A question to those who know,,, what job does each battery have, or are they tied together. I was just wondering if the battery used to crank the engine or the opposing one fails first.

I have noticed on mine when you turn the key on and the pre heater comes on it seems to be quite a big draw of power..
It seems to idle for a good little while before the volt gauge will come off the 12volt mark and move up to the 14 volt mark..
It does this same thing even if I start to drive off although the gauge does rise a little quicker this way.

 

I believe that they're tied together so to speak, since the high compression engine needs a lot of charge to get it moving. I do know that you can't start it with only one of them hooked up.

FWIW

Ken

 

I disagree, I know several people that have gotten rid of the second battery on the right side and they start just fine on one battery. There are two batteries for the amps for the starter and also the intake and fuel heaters.

 

They are wired together(parallel).

 

The batteries are run in parallel. This is a very common feature on all pickups, not just diesels (check underhood of F-350s that you rent from UHaul, or my dad's 88 1/2-ton Chevy with a 350).

If both batteries are properly charged up and it's warm out, then it should be able to start just fine on one battery. The real thing is that when it gets cold out and the truck has been sitting for a while (i.e. the batteries are now even colder), this will provide the amps necessary to get the thing started. After all, there's nothing that sucks more than turning the key when it's -20 out and hearing a "crank... craaaaaaaaank................ craaaaaaaaaaaaaaaaaaaaaaaaaaank.................." and then the thing just goes dead. This goes doubly so if you're in the middle of nowhere.

 

The intake heeters cycle for a couple of minutes after start up. Watch your meter, it will bounce between 12, and 14.

The reason she jumps to 14 after you take off is because once you hit 10, or 15 MPH the heet cycle stops.

 

What do you do with the other wires if you go to one batter? Tape them up? I'm thinking about going to a single Optima Red or yellow top when mine finally die. I plug mine in at night so I'm not worried about it drianing it in the cold.

 

The batteries are in parallel. That effectivelly doubles the ampage and keeps the voltage at 12 volts. For example two 12V 800 amp batteries in parallel would produce 12V and 1600 amps. Not to say the tryck could not start on a warm day with only one battery. As said before when the temps are low the airtake heaters pull big amps, along with the fuel heater, then add the starter amps, get the picture. IMO I would stay with the dual battery setup, unless you could find a single battery that could supply the same amount of amps as two batteries in parallel.


Another good reason for staying with the dual set-up is when you want to add winches or other high amp demand equipment.

 

Take it from an electrical engineer... The CTD is not designed to run with a single battery, it will, but a single battery will die early due to the large demand put on one battery and you WILL loose starting capability in cold weather.

Explanation:
The batteries are wired in parallel because the starters and grid heaters for the CTD's require LOTS of power (measured in Watts). It's takes a lot of power to crank over an engine with a 17:1 compression ratio in cold weather. There isn't a single battery on the market that can supply enough power to reliably start the CTD.

The engineers had two options to provide the power needed to reliably supply the starting system with enough power, reliably being the key word.

For the following examples I'll say the batteries are rated at 800 CCA (Cold Cranking Amps, i.e. the batteries can source 800 amps in colder weather)

OPTION ONE: Use two batteries in series, raising the system voltage to 24 V (batteries in series add voltage, 12 + 12 = 24). (total power = 24 V * 800 A = 19,200 Watts). But probably 99% of the auto industry runs 12 V components and it would be expensive to outfit the trucks with 24 V gear.

TWO: Use two batteries in parallel which keeps the system voltage to 12 V but doubles the electrical current (total power = 12 V * 1600 A = 19,200 Watts)

If you go with one battery you will loose starting capability in cold weather and battery life. There is no reason you should to switch to one battery.

 

I do not know for a fact that this could be a problem on CTD, but on the last Ford we had when one battery failed the remaining battery did not have enough power spin the engine fast enough to start.. i.e. it would crank, but it would not start. According to the Mechanic he said that diesel motors must be cranked fast enough for the compustion process to begin, with only one battery I would be affriad that the starter would not produce enough revs. to start the motor.

 

My old 89 only had one battery and I started it up north (Pa) at 10 degrees below zero with no problems. Heaters cycled and everything, so don't say it won't work. I got three to four years out of one battery also (1225 amp NAPA battery). I've had more problems with the dual battery set up on the 95 and the 99 than I ever did with the single battery set ups in the last two trucks. The right side battery goes bad bad drags the left side battery down with it. It depends on where you live whether one or two batteries will work better. Here in Virginia, it rarely gets cold enough to really need two batteries. If I were still living up north, I would not even consider one battery.

 

Tim just eliminated the big cable over to the right side battery by unbolting it from the left side.