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Effects of temperature on VRLA battery performance 
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Post Effects of temperature on VRLA battery performance
As we know, VRLA battery would have an infinite life - especially if it is not being "used" (cycled) and only remains on continuous charge being maintained for eventual use. However, this is not the case. The typical AGM VRLA battery will eventually decline in capacity and fail due to grid corrosion and drying of the electrolyte as a result of continuous overcharge. Everything else being equal, this will occur as a result of the design of the battery including plate grid thickness, oxygen recombination cycle efficiency and the quantity of reserve electrolyte. Since the grid corrosion and electrolyte during are a direct function of the float current, it is important to control the float current to that required to maintain the cell fully charged while minimizing overcharge due to excess float current.
The effects of temperature on valve-regulated lead acid battery performance are quantified for the following areas:
(1) The capacity-temperature relationship (dC/dT) for discharge rates of 0.17 to 8.0 hours and a temperature range of 30 to 140°F (-1 to 60°C); (2) empirical equations are derived to allow the calculation of dC/dT for most discharge rates;
(3) The external surface temperature which best tracks the cell internal temperature during discharge was found to be the container wall surface, parallel to the plates;
(4) Tests in which the -3 mV/°C coefficient is applied to prevent thermal runaway are shown to cause negative plate self-discharge at temperatures as low as 37°C (99°F);
(5) A container wall surface temperature was found to be within 2°C of the internal cell in lift: tests at 50°C (122°F);
(6) Experimental results indicated that cell failure due to negative plate self-discharge at 25°C may not be detected in elevated ambient or life test temperatures.

Nov 14th, '11, 01:58
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