Odd battery drain. Rectifier?

[shakesnow]

I've searched around and found some similar battery issues as mine but nothing quite as odd. I just wanted to run this by everyone before i shelled out the coin for a new rectifier.

I tried to start up my '01 GTX Di this morning (it was fine in Oct). Plugged in the key and she came on. Hit the start and it click a couple times and shut completely down.

I didn't have the battery charger on it at the moment so i thought it might be dead. Sure enough it was at 6v. I put it on the charger and it was 13v in just a few minutes (which seemed fast). I tried to start it up and the same thing happened.

I figured the batter was shot so i took it to a battery shop and they tested it at 12.7v and then load tested it 4 times under a very heavy load and it was perfect. They did not recommend replacing it.

I get it home and go through everything again with the same results. This time i put the multi meter on the battery while i try to start it.
As soon as i plug in the key it drops from 13v to 5.5v. If i try to start it, the starter clicks, the ski shuts off and the meter reads 0.5v.
If i wait around long enough the voltage climbs back up slowly.

 

[shakesnow]

just a quick edit because i can't seem to edit my post. The voltage did drop once or twice when i plugged in the key but now it doesn't seem to do it.
The meter reads 13+v when i plug it in and then drops to 0v when i try to start it. It slowly climbs back up after a few minutes.

Maybe the starter is draining the battery? A short somewhere? All cables are snug and in good condition at the battery.

 

[Bills86e]

If the Bcables are getting hot, more likely that not they have deteriorated internally
at the lugs. The starter can be removed and Also load tested. Its a good time to
replace the starter brushes and clean the armature and grease the bushing.

 

[lnc2bldr]

Are you taking the voltage drop directly across the battery or somewhere else (touching the battery terminals, not the cables)? A high resistance starter would pull the voltage down but not to zero (I have never seen). If you are taking the drop directly from the terminals I would guess there is an open across the battery that occurs under load that the load testing didn't replicate. Otherwise a cable problem.

 

[flip6]

Take the leads off the battery and measure the resistance across the leads.

Should be very high to infinite resistance so no meaning nio current can be discharged from the battery at rest.

If the resistance is low it means there is a short somewhere.

Th cause of my short was a rectifier - and if you pull the front plug off the mpem - the one with the three white wires in a row down the bottom of the plug. Measure the resistance across the battery leads again and if it's infinite then it's prob the rectifier. i.e you've unplugged the problem area

 

[James.Moon]

Good Battery, Drop off in voltage, Short

The only thing that will pull a good battery voltage down to nothing is a dead short. Either the starter, solonoid or something else. A battery can have a high resistance cell which will do it as well, but in that case it should fail a load test.

 

[James.Moon]

Short

Looked at your symptoms again. Losing voltage before hitting start button means it is not the starter but something else shorted causing a heavy current draw. Shorts are hard to find. Take off one circuit at a time by removing fuses.