Right from the top, I rewired the car entirely and am sure therein lies the problem. I have two fuse panels, one is hot all the time and the other is hot when ignition switch is turned on; I also have a 50 amp master fuse which I can switch off. When I turn the master to off there is no drain on the battery but still hot at the starter solenoid switch but no power to either fuse panel. If I leave the switch on overnight it drains the battery down to 2.5 volts. The system is 12V negative ground.How do I isolate the problem?
or...pull all of the fuse, hook a volt-ohm meter between the disconnected positive battery and cable end and reinstall fuses until you see a voltage (more that .2 volt)spike, that is your circuit to check for a draw. generator or alternator? That is a quick and large draw to drain the battery that quick. I would suspect a diode trio in a alternator or sticking points in a generator regulator.
Find an old headlamp install two wires. Now use the headlamp in place of each fuse. When light comes on in a circuit then disconnect each item till the light goes out. This would be your draw. Posted using the Full Custom H.A.M.B. App!
My bet would be on a bad Diode in the alternator, it will kill a battery overnight. Simple fix and just as simple to check...just disconnet the wire(s) at the alternator overnight, reconnect in the morning and try to start...I have chased this same issue on several OT vehichles, and it's ALWAYS come back to rebuilding the alternator.
Rick, "disconnected positive battery and cable end" does this mean the hot wire going to the fuse panel and not the cable at the battery post?
OK not to over simplify things but is the master switch mechanical, that is to say a hard wired switch, or a electrically controlled switch which uses current to keep it engaged?? if it is the latter there is your draw.
Did you have this problem before you rewired? 52 poncho suggested a head light I would use a small 12 volt bulb either plug it into a socket with pigtails or solder a couple of leads to the bulb. turn on your main disconnect switch then disconnect the positive battery cable , connect one wire of your bulb to the battery cable the other wire to the battery post. If the filament glows you have a current draw. now disconnect the wires to the alternator if the light goes out that's the problem . if not leave it disconnected now pull one fuse at a time when the bulb goes out that's the problem circuit. Hope this helps. Do you know how to use a amp meter? it could be used instead of the bulb.
No problems until I replaced the stock wiring and went to 12 volts. I have a 50 amp circuit breaker that I can manually turn on or off as if it were a master switch. I have an amp meter but only know know how to check continuity and measure volts. If I have bad diodes in the alternator would it still be functioning, as it indicates 12V when I turn ignition on and shows 14V with the engine running on dash volt gauge and battery fully charged. Right now am having difficulty charging 12V Optima at 2 amps, when battery reaches 6V battery charger stops. This happened before and thought I had a bad battery, battery shop says no and charged it overnight at 6 amps (thought this was a no no with an Optima) and held charge for two weeks with battery cable disconnected and then fired right up. I usually flip circuit breaker off at night but recently didn't and now battery went to 2.5V. I do have a small 12V test light I can use.
Depending on your charger, it may sense the dead battery as a short and turn itself off. Articles I've read say to connect a known good battery in parallel to the dead battery and the charger. It fools the charger into thinking there is a good battery and will recharge the dead one. I have done this on an Optima and it worked.
Here is the way we do it. We remove the NEGATIVE battery terminal and put a test light between the post and the removed cable. If the light glows at all there is a drain somewhere...........the brighter the glow, the higher the drain. Now start removing fuses one at a time and have someone watch the test light. When it goes out you have found your drain. (You want a 12 volt test light, NOT a continuity checker. Harbor Freight sells them for something like $7 ) To drain the battery overnight you have a pretty good drain going on there. I agree that the alternator diode can be a source of such a high drain, not many other things, like a radio memory, will do that. But by doing the one fuse at a time routine you will find the accessory that is causing it. If you have removed all the fuses and still have a glow, remove the "battery" wire from the alternator and see what happens. Don
Don, if I can get the battery to take a charge will use test light like you suggest, if bad diodes in the alternator would it still show 12V when I turn the ignition on and 14V when it's running?
Don't let the battery shop try to tell you your battery is "Bad"....an Optima battery can be rescued from being totally flat with a little persistence. If you have a good battery, connect it to the Optima with a set of jumper cables and charge BOTH at the same time....until the Optima on it's own is above 11 volts...then complete the charging with JUST the Optima on the charger. If you can get your hands on one of the newer chargers with a "Deep-cycle" setting, use that to complete the charge. FYI: There are battery maintainers on the market (I have a C-tek unit) designed specific to the needs of the Optima... Hope this helps.
There is one other possibility. The battery may be draining itself internally, sometimes the plates inside short out. You can isolate that by simply disconnecting one of the battery cables on the battery when it is fully charged and then come back the next day and see what it is at. BTW, you can't really check the condition of a battery with a regular volt-ohm meter, it will only read surface charge. To do it right you need a battery load tester or one of the new testers designed for that purpose. Most auto parts stores will check them for you for free, just make sure the guy doing the test knows what he is doing. Don
I've seen more than a few new batteries that have a shorted plate. Those sink like a stone once a load is put on it. I would even suggest have the entire charging system checked, do a draw test on the starter as well. We would do systems checks and good shops will swap in a fresh battery if they sense that your battery has a bad cell or 2 in it.
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