what will i kill by starting my car without a battery?

i was suspicious that a short between cells in my battery was not allowing full jump-start voltage to the starter, so i removed the battery from the dead car and hooked the jumper cables from the good car directly to the battery cable terminals in the dead car. it started right up. i didn't let any smoke out of anything AFAIK, and i didn't disconnect the jumper cables until after i shut down the engine on the battery-less car.

almost let some smoke out when i hooked up the jumper cables red-to-black instead of red-to-red, but the 100A main fuse did it's job, and $4 later i was back in the game.

on a related note, berkeley o'reilly's auto parts. they bought the murray's chain here in SE MI, and the new ownership says "no receipt, no luck" on the replacement of my 84-month battery that won't hold a charge after 27 months of use.

nothing. the only time that your car needs the battery is in start up and key-on-engine-off. running, its all alternator

grimmelshanks wrote: nothing. the only time that your car needs the battery is in start up and key-on-engine-off. running, its all alternator

i have read that the battery provides some kind of voltage damping or something, and that running without the battery in the system will allow voltage spikes to (maybe) cook ECUs. i decided to roll the dice since the battery in the good car was connected to the battery-less car via the jumper cables.

In reply to AngryCorvair:

Re-your dead battery: Take it to any place that sells that brand. You will get the warranty credit based on the manufacture date instead of the sale date, but that should be within a few months.

MrJoshua wrote: In reply to AngryCorvair: Re-your dead battery: Take it to any place that sells that brand. You will get the warranty credit based on the manufacture date instead of the sale date, but that should be within a few months.

?que? Is that some kind of rule? It's an Autolite battery, manufactured Jun 2008.

I have heard it can cook the alt not to have the battrry hooked up.. But technically you never ran kt without a abattery

AngryCorvair wrote:

MrJoshua wrote: In reply to AngryCorvair: Re-your dead battery: Take it to any place that sells that brand. You will get the warranty credit based on the manufacture date instead of the sale date, but that should be within a few months.

?que? Is that some kind of rule? It's an Autolite battery, manufactured Jun 2008.

Not a rule, just personal experience. I have taken batteries back to places without receipts and that's what they have done. I always took them back to the store I purchased them from, but without the receipt I had no proof I bought it there. Seems like it should work at any store that sells that type of battery. I would think they collect from the manufacturer and you get a prorated credit towards a new battery at their store so you aren't ripping them off.

In reply to MrJoshua:

over the phone they told me i'm berkeleyed. i will walk into the store with the failed battery tomorrow and see if the in-person answer is any different. phone guy sounded like a disgruntled tool of the new man.

AngryCorvair wrote: In reply to MrJoshua: over the phone they told me i'm berkeleyed. i will walk into the store with the failed battery tomorrow and see if the in-person answer is any different. phone guy sounded like a disgruntled tool of the new man.

and you think the guy behind the counter won't be a disgruntled tool of some sort?

Bummer, I liked Murray's.

grimmelshanks wrote: nothing. the only time that your car needs the battery is in start up and key-on-engine-off. running, its all alternator

You will destroy a modern high output alternator if you run it without a battery.

as a rule I don't usually buy my batteries at a parts house, I use the big box retailers like Wally mart or Sears, because there alway's seems to be one of them wherever you go. Plus they are all branded with their store name all over them and with date codes for warranty issues.

doesn't matter at this point, as i bought a new one at costco and used the old one for core return. of course costco doesn't carry a 58R so i had to use what their application guide said was a suitable replacement, which is too tall and wouldn't let my hood close. so it's off to costco to return this battery and maybe even get my old one back so i can trade it at autozone. no way am i buying something from o'reallys.

AngryCorvair wrote:

grimmelshanks wrote: nothing. the only time that your car needs the battery is in start up and key-on-engine-off. running, its all alternator

i have read that the battery provides some kind of voltage damping or something, and that running without the battery in the system will allow voltage spikes to (maybe) cook ECUs. i decided to roll the dice since the battery in the good car was connected to the battery-less car via the jumper cables.

This is true. But since you never disconnected the jumper cables while it was running, it technically never ran without a battery. I know a guy who did this with a low mileage '03 Caddy. I don't remember why, but he took the battery out while it was running, and fried all kinds of E36 M3. He replaced the ECM and the BCM, but the car still had issues that he (and a couple of local shops) could never figure out. He ended up selling the car for $2k as-is.

The regulator will try to maintain nominal 12V by controlling current through the field winding. Problems can occur without a battery (which does serve to damp spikes and transient voltage excursions) when the RPM slows down (like when the motor is stopping), and the regulator tries to maintain 12V by dumping a bunch of current through the field. Many battery cutoff switches (mandated by SCCA and most other racing bodies) have two circuits, one for the high amp battery connection, another for the alternator.

I have gotten credit on a battery based on the manufacture date. It was a battery that came in a used car, so I didn't even buy it, which was a bonus.

If you jumper to the battery in another car, outside of having an extra 10' of cable, I can't imagine that the car would know or care.

In reply to erohslc:

thanks Carter. i appreciate the explanation.

As long as there was any kind of a battery connected, even only by jumper cables, you are good to go. Now, disconnecting those cables with the battery gone and the engine running is Not A Good Idea.

In the olden days, it was common to take a battery cable off with the engine running as a test to see if the generator/alternator was working. That was fine in the days of point type regulators and stuff like that.

Newer stuff with high amp alternators (100+ amps output is not uncommon) have a different problem: once the battery is disconnected the alternator thinks 'OMFG the battery is stone dead' and goes to 'full field' to try to catch up.

The problem is that you now have 100+ amps at around 16 volts with no place to go. Something could very well get fried. Or not. But why take the chance?

I've always left the dead battery in the box, just because of the alternator output question. Yeah, the thing's really running on the alt..but part of the alt's job is to recharge the battery. I've been doing that since I was "into" Britcars as a kid (in the American South in the 1980s, there were a bunch of em in barns that needed a lot less than the owners thought they did to get going again, just because they were "foriegn"). Actually started carting a dead battery around as part of my "Resurrection Kit" because I saw so many without batteries, and figured an alternator (or even a generator) produced a little "extra" current that had to go somewhere, just because that's what it was designed to do.

And J-man has described much better than I could about the risk to high-amp alts combined with boxes full of chips.

EDIT: Forgot Angrycorvair's possible battery short problem..the one I carried around with me in those days wasn't shorted, just discharged.

Yup-The trifecta of failure usually includes the battery, starter, and alternator. If one goes, the other two are usually soon to follow.

in my no defunct NG 900.. the starter, alternator, and battery all went within a week of each other. The alternator went RIGHT after I replaced the starter.. as in the first time I fired the car up after replacing the starter, the alternator seized and shredded the serpentine belt.

mad_machine wrote: in my no defunct NG 900.. the starter, alternator, and battery all went within a week of each other. The alternator went RIGHT after I replaced the starter.. as in the first time I fired the car up after replacing the starter, the alternator seized and shredded the serpentine belt.

I had the same thing happen with my NG 900, only without the serpentine belt shredding bit.

What you describe is perfectly fine. Newer cars are insanely succeptible to voltage buffering from a battery so if you disconnect the jumper cables you could fry any one of about 10 very expensive parts. On older cars without computers you only risk damage to the alternator and maybe an ignition module.

But what you did was fine. Technically it was connected to a battery, just not the one in the car.

Running the car without the battery will ruin the alternator b/c the voltage regulator is seeing no voltage from the battery, thus making the alternator work really hard to resupply the battery that is not there, so basically, your alternator was working at its maximum strength the whole time the car was running. It's probably OK, but it may not put out the amperage that it used to.

Steven