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Max Johansson
Joined: 09 Jan 2006
Posts: 25
Location: Helsinki, Finland
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 Posted: Sun Mar 05, 2006 3:05 am Post subject: 912uls battery for cold starting |
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RE: 912-ULS starting battery - lessons from cold Finland:
SAL, my friends in their 912ULS equipped 701 have had
a lot of battery related starting problems this winter
and this is what they recommend:
(1) Never mind to get the biggest Ampere-hour (Ah)
capacity, go for the minimum internal resistance
(milliohms) instead.
(2) Make the battery cables short and exchange the
starting current cables to low resistance types,
typically thick, and expensive and with soldered ends.
(3) The engine grounding strap is equally important.
(4) Buy a spare relay and try with that if you suspect
that you might for some reasons have increased relay
contact resistance. Good to have as a spare anyhow.
(5) Use the correct starting procedure, that is no
throttle at all when the choke is engaged and use
throttle only after the engine has started.
The battery they finally selected was a low-resistance
VARTA of less than the required 17Ah capacity but with
the lowest internal resistance thus giving the highest
starting current. Today they are surprised if the engine
does not start at the first try even if not pre-heated.
The battery weight savings was unfortunately eaten up
by the heavier cables. On the positive side the battery
allows faster charging with a mains connected charger.
Hopefully these hints are helpful
regards
Max
CH701-912ULS builder in Helsinki
[quote] --
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_________________
Max
Max Johansson, Helsinki, Finland
Building a CH701SP-912S
on CZAW amphibian floats |
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David X
Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA
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| Posted: Mon Mar 06, 2006 8:56 am Post subject: Re: 912uls battery for cold starting |
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There are several VARTA models. Can you recommend a specific model?
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Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE |
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Max Johansson
Joined: 09 Jan 2006
Posts: 25
Location: Helsinki, Finland
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| Posted: Mon Mar 13, 2006 3:00 am Post subject: 912uls battery for cold starting |
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David
The starting battery successfully used for our 912 and 912S engines
have been selected from the VARTA LF range of motor cycle batteries.
The Varta LF range of motor cycle batteries is suited for offroad conditions
and is tilt, leak and shockproof - and due to having a fixed electrolyte,
it will not leak even upside down. These batteries are also absolutely
maintenance free, checking and refilling with water is not necessary.
Thes LF batteries have also a very low level of self-discharge, resulting
in a long service life. But it is the low internal resistance that makes
the LF range attractive for home-builders using the 912. This is due to
the fact that the LF range test starting currents exeed those required
by the DIN and EN industrial norms.
Varta LF type 508-901-015-3104 12V, 9 Ah, 200 amps cold cranking current
Varta LF type 511-901-014-3104 12V, 11 Ah, 220 amps cold cranking current
Varta LF type 518 901 026 3104 12V, 18 Ah, 260 amps cold cranking current
Even a still smaller LF battery is capable of starting your Rotax.
A LF battery of only 6 Ah (amperehours) capacity has been used with success
as a starting battery for a 912S, but this battery was installed mainly
for weight reasons and a higher Ah capacity is recommended.
All these batteries exhibit unusually low internal resistance resulting
in a high starting current resulting in enough rpm to ensure quick
startup of the 912 engine, and thus minimizing mechanical shaking.
It is also well worth to install the heavy duty Rotax starter, but you
might already have one as the 912S engines now are delivered with it.
VARTA is just one quality manufacturer, well known in Europe, there must be
others in US with the same kind of specifications. Just go for the lowest
internal resistance, to provide more than 200 amps of cold start current.
regards
Max
Electrician for several 912 equipped homebuilts, including my own
[quote] --
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
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_________________
Max
Max Johansson, Helsinki, Finland
Building a CH701SP-912S
on CZAW amphibian floats |
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