Battery Problems

<body topmargin="0" leftmargin="0" marginheight="0" marginwidth="0"> <table cellpadding="0" cellspacing="0" border="0" height="100%"> <tr> <td valign="top" width="130" bgcolor="#0000FF" text="#080000" background="061f0c00egayea.jpg"> <div> <b>Batteries Digest</b> </div> <div> <b> Navigator</b> </div> <div> <b>Topics</b> </div> <div> <b></b> <table border="2" cellpadding="2" cellspacing="1" width="98" bordercolorlight="#C0C0C0" bordercolordark="#808080" frame="BOX" rules="ALL" hspace="0" vspace="0"> <tr> <td valign="top" height="16" width="86"> <div> <a href="index.htm" target="_top" title="Home Page"><u><b>Home</b></u></a> </div> </td> </tr> <tr> <td valign="top" height="16" width="86"> <div> <a href="batteries_topics.htm" target="_top" title="Batteries Topics"><u><b>Batteries</b></u></a> </div> </td> </tr> <tr> <td valign="top" height="19" width="86"> <div> <a href="fuel_cells.htm" target="_top" title="Fuel Cells"><u><b>Fuel Cells</b></u></a> </div> </td> </tr> <tr> <td valign="top" height="16"> <nobr></nobr> <div> <a href="photovoltaics_topics.htm" target="_top" title="Photovoltaics Topics"><u><b>Photovoltaics</b></u></a> </div> </td> </tr> <tr> <td valign="top" height="16"> <nobr></nobr> <div> <a href="miscellaneous_topics.htm" target="_top" title="Miscellaneous Topics"><u><b>Miscellaneou</b></u></a><a href="miscellaneous_topics.htm" target="_top" title="Miscellaneous Topics"><u><b>s</b></u></a> </div> </td> </tr> </table> </div> <div> <b>Departments</b> </div><br> <div> <table border="2" cellpadding="2" cellspacing="1" width="98" bordercolorlight="#C0C0C0" bordercolordark="#808080" frame="BOX" rules="ALL" hspace="0" vspace="0"> <tr> <td valign="top" height="16"> <nobr></nobr> <div> <nobr><a href="advertising.htm" target="_top" title="Advertising"><u><b>Advertising</b></u></a></nobr> </div> </td> </tr> <tr> <td valign="top" height="16"> <nobr></nobr> <div> <nobr><a href="corrections.htm" target="_top" title="Corrections"><u><b>Corrections</b></u></a></nobr> </div> </td> </tr> <tr> <td valign="top" height="16" width="86"> <div> <b> </b><a href="meetings.htm" target="_top" title="Meetings"><u><b>Meetings</b></u></a> </div> </td> </tr> <tr> <td valign="top" height="16" width="86"> <div> <a href="suppliers.htm" target="_top" title="Suppliers"><u><b>Suppliers</b></u></a> </div> </td> </tr> <tr> <td valign="top" height="16"> <nobr></nobr> <div> <nobr><a href="index.htm" target="_top" title="Home Page"><u><b>What's New</b></u></a></nobr> </div> </td> </tr> <tr> <td valign="top" height="16"> <nobr></nobr> <div> <nobr><a href="search.htm" target="_top" title=" Search"><u><b>Search Tool</b></u></a></nobr> </div> </td> </tr> </table> </div><br> </td> <td valign="top" bgcolor="#A6CAF0" text="#080000"> <div> <table border="2" cellpadding="2" cellspacing="1" width="620" bordercolorlight="#C0C0C0" bordercolordark="#808080" frame="BOX" rules="ALL" hspace="0" vspace="0"> <tr> <td valign="top" height="214"> <nobr></nobr> <div> <nobr>BatteryProblems040128</nobr> </div><nobr><br> <br> <br></nobr> <div> <nobr><b><img src="4a012470.jpg" border="0" width="274" height="71" align="bottom" hspace="0" vspace="0"></b></nobr> </div><nobr><br> <br></nobr> <div> <nobr><b>Battery Problems</b></nobr> </div> </td> <td valign="top" width="325"> <div> <b>You can only get the</b> <font size="3" color="#FF0000" face="Arial"><b>latest</b></font> <b>Batteries Digest Newsletter when you request your free monthly subscription to  BD as an Acrobat file by email. Just send us an email request to:</b> </div> <div> <b> Staff@www.BatteriesDigest.com.</b> </div> <div> <b>Include your name, position, organization, and phone number. This information will be held in confidence. No junk email will ever be sent nor will the information be sold to others.