What to consider when buying a Deep Cycle battery:

It is our opinion that to determine the actual best “bang for your buck” for batteries in cycling applications, you should gather the following information and perform the following calculations.

Information gathering before buying?


  1. Determine the amount of energy the battery will deliver in its life using test procedures recognized by worldwide manufacturers and published in the BCI technical manual. This information should be available from all manufacturers and should include the following:
  • Discharge current used (25Amps, 75Amps, 20-hour rate,)
  • Discharge time (Cycle Life) to an effective 100% depth of discharge (1.75 volts per cell)
  • Discharge cycles (Life Cycles) achieved before the battery could not deliver at least 50% of its original rated capacity

NOTE: Different types of batteries use test procedures that allow different end-of-life criteria. For example, an electric vehicle or standard Deep Cycle product would be considered at its end of life when it could not deliver 50% of its rated capacity. At the same time, a golf cart battery would not be determined to be at its end of life until it could produce at least 1.75 volts per cell during 40 minutes of discharge at 75 amperes.

Determine the number of times the battery will be serviced in its lifetime, as the manufacturer recommends. It is essential to use the manufacturer's recommended service schedule. For time/cost analysis, we recommend you use an average of 10 minutes per service per battery.

  1. Determine the average per hour/minute labour costs in your


This number varies by region and industry - should not include anything but direct labour costs. You can safely use a figure of $18.00 - $25.00 per hour ($.30 - $.42 per minute) (2003 dollars) without benefits etc. One transit authority stated that their direct labour cost associated with maintaining batteries in each transit bus was $180.00 per year; another stated it was as high as $550 per battery. We suggest using $22.00 as an average hourly cost ($.367 per minute).

  1. Cost of service materials over the life of the battery, such as; distilled or specially treated water - using a per cell fluid usage by volume of 20% on an average cell volume of 2.35l/80oz and a 75% consumption efficiency or between $.02-$.04 per oz. Battery fluid volumes are as low as 5l/169oz and as high as 16l/540oz; cleaning and neutralizing agents at 1oz per battery or $.25 per battery per service; special clothing; repair and replacement of battery boxes and trays and
  1. Cost Per Battery
  • Purchase price of the battery
  • Freight or handling charges (overland or can they be shipped via courier or air)