Battery voltage question

-

Darren

FABO Gold Member
FABO Gold Member
Joined
Mar 1, 2006
Messages
1,584
Reaction score
690
Location
ontario
Hi everyone..
I took my 68 barracuda for a nice ride tonight.. 65 miles , I recently installed A new cluster so had a close eye on everything.
It ran great , so for the heck of it when I got home I put a volt meter on the battery and it's reading 13.05 volts ( with engine not running) seams high?
 
You can turn the lights on for a few minutes to take the initial charge off the battery, and then watch the voltage come back up. A good battery that has a full charge will come back to 12.8 volts
 
Brand new in the battery factory most 12 volt batteries are 13.2.
2.2 volts per cell.
So its good.
 
You can turn the lights on for a few minutes to take the initial charge off the battery, and then watch the voltage come back up. A good battery that has a full charge will come back to 12.8 volts
This by the way is called "surface charge."
 
It is actually a new battery..
Thanks all for your input.. I'll look at volts in AM Thanks
 
Put the volt meter on battery this morning
12.90 volts
 
So little update..
Looks like I do have a possible problem ..
I took the cuda (68 383) for another ride tonight,, ran great..
So when I got home I put the volt meter on the battery and car running with no accessories on the voltage at battery got as high as 15.50 and on alternator stud I took a reading of 15.90.
I took the VR off and cleaned it and it made no difference. Also I am still running the ammeter and it's not gone anything over 3/4 on the gauge any ideas?
Thanks
 
Another update lol.
It just happens I had a new in the box VR
I installed it and voltage at alternator came down to 14.70 and voltage at battery is now 14.40 ..
 
Interesting. Most the time a VR either works or doesn't. Wonder if it might be a poor connection at the connector?
 
Interesting. Most the time a VR either works or doesn't. Wonder if it might be a poor connection at the connector?
Possibly.. it was getting late so I'm lucky I got the info I did but hopefully I can test it out tomorrow evening and I'll come back with some results..
Thank you .. much appreciated
 
Another Update.. so I decided to go for another ride earlier today.. on initial start up I put the volt meter on battery and it is reading 15.30 volts ( no accessories on).. seeing I had the kids and wife ready for a little ride I went anyway..
My ammeter reading was pretty much in middle of gauge the whole ride.. I get home and put the volt meter on battery again and it's down to 13 volts.. I'm going to hook up a volt gauge (in car) to keep a closer eye on it , but is this normal?
Thanks in advance
 
I don't understand. Was the 13 reading with engine running or stopped? If running was it a slow idle, or were there heavy accessories running?
 
I don't understand. Was the 13 reading with engine running or stopped? If running was it a slow idle, or were there heavy accessories running?
The 13 volt was a running low idle (1000 rpm) with no accessories on.
So basically first start up of the day ( low idle 1000 rpm) it climbs ( slowly) to 15.30 volts on battery with no accessories on.. Then when I go for a ride ( roughly 10 miles) it drops to 13.10 ish volts at low idle (1000 rpm) no accessories on. and all the time my ammeter is sitting pretty much center of the gauge..
I have never changed the alternator nor had it tested in 6-7 years.
Thanks .
 
It could be that the alternator has enough load, and is not a real high output unit, that could be considered normal. If you can set it up at home so you are getting the 13, and without changing anything at all, move the voltmeter to the alternator output stud and see what that says.
 
It could be that the alternator has enough load, and is not a real high output unit, that could be considered normal. If you can set it up at home so you are getting the 13, and without changing anything at all, move the voltmeter to the alternator output stud and see what that says.
I actually did that and each time it was (approximately ) a .40 volt gain on the alternator stud..... So for example..if it was 13 volts on the battery at low idle ( 1000 rpm) no accessories on, than i move to the alternator stud .. volts were 13.40 volts.
Thanks
 
Hello Can someone pin point the main areas to look for voltage drop and the correct procedure?
I'm not the best with a volt meter..
Thanks for any help.
BTW my car is a 68 383 barracuda mainly stock with MP electronic ignition
Thanks
 
"Generally there are several areas for voltage drop. The drop you posted for the alternator stud is not bad at all. So the charging path is basically.........

Alternator stud........wire terminal.........bulkead terminal.........to welded splice (under dash harness in black wire)...........continue to ammeter............ammeter wire terminal............through ammeter..........ammeter wire terminal..............out big red wire.............back out through bulkhead.............fuse link and splices...........starter relay "big stud".............to battery

So each one of those points is a place for voltage drop on a stock car, and there of course can be more than one, and they add up. When you decide you have too much, you "simply" start going through the system with a meter to find it. "Let's say" in your test you had 2.4V instead of .4. To find that "Rig" some long leads on your meter for at least one probe. There are several ways to do this You can measure "to ground" and subtract voltage readings or you can measure "drop." You can put one probe onto battery PLUS post and track through the harness. Check where you can reach, at the ammeter, both terminals, at the interior side of the red and black wires for the bulkhead, and at the engine bay side of the bulkhead.

