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Thank you Hamid-
You mean internal losses? The Concorde manual states that "The battery shall deliver a capacity of not less than 100% C1 (discharge time 1 h)". In the case of the RG35AXC C1 is 33 AH over the course of 1 hour. By using 30 AH I can make a rough estimate of what my options might be. Depending on the situation I would have extra capacity remaining in the primary battery as well. I wouldn't expect to be running at 60A. From what you said I can see that on approach with the battery drained down running high-current items might not work well. Thank you.
It may have sounded that I'd just continue on with everything fired up. Not so. The point I was trying to make was that some items would become unusable before others due to reduced voltage. My aim would be to navigate to the nearest airport and land safely rather than lose communication and have to remember lost radio procedure in a stressful situation.
It seems to me that my setup could operate on low voltage and still maintain good functionality overall. How would a single or dual glass panel system perform under those conditions and what current would be required?
I did overlook the electro-hydraulic system in the Lancair- my plane has engine-driven hydraulics with a hand pump as backup. I have used the hand pump in an emergency situation to lower gear and flaps. In an emergency with the battery drained I would expect to use the IV-P hand pump. Is the hand pump difficult to use or otherwise unreliable?
-Bill Wade
----- Original Message ----- From: "Hamid Wasti" <hwasti@lm50.com>
To: <lml@lancaironline.net>
Sent: Sunday, December 23, 2007 12:07 PM
Subject: [LML] Re: Glass Panel Backup
Bill Wade wrote:
If anything happens to the alternator or the other battery I know I have a conservative (and easy to figure) 30 Amp-hours before voltage drops to 10V.
You do realize that 30AH does not means 1A for 30 hours or 60A for 0.5 hours? The capacity of a battery goes down as you increase the current. Yes, I am talking CAPACITY, not just the time. In fact, the parasitics, which cause this accelerated decrease in capacity, increases as the square of the current. So as you increase the load, especially things like the hydraulic pump, pitot heat & landing lights, you may find that the battery does not last quite as long as you were counting on.
You may find it quite instructive to do a test on the ground (on jacks so you can move the gear) and see how long the battery actually lasts. The only down side to that is that after you torture your battery like that, you really ought to consider replacing it.
And when you are doing this test, remember to retract and lower the gear a second time to account for a missed approach or go-around.
Regards,
Hamid
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