Information — Questions to ask

CAUTION/DANGER:

Do not allow battery electrolyte to mix with salt water. Even small quantities of this combination will produce Chlorine gas that can KILL you!

Because of the growing number of performance rating schemes — and/or ways to value your buying decision in the market today — it has become difficult to make a decision that doesn’t come with some form of buyer’s remorse at a later date. 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 which is 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 are comparing the same rate. The “Battery Council International” manual BCIS-05 Rev. Dec02 provides some guidance regarding comparing amp hour capacity relationships. In it they state that “for guidance in establishing rates, ampere hour capacity relationships are approximately”:
         1. 20 hour 125%
         2. 6 hour 100%
         3. 5 hour 95%
         4. 4 hour 89%
         5. 3 hour 82%
         6. 2 hour 72%
         7. 1 hour 55%
    * 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 invent their own rating system; Recognizing that the process of comparing deep cycle batteries should be simplified, An American based manufacturer of batteries invented a new labeling system incorporating the “Lifetime Energy Unit” (LEU). This was their way of attempting 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 more total work the battery can perform. Before the introduction of 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 run time and 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™ completely 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. In fact the manufacturer leaves out the exact method of determining LEUs in order that an exact comparison be done, which was their stated purpose for establishing the rating. This creates a situation where two suppliers could use two sets of methodology 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. In fact however, 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 batteries “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 re-charge control methods (test procedures) prior to the next discharge procedure.
   5. The exact control methods used in determining the batteries “Life Cycles”.
   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 comparison amongst different batteries, using the LEU marketing tool to make a serious value comparison is equally flawed. The value comparison requires more in the way of details also. 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 cycles.
   2. Costs associated with Workers Safety and Clothing needs (as recommended by the manufacturer).
   3. Cost associated with Environmental Issues, Storage and Equipment Damage resulting from the emission of free hydrogen molecules during discharge and re-charge.
   4. Freight/time costs and/or restrictions related to shipping.

If these data were know the buyer would then be able to determine the true energy units per dollar, or lifetime energy value as suggested by the manufacturer who introduced the LEU calculation.

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

   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. Determine the number of times the battery will have to be serviced in its life time as recommended by the manufacturer. Remember that the manufacturers published battery life data will be the best achievable in the best of circumstances. Therefore 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.
   2. Determine the average per hour/minute costs of service people in your organization This number varies by region and industry — 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 etc. One transit authority stated that their direct labor cost associated with maintaining batteries in each of their transit buses was $180.00 per year. We recommend $22.00 as an average hourly cost ($.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 more.
   4. Cost Per Battery
          * Purchase price of the battery
          * Freight or handling charges (overland or can they be shipped via courier or air)