though a less effective technology can be difficult to switch from, the current social consensus on energy transition from fossil fuels, coupled with economic benefits, will push many industries toward lithium battery-powered electric equipment. The same principle of proper maintenance applies across all battery types: as with cordless power tools, understanding care requirements matters. Just as many operators have learned about Draining the Battery Memory Myth the Truth About cordless power tool battery care, lithium forklift batteries require specific charging and maintenance practices to maximize their lifespan.
Lithium battery adoption is now expanding beyond material handling into heavier machinery. Successful commercial projects include electric cranes and excavators in construction, locomotive engines in trains, and experiments in marine transportation. Aviation is next in line. The future of powered equipment is electric, and understanding how to correctly calculate battery Ah capacity is the first step toward making a successful switch.