Reference/Battery Charging Stuff NiMH

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" rowspan="2" width=156 BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="00e9cc00egerdp.jpg"> <div> <B> <STYLE>  </STYLE>  </B></div> <bR> <bR> <bR> <bR> <bR> <div> <B> <TABLE BORDER="0" CELLPADDING="2" CELLSPACING="1" WIDTH="97" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP HEIGHT= 313 ><NOBR><div> <A HREF="index.htm" TARGET="_top" TITLE="Home Page"><U><B>Home</B></U></A></div> <div> <A HREF="id2.htm" TARGET="_top" TITLE="Archive"><U><B>Archive</B></U></A></div> <div> <A HREF="id5.php" TARGET="_top" TITLE="Contact"><U><B>Contact</B></U></A></div> <div> <A HREF="id6.htm" TARGET="_top" TITLE="Downloads"><U><B>Downloads</B></U></A></div> <div> <A HREF="id7.htm" TARGET="_top" TITLE="Events"><U><B>Events</B></U></A></div> <div> <A HREF="id8.htm" TARGET="_top" TITLE="For Sale"><U><B>For Sale</B></U></A></div> <div> <A HREF="id9.htm" TARGET="_top" TITLE="Galleries"><U><B>Galleries</B></U></A></div> <div> <A HREF="id14.htm" TARGET="_top" TITLE="Games"><U><B>Games</B></U></A></div> <div> <A HREF="id15.htm" TARGET="_top" TITLE="Links"><U><B>Links</B></U></A></div> <div> <A HREF="id16.htm" TARGET="_top" TITLE="Magazine"><U><B>Magazine</B></U></A></div> <div> <A HREF="id17.htm" TARGET="_top" TITLE="Newsletter"><U><B>Newsletter</B></U></A></div> <div> <A HREF="id18.htm" TARGET="_top" TITLE="Reference"><U><B>Reference</B></U></A></div> <div> <A HREF="id88.htm" TARGET="_top" TITLE="Video"><U><B>Video</B></U></A></div> <div> <A HREF="id19.htm" TARGET="_top" TITLE="Weather"><U><B>Weather</B></U></A></div> </NOBR></tD> </tR> </TABLE></B></div> <bR> </td> <td valign="top" colspan=2 height=100 BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="00f00640egerdp.jpg"> <bR> <bR> <bR> <div> <I><B>Reference</B></I></div> <div> <B> </B></div> </td> </tr><tr> <td valign="top" height=380 colspan=2 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <FONT SIZE="2" COLOR="#000000" FACE="Arial" > <STYLE>  </STYLE>  </FONT><B><<   </B><A HREF="id63.htm" TARGET="_top" TITLE="Reference/BMFA A Test"><U><B> >></B></U></A></div> <div> <TABLE BORDER="0" CELLPADDING="25" CELLSPACING="1" WIDTH="602" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=CENTER HEIGHT= 1475 WIDTH="550"><div> <B><U>Battery Stuff</U></B></div> <bR> <div> Be careful charging batteries of a higher capacity than usual when using the charger supplied with your radio gear. Beyond a certain point the battery may never peak. According to several articles if the capacity of the battery is too large it will never peak if the charge current is to low, no matter how long you leave it charging. Below is a list of charge rates to suite various capacity NiCads and NiMH batteries. These figures came with a charger purchased a little while ago. </div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <TABLE BORDER="4" CELLPADDING="2" CELLSPACING="1" WIDTH="353" BORDERCOLORLIGHT="#FFCC00" BORDERCOLORDARK="#FF9900" FRAME="BOX" RULES="ALL" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=CENTER BGCOLOR=#FFFFFF HEIGHT= 55 WIDTH="88"><div> <B>Charge Rate </B></div> <div> <B>[ mA ]</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="55" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF><NOBR><div> <B>Battery Capacity  [ mAh ]</B></div> </NOBR></tD> </tR> <tR> <tD VALIGN=CENTER BGCOLOR=#FFFF99 HEIGHT= 16 WIDTH="88"><div> <B>50 mA</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFF99 WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="16" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFF99 WIDTH="164"><div> <B>300 to 800 mAh</B></div> </tD> </tR> <tR> <tD VALIGN=CENTER BGCOLOR=#FFFFFF HEIGHT= 16 WIDTH="88"><div> <B>60 mA</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="16" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="164"><div> <B>400 to 900 mAh</B></div> </tD> </tR> <tR> <tD VALIGN=CENTER BGCOLOR=#FFFF99 HEIGHT= 16 WIDTH="88"><div> <B>80 mA</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFF99 WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="16" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFF99 WIDTH="164"><div> <B>600 to 1200 mAh</B></div> </tD> </tR> <tR> <tD VALIGN=CENTER BGCOLOR=#FFFFFF HEIGHT= 16 WIDTH="88"><div> <B>140 mA</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="16" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="164"><div> <B>1200 to 1800 mAh</B></div> </tD> </tR> <tR> <tD VALIGN=CENTER BGCOLOR=#FFFF99 HEIGHT= 16 WIDTH="88"><div> <B>180 mA</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFF99 WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="16" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFF99 WIDTH="164"><div> <B>1500 to 2200 mAh</B></div> </tD> </tR> <tR> <tD VALIGN=CENTER BGCOLOR=#FFFFFF HEIGHT= 16 WIDTH="88"><div> <B>500 mA</B></div> </tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="71"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="16" ALIGN="bottom" WIDTH="71" HSPACE="0" VSPACE="0"></tD> <tD VALIGN=CENTER BGCOLOR=#FFFFFF WIDTH="164"><div> <B>4000 to 7000 mAh</B></div> </tD> </tR> </TABLE></div> <bR> <div> Here's the formula for working out your charge time with any given battery capacity and charge rate.