</b> </div> </td> </tr> </table> </div><br> <div> ( January 2004)  <a name="non_correctable_battery_problems" id="non_correctable_battery_problems"><img border="0" src="1x1.gif" height="1" align="bottom" width="1" hspace="0" vspace="0"></a><font size="4" color="#000000" face="Arial"><b>Non-Correctable Battery Problems</b></font> </div> <div> Some rechargeable batteries can be restored through external means, such as applying a full discharge. There are, however, many defects that cannot be corrected. These include high internal resistance, elevated self-discharge, electrical short, dry-out, plate corrosion and general chemical breakdown. </div><br> <div> The performance loss of a battery occurs naturally as part of usage and aging; some is hastened by lack of maintenance, harsh field conditions and poor charging practices. This paper examines the cause of non-correctable battery problems and explores ways to minimize these breakdowns. </div><br> <div> <b>High Self-discharge</b> </div> <div> All batteries are affected by self-discharge. This is not a defect per se, although improper use enhances the condition. Self-discharge is asymptotical; the highest loss occurs right after charge, and then tapers off. </div><br> <div> Nickel-based batteries exhibit a relatively high self-discharge. At ambient temperature, a new nickel-cadmium loses about 10% of its capacity in the first 24 hours after charge. The self-discharge settles to about 10% per month afterwards. Higher temperature increases the self-discharge substantially. As a general guideline, the rate of self-discharge doubles with every 10<font size="2" color="#000000" face="Symbol">°</font>C (18<font size="2" color="#000000" face="Symbol">°</font>F) increase in temperature. The self-discharge of nickel-metal-hydride is about 30% higher than that of nickel-cadmium. </div><br> <div> The self-discharge increases after a nickel-based battery has been cycled for a few hundred times. The battery plates begin to swell and press more firmly against the separator. Metallic dendrites, which are the result of crystalline formation (memory), also increase the self-discharge by marring the separator. Discard a nickel-based battery if the self-discharge reaches 30% in 24 hours </div> <div> The self-discharge of the lithium-ion battery is 5% in the first 24 hours after charge, and then reduces to 1% to 2% per month thereafter. The safety circuit adds about 3%. High cycle count and aging have little effect on the self-discharge of lithium-based batteries. </div><br> <div> A lead-acid battery self-discharges at only 5% per month or 50% per year. Repeated deep cycling increases self-discharge. </div> <div> The percentage of self-discharge can be measured with a battery analyzer but the procedure takes several hours. Elevated internal battery resistance often reflects in higher internal battery resistance, a parameter that can be measured with an impedance meter or the <i>OhmTest</i> program of the Cadex battery analyzers. </div><br> <div> <b>Cell matching</b> </div> <div> Even with modern manufacturing techniques, the cell capacities cannot be accurately predicted, especially with nickel-based cells. As part of manufacturing, each cell is measured and segregated into categories according to their inherent capacity levels. The high capacity `A' cells are commonly sold for special applications at premium prices; the mid-range `B' cells are used for commercial and industrial applications; and the low-end `C' cells are sold at bargain prices. Cycling will not significantly improve the capacity of the low-end cells. When purchasing rechargeable batteries at a reduced price, the buyer should be prepared to accept lower capacity levels. </div><br> <div> The cells in a pack should be matched within +/ </div> </td> </tr> </table> </body>