okay maybe doc vette has the answer somewhere in his millions of posts.... rip doc. but i would like a quick answer to this.
i thought if the alternator worked that you could disconnect the battery and the engine would still run. on this pos last night the engine died.
but here is the mystery: when it was running the battery measured 14.7 volts across it. hence, the alternator was charging it. why wouldn't it stay running then??? dont know the type of car, a ten year old u.s. made with a v-6. think gm product. thanks
"Never disconnect the battery cable while the engine is running !!
That procedure does not prove the worth of an alternator, and the resulting voltage surge may damage the alternator and other electrical system parts."
My Diesel case 580 backhoe uses a Bosch alternator. It quit charging a couple years ago and I installed new brushes. Very easy on the bosch, I thought it was working but after a month the battery was dead. When the engine is running it only uses a very low current draw fuel solenoid. The fuel injection is all mechanical. I took the alternator in to have it tested and it charged for a while then quit. after a few seconds started charging again. I am still running the old alternator. the repair shop said he could order a rebuilt one for $ 300 and a new one for $ 500 I haven't had the battery go dead since last summer when I used the flashing light system when I had to drive on the highway. I do have a gm one wire to put on it if needed. The repair shop said he ocassionally sees the intermittent problem.
i thought if the alternator worked that you could disconnect the battery and the engine would still run. on this pos last night the engine died.
but here is the mystery: when it was running the battery measured 14.7 volts across it. hence, the alternator was charging it. why wouldn't it stay running then??? dont know the type of car, a ten year old u.s. made with a v-6. think gm product. thanks
I've done the battery disconnect test on many older GMs with no problems. I would not recommend it on anything with a computer or with a newer alternator like a CS130, since the voltage spikes can cause damage. In any case, take the alternator to any Advance Auto and have it tested for free.
ok, so as usual, i don't know squatdiddly about newer cars! big surprise.
so the car was being actively driven shopping around, then they stopped for a bite at Dairy Queen (all at night) and it wouldn't stop. i gave it a jump, it started right up. they put it in gear, it lurched forward and died again. the lead the cracked on the pos side of the batt so i went to walmart got a bolt on and thought that was it. it didn't do anything.
As the gal's father drove it home. it's weird that the lights never looked dim or got dimmer as the car drove farther and farther. usually if the alt doesnt work and the batt is shot the lights get dimmer and dimmer. and then it died, with the brake lights shining brightly, they jumped it again and drove away.
Concepts that explain this are even common in how PSUs work in a computer. And were understood even with early 1960 auto alternators.
Some problems created by 'no battery' were describes by others - such as diodes in an alternator blown due to no battery. This problem is not as predictable as it was 50 years ago because diodes are now more robust. But the threat still remains.
SAE and ISO standards define voltages even over 200 volts on a 12 volt system when a battery is disconnected. However most vehilce electronics are only good for up to 60 volts - a more common overvoltage when the battery is disconnected.
Obviously an altnerator converts AC voltage to DC ripples. Periods of high and near zero voltage exists without a battery. Some electronics make near zero voltage periods irrelevant (ie incandescent bulbs). But the ignition system can more easily get confused or shutdown.
You have described what could be a battery cable and connector disconnected from a fully charged battery. Jumping it connects another battery to that cable. But the internal battery never makes a connection or makes one that is way too tiny. Often seen is a car that starts and runs when jumpered. And then stalls as soon as the jumper disconnects. Or stalls as a moving car or headlights demand more current.
Bottom line - the problem should have been obvious. Guys learn this stuff by suffering and then trying to solve similar problems. Obviously, running a car without a battery means only the emergency backup protection is saving all car electronics from total destruction. That should be obvious once the first paragarphs (above) are grasped.
"The battery serves as a big cushion in the system, which also smoothes out voltage level. The battery will provide momentary surges of power, which are needed when devices are switched ON. The battery also can absorb momentary excess of power in the system as devices are switched OFF. The battery prevents major and sudden voltage changes in the system."
"Bottom line - the problem should have been obvious."
i still don't know what you are saying is the obvious problem. maybe after i read malcs link i will know then. hey thanks for trying tho. i know i'm dense, but didn't know i was so dense i can't see the obvious! seems like youre saying "dead battery"? i will pass it on.
Alternators obviously do not output a constant DC current (or voltage). AC power is converted into pulses. Electronics (ie ignition system) can become upset during those periods of no power.
Also obvious is what happens when the "cushion" (as described by EOD guy) does not exist. According to SAE and ISO standards, the resulting voltage spike could even be hundreds of volts.
What happens if any one battery cell was completely dry? Battery operates as if it did not exist. Then either of above two problems can exist. Learning these basics come from events such as yours. We never just solve problems. We also learn why the problem existed, its symptoms, and consequences of those problems. If no damage exists, then functions t avert excessive voltage and electronics damage worked.
A dry battery often indicates a different charging system failure.
Bull don't sweat it..... I didn't understand what that was all about either.
I still think you might have some dirty connections, pos batt terminal, the sm alt charge wire that's hooked to the pos batt terminal.
I agree unhooking the batt to ck the alt can produce alot of damage and isn't recommended.
Back in the day it was an excepted practice to unhook the battery etc..... folks got away with it because there weren't alot of of electronics in the system. When computers entered the picture, the spikes from the alt with the battery unhooked raised havoc. Sometimes the damaged resulted in a smoked computer/components and sometimes it created a "Ghost in the Machine" syndrome that folks had lot's of fun trying to resolve.......
The battery acts as an electronic shock absorber that prevents the spikes from shocking the system and it's components etc.......
holy crap guys! talk about the most obvious of the obvious!!! but with a cracked battery cable end i didn't even think about it!
THE BATTERY WAS OUT OF WATER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:spank: (ok acid).
gals boyfriend (my nefew) says they put water in it and it's been running great ever since.
now that i know that disconnecting the battery aint the thing to do to check the alt. maybe i will save my car in the future, so at least i learned something. once again, learn something every day here. glad i didn't seem to f up her car any more than it was. thanks for the help.
I would say that a majority of the batteries out there are serivicable, except the truly sealed batteries. They switched from the indivual cell caps, to a combined cap that covers three cells, you can remove that cap and add water etc....
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Hot Rod Forum
2.2M posts
175.7K members
Since 2001
A forum community dedicated to hot rod owners and enthusiasts. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!