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<DIV>Question: Are the batteries really failing? I haven't seen one in many years. I guess that is happening but the percentage must be very small. Any feedback is welcome. Clearly the highest percentage is easy to guess: "pilot failure" for about 99.9999% of the times. </DIV>
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<DIV>Have a nice weekend, </DIV>
<DIV> </DIV>
<DIV>Vicente Bortone</DIV>
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<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">-------------- Original message -------------- <BR>From: "John Ferrell" <johnferrell@earthlink.net> <BR>
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<DIV><FONT face=Arial size=2>I think this procedure is essential with NiMh packs. You can do OK with individual cells (like digital camera applications) using a charger that shuts down with peak detection. When you charge a set of NiMh's in series with a peak detector it stops with the first cell peaking. It doesn't hurt anything, you just don't get a full charge on the pack. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It is possible to build a pack charger that charges each cell individually but it gets cumbersome. Especially when you consider that an occasional 16 hour charge will solve the problem.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I find the same procedure also works well for NiCad's. If you reset the peak charger and restart it you will cook the batteries and suffer short battery life. NiCad's normally fail shorted and you have enough power to land. NiMh's normally fail open and you will need another airplane to go with your new battery.</FONT></DIV>
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<DIV><FONT face=Arial size=2>That is also why I use NiMh in the transmitter and NiCads in the flight packs.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>John Ferrell <BR><A href="http://dixienc.us/">http://DixieNC.US</A><BR></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=bob@toprudder.com href="mailto:bob@toprudder.com">Bob Richards</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=nsrca-discussion@lists.nsrca.org href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, February 24, 2006 6:31 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] NiMH Question</DIV>
<DIV><BR></DIV>
<DIV>The problem with some of the cyclers is that they do a fast charge, then discharge, then fast charge, etc. without ever "equalizing" the cells. The problem is that one or more cells in the pack can become depressed more than others, and without a good equalization charge they will never be topped off fully since the cells that ARE fully charged will trip the peak detection when they come up.</DIV>
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<DIV>I suggest doing a C/10 charge for 16 hours, then cycle the pack and see what happens.</DIV>
<DIV> </DIV>
<DIV>Bob R.</DIV>
<DIV><BR><BR><B><I>Michael Cohen <precisionaero@comcast.net></I></B> wrote:</DIV>
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<DIV><FONT face=Arial size=2>I am cycling my batteries and getting ready for the flying season. On my initial 5 cycle run at my NiMH batteries, ! both my 1650 mAh packs cycled very low. One pack that I have not used since end of November only cycled up to 850 mAh and the other pack I have not used since end of September only cycled up to 1000 mAh. My charger is set to 5 cycles, charge and discharge are set to .65 amps with a cutoff voltage at 1.1 Volts per cell. I am now trying 1.00 amp charge/discharge with a 1.0 volt per cell cutoff and it is looking better, but I have some questions:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>1) Did I damage the batteries by letting them self-discharge too low? I know NiMH batteries have a higher self discharge rate than NiCD batteries, but I am not aware letting the NiMH batteries run down could cause damage.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>2) Is this a normal behavior? Maybe NiMH just need a little more juice at the beginning of the season.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>3) Is the cold garage a factor?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thoughts?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Mike Cohen</FONT></DIV>_______________________________________________<BR>NSRCA-discussion mailing list<BR>NSRCA-discussion@lists.nsrca.org<BR>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</BLOCKQUOTE><BR>
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