The alternator checked out OK. The last flight I flew I left both the
  fuel pumps on
   the whole flight. Usually, I only use both when on take off and landing.
  Maybe the
   current draw was too much for the 40 amp alternator. The guy at the
  alternator shop
   said that at and above 2/3 the rated current, the voltage starts
  to drop off. Hmm. I  have two of the fuel pumps that Tracy sells, I
  don't know what the current draw on  them is, a dynon D10- 1 amp
  aproximately, Xcom radio- . 5 amp, Terra transponder- .75  amps, EC2
  and EM2- ? amps, 4 LS1 coils- ? amps and two 18 AH saturated mat batteries.
   Maybe time to do a current check on the batteries and trade one
  out for a new one. I  have a new one, the old ones are coming up to
  two years old. I have them on a float  charger anytime I'm not
  running the engine.   Any thoughts?

   Brian Trubee

   You need an ammeter.

   Paul Lamar

   Brian,
               In my opnion you do not need a ammeter as only more
  weight! The voltmeter will tell you what state your battery is, you
  do not really need to know what the alternator is putting out. If
  the voltage is going down and the alt is OK then you alt is not up
  to the job! as dale? said put a clamp-on the alternator output and turn
  EVERYTHING on and watch the voltmeter and if the draw is more than say
  30 amps get a bigger alternator or ditch some of the load.
                John Burey
 .
  Get realistic John. The weight is ounces. You cannot have too much
  information. An ammeter gives an instant early warning of what can happen.
  If suddenly the ammeter shows a discharge the EFI and electronic ignition
  engine is
  going to stop sooner or later. You can then turn off non essential
   electric devices
  to give you more time to land. You will instantly know if you have solved
  the
  problem. You can't just pull over to the side of road and stop.

  Paul Lamar


 I generally don't like to wire an amp meter in the instrument panel
  as it would require either a 8 or 6 AWG gauge wire for a maximum
  curare of 40a or 50a, respectively .

  A good alternative is to wire in a low voltage warning light in addition
  to the
  voltage meter.

  Joel

  Another alternative is have a red warning light come on when there
  is discharge condition.

  Paul Lamar

  Use an induction coil ammeter with the coil around the main battery wire.
  Simple, just needs to be calibrated.

  Kevin Alderman



  Paul is correct with the idiot light. Use a LED red. Takes up almost no space
 in the panel and is highly visible when there is a problem. Check the voltage
 the LED is designed for and install a dropping resistor in series if required.
 A lower resistance will let it be brighter. Small wire from alternator light
 terminal to the LED, which saves weight.
  Note my previous post with Bosch fuel pump amps. Could be between 5A and
 15.5A. If yours are in the 15A range times two is 30 plus the panel and don't
 forget lights. You could be at the 40A output. You need to try a clamp-on amp
 meter for test to verify. Even if you measure the pump amps times 2.

 Dale Davies

WTF if weight is an issue empty the change in ya wallet, take a pee
before flying,  Do your checks, look at your gauges, then fly. you
know better mate, c'mon. Knowledge is power.

Graeme Riley

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