Subject: Batteries
From: rotaryeng
Date: 5/29/2012, 7:45 PM
To: AAAA Put this in the To box 


 I'm nearing the finish of my phase 1 testing, and am now looking
 for replacement  batteries. right now, I am using two of these:

  http://www.power-

sonic.com/images/powersonic/sla_batteries/ps_psg_series/12volt/PS-12180_11_Feb_21.pdf
   .
   They are on separate contact-ors, so I can use either or both when
  flying. I use both
   when starting. They are two years old, and today when I went
 flying I noticed that  the voltage was getting down to 11.6 volts.
 after landing, the voltage was up around
   12.3 volts. Usually I show around 13~13.6 volts when running. I always
  use a float
   charger specifically designed for these batteries when the plane
 is put away. Usually  the float charger shows a slow charge, but
 when I cam back from flying today the  charger was showing a fast
 charge, meaning that the batteries were discharged a fair  amount.
 Any comments on the suitability of these batteries and suggestions
 on how to  test them out for holding a charge or otherwise
 determining  their suitability or not for my plane. I have a 40 amp Nippondenso
  alternator, and
   run an Xcom radio, a terra transponder, Dynon D10, Tracys EM2 and
 EC2, and one fuel  pump(at a time unless landing or taking off) that
 draws around 4 and no more than 6  amps.

   Thanks,
   Brian Trubee

   The 11.6 V is normal for sealed lead acid battery when not
 charging.  Other people are using the same type successfully.  They
 need to be charged from time to time when sitting around.  My guess
 is every 2 weeks.

   Paul Lamar

   I'm pretty sure that this is a charging issue that just cropped up
 on this last  flight- I usually run in the upper 13s voltwise but
 noticed the low voltage while out  flying yesterday. My float
 charger will automatically go to float charge unless the  batteries
 are discharged when I put the charger on when I put the plane away.
 I will  then turn on the master to see if the charger goes to fast
 charge, which it will do  if there is a drain on the battery. So,
  what I deduce is that the charging system has  been working up
 until the last flight. It should be easy to troubleshoot the
 problem.  I'll post what I find after I find it.

   Any comments on  the suitability of the Powersonic PS 12180 NB batteries?
  I use two
   of them, they are 18 AH, so I suppose with the relatively small
 load I use in flight,  I should have a fair amount of reserve if the
 alternator quits.

   Brian

   The battery voltage when charging should be 13.5 to 14.8. Do you
 have an ammeter in  the circuit.

   Paul Lamar

   No ammeter.

   Brian Trubee

    Hi  Paul,
                     Re charging voltage into a 12 volt lead acid
  battery, most car regulators charge at between 13.8 hot weather and
 14.4 cold weather, the regulators are temperature compensated, I
 have found that if they are charging at less than 13.8 v (at least
 in Australia), the batteries will not fully charge, and conversely
 if charged at over
  14.4 v they will boil the guts out of the battery! Of course our
 temperature range is not as extreme as you have in the States;-) .
 Brian, if your voltage is getting that low when the engine is
 running at a moderate speed, your alternator is at fault, probably a
 diode bank has gone to diode heaven!! If the alternator is rated at
 40 amps it should be able to charge enough to keep the voltage above
 13 volts at a current draw of 40 amps, it sounds like you have
 nowhere near that load. If your batteries will start the engine they
 are good enough, just need the alternator to keep them charged,
  sounds like your float charger is keeping them charged then when
 you fly they are going flat!! When flying you should have a minimum
 of 14 volts by the time you have warmed up the engine and taxied to
 takeoff you should have 14 volts.                  John Burey.

     I have run across some charging problems with all good
 components. The terminals and cables may appear clean on the outside
 but if I take  off the cables there has been a black oxide on the
 posts of the battery.  It seems that this causes a resistance at the
 connection and prevents the battery from reaching full charge. While
 baking soda cleans off the corosion it doesn't do anything to this
 black oxide and it must be removed with a wire brush or sandpaper
 from both the battery posts and cables.

         Since the problem in this case seems to have occurred
 suddenly it is likely the diode bridge rectifier or brushes in the
 alternator. Years ago we could disconnect the battery while a car
 was running and if it quit the alternator was dead, however the
 newer alternators are damaged by the loss of a reference voltage.
 The instructions that come in the box with a new alternator often
 require the alternator to be unplugged while the battery is
 connected and the battery to be at full charge so that the proper
 reference voltage is available when the plug is inserted.

 george grimes


 A quick check to see if the regulator/brushes (the field circuit) is working
is to hold a screw driver close to the shaft at the pulley or at the rear
bearing. If it is magnetic those components are good. If not magnet, it is one
of them.

Dale Davies



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