battery

[n86121]

CAPACITY
Being a nerd, the last time I checked, the concord had 14 AH capacity and the Gil around 10 AH. As to starting, unless you are cranking so long to eat up a a battery, it doesnt matter (for starting, but more about useful life later)

ONLY USED FOR START
Once even one engine is running (above maybe 1,000 RPM for the alternators to, like a cheap woman, 'put out'), the load SHOULD shift entirely to the alternators.

The batteries are then being recharged from excess capacity from the alternators, as well as acting like big filter capacitors on the power bus while charging.

LONG TERM FLOAT VOLTAGE
Different battery chemistries have different optimal voltages for sustained charge (battery minder). While any 'ye olde charger will bring any battery up, "amps are amps." The caveat is what happens when left on a charger for an extended time. That's why better chargers have selectable settings for different batteries, that set the max output voltage appropriate for each type of chemistry.

If the long-term float voltage is a wee bit too high it will slowly 'boil off' (more like slowly simmer) the battery chemistry internally. Over time internal battery resistance will go up, seen as decreased capacity and weak starts under high starter loads.

Similarly, if the alternator max output voltages are too high, like using the wrong battery charger over a long term, you may be cooking your battery chemistry a bit each time flying.

Each time a battery cycles through charge and discharge, its internal chemistry is getting mixed and slightly diluted, so they get weaker over both time and number of cycles.

Thats also why EV manufacturers say to avoid fully charging batteries, the last bit up to the redline charge that works the chemistry hardest.

HOW TO GET MAX YEARS
I go with the max capacity concord. Having more AH initially has ZERO impact on starting (unless you have to keep cranking for extended times), but more importantly, as it ages, it will take more years before its slow decline in capacity gets too low to start the airplane.

CHARGING FLOAT VOLTAGE
I also swallowed hard and bought the specific charger made for it ($300 vs $15), because the precisely right float voltage and desulphating meant the battery would last the longest.

ON TIE DOWN
Lastly, on my tie down, I have a marine gel cell trickle charged by solar panel in a tie down box, with a 12 vdc to 120 VAC inverter, and the $300 charger made for the concord battery.

In my airplane, my 2nd cig lighter(passenger side) is wired to the battery (near master solenoid) with a 7 A fuse. That way I can connect quickly to the battery anytime. Whenever I want to refresh or top off my battery, or do database updates, or whatever, I just plug the $300 DC charger output into cig lighter #2 and presto, battery fully charged and being de-sulphated. The max I leave even the fancy charger on is overnight, and then only occasionally.

FAST CHARGE
I spoke with a concord engineer some years back. He claimed their batteries could handle high current charge just fine, (as they do everytime the airplane is running after the batteries get low).

Within reason of course, 200 AMPS into a near dead battery wont end well, as it would produce too much internal heat. But the typical 4 or even 10 amps from a charger wont hurt it.

Slow charging for extended times is always happier then jamming it all in at once, simply from a heat management standpoint, A 10A charge into a 12 volt battery is literally like sticking a 120 watt light bulb inside the battery.

But most basic chargers are just voltage devices (not constant current), that put out just a bit more voltage than the battery. As the battery under charge voltage gets closer to the chargers intrinsic output voltage, the current into the battery drops off. Which is also why the last 5% takes so long.

And enough about that!