At what RPM should ALT VOLTs annunciation extinguish?

[hazek]

I noticed my voltage drops at quite high RPM and one alternator ALT VOLTs light stays on longer than the other at idle power.

Is this normal:

[Marc_B]

@hazek I can't tell you what RPM it should drop off, but according to the service manual if appropriately set it should extinguish at 26.5 V.  (This is from service manual for a M20K, but the annunciators are all IAI and the logic should be similar).

[hazek]

37 minutes ago, Marc_B said:

This is from service manual for a M20K

I think that's exactly what I see in the cockpit, the L ALT VOLTS is flashing at say 850 RPM which is above all the way to idle. I recently had both batteries die on me, granted 8 years old so probably lasted longer than meant to, but still, I wonder if this is proper operation.

Bravo POH says: 

I'm wondering if during idling on the ground I was depleting the batteries and with most of my flights being on the sub 1h shorter side, they didn't get the proper recharge in flight. I don't use a batteryminder.

[Fritz1]

my alternators do the same, one starts flashing at about 850 RPM, battery minder is helpful, if batteries are same age you can charge in parallel, need only one battery minder makes for a nice ground power unit to run avionics in the hangar, parallel batteries give you 20 Ah, battery minder gives you 5 A, running the radios typically draws 8-10 A, plenty of time to program avionics etc. 8 years is excellent for a battery, replaced both my Concords after about 7 years

[PeteMc]

20 minutes ago, Fritz1 said:

minder makes for a nice ground power unit to run avionics in the hangar

Just curious...  With 5 Amps coming from the minder, I'm guessing you're still seeing a slight discharge on the Amp Meter when you've got your avionics on?  

 

[Raistlin]

In my case, below 950RPMS I see the alt lights flashing (I have a G1000 model with several additional devices such as skywatch, so probably I am on the high end of power consumption).

They flash or extinguish at the same time though.

[Fritz1]

Minder is connected directly to batteries, amp meter shows full discharge, thus about 8 amp, about 5 come from the minder and 3 from the batteries, gives you at least 4 hours to run avionics before the battery voltage drops, then minder tops off batteries overnight, poor man's ground power unit