Lude Generation

I am entering this under "new topic" but of course it is not, as batteries have been going dead since the day after they were invented. My newly acquired 5g failed to do anything after sitting a few days and since the batt appeared rather grungy I installed a shiny brand new one. The engine spun over and started instantly. Aha, says I, problem solved. A few days later it's gone again. Undaunted, I charged it up, pulled one cable and put a small (1166) bulb between the cable and post. It promptly lit up brightly so I pulled fuses one at a time till it dimmed (just barely red) with the "radio-clock" out. Aha, I repeated, the radio doesn't work anyway and who cares what time it is so the problem is solved. Guess what?
So my question is, where do I look next and how do I go about looking? I am assuming that some small drain (dull red filament) is normal.
Tom#1

could it be the alternator is not charging the battery - maybe check that out

while its running put a voltmeter accross both battery terminals and see if you are getting 14 volts.

^^^
yep.
here are the results of voltage across battery terminals from both my ludes
BB4 with genuine Honda Battery 6 months old.

Battery
(engine off) 12.68
At idle 14.76
rear demist&stereo 14.60
demist,stereo&headlights 14.33
as above with heater&fan on ac removed 14.12

compared to results from BB1
Yuasa Pro battery 3 years old.

Battery
(engine off) 12.56
At idle
(stereo on) 14.55
rear demist&stereo 14.48
demist,stereo&headlights 14.32
as above with ac on 14.16

marginally higher results but practically the same so both batteries and alternators working as they should.

Thanks for the responses guys, but I fear I was not clear in my explanation. A new and fully charged batt will go dead while sitting in the garage with nothing (apparently) turned on.
Tom#1

Oh, if it drained over night after installing it the night before then definitely you got a voltage drain somewhere...

Did you install anything recently? Security system, audio system etc...

If the radio circuit was drawing all the current, then sounds like it wasn't wired in properly (perm live with switched live mixed up). I don't know what else is powered from the stereo circuit, any aftermarket 'bits' added?

id expect a very small amount of drain (clock / central locking ecu etc) - a bulb isnt the correct way to measure really, ideally you'd use a multimeter. The bulb trick is fine for old fashioned stuff, but in a car with numerous digital systems, anything that doesn't get up to voltage (because there is a bulb in series) might behave oddly. I suspect the radio is the only issue though.

You could try unplugging the radio from the loom to isolate is versus anything else on the same circuit (the fuse would isolate all of them, not just the radio).

If with the radio disconnected, its still draining a battery overnight, then something must be getting warm somewhere. Alternators can 'half fail' , only half charging the battery, but at the same time , when the car isnt running, half drain it. Check the alternator isn't warm near to where the 'gubbins' are. if the diode pack / regulator has failed, you will get heat build up in this area.

I've had several bad brand new batteries through my driving carer. Where did you get your battery from? Make?

ek9
As have I. At one time I got TWO bad ones in a row. Trying to troubleshoot that will test one's patience. This battery is an "Interstate" which is a common and well known brand here in the colonies and not cheap either at $132. I suppose my next step is to charge it up, disconnect one cable, check the voltage, let it set for a few days and check it again. This will be awkward with my fingers crossed.
Tom#1

That would be a good way of ruling out the battery