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Posted By Discussion Topic: sudden battery discharge? -- page: 1 2 3     fordmerc 09-21-2011 @ 10:40 AM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 After driving my '39 6-8 miles, engine shut off. Initially turned over vigorously and coughed, but didn't start. I cranked a few more times but battery died rapidly(few=3-4 for 5-6 sec). This has happened before with a different battery. I did not test for spark since I was on the street but near to home so I towed it home. Battery SpGr 1.015! Put in a new battery and it started right away. Last time I blamed coil, and present coil is different.The starter solenoid is also not the one in place when this happened before. Any ideas on what could cause such a sudden and total battery discharge? supereal 09-21-2011 @ 1:14 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Are you sure the battery discharged, or did one of the cables open up? Sudden full discharge of a battery is rare, unless there is physical damage to the battery itself. Your specific gravity test should clear the battery issue. Unless there is a very loose connection between the battery terminals and the cables, or the cables to the solenoid, I'd look for internal corrosion where the battery cables meet the clamp-on terminals. Acid creeps into that area and insulates the contact. Sometimes the heavy draw at cranking will cause enough heat at that point to reduce the output. That may be the reason installing a new battery seemed to cure the problem. The terminals were exercised enough to reestablish the contact. Occasionally, enough acid enters the cable at the terminal to corrode the cable, itself. There may be signs of heating, but not always. The best way to isolate these problems is to place the leads of a voltmeter across each connection, such as the actual battery post and the terminal. Any reading is an indication of loss. At 6 volts, it only takes one high resistance to cause the system to go dead. Unless your cables are of good quality copper, and properly sized, they should be replaced. Many cables sold today have undersized conductors hidden by thick insulation. Some are even aluminum, which oxidizes and forms an insulator. Good cables are expensive, but absolutely essential for reliable operation. ford38v8 09-21-2011 @ 1:14 PM reply profile send p.m. Senior Posts: 2762 Joined: Oct 2009 fordmerc, I'm such a wizbang expert on electricity, I can afford to offer my golden rule tried and true advice: Don't touch electricity or it will snap at you like a vicious dog or an old wife. That said, I remember when I was a kid, a sick battery would take a charge and last a few more days, but now, they give no warning at all before they go belly up. My vast electrical knowledge now tells me to dump some money into a new battery, and I'm an electrical genius. Alan fordmerc 09-21-2011 @ 3:06 PM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 Cables are "new", no visible corrosion; I cannot attest to their proper size. This has happened with a 3 year old battery (this time)and with a brand new one.(In fact I blamed the new one as bad, but later it took a charge well and I think it is OK; the newer one started the car this time). When the car "shut off", I was able to crank it with "full power"(?), but it didn't start and then further cranking just quickly ground to a halt. 37RAGTOPMAN 09-21-2011 @ 4:45 PM reply profile send p.m. Senior Posts: 1961 Joined: Oct 2009 fordmerc did you check the battery for a draw when attaching the battery cables.? check this out and get back to us with your finding thanks 37RAGTOPMAN 51f1 09-21-2011 @ 4:48 PM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 Check all of the cables and all of the connections between the battery and ground and the battery and the starter. Check the solenoid. There is probably a bad connection somewhere. If you have access to a battery load tester, check the battery. Richard TomO 09-21-2011 @ 6:19 PM reply profile send p.m. Senior Posts: 7253 Joined: Oct 2009 I agree with Supereal that sudden discharge of a battery without smoke is very unlikely. If the Neg battery cable or post touches the battery hold down, you would drain the battery, but there would be sparks and smoke. You should be able to see signs of this happening. The gas gauge reacts the quickest of all gauges. Do you notice a sudden change in the reading when this happens? If it goes towards empty or fluctuates, you may have an intermittent short circuit in the wire that feeds the dash. Your lights would also be affected, but you would only notice this at night. Just as a SWAG, I would examine the wires on the drivers side of the solenoid for signs that they may be making contact with the firewall. I would also look very closely where the harness goes through the firewall under the loom cover. I would also drive without the loom cover until I found the problem. As you have been fighting this problem for a while, it would be better to keep this thread going until it is fixed. It would also help if you listed all of the actions you have taken since this problem started. Did this start right after you finished the restoration, or did it start after you did some repair? Tom supereal 09-21-2011 @ 8:19 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 The clue is that your cables are "new". That doesn't assure that they are not the cause of your problem. Defective parts are everywhere. Reread my original post. I've seen this problem many times, even with one of our shop trucks that left me stranded last year. The battery cable that was molded to one terminal on the battery made almost no connection when it was moved. It, too, was "new". This message was edited by supereal on 9-21-11 @ 8:21 PM fordmerc 09-22-2011 @ 11:56 AM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 Thank You all for help. I will take advantage of TomO’s offer so here’s a rough chronology: I think this problem has been present ever since reassembly of the car. It is intermittent and not really reproducible, although it happens in about the same situation each time: drive 5-10 miles and the car stops. Therefore I'm afraid of it and am reluctant to venture farther. Things that have been done: (“new” means whatever is on offer at the vendors) 1. New wiring harness throughout 2. New ground and neg-to-solenoid cable. 3. 2 voltage regulators ( 1 new, 1 old) 5. 4. 2 different coils (one old, one new) 6. 3 different starter solenoids (1 old and 1 new ,1 used repro) 7. 3 different batteries (1 new, 1-3 yrs old, 1-4yrs old) Testing: 1. No current from neg terminal to solenoid with ign off 2. No cables touching firewall or battery hold-down 3. Starter button removed from circuit 4. No obvious corrosion or discoloration at any visible terminal 5. No warm or hot wires 6. Under loom cover looked fine 7. *On one occasion only (in past), spark when ground disconnected – I cannot reproduce this. Today: 1. No electric shorts identified. Newly charged battery=7.6V 2. Recheck after connecting battery same 3. Car started readily, runs fine. Drove around the block twice in space of 25 minutes, engine ran 25 min(mostly at idle) 4. At 24 minutes : a. *Batt gauge midposition, rather than “N” where it had rested b. Temp almost beyond “H” c. *Gas gauge closer to empty than half where it had been earlier (but mine moves around a lot) 5. At 26 min engine shut off; restarted quickly 2 min later 6. Testing: a. Batt voltage 7.4 V b. 7.4 V at batt terminal on solenoid c. 0 V at starter terminal on solenoid d. *No resistance between batt and starter terminals on solenoid !!!*** (there was no continuity when tested earlier) e. To the best of my ability to tell, no hot wires f. No current flow detected from batt at neg terminal 1 hour after shutting off engine: a. no change in testing b. Batt acid : approx SpGr 1.220! That’s too many words but I think I have covered most questions raised. The only suggestion not addressed is the cable but it seems that if it were too small it would be hot and if it were corroded I’d see it. supereal 09-22-2011 @ 2:59 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 You have pretty well covered it. The corrosion or poor connection between the cable and the terminal is seldom visible. If the problem reappears, I'd change cables, just to be sure. I always run a second cable from the point where the ground strap connects to the the body and/or the engine to one of the starter mounting bolts. A common 12 volt cable with eyelet ends works fine. If you don't have a ground strap to one of the head nuts, be sure to add one. Remember, the starter draws a lot of current, usually measured in 100's of amps when under load. A good battery, such as the Optima, provides as much as 850 cold cranking amps, and is ideal for old 6 volt vehicles. If batteries in your car have a short (no pun) life, it is time to run a check of the charging system. I've spent over a half a century chasing electrical problems, and learned not to take anything for granted.

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