Am experiencing battery discharge while car is parked for days. Battery is nearly new. In relatively dark conditions I remove the negative terminal from the battery, then move it slowly back to the battery post and when about one mm away from the post I was getting a noticeable blue spark before contact. After removing the fuse in the after market radio power wire, the spark is noticeably smaller - almost difficult to see. Perhaps the electrical gurus have comments, such as; the overall electrical system has a "built in amount of capacitens" which discharges when the battery lead is returned to the battery post? I will be testing the battery over the next few days to see if the disconnected radio is the culprit.

Do you have an ammeter? If so, hook it up between the battery ground post and the ground wire. See what the draw is with everything off. Anything more than a half an amp is way too much, especially in our old cars.

Start removing fuses. Note what fuses change the draw and how much. Then check what connects to those fuses to give you an idea where to look for the draw.

Numbers are better than "well it's a small spark".

--DD

What's the make/model radio.

Some of the aftermaket and later radios have capacitors to keep the station preset, clock, etc. working so you don't have to reprogram. think like a rechargeable battery.
Leave the radio disconnected and then like Dave said check with a v/o meter.

I had a similar issue, and I did what Dave is describing with a multimeter. Turns out I had a parasitic draw of around 125 milliamps. That was enough to pretty much discharge the battery in a couple of days. I think you definitely want something below 25 milliamps, IIRC. In my case it was definitely the radio. I'm not sure if the power was wired wrong or if there was something else going on, but I ended up just taking the fuse out of the radio. Someday I'll fix it, but for now my "music" is the T4 motor...

Thanks for your responses. My meters do not measure amps, so I will see what happens with the radio power fuse removed as a first step. If that isn't enough I will locate an amp meter to do the sequential fuse removal routine.

Not looking to measure amps, most multi - meters read milli- amps.
Even the free units from Harbor Freight will work.

Remove the battery negative, put the meter between the ground + (red) lead and the black lead to the battery neg post, check the draw 250 ma and above is pushing it.
Pull one fuse at a time, watch for a big drop, that's the problem.
ps: do not run the engine or big draw items (headlights, fans) that will burn out the meter configured like that.

You can use a test light just as well as a DMM.

My old optima battery won’t keep a charge longer than a week. I rewired the cigarette lighter with a fuse of course directly to the battery. I plug a low current trickle charger from Walmart into the cigarette lighter to keep it charged.

Optima says the max current for maintenance charging is 1 amp. Check the specs?
Just recently found that my regulator was only passing 12.5 volts, new one is charging my optima to 12.67 volts.
Full charge is 12.8.
Check for parasitic drains.

Radio in off position was drawing 0.9 amps. After removing radio fuse, draw is not detectable on Harbor Freight $7 meter in the milliamp zones. Radio is an Alpine relatively new model (several years PO). So will cary fuse to activate radio when I need it which is almost never. I placed the meter in series with the battery negative terminal per Dave's instructions.