Battery tender

What battery are you using? What is your charging voltage, engine running, above 1500 or so? Anything between 13.8(bare minimum to keep it charged) and 14.7 is good, depending on electrical load.

Subaru engines seem to be VERY sensitive to proper clean grounding in order for the charging circuit to work well. I ran a couple extra ground straps on my wife's Subaru and haven't had a problem since. Check difference in voltage at the alternator output AND the battery. Any more than 0.1 volt difference indicates a battery cable/ground problem.

Also, since you've added all those modern-day gizmos, maybe one or more of them is drawing a little juice all the time, killing your battery softly, you know, like the song...

To test, remove ground or positive(your choice) and put an ammeter there in series between the empty post and the terminal you removed. You'll find out if there's any kind of draw/short.

Thanks for this Danny, I have a Red Optima 34 R I believe new from last year or the year before. I will go through those steps and post what I get. It is now being reconditioned with the CTEK, will take over night.

Thanks again.

Finding and fixing a parasitic battery drain sounds fairly simple in concept, but can be very difficult in application.  Lots of online tutorials, youtubes, etc. on what to do.  Most of them follow the same principles.  It can be much more difficult to assess without an accurate wiring schematic.  If you don't find the draw in one of your circuits, which you will disconnect one at a time, watching your multimeter for milliamp fluctuations, don't forget to check your alternator diodes.  A bad diode will allow current to flow in both  directions.  A rule of thumb is anything over 85 milliamps needs to be corrected.  50-85 mlA is normal in a modern car, less than 50 in older cars, but our replicas are all over the board regarding add-ons, geegaws, sensors that stay active, even with the key off, etc.

I saw the thread title and got all excited. I discovered today my BatteryTender killed my Ducati battery (I think) But I’m talking the Deltran brand. Used them for years, never had a problem.

Jim, your right about the need to track down stuff and the adds ons are somewhat rambo at times when you have to fix them.

I have a battery tender but don't keep connected full time. If you are using the vehicle every two weeks or so there should be no problem. parasitic drain (Jim Kelly) is likely the problem.

I have LED lights in my engine compartment. If my battery is down it's because I left them on.

Yeah, I realized I had plugged in the charger but instead of plugging in the charging wire on the battery I plugged in the plastic plug ,..,  DUH,    Well I am all charged up now went for a nice ride yesterday and it is working now to do the verifications to see if I have any drain.