YOU MUST DO THIS IN THIS PART OF THE SYSTEM with a heavy load so to cause the alternator to be charging heavy, that is what causes the drop, is the CURRENT going through the wire. So you need, say, the engine running, the lights and heater blower running, etc

You simply compare readings. If you measure the black wire (charge wire) at the engine bay side of the bulkhead and at the interior side of the bulkhead, and get a reading of say, 1.5V difference that is a LOT OF DROP through a bulkhead terminal and it needs replaced

OTHER DROP: The ignition supply power, I often call "ignition run" or IGN1 is also a drop problem as this causes OVERcharging because the voltage regulator "thinks" that the battery voltage is low....because of the drop

This path......on a stocker..........is battery..........starter relay stud.........fuse link..........through bulkkhead on BIG RED.........to and through ammeter..........out on BIG BLACK..........to welded splice where it branches off to headlights, ignition switch, etc.................

through the ignition switch connector.........through switch........back out connector on (usually) dark blue IGN1 "run".............out through bulkhead connector into engine bay.........and branches off to feed VR, ignition system, electric choke, etc.

IF THIS PATH has poor connections, it drops the voltage to the voltalge regulator, and the regulator keeps ramping up battery voltage until the terminal (which is dropped) at the VR meets the VR setupoint. By this time the battery is OVER voltage

Finding it, same idea as the charging path
 
"Generally there are several areas for voltage drop. The drop you posted for the alternator stud is not bad at all. So the charging path is basically.........

Alternator stud........wire terminal.........bulkead terminal.........to welded splice (under dash harness in black wire)...........continue to ammeter............ammeter wire terminal............through ammeter..........ammeter wire terminal..............out big red wire.............back out through bulkhead.............fuse link and splices...........starter relay "big stud".............to battery

So each one of those points is a place for voltage drop on a stock car, and there of course can be more than one, and they add up. When you decide you have too much, you "simply" start going through the system with a meter to find it. "Let's say" in your test you had 2.4V instead of .4. To find that "Rig" some long leads on your meter for at least one probe. There are several ways to do this You can measure "to ground" and subtract voltage readings or you can measure "drop." You can put one probe onto battery PLUS post and track through the harness. Check where you can reach, at the ammeter, both terminals, at the interior side of the red and black wires for the bulkhead, and at the engine bay side of the bulkhead.

YOU MUST DO THIS IN THIS PART OF THE SYSTEM with a heavy load so to cause the alternator to be charging heavy, that is what causes the drop, is the CURRENT going through the wire. So you need, say, the engine running, the lights and heater blower running, etc

You simply compare readings. If you measure the black wire (charge wire) at the engine bay side of the bulkhead and at the interior side of the bulkhead, and get a reading of say, 1.5V difference that is a LOT OF DROP through a bulkhead terminal and it needs replaced

OTHER DROP: The ignition supply power, I often call "ignition run" or IGN1 is also a drop problem as this causes OVERcharging because the voltage regulator "thinks" that the battery voltage is low....because of the drop

This path......on a stocker..........is battery..........starter relay stud.........fuse link..........through bulkkhead on BIG RED.........to and through ammeter..........out on BIG BLACK..........to welded splice where it branches off to headlights, ignition switch, etc.................

through the ignition switch connector.........through switch........back out connector on (usually) dark blue IGN1 "run".............out through bulkhead connector into engine bay.........and branches off to feed VR, ignition system, electric choke, etc.

IF THIS PATH has poor connections, it drops the voltage to the voltalge regulator, and the regulator keeps ramping up battery voltage until the terminal (which is dropped) at the VR meets the VR setupoint. By this time the battery is OVER voltage

Finding it, same idea as the charging path
Thank you for the detailed reply..
Yesterday I got a dam root canal in my tooth so I won't be able to work on car for a few days.. I might start off with buying a new alternator because like I said mine could be 15 + years old.. (and it's nice to have a spare)
Can you suggest a safe AMP alt ?
My barracuda has no axtra accessories and running original AM FM radio..
Thanks again.
 
Another Update.. so I decided to go for another ride earlier today.. on initial start up I put the volt meter on battery and it is reading 15.30 volts ( no accessories on).. seeing I had the kids and wife ready for a little ride I went anyway..
My ammeter reading was pretty much in middle of gauge the whole ride.. I get home and put the volt meter on battery again and it's down to 13 volts.. I'm going to hook up a volt gauge (in car) to keep a closer eye on it , but is this normal?
Thanks in advance
I'm still not convinced that you have a problem. Immediately after the starter uses up some battery charge the system will put out a little more briefly to recover then fall back to normal.
I turn mine over a few seconds before I set the choke and start it. That uses up more of the battery.
 
Hopping to do some drop down test this weekend..
Also another few questions.. if I'm running a original single field alternator with a mechanical V/R with MP electronic ignition ..Will this cause an issue?
and I read somewhere about running a electric choke off the Balist resistor is a possible problem?
Thanks
 
-
Back
Top