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <IMG SRC="258d7220.png" border=0 width="215" height="34" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> e.g. Say you want to charge a 700 mah nicad on a 50 mah charger and want to know how long to charge it for.... </div> <bR> <div> 700  x 1.4 = 980 divided by 50 = 19.6 hours. </div> <bR> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>Advantages of Nickel-Metal Hydride Cells</B></div> <bR> <div> I've been using Nickel Metal Hydride (NiMH) batteries for two years now with no trouble at all. The main reason I began using them was to save weight. The NiMH offers the same capacity for roughly half the size and weight and also eliminates some of the concerns over the use of heavy metals in Nicad cells. </div> <bR> <div> Also there is no 'memory' effect as in NiCads. The problem of 'memory' or voltage depression has long been of concern when using nickel-cadmium cells. In some applications where nickel-cadmium cells are routinely partially discharged, a depression in the discharge voltage profile of approximately 150 mV per cell has been seen when the discharge extends from the routinely discharged to rarely discharged zones. In other words, if you routinely have four flights per session and then decide, one day, to have a fifth, you may experience the 150 mv drop per cell just mentioned. The source of the effect is generally agreed to be in the structure of the cadmium electrode. As we all know, regular cycling keeps this effect at bay.  With the elimination of cadmium in the nickel-metal hydride cell, 'memory' is no longer a concern. </div> <bR> <div> The only area that is of concern seems to be overcharging. All I can say on this is that I've treated my NiMH's in exactly the same manner as I treat my NiCads with no ill effects so far. For example, on a five servo set up, if I had five flights during the last session they get the full 17 hrs charge. (600mah @ 50 ma = 16.8 hours) If I had, say, two or three flights then I'd charge overnight, say ten or eleven hours. So far I've encountered no problems. Just don't let them get warm. NiMH's vent hydrogen gas when hot whereas NiCads vent oxygen. Wonder if this'll have an effect on the 'black wire syndrome'? </div> <bR> <div> I've often monitored the voltage (no load) during a days flying. The cell usually starts out at around 5.8 volts and drops to around 5.5 volts after the first flight from which point it seems to flatten out at about a .1 volt loss for every flight thereafter. I always quit at 5 volts anyhow but it seems that the voltage drop is less after each successive flight. I've had that sixth flight many times without a problem but wouldn't go further. One day I'll connect a Nimh to a 250 ma load and monitor the voltage drop against time. </div> <bR> <bR> <div> <B><U>NIMH versus NICAD</U></B><B> </B><B>(courtesy of somewhere on the net)</B></div> <bR> <div> Nominal Voltage - Same (1.25V) </div> <div> Discharge Capacity - NiMH up to 40% greater than NiCd </div> <div> Discharge Profile - Equivalent </div> <div> Discharge Cutoff Voltages - Equivalent </div> <div> High Rate Discharge Capability - Effectively the same rates </div> <div> High Temperature (>35C) Discharge Capability - NiMH slightly better than standard NiCd cells </div> <div> Charging Process Generally similar; multiple-step constant current with overcharge control recommended for fast charging NiMH </div> <div> Operating Temperature Limits - Similar, with NiMH performing slightly better at cold temperatures. </div> <div> Self-Discharge Rate - Similar to NiCd </div> <div> Cycle Life - Similar to NiCd </div> <div> Mechanical Fit - Equivalent </div> <div> Mechanical Properties - Equivalent </div> <div> Selection of Sizes/Shapes/Capacities - Equivalent </div> <div> Handling Issues - Similar </div> <div> Environmental Issues - Reduced with NiMH because of elimination of cadmium toxicity concerns. </div> <div> So, go get a NiMH!</div> <div> <I>FF 21.08.01</I></div> </tD> </tR> </TABLE></div> <div> <B> <<   </B><A HREF="id63.htm" TARGET="_top" TITLE="Reference/BMFA A Test"><U><B> >></B></U></A></div> <bR> </td> </tr></table></body>