How do I find where battery is being drained from?

[ichthos]

I am having problems with the battery running down in my bugeye. When I let it sit for an extended period of time, I use a cut off switch. My car was sitting for two months. I turned the cutoff switch on, and the car started right up. I forgot to turn it back off when I went for a drive Sunday, and today when I tried to start the car, the battery was drained down and there wasn't enough juice to get it started. How do I find out where my battery is being drained? I am not the greatest with electronics, so please keep it simple. Thanks for your help.
Kevin

 

[BlueMax]

First you need to have a fully charge battery. Then I would make sure your battery is well grounded. Then you start unplugging stuff. I would start with the two major components, voltage regulator and generator first. Make sure you have your voltmeter hook up to the battery properly. You are looking to see when the voltage increase when you start unplugging things. The thing that you unplug that makes the voltage increase is your culprit. That is about as simple as I can make it!

 

[Boink]

I'd agree that you have to approach this logically... isolating things as much as possible. First, though, do you have ANY ancillary things hooked up (like even a digital clock or other gizmo add-on)? Sometimes these leaks can be so slow that they are difficult to measure (thus the need to isolate as a crude way to get at it). Are you using an alternator?

 

[JPSmit]

Here is easy way. I made a 12 v test light with alligator clips. I took out the fuse and replaced it with the light. It should glow dimly. You then unplug things till the light glows brightly - at which point you will have found your short.

https://classicbroncos.com/electricalbasics.shtml

 

[smaceng]

For the more technically minded, a current meter attached between the power battery cable and the battery will also do the trick.
Scott in CA

 

[ichthos]

Thanks everyone. I will take a shot at it this weekend and let you know how it goes.
Kevin

 

[nomad]

If you have fitted a alternator the most likely culprit is shorted diode's in the alternator. Try disconnecting it first.

Kurt.

 

[Boink]

If you have fitted a alternator the most likely culprit is shorted diode's in the alternator. Try disconnecting it first.

My thoughts as well.
I've also found that average inductance ammeters don't always tell me too much.

 

[ichthos]

No alternator - my car is still basically stock.
Kevin

 

[Boink]

Hmmm... then I'd be back to the more traditional methods. You could try an inductance ammeter on various lines and pull a few fuses.

 

[nomad]

Any added electronics such as a Garmin or a radio? Likely culprits.

If nothing like that I can't begin to guess where the leak would be. Are you sure you just don't have a bad battery?? Check the age.

Kurt.

 

[mightymidget]

Battery. either bad ground loose connections bad or batter itself.
quick test to see if you have a draw:
disconnect positive battery cable, hook test light between battery and positive cable. If test light lights up something is retrieving power from your battery.

 

[regularman]

You can have a low enough draw that it won't light a bulb but will kill a battery in a week or two. Also, check the water in the battery.

 

[ichthos]

I finally got out to the garage. Sorry, but I gave out inaccurate information. I tested the battery and it is still fully charged after all. So, here is what happens: when I turn on the lights they work great. However, when I pull the starter switch, the lights go dim, the instruments die, and the starter barely moves. The last time I had something similar happen, it involved a starter cable lug that was bent just enough to arc across the starter. I put in new wires and lugs, and had the starter checked at a local shop. It was working great until this week. Any ideas?
Kevin

 

[kalist]

You have a bad connection in the starting circuit, probably on the ground side. I would check the connection where the ground cable bolts to the block. I would also make sure all connections are tight.

 

[Billm]

Also just check for corrosion on the battery posts themselves and the insides of the battery cable ends - this is the most common problem for this issue.
BillM

 

[Jim_Gruber]

May perhaps a few $ invested in some new battery cables. The radio keep alive drains Bugsy's batttery if now started in 30-45 days. There is some crud and corrosion that continues to come back to the negative terminal all of the time so I go through a regular maintenance period of grabbing the battery charger off of the back shelf, walking 5 feet, popping the bonnet open, trickle charge for 2 hours and Vroom that is good again for 30-45 days over the winter. You'd think a Type 53? Honda battery could support the radio keep alive longer than that but that's my guess on what drains Bugsy's battery. Need to invest in one of those permanently installed battery tender thingies.

 

[Mychael]

Takes a bit to drain a healthy battery to the point you cannot start. When I still owned my TR I had a Smiths analouge clock running in it all the time and could leave the car for a month and still start so you must have a much larger drain imho.

Mike