If the voltage increases as you rev the engine, without any extra load, your electron pump is pumping.

Connect a headlight for 20min.  With an 18AH should shine strong.  A battery near the end of its life will die off within a minute.

The only true way to know if you have enough battery reserve is to go flying, turn off everything except what you need for safe flight, then cut the power to the electron pump so that your running on just battery.  A stop watch will let you how long the battery will keep everything going.  I think it would be patronizing to point out the obvious defect in this plan.

A major complication with running off a battery is that different electronic components will stop operating at different voltages;  but, whether it is the fuel pump, the ignition or the control computer, the first component to stop will make everything suddenly quiet.  Which part goes first is not necessarily obvious.

Seeing how long it will idle on the ramp with just the battery is a good first approximation.


Bill Bradburry <bbradburry@bellsouth.net> wrote:

>Sounds like your alternator was not running while you were reading below 13
>V???
>
>
>
>Bill B
>
>
>
>  _____  
>
>From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
>Behalf Of bktrub@aol.com
>Sent: Friday, May 25, 2012 8:14 PM
>To: Rotary motors in aircraft
>Subject: [FlyRotary] Fwd: Batteries
>
>
>
>
>
>
>
>-----Original Message-----
>From: Brian Trubee <bktrub@yahoo.com>
>To: bktrub <bktrub@aol.com>
>Sent: Fri, May 25, 2012 5:11 pm
>Subject: Fw: Batteries
>
>
>
>
>
>----- Forwarded Message -----
>From: Brian Trubee <bktrub@yahoo.com>
>To: Rotary engine <rotaryeng@earthlink.net>
>Sent: Friday, May 25, 2012 5:11 PM
>Subject: Batteries
>
>
>
>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/12v
>olt/PS-12180_11_Feb_21.pdf
><http://www.power-sonic.com/images/powersonic/sla_batteries/ps_psg_series/12
>volt/PS-12180_11_Feb_21.pdf >  ;. They are on separate contactors, 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 suitablitiy of
>these batteries and suggestions on how to test them out for holding a charge
>or otherwise deterining their suitablity 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
>
>
>