Newbie question: Why two batteries?
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Senior User
Joined: Mar 2011
Posts: 173
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From: Richmond, VA
Newbie question: Why two batteries?
Ok, I picked up my truck last night. Like all guys, I look under the hood and, like most guys, I have no idea what I'm looking at (except it's really cool!)
Newbie question: Why does the 6.7PSD have two batteries?
Second newbie question: Since all batteries eventually die, how do you know when one is bad? No start? Slow start