Usage:
Maintenance free batteries provide an excellent opportunity for incremental sales. However, precautions must be taken to assure optimum performance and service. Unlike conventional and low maintenance batteries which are dry-charged and activated only when required for service, maintenance free batteries are both charged and activated during manufacture. Thus, maintenance-free batteries may require a recharge after a period of storage.
Caterpillar fully maintenance free batteries represent a different technology to conventional and low maintenance batteries and give many user benefits. Compared to low maintenance batteries, some of these benefits are:
- * Ten percent more cold cranking power provides faster starting.
- * Envelope separators reduce potential short circuits.
- * Polypropylene case provides higher impact resistance for rugged applications.
- * Reduced gassing and less terminal corrosion eliminates the need to add water and reduces service requirements.
- * Greater resistance to overcharge provides longer service life if alternator failure occurs.
- * Wet batteries require no acid fill or activation prior to installation.
- * Reduced self-discharge provides longer out-of-service storage.
- * No acid access reduces the potential for acid contamination (which reduces battery life) and also eliminates the possibility of overfilling the battery.
- * Envelope separators reduce potential short circuits.
Make sure the user receives not only these benefits but also the optimum service life by maximizing stock turnover while maintaining the state-of-charge above the given minimum level.
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In 24 Volt systems, do not use a maintenance free battery with any other type of battery (low maintenance on conventional). The batteries will be destroyed when they are charged.
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Self-Discharge
When any type of battery has been activated and not put into service, it is subject to self-discharge. The rate of self-discharge is basically related to two factors. First, is the metal composition (alloy) of the grid for the battery plates and second, is the ambient temperature in which the battery is stored. Caterpillar maintenance free batteries have lead calcium alloy grids and an extremely low self-discharge rate. It is so low that in an ambient temperature not exceeding 27°C (80°F), shelf life before recharging is 12 months from the date of manufacture. At this point, the OCV (Open Circuit voltage) will have reduced to approximately 12.4 volts. The illustration shows relative discharge rates between maintenance free, low maintenance and conventional batteries.
Discharge rates.
Storage at Elevated Temperatures
As ambient temperatures increase, all activated batteries self-discharge at an increasing rate. For all batteries including maintenance free batteries, this is approximately double for every 10°C (18°F) above 27°C (80°F). Thus, at an ambient temperature of 37°C (98°F), recharge will become necessary after six months and at 47°C (116°F) recharge after about three months. Whenever possible, avoid storage at elevated temperatures. Since climatic conditions vary with the seasons of the year, the best indicator for the correct recharge time in temperatures above 27°C (80°F) is when the OCV falls below 12.4 volts. Recharge as many times as required without exceeding a total of two years shelf life to maintain the OCV at or above 12.4 volts. Keep this recharging to a minimum by maximizing stock turnover. Should the OCV be allowed to fall below 12.4 volts for a long period of time, battery deterioration and eventual reduction of service will occur. The end result can be permanent reduction of capacity, lack of cranking capacity and internal short circuits. To avoid these conditions, the best safeguard is to maintain the OCV at 12.4 volts or more.
Stock Rotation
All battery stock should be rotated on a first in, first out basis. This is especially true for wet maintenance free batteries. Proper battery rotation will reduce recharge and warranty cost. It will also provide the user with a better product. If stock recharge is required, the after charge, open circuit voltage should be 12.6 volts or above when surface charge has been removed.
Recharge for Storage
To fully recharge a maintenance free battery:
1. Select the lowest charge rate for the amp hour rating of the battery from the chart on page 13 of Special Instruction SEHS7633-01, "Battery Test Procedure" or Special Instruction, SMHS8561, "Battery Rating And Cross Reference Chart".
2. Using a 6V7070 (or equivalent) Multimeter Group, charge until the terminal voltage reaches 15.5 V, but do not exceed 16.0 V.
3. After reaching 15.5 V, charge an additional one hour. This should bring the charge level of the battery to full charge for restorage.
Test
Two criteria are used for testing a maintenance free battery. These are measuring the OCV and applying a load test. The OCV is used to give an indication of the state-of-charge. A reading of 12.4 volts represents approximately 60% state-of-charge and is the minimum required for both a valid load test and putting into service. The reading must, however, represent the stabilized voltage and, if a battery has just been recharged, the surface charge on the plates must be removed. Surface charge is a false voltage on the plates that can increase the true OCV from one to three volts. It can be removed by applying a load of one-half the BCI CCA (Battery Council International Cold Cranking Amperes) rating of the battery for five seconds. Then allow two to four minutes stand recovery time. After 48 hours, batteries do not need removal of surface charge. If the OCV recovers to a minimum of 12.4 volts, the battery can be load tested. Load test by applying half the BCI CCA rating and measure the terminal voltage after 15 seconds with the battery still under load. This voltage should not be less than 9.5 volts with the battery temperature at 10°C (50°F) or above. Full details on battery testing can be found in Special Instruction Form SEHS7633-01, "Battery Test Procedure".