1980, new alternator and battery. When I start the car volt meter bottoms out at 8. After driving short distance gauge rises to normal operating range. Battery seems to stay charged. Anyone else had this is or is it normal behavior?

 

not normal.
never seen that.
electric choke jumps to mind, but?

 

I would suggest that you consider disconnecting the battery and connecting it to a good 10 amp or larger battery charger. "New" batteries can often spend months on the shelf before being sold. If the battery was just pulled off the shelf and installed it might not be completely charged. It is a good move to charge any "New" battery BEFORE installing it in your car. Batteries that have sat for a while can stratify the electrolyte, this makes the appear fully charged when they are not completely charged up. This is one of the reasons it is good to charge a battery up to 15 Vdc to ensure that the electrolyte is mixed well. A small battery tender charger often will not have enough power to charge a battery to this level and this is why I suggest using a larger battery charger.

A good test would be to put a multi-meter with the Min-Max function on the battery terminals. Then switch ON the Min-Max function and start the engine. This should capture the lowest voltage point that the battery hits while cranking. This is the primary way I test my vehicle batteries. If your battery is really going down to 8 volts then you want to fix the problem, that is too low for the electronics in the car and it could damage parts. I tend to replace any battery that drops below 9.5-10 Vdc while cranking.

The battery voltage should jump back up quickly after releasing the ignition key from the Start/crank Mode. You might want to test the alternator to see if it is working properly. Immediately after starting the engine the battery voltage should start going up to ~14.5 or so and then start regulating as needed. Also test the battery cables while you are at it. They may look just fine but always test the battery voltage (with the engine OFF) at the battery and right away test the battery voltage at the Starter Positive post and the engine for ground. They should be very close to the same number.

 

Start it up and use a multimeter to measure the actual output at the Alternator pos. output stud.

Jebby

 

Is it a 1 wire alternator? Perhaps it isn't getting excited until after you start driving a bit.

 

good

 

Even when I ran a one wire alternator I never seen this.
yes voltage drop on the gauge when cranking. But then pops up to 14.8 volts as soon as it lights up.
something is definitely not correct here. If my voltage drops below 14 with fans, windshield wipers, headlights on, etc. I'm looking for the problem.

 

If I summon @interpon, perhaps he can link the thread where a brand new alternator had a bad bearing out of the box. New alternator and new battery? My money is on bad, or improperly wired, alt.

8V is really low, but we all know not to trust the stock gauges. Hopefully the OP gets back to us with some voltmeter readings.

 

I ran a one wire in a kit car I had. I had the bulb burn out that would normally create the field... It behaved like this where you really needed to rev it up to get it going and charging.. ymmv