battery amps low on start

[Bd Bridgewater]

alright guy so a few days i picked up a new 7.3 and im in love with it. this morning i got in my truck and drove to school with no problems what so ever. after school i walked out and my truck battery amps were reading very very low like (10 amps) would not crank over so i had to be jump started, drove the 45 minute drive home and no problems. right when i got it started amps returned to normal btw. i just went out and checked it and it cranked over and started after sitting about 6 hrs but batterys are still lower then normal. even when i just shut it off and turn it back on real quick without cranking it over amps still read to low until started then return to normal. whats draining my batterys?? bad terminals? not drawing enough amps on start up? im just confused and a little frustrated seeing as i just got it a few days ago. previous owner said both batteries were replaced in jan of 2010and replaced just one in nov of 2010 after draining it with a sub and an amp. batteries are both duralast. also battery cable connectors are pretty tore up so could that be it? just not being able to get enough power from the batteries before its started??
thanks

[loopygroup]

three things to look into
1. subs and amps should not draw enough to kill the batteries if you have a 2000 or newer truck it has 2 alternators one working will not keep up but also wont trip the idiot light.
2. the cables need to be in good shape
3. dual batteries should be replaced in pairs.
when I had my 2001 7.3 I had one alternator quit and it was a week of running before it showed up as low charge on the batteries. if it is not fixed in a timely manner it will overwork the secondary alt. and kill it.

[Bd Bridgewater]

it is a 99 single alt

[loopygroup]

ok so no dual alt the rest still applies.
would definately replace the cables and check the alt. output afterward.

[Austin G]

Originally Posted by loopygroup

2000 or newer truck it has 2 alternators one working will not keep up but also wont trip the idiot light.

Dual Alternators was an option, not a standard feature. Most common on ambulance models.

[JSchuricht]

Like AgentAustin said, Dual alternators are an option, not standard.

I assume your seeing 10 volts, not 10 amps. When you first turn the key to run, the glow plugs turn on which will cause you to see lower than normal voltage. To get a true voltage reading, use a multimeter and check the truck before starting and after it has been running a few minutes. You should see about 12v with the truck off and 13.5-14v with the truck running.

[loopygroup]

Originally Posted by AgentAustin

Dual Alternators was an option, not a standard feature. Most common on ambulance models.

correction noted. almost all I have seen/ worked on/owned have been dual alt.
plow prep package also