Yes – a load test involves a low load current. You don’t draw 200 amps and see how long that lasts 
A load test does no harm.
I can’t recall the details for Concorde but it is something like 1C i.e. a 15Ah battery is loaded to 15A. With the alternator field OFF, my plane draws 25A! And a lot of planes draw a lot more.
The capacity [load] test consists of placing a specified load on the fully-charged battery and then measuring the time it takes for the battery to be drawn down to a specified voltage (10 volts for a 12-volt battery, 20 volts for a 24-volt battery).
If your battery’s rated capacity is 25 ampere-hours, then it should be able to deliver 25 amps for 60 minutes or 42 amps for 30 minutes. (Notice the discharge time does not vary linearly with discharge current.) If the capacity test reveals that the battery has at least 80% of its rated capacity (in this example, at least 48 minutes at 25 amps or 24 minutes at 42 amps), then it’s considered airworthy and can be returned to service. On the other hand, if it has less than 80% of rated capacity, it should be replaced.
Typically, the test is done @ 30 minutes @ the high amp load.
alioth wrote:
We used to use the Gill flooded cell batteries, the last one didn’t even last 3 years
My 24 V Gill battery is from 2006 and is still ok. In the winter season I take the battery home to protect her from frost.
Michael is right that these capacity tests are very hard on the battery. Concorde recommends C1 or even more: http://www.concordebattery.com/otherpdf/TB13.pdf
Here’s the Concorde maintenance manual that has the procedure described in detail: http://www.concordebattery.com/otherpdf/5-0171.pdf
I built my own fixture using 12V halogen lamps.
But 1C/C1 is nothing – 15A for a typical aircraft battery.
The starter motor draws 100-300A.
1hr 25 mins – does he say anything interesting?
Peter wrote:
1hr 25 mins – does he say anything interesting.
It depends on your level of experience. I watched it two years ago, but had forgotten most of it, so it was a good refresher for me. Of course all information exists somewhere on the internet, but it is widely dispersed, and having it summarized in less than one hour is more efficient. Just lie relaxed on a coach and have the content be pushed to you. The convenience factor is hard to beat after a stressful work day. :-)
The convenience factor is hard to beat after a stressful work day
To each their own, but after any day at work, not even a particularly stressy one, I am reluctant to pain my poor old brain by inflicting more facts and information onto it in the blissful hours of evening relax.
The reason I asked that question about an Executive Summary was because while Mike Busch is a great guy and very knowledgeable, his videos could do with about 90% being cut out. And I get a bad back sitting in front of my PC for 1.5hrs
In Europe, on the certified lead-acid market, there are basically Gill and Concorde, with Concorde being of vastly better quality (at a higher price). The vast majority of planes were certified with Gill batteries and a lot of engineers are afraid to sign off a Concorde replacement, and there has been much discussion around that. In the meantime, most “smarter” owners have quietly just put in the Concorde ones 
Gill have recently started making solid electrolyte batteries like the Concorde ones, but I don’t think there has been much feedback on them as yet.
I will watch it when I get a chance and will post anything earth-shattering.
