Car Battery Fault? - Page 1
Forum section: electronics / general

author: kolbep
author_rank: Frequent Contributor
timestamp: December 26, 2012, 03:46:13 pm
content: Not Exactly Electronics Related, but I hope one of the knowledgeable members on this forum can shed light on this.The wifes car (Yes SeanB, the Chico), has a strange fault that has been going on for several months.Sometimes when we get in the car, we notice the clock and radio have reset.Once As I was climbing into the car, the radio cut off and reset.Several times the car has completely cut out (electrically) while driving. A quick start again is fine.The other day the car was completely dead in the parking lot (not even clock or anything running).As soon as I touched the -Ve Battery terminal (with my finger, just a touch. Not even a press), the electronics and interior fan kicked into life.When I tried to turn it over, Click and all dead again.I then Moved all the Battery cables without touching that -ve terminal. All was tight, nothing moving, but still nothing.Then I tried to wiggle the -ve battery terminal, and Bingo - Back to life, Turning over and starting fine.Now that the car is in the garage, I hooked my Voltmeter up to the Battery +ve and the chassis - Voltage is fine. Wiggling and banging things do not cause any change to the voltageI have tried to wiggle the battery termial itself, and it is still tight in the moulding.Anybody experienced anything like this?Peter

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2012, 04:01:17 pm
content: Taken the terminals off the battery and cleaned both the posts and the inside of the terminals, along with adding a dab of Vaseline to the terminals and the posts before tightening them again? If it was put on by a monkey by hammering on the terminals they can have broken the internal tab, which then is intermittent. Have you checked the mounting onto the bodywork, take off, clean then use the Vaseline on the bolt and the terminals. Still hunting the intermittent on mine, it is just annoying but not a stopper. Note as well check the fuse links on the top and the fuses and the link on the positive terminal, they can become loose and intermittent.

author: G7PSK
author_rank: Super Contributor
timestamp: December 26, 2012, 04:13:52 pm
content: Sounds like a crack in the internal connections of the battery, A DVM is no good for checking the voltage from a car battery unless you put a load onto the battery,try the reading with a headlamp bulb connected.

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 26, 2012, 04:32:42 pm
content: Possible oxidized connection, but more likely a bad internal connection in the battery. If you clean all the connections and it still happens, replace the battery. If that were my vehicle, I'd just replace it anyway.The alternator generally will not put out anything if the battery is disconnected and that will kill your engine if you're driving while it happens. I had that happen to a 1 ton dually pickup. That was a lot of fun to steer without power assist!

author: M0BSW
author_rank: Frequent Contributor
timestamp: December 26, 2012, 05:02:22 pm
content: Youv'e not bought "Christine" the devil car have you.

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: December 26, 2012, 05:26:30 pm
content: The battery is only used for starting the car, after that everything is powered by the alternator, you can; but don't try this at home with modern electronic ignition cars, completely remove the battery after it has started ( the old points and coil systems) and it will happily run.If it die's while running and your alternator is good then i wouldn’t blame the battery

author: tbj
author_rank: Contributor
timestamp: December 26, 2012, 10:19:21 pm
content: Quote from: Mr Smiley on December 26, 2012, 05:26:30 pmNot true. One of my cars certainly didn't like having the battery disconnected whilst running, and the alternator was fine.I'd suggest the OP tries first cleaning up the battery terminals and connections, and if the problem occurs again replace the battery.

author: tom66
author_rank: Super Contributor
timestamp: December 26, 2012, 10:49:19 pm
content: Without a battery to dump the energy in, most car electrical systems will be very unstable, and it would be unlikely they would work properly (IMO.)

author: Psi
author_rank: Super Contributor
timestamp: December 26, 2012, 11:19:39 pm
content: That's why he said not try it on modern cars. It only works for old cars with a distributor-cap/points and no electronics.

author: nixxon
author_rank: Frequent Contributor
timestamp: December 27, 2012, 12:02:48 am
content: Quote from: Psi on December 26, 2012, 11:19:39 pmI would never disconnect the battery from any car engine that is running. No matter how old and analog. It spells t r o u b l e

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: December 27, 2012, 04:03:09 am
content: If your battery is FLAT, and you get a jump start, what is the car ( as a whole and donor jumper now removed ) now being powered from, the flat battery ( which is now placing a higher load on the charging system ) or the alternatorSo once the engine is running and the alternator kicks in, the battery is no longer supplying the load, the load is charging the battery

author: SeanB
author_rank: Super Contributor
timestamp: December 27, 2012, 04:37:45 am
content: True, but the battery by virtue of it's chemistry is providing voltage regulation. I can use a standard alternator and get 30V out of it just by disconnecting the output and loading the internal regulator with a lamp. Normally the diodes break down at 30V or so.

author: tom66
author_rank: Super Contributor
timestamp: December 27, 2012, 12:29:01 pm
content: You are missing that the battery acts a lot like a capacitor, though obviously a very large one with very nonlinear characteristics.

author: G7PSK
author_rank: Super Contributor
timestamp: December 27, 2012, 05:44:42 pm
content: The best way to burn out the alternator or the dynamo on old cars is to remove the battery, the battery loading is required to keep the voltage produced by the alternator or dynamo in check. The biggest no no with a car is to remove the battery while the engine is running.

author: Tube_Dude
author_rank: Regular Contributor
timestamp: December 28, 2012, 06:36:34 am
content: The battery works the same way as the filter capacitors in a power supply, do some smoothing of the voltage produced in the alternator or dynamo, while providing some spikes suppression at the same time...