How To Calculate Battery Charger Sizes for Motive Equipment

What information is needed to size a forklift battery charger? You will need the following informati

What information is needed to size a forklift battery charger?

You will need the following information when sizing a fork truck battery charger; battery voltage, capacity and charging rate.

Voltage: The battery voltage is the “Electrical Pressure” required to push the charge out of the battery.
The voltage (V) rating of the battery is the nominal voltage of the battery.
The nominal voltage is 2 Volts Per Cell (VPC) and typically 24V, 36V, 48V, or 80V.

Capacity: A battery’s capacity is the amount of electric charge it can deliver at the rated voltage.
Capacity is listed in Ampere Hours (AHR) and is determined by the number of plates and the plate size.

Nominal voltage and capacity rating can be found on the battery nameplate
(listed as NC-SSS-NP):

  • NC is the number of cells
  • SSS is the size of plates
  • NP is the number of plates

Battery Rated Voltage: V = 2*NC
Battery Capacity:  AHR = ((NP-1)/2)*SSS

The start rate or current output of the charger is rated in amperes, or amps (A).
A = AHR*Start Rate

The standard charger rates are:

  • Conventional Charge:  17% (.17) of the battery capacity
  • Opportunity Charge:   25% (.25) of the battery capacity
  • Fast Charge:              40% (.40) of the battery capacity

If you are unsure on what start rate will fit your application, or if it makes sense to convert to opportunity or fast charge, we can analyze your current battery usage with one of our PowerTrac DT battery data loggers.

Charger Sizing Example: Battery ID of 18-125-17:

Calculate battery rated voltage: Voltage=2*NC
18 is the number of cells at a nominal voltage of 2 Volts per Cell (VPC)

Calculate battery capacity: AHR = ((NP-1)/2)*SSS
125 is the plate size and 17 is the number of plates
AHR=((17-1)/2)*125 = 1000AHR.

Calculate the output amperes (A) based on charging start rate: Amperes = AHR*Start Rate

  • Conventional Charge      1000*.17 = 170A
  • Opportunity Charge       1000*.25 = 250A
  • Fast Charge                  1000*.40 = 400A


  • Conventional Charge    RV08-8KW-36V
  • Opportunity Charge      RV12-12KW-36V
  • Fast Charge                     RV16-18KW-36V

The REVOLUTION Series is comprised of multiple 1.3kW power modules that can be can be programmed for use with 24/36/48 volt batteries. The REVOLUTION series chargers spans conventional, opportunity, and fast charging applications. The REVOLUTION charger with its modular design is sized to meet your specific applications so you are purchasing a charger that more closely matches your needed power output.