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.

2. 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).

3. 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

4. Cost Per Battery

• Purchase price of the battery
• Freight or handling charges (overland or can they be shipped via courier or air)

Because of the growing number of performance rating schemes and/or ways to value your buying decision in the market today, it has become challenging to make a decision that doesn’t come with some form of buyer’s remorse at a later date. The following are some of the more obvious things to watch out for when buying;

Some companies rate their Reserve Capacities (minutes that the battery will deliver a discharge current) at 23 amps instead of the industry standard (BCI published) way of establishing Reserve Capacity at 25 amps.

Amp Hour (AH) ratings can be at 5-hour, 10-hour, 20-hour and even 100-hour rates, so make sure you compare the same rate.

Cranking Amps (the ability of the battery to deliver a higher starting current over a shorter period for engine starting) are given at different temperatures, so make sure that you compare the published “Cranking Amps” of each battery at the same temperature. CCA or Cold Cranking Amps at 0°F/-18°C is the industry standard rating. You may see ratings published at CA, MCA, MCCA and HCA. All reputable suppliers will publish the CCA.

Some companies have invented their own rating system by recognizing that the process of comparing Deep Cycle batteries should be simplified. An American-based manufacturer of batteries invented a new labelling system incorporating the “Lifetime Energy Unit” (LEU). This was their attempt to help a buyer determine the lifetime performance and value of any given battery in the market. Simply stated, and in the words of the SANTA FE SPRINGS, CA. manufacturer.

“Lifetime Energy Units signify the number of kilowatt-hours of energy a battery delivers over its lifetime. The bigger the number, the total work the battery can perform. Before introducing LEUs, accurately determining battery performance and value required complex calculations. Engineers compute the true worth of a battery as the total energy it contains, measured in kilowatt-hours (KWH). To derive a number for KWH, they build a curve that profiles the relationship between runtime and the number of cycles. The area under the curve is the total energy the battery delivers over its lifetime. When amp-hours are multiplied by battery voltage, the result is the battery's capacity in watt-hours. The next step - comparing a battery's value - is also simplified. By dividing the LEU by the battery's price, the prospective purchaser obtains a value figure (energy units per dollar) that ensures an apples-to-apples comparison between competing products.”

Discover ultimately rejects this position. As with the variations in determining Reserve Capacity and Cranking Amps mentioned earlier, this is NOT a recognized Battery Council International (BCI) method for rating or comparing batteries as suggested by the manufacturer. The manufacturer leaves out the exact method of determining LEUs, for an exact comparison to be made, which was their stated purpose for establishing the rating. This creates a situation where two suppliers could use two sets of methodologies to determine their respective LEUs, making reasonable comparisons impossible. This implies that the LEU idea or concept in practice is simply a marketing tool with no real scientific basis for engineers, as the manufacturer suggests. LEUs – as a way of helping buyers make an informed decision – would work very well if the buyer was given some additional pieces of data (data that IS available from other manufacturers and that could be used to make meaningful comparisons):

1. The exact discharge control methods (test procedures) used in determining the battery's “Cycle Time” (what discharge rate and to what depth is the battery discharged?).
2. Whether or not the batteries can be pre-conditioned before running the procedure.
3. The resulting ampere hours of power discharged per cycle.
4. The recharge control methods (test procedures) before the next discharge procedure.
5. The exact control methods used in determining the battery's “LifeCycles.”
6. The resulting ampere hours of power discharged over the life of the battery.

In addition to the problems listed above for making good performance comparisons amongst different batteries, using the LEU marketing tool to make a serious value comparison is equally flawed. The value comparison requires more detail. Some, but certainly not all, of the issues to be examined and required in determining value are:

1. Time and Supply costs associated with servicing the battery (as recommended by the manufacturer) to ensure it achieves its assumed life
2. Costs associated with Workers' Safety and Clothing needs (as recommended by the manufacturer).
3. The cost associated with Environmental Issues, Storage and Equipment Damage resulting from the emission of free hydrogen molecules during discharge and recharge.
4. Freight/time costs and/or restrictions related to

If these data were known, the buyer could then determine the true energy units per dollar or lifetime energy value as suggested by the manufacturer who introduced the LEU calculation.

The most essential consideration in buying a Deep Cycle battery is first to make sure the battery you are considering is a “True or Real” deep cycle battery. Once you have determined that the battery type is correct, ensure the Ampere-Hour or Reserve Capacity rating of the battery will meet or exceed your requirements. Most deep cycle batteries are rated in discharge rates of 100 hours, 20 hours, 10 hours, 8 hours or 5 hours, and/or reserve capacity minutes.

Reserve Capacity (RC) is the number of minutes a fully charged lead acid battery at 80° F (26.7°

1. can be discharged at 25 amps before the voltage falls below 1.75 volts per cell (100% DOD). To convert RC to Ampere-Hours at the 25 amp rate, multiply RC by.4167.

It is better to have more ampere-hours (or RC) because, within the same battery type, footprint or industry group size, the battery with higher ampere-hours (or RC) will tend to deliver longer discharge times. It is also essential to know the battery's electrochemical design. A 100 ampere-hour battery of a certain dimension designed for UPS applications may deliver more initial runtime than a Traction or Deep Cycle battery of the same dimension. Still, it will not provide the life or number of cycles that the Traction or Deep Cycle battery will. Contrary to popular belief, battery weight (while important) is “not” the perfect indication of the quality of one battery to another. It is almost certain if two batteries of the same dimension are weighed.

- one battery designed for UPS service and the other battery designed for Deep Cycle service- the UPS battery should weigh more. Be sure you understand what you are buying!

The “Battery Council International” manual BCIS-05 Rev. Dec02 provides some guidance with amp hour capacity relationships when comparing battery design for the same service application. In it, they state that “for guidance in establishing rates, ampere-hour capacity relationships are approximate”:

Finally, the available space and weight restrictions will have to be considered when determining the appropriate deep cycle battery.

Discover has made available the most extensive range of AGM and GEL (Semi-Traction Industrial Deep Cycle, Deep Cycle, and High Cycle AGM, AGM SVR and GEL) product lines worldwide! This means you have several sizes and performance options when making your purchase decision. First, consider the following;

• Do you have any size restrictions (Height, total W x L area available)
• Do you have multiple areas available for batteries? If so, how far apart are they, and are they similar in area?
• Is the area hard to get to, or is it going to be easy to get heavy batteries installed?
• Do you have weight restrictions? Both on a per-battery basis and as a total
• Will the installed batteries be easy to service? If not, DO NOT consider Floodedtypes!
• Does a dedicated exhaust fan service the installation area? If not, DO NOT consider Floodedtypes!
• What type of battery(s) are you using now?
• What type of charging system do you have?

With these questions answered, you are now ready to consider the options available to you. Make sure you have read and understand the sections on How do I increase the capacity of my battery and system.