C1 rate should discharge in 1h to 20V if full rated capacity (by definition) .
Cap checks at C1 rate always last <1h except a brand-new, top-5-percentile battery.
Ideally you should have a constant 15A discharge, but a constant resistor is good enough for your purpose, I just think you need more like 1.5ohm
2.7 ohms is close to C1 discharge (15Ah 24V battery), no?
Funnily enough I have a box here with the bits needed to build a proper constant current discharger, with a counter of seconds on it 
It’s just that the incentive to build it surfaces just once a year…
I also use the CTEK 4.0 AMG for the Concorde battery, and I even have a built-in connector in the rear of my plane to just snap in the charger to that connector. This had been installed many years ago, but in the last years nobody cared about that. I just had to buy a CTEK charger so that it would fit into this connector.
Initially, when I bought th plane, the battery was a bit on the low side, but the charger made it behave like new again. The connector in my plane has three lights to indicate battery status (green, yellow and red of course). Initially, the battery was always showing yellow when all electrics switched off and in the hangar, even shortly after flight. Now it is on green, even after 4 weeks of not flying and without the charger connected to the plane. This has really renewed the battery.
So far haven’t done a capacity test.
I have absolutely nothing to do with CTEK, and there will surely be other chargers performing the same. But the invest of around 60 Euros seems to be a good invest to me when thinking about the price of a single battery.
I’ve just realised the CTEK charger has a MODE selector button on it. Never used it
Thanks Chris!
I wrote to CTEK re charging Concorde batteries and the use of AGM mode (sent them Concorde doc with spec) but they were non committal, just saying that if I was unsure to use the normal mode as that could not damage the battery.
As you say, I had read somewhere that reconditioning mode was for wet cells only…it is supposed to mix the acid up in a wet cell.
I have the same model and use it in the “AGM” Mode for my Concorde, although the output voltage is a bit higher than recommended in the Concorde Manual. I´m not sure if that could damage my (new) battery. The reconditioning I would not recommend on AGM batteries. The recond mode worked well on my last Gill 242 (lasting 7 yrs. and at the time of change been not really down – it just needed proper topping up with water, cleaning and yearly use of recondition program), however I switched to Concorde according most of recommendatons and being (water) service free.
MXT 4.0
Ok, fwiw I have one of these
https://www.ctek.com/business-uk/products/workshop/mxt-4-0-uk
Sounds like you have a different version
It doesn’t have any mode selection. You just connect it up and it charges the battery, and after it has charged it, it goes into the reconditioning mode.
I have been using it more or less only at the Annual so perhaps it is irrelevant.
