How long on battery alone?

[D.O.G.]

I've bought a Mazda Astina for spare parts, or maybe resale, depending how good (or bad) it looks in person.

The first problem is, I have to pick it up about 140 km away and the alternator is dead, hence the point of this post. - How long can a car run on just the battery alone?

I'm hoping that those of you who've done alternator deletes would have a pretty good idea ... please.

For those who don't know the Astina, it's pretty close to a Mazda Protege with a 1.8 and 5 speed.

I'm pretty sure I couldn't make it home with headlights on, so it'll have to be a daytime run, with heavier traffic.

I'm not concerned with fuel economy for this run, so - would faster be better?

Whether or not the rest of the car is healthy enough for a run on country highways and motorway with suburban traffic either end is something I'll only find out by trying.

[Cobb]

Ill tell you this, a 85 vw golf diesel with a group 34 battery can go 70 miles highway, but be warn the brakes suck power for the lamps. Killed it nearly twice, but it was a stick so bump started.

Whats the reserve capacity printed on top of battery? its listed in minutes and it is a good estimate assuming you limit your accessories and its in good shape. A bad battery can last minutes. If its a bad alt, the battery maybe at a reduced capacity already.

[redpoint5]

Originally Posted by Cobb

A bad battery can last minutes. If its a bad alt, the battery maybe at a reduced capacity already.

As Cobb points out, it is highly probable that the battery is in poor condition if the alternator is dead. You will want to bring your own battery of known good condition.

Driving faster will not drain a battery faster. The distance traveled has almost nothing to do with battery drain, however run time is the most significant factor.

Cars with less electronic doodads tend to draw less energy. I estimate my car, which is full of doodads, running at minimum power draw, would run about 2hrs before the battery gave up.

If you attempt this (and I probably would), try to avoid using the brakes, as this will significantly eat away at your energy reserves. Bring along a spare battery while you're at it. Between 2 batteries, you should have no problem making the run, assuming there isn't something wrong with the cars electrical that killed the alternator in the first place.

[D.O.G.]

Thanks for the replies guys.

I picked up the car this morning and after about 15 very nervous kilometers, checked the battery voltage, only to find the alternator was working after all.

I took two fully charged batteries with me, along with oil and tools and didn't need any of it.

[redpoint5]

Originally Posted by D.O.G.

I took two fully charged batteries with me, along with oil and tools and didn't need any of it.

There is a Russian saying that says something like, "problems avoid those that can fix them".

Your preparedness scared the problems away.

[gone-ot]

About 9Vdc is where *most* ECM and electronics systems cease to function (correctly) although some will *try* to function albeit intermittantly.