The unit is specifically internally adjusted to the requirements for a Concorde battery. Same for the Gill B-minder which are slightly different than Concordes. Limited market so higher price. The use of a standard B-minder will damage aircraft batteries over time due to the way they are adjusted for vehicle batteries.
How often do you fly, and do you monitor the voltage in-flight?
Only if you exceed the OEMs recommendations on its use. Otherwise the use of a proper battery minder is recommended by most OEMs to include Concorde to achieve the max battery life. As with anything battery related, too much or too little of proper charging reduces battery life in most cases. However, I've found in my experience even if you lean toward a bit excess with a battery minder you come out with a longer life than if you leaned in the other direction and let the battery OCV drop to a low value which definitely will lead to sulfation and permanent damage.
Concorde has always recommended specific "BatteryMINDer" (specific brand, not generic descriptor) models for specific battery models. A few years ago, they updated the BM settings for better "full charge" performance.
concordebattery.com
Be careful what you're comparing. There is a big difference between a trickle charger and a Battery Minder, and looking at Battery Minder's web site right now, all of the aviation battery minders are the same price, regardless of whether it's Concorde or not.
I've had a (car) battery go 10 years without a battery minder, but that's definitely not the norm.
But it will not be a desulfator like a Battery Minder is, just a trickle charger.
I've never heard of an actual user of battery minders say anything of the sort. I can see why battery manufacturers would warn against them, though, given that you'll buy batteries a lot less often if you use a battery minder.
That is interesting - However, keep in mind that on the TBM you can disconnect the battery far easier than most of us can. You also have a port for the Battery Minder, and one is included when you purchase the aircraft new so it clearly isn't a bad thing! I'm sure TBM owners are more sensitive to keeping batteries going because not only do you have a massive draw (400+ amps) at start, your battery also costs 5-10x what a piston battery costs. I know there's a lot of turbine owners that like to use a GPU for start as much as they can, but some FBOs don't like to do that for the TBM due to the location of the GPU port.
There are "battery chargers", "battery tenders", and "BatteryMINDers". They are not the same. There are also multiple versions of BatteryMINDers that are intended for different batteries.
www.batteryminders.com
Interesting. Thats the complete opposite of my experience with both airplanes and helicopters. Below is the Concorde bulletin on maintenance charging. You'll note at the top of page 3 it states while continuous mx charging is possible its not recommended "over a long period of time." You'll find in practice that "long period of time" will equate up to 7+ years vs batteries that are not mx charged which may only last 3-5 years depending on usage. Regardless, most batteries are permanently "damaged" at installation by not following OEM instructions or allowed to discharge for extended periods without a proper recharge cycle which continous mx charging with a proper charger doesnt even come close to.
As you mention in your first sentence, self-discharge rates decrease with decreasing temperature. Your last sentence might be better written as, "Especially in the snowy winter months..."
Because you are talking about to separate tasks. In general, when you are operating the aircraft the battery power is being consumed by the electrical system and the alternator/regulator are designed to support the entire electrical system to include the battery. And the regulator is "tuned" to provide optimum charging rates and electrical load requirements. The only variance in "tuning" a regulator would be for a system change/requirement or in some instances you would change the voltage setting due to ambient temperature changes. For example, at my old day job we had a summer regulator setting and a winter regulator setting for certain helicopters to keep the batteries at the proper levels.
If you fly regularly, then you don't need a BatteryMINDer. You would see little difference between the batteries in the test you describe.
When a battery is charged during a 2 hr flight the charge environment only needs to be "good enough". But you wouldn't want the battery to see that charge environment 24/7/365. The more tailored design of the BatteryMINDer addresses the scenario where you hook it up not knowing whether it will be plugged in for a day or for 3 months.
Last Concorde I bought for the Mooney was a decade ago and that was $500. And a TBM's battery was about $5K, 5 years ago. I'm sure both have increased significantly by now.
