Subject: Batteries
From: rotaryeng
Date: 5/29/2012, 8:23 AM
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



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