ESM ULTRA 31/900

Whether the medium duty trucks in your fleet are step vans, package cars, utility vehicles, lease/rental trucks or food & beverage delivery trucks, Maxwell has the solution to your jump-start and stranded vehicle headaches.

Don’t leave starting to batteries. The ULTRA 31/900 Engine Start Module from Maxwell Technologies provides high power to start your truck consistently – potentially for the life of your truck.

Replace a battery or add the Engine Start Module to a heavy duty truck for reliable starting from -40°F to 149°F (-40°C to +65°C)

Features and Benefits

  • 900 Cold Cranking Amps (3-sec start) provides Engine Start reliability
  • No lead. No acid
  • Improves overall system power performance
  • Shock & vibration resistant
  • Built-in overcharge protection
  • Low total cost of ownership
  • Cold weather reliability down to -40°F
  • Faster cranking
  • Industry standard BCI Group 31 form factor
  • Recharges fully in less than 8 minutes | (Initial charge is 15 minutes or less)
  • Long-life - limited 4 year full replacement warranty**
  • Assembled in the U.S.A
Vehicle Type Medium Duty (Class 3 – 6)
Diesel Engine Size 4L to 9.9L
Input Voltage (B+) Terminal 10 - 18 V
Output voltage (max.) 16.2 V
Cold cranking amps1 900 CCA (3 sec. crank)
Peak power2 16.4 kW
Maximum recharge time 8 minutes (recharge from battery at 20 A)
Dimensions BCI Group 31
13”L x 6 13/16” W x 9 7/16” H
(330mm L x 173mm W x 240mm H)
Terminals SAE 3/8"-16 UNC, 3 each
Environmental Designed for heavy truck battery box environments
Weight 16 lbs (7.3kg)
Current draw 25 A max. (from battery) (< 10ma when fully charged)

1. CCA = C x (Vmax - Vmin) / (T + C x ESR)
2. Peak Power = V2max / (4 x ESR)
3. The vehicle starter solenoid must be the only connection to the STARTER+ terminal. May require new cable to connect cab loads/alternator to batteries.
C = 500 F (min.) Vmax = 16.2 V (for 0° C) Vmin = 7.2 V (per SAE) T = 3 sec. ESR = 0.004 Ohm (max.)


1. Disconnect cable(s) connecting the batteries o the starter, and remove one battery.

2. Install the ESM and connect the negative battery cable to the BATTERY - terminal of the ESM.

3. Connect the existing cable(s) from the Starter Solenoid to the STARTER + terminal of the ESM.

4. Connect Cable from the primary Battery Positive terminal to the BATTERY + terminal of the ESM.

5. Initial Charge - The ESM takes up to 15 minutes for an iintial charge.

6. See the ESM Installation Video Here