Our 2.8 kg 8 amphr battery is however fine for cranking although it has only
M4 nuts to deter users from over tightening the contacts and damaging the
battery. I use the 13 amp version on my 912 and its been working very well
for almost three years.
Our batteries
Ahr kg L W H Amp Price Inc VAT
51 17.5 220 121 255 1400 210.00 246.75
35 12.5 250 97 204 1100 138.00 162.15
26 9.0 250 97 152 850 130.00 152.75
16 6.1 182 77 168 480 80.00 94.00
13 4.9 176 84 130 400 80.00 94.00
14 5.0 200 77 137 550 79.00 92.83
8 2.8 138 86 101 300 70.00 82.25
cranking current = 10 minutes discharge to an end voltage of 9.8 v at
constant power discharge.
The 14 amphr is the one we now usually stock with the others available to
special order. Note the 550 amphr starting current.
Jerry
LTS@avnet.co.uk
www.avnet.co.uk/touchdown
----- Original Message -----
From: "Shaun Simpkins" <shauns@hevanet.com>
Subject: Re: Looking down the road at batteries
> Thanks for providing a working point of reference, Fred. I appreciate the
> correction.
>
> Not having the actual equipment at hand, one has to use manufacturer's
> specifications, which are
> often quite conservative. I did try to approximate typicals on the engine
> stuff. And avionics power
> drain is so variable...Those of you out there in love with the Garmin
> 430/530 must prepare for a
> stuff is far more energy efficient. For example. And 2A typical for a
fuel
> pump? OWWch.
>
> But we still have to contend with 6-8A drain for position/nav lights and
> 4-7A drain for strobes.
> So for night flight, we'd need to add the SD-8 and call it the "night
> alternator"...
>
> On the battery front - that 7.2AH/12 RG battery sold by B&C is not
> recommended by them for
> cranking since the terminals are not bolt-down but fast-on and can't
handle
> high currents. Backup
> only. This leaves the 20AH/12 RG battery at 15.3 lbs as the energy
density
> champ. 300CCA min,
> -20C, 30 sec. B&C does discharge test their batteries, 60F/10 sec/8.5V
min.
> I have some numbers.
>
> Shaun
> ----- Original Message -----
> From: "Fred Fillinger" <fillinger@ameritech.net>
> Subject: Re: Looking down the road at batteries
>
>
> > You overall analysis is good, Shaun, but the actual current draw will
> > not be the same as what the mfr says and is often high. Transponders,
> > e.g., are spec'd at max reply rate of 500/sec. On my 2 electric
> > gyros, xpondr, GPS map/comm, and monitor draw is less than 1/2 the 11A
> > you've estimated, based on actual measurement. Thus, even the SD-8
> > vacuum pad alternator could be enough add'l power if one shops also
> > for current draw on avionics and is content with minimum goodies on
> > the panel.
> >
> > Regards,
> > Fred F.
> >
> > Shaun Simpkins wrote:
> > >
> > > The 16AH hour minimum quoted on the Europa factory schematic is Rotax'
> > > recommended minimum battery size for the 914 (section 9.4.14).
> > >
> > > Note also that available power is not the full 18A; according to
section
> > > 19.5, the maximum loading from the fuel pumps, TCU, servo motor, and
> > > warning lamps is 8A.
> > > Typical for each pump is 2A; the TCU, probably about 0.15A; the rest
are
> > > intermittent. So at best, we have perhaps 15A available to us.
> Airmaster
> > > CS prop loads are also intermittent. Another consideration is the
> battery
> > > charging capacity of the system. I believe the FAA rule of thumb is
> that
> > > 20% of the alternator capacity should be reserved for charging. Your
> > > personal specs may differ, but this is another 3.6A off the top.
> > >
> > > Thus, the 18A alternator is able to power about 11A of external loads
> with
> > > charging reserves. That's what basic electric gyros, VFR nav/comm,
> xnpndr,
> > > and engine monitor will eat up.
> > >
> > > Incidentally, this thread was last active in late 2000. Check out the
> > > archives. Many are running heavy electrical loads on the factory
> alternator,
> > > but probably with very small charging reserves.
> >
>
>
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