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Tech Tip: How to Select the Right Battery Type for Your Maxwell Engine Start Module Installation

Tech Tip: How to Select the Right Battery Type for Your Maxwell Engine Start Module Installation

| Jeff Brakley, Sr. Marketing & BDM — Truck, Heavy Transportation, Military & Aerospace

Customers often ask, "What type of battery works best with the Maxwell Engine Start Module (ESM)?" Since the Maxwell ESM handles the engine cranking, the number and type of batteries you need can be determined by these factors. 

Consider CCA ratings and RC minute ratings.
To begin with, once you install the Maxwell ESM, you no longer need batteries with a high cold cranking amp (CCA) rating since the batteries are no longer connected to the starter motor (only the Maxwell ESM connects directly to the starter motor). Industry experts familiar with the ultracapacitor-based ESM recommend batteries with a high reserve capacity (RC) minutes rating. If you take a look at battery manufacturing datasheets, you’ll see that high RC minutes rating batteries provide longer run times for onboard electronics when the engine is off. 

The battery choices available today include standard flooded lead-acid, deep cycle or high cycle batteries, and absorbed glass mat (AGM) batteries. Several battery manufacturers offer these types in a standard Battery Council International (BCI) Group 31 form factor for heavy duty commercial vehicles. The specifications of several battery manufacturers reveal that standard flooded lead-acid batteries typically have higher CCA ratings and lower RC minute ratings. The deep cycle or high cycle batteries and AGM batteries will typically have a higher RC minute rating. Several customers install the Maxwell ESM with high cycling or AGM batteries with great results. 

Take into account your type of commercial vehicle operation. 
Are you operating a sleeper with a lot of hotel loads that need extended battery run time when the engine is off? Are you operating a day cab with minimal electrical loads? In either case, experts typically recommend high RC minute rated batteries. The number of batteries required in parallel with the Maxwell ESM depends on your engine off and parasitic loads.1 We have several vocational fleet customers operating day cabs with only one battery and the Maxwell ESM. These fleets have found that deep cycling, high cycling or AGM batteries meet their requirements. 

Electronic hours of service logging equipment, GPS units, telematics communication systems and camera systems are prevalent today as well. Sometimes drivers or fleet personnel connect these loads directly to the vehicle batteries without thinking about how the power requirements will affect battery life. Be sure to consider all of your loads and then determine the type of battery that best fits your vehicle’s needs. 

Owner operators and fleet maintenance personnel should fully understand their overall power requirements and select batteries based upon their hotel, parasitic load and add-on aftermarket equipment current requirements. It is also important to make sure the alternator is appropriately sized to recharge the batteries based upon your vehicle loads. 

Priya BendaleJeff Brakley
Jeff Brakley, Sr. Marketing & Business Development Manager — Truck, Heavy Transportation, Military & Aerospace
About this author

Jeff Brakley has contributed to the development of the Engine Start Module (ESM) from its inception. He is a member of SAE International and an Associate Corporate member of the American Trucking Associations (ATA) and the Technology & Maintenance Council (TMC). Jeff serves on the S.1 Electrical & Instruments Task Force, and recently contributed to the SAE J3053 Task Force to develop the Heavy Duty Truck Electrical Circuit Performance Requirement for 12/24 Volt Electric Start Motors Recommended Practice.

Throughout his 30-year career, Jeff has held both engineering management and program management positions for several leading national defense contractors and commercial companies, including General Dynamics, Martin Marietta, L3 Communications and Ametek Programmable Power. Jeff holds a Bachelor of Science in engineering from Purdue University and an MBA in technology management from the University of Phoenix.


1Engine off loads or hotel loads include battery powered refrigerators, microwave ovens, DVD players, and coffee makers. Parasitic loads include onboard computers, also known as engine control units (ECUs), and are active 24 hours a day.
This article contains general technical information for educational reasons only and should not be used as a substitute for technical training or manufacturer’s recommendations.

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