This might seem like a dumb questions, but why does my 2001 F350 7.3L PSD have two batteries? I have two other F250, a 5.4L and 6.8L gassers, which both have 1 battery. Normally I drive the F350, but went on vacation for 3 weeks and of coarse the battery dies. When I went to jump it I notice two batteries. Do I charge both or just one? Is that normal for a diesel? or was the second one a add on?

 

Just about all diesel pickups get two batteries. The main reasons are 1) it takes a lot of starter motor power to crank them, and 2) glow plugs pull a lot of current.

If you have a bad battery you should replace BOTH batteries together.

I guess you don't open your hood too often, LOL.

 

I thought it was so they could fill that empty space on the drivers side.

 

Thanks Bill, I don't open the hood much, as I routinely maintain my trucks at least every 3 months through my mechanic. I am somewhat handy mechanically, but if it's something new that I never worked on it will take me forever to fix. Also I'm a perfectionist on my own stuff. Free time with family these days is more important. The diesel was bought a few months ago and really didn't take a close look.

 

you try to turn over 16:1 compression ratio and then you will know. plus the glow plugs and stuff, peak demand is why.

 

and yes to your other Q they are connected so charging one will charge the other

 

Thanks Guys, giving the F350 a good charge now and if it doesn't work, new batteries.

 

I agree with you...

 

Ok, since you are in the market for new batteries, I suggest you to buy a higher CCA than stock. I use 875 CCA yellow top ones from Autozone. Optimas are little pricey but are very good...just a thought.

 

I bought the same auto zone batts ! the warranty was better than the optimas but I do like optimas for some applications just not pairs like this set up the chances of both optimas failing at the same time was low and good luck telling them you want 2 because 1 went south .. on the other hand wet cells are easy to make no worky so you can get 2

 

I priced both Optima's and Yellow top ones from Autozone. It just made sense to buy Autozone brand at that time...

 

I'm also running the yellow tops from Autozone. The original Motorcraft batteries lasted 4 years before giving up the ghost. I threw on some Energizers after that, and they died in no time.

I've had the Autozone batteries for a few months now and they seem to hold a charge really well. Had some injector o-ring problems recently that I haven't fixed yet, so my truck has been sitting in the driveway for some time now. I had to use my truck last night, and the batteries were strong as ever. If they last as long as the Motorcraft ones, I'll be happy.

 

Fully charged, so hopefully stay charged. CA doesn't get too cold, but this last 2 weeks been cold. I'll keep the Autozone battery in mind.

 

Primary purpose of batteries is to power the starter motor for engine start up. Two batteries double the available power available for the starter. This is important because the 7.3L diesel is harder to start then the gas engines. It is a larger displacement engine, has greater compression ratio, and needs plenty of cranking speed for the fuel system to pressurize and combustion to be supported. All this adds up to a more power hungry starter motor, greater current draw, and need for larger set of batteries.

Glow plugs also draw some current (100 Amp??) but it is not significant compared to the starter motor. If anything, the activity to operate the glow plugs helps to warm the battery a bit before starting, making the batteries more potent then if you did a fresh cold start crank.

 

On the 6.0 each glow plug draws 10-12 amps.