1. Determine the amount of energy the battery will deliver in its life using test procedures recognized by world wide manufacturers and published in the BCI technical manual. This information should be available from all manufacturers and should include:
- Discharge current used (25Amps, 75Amps, 20 hour rate etc.)
- 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 to be at its end of life when it was not able to deliver 50% of its rated capacity while a golf cart battery would not be determined to be at its end of life until it was not able to produce at least 1.75 volts per cell during 40 minutes of discharge at 75 amperes.
2. Determine the number of times the battery will have to be serviced in its life time as recommended by the manufacturer.
- The manufacturers published battery life data will be the best achievable in the best of circumstances
- You must use the manufacturers recommended service schedule
- For time/cost analysis we recommend you use an average of 10 minutes per service per battery
3. Determine the average per hour/minute costs of service people in your organization
- This number varies by region and industry and it should not include anything but direct labor costs
- You can safely use a figure of $18.00 - $25.00 per hour ($.30 - $.42 per minute) without benefits
- One transit authority stated that their direct labor cost associated with maintaining batteries in each of their transit buses 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).
4. Determine the cost of service materials over the life of the battery:
- 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 more
5. Cost per battery
- Purchase price of the battery
- Freight or handling charges (overland or can they be shipped via courier or air)