[NSRCA-discussion] Kavan starter with Li-Po battery

[Don Ramsey]

Adrian,

I've had the windings of the armature break and stop the rotation.  I did
once epoxy them back in place and it work for a while but soon failed.  Did
you take the starter apart? If this is the problem it's easy to spot.  I
couldn't find anyone who sold the armature as a part.  Anyone know of a
source?

BTW, the secret to reassembly is using 2 pins through the top of the started
to hold the brushes apart.  Straight pins will work.

Don

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
adriancwong at earthlink.net
Sent: Friday, August 22, 2008 2:26 AM
To: NSRCA-discussion at lists.nsrca.org
Subject: [NSRCA-discussion] Kavan starter with Li-Po battery

To all,

I have been using a Kavan starter with a 10 cell, 12V, 2.2A ni-cd pack for
many years with good results. However, ever since the 1400DZ came out, it
required more cranking power from the starter and one charge would normally
only last for two weekends of flying. By the time the 160Z came along, I've
switched to a 12 cell, 14.4V, 2.2A ni-cd. Again, it performs flawlessly.
However, as you are aware, the 12 cell pack is really heavy.

At the beginning of this year, I have switched to two li-po packs - 2 cell,
7.4V, 2100 mAh with 15C continuous, 20C burst on each pack. The first
starter lasted for 6 months until it stopped working after normal wear and
tear. The second one stopped working - frozen solid - after about 2 months -
I could tell this one had some strange noise to began with, like something
was rubbing inside. Therefore, I wasn't surprise that it stopped working
only after two months. 

The third starter I rigged up was relatively new, and has been working
perfectly, until this afternoon. After the first flight, it was frozen solid
again. Like the second starter, it didn't give any warning sign whatsoever -
slowing down, getting hot on either the starter or the battery.

My question:-

1) Am I using the wrong battery pack? 

2) Too high of a discharge rate because it's a li-po instead of ni-cd?

3) Once the starter is frozen, is there a way to fix it? Sure hate to keep
tossing away starters.


Any advice or suggestion from you electric gurus are greatly appreciated. 

Thanks in advance,

Adrian


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