Storage and Recharge Criteria
For any rechargeable battery, storage and recharge are important criteria, and this section develops some useful guidelines that should be followed.
(A) How do I know the state of charge of the battery?
Provided the battery has not been charged or discharged for at least five (5) hours, one can use the following graph to determine the state of charge (SOC) of the ODYSSEY® battery by simply using a good quality digital voltmeter to measure its open circuit voltage (OCV).
The graph below indicates that a healthy, fully charged ODYSSEY® battery will have an open circuit voltage of 12.84V or higher at 25ºC
The open circuit voltage (OCV) numbers on this graph are applicable only if the battery has not seen any activity (charge or discharge) for at least a few hours before voltage measurements are taken.
ODYSSEY® OCV vs. state of charge
® OCV vs. state of charge
(B) How long can the battery be stored?
The next graph shows the remarkable storage properties of the ODYSSEY® battery. At a storage temperature of 25°C, one can store these batteries for up to two (2) years. As the graph illustrates, the lower the storage temperature, the longer the storage time.
The graph also illustrates the large impact of temperature on storage — for every approximately 10°C (18°F) increase in temperature the storage time is cut in half. Thus, although the ODYSSEY® battery may be kept on the shelf for two years at 25°C (77°F), if the temperature rises to about 35°C the battery may be stored for only one year before it needs a recharge.
The numbers on this graph are applicable only if the battery is fully charged before being placed on storage..
ODYSSEY® storage time vs. temperature
C) Can the battery recover from abusive storage conditions?
The short answer is yes, the ODYSSEY® battery can recover from extremely deep discharges as the following tests demonstrate.
(1) German DIN standard test for overdischarge recovery
In this test, a charged ODYSSEY® PC925 battery was fully discharged over 20 hours (0.05C10 rate) to 10.20V. After the discharge was complete, a 5W resistor was placed across the battery terminals and it was set aside for 28 days.
At the end of 28 days’ of storage, the battery was charged at 13.5V for only 48 hours. Another 0.05C10 discharge yielded 97% of rated capacity, indicating that a 48-hour charge after such as deep discharge was not sufficient; however, the test is designed to show whether the battery can be recovered from extremely deep discharges using only a standby float charger. A standard automotive charger at 14.4V would have allowed the battery to recover greater than 97% of its capacity.
The results of this test prove rather conclusively that ODYSSEY® batteries can indeed recover from very abusive storage conditions. This conclusion is further reinforced by the following test which is even harsher than the DIN standard test due to the fact that the battery was stored in a discharged state at a high temperature of 50°C or 112°F.
(2) High temperature (50°/112°F) discharged storage test
In this test two ODYSSEY® battery samples were discharged at the 1-hour rate to 9V per module, then set aside for storage at 50°C (112°F) in a discharged condition for four weeks.
At the end of four weeks the two batteries were recharged using a constant voltage (CV) charger at 14.7V per battery. As the graph below shows, both samples were able to recover nicely from this extreme case of abusive storage.
Recovery from high temperature (50°C) discharged storage
(Constant voltage recharge at 14.7V per module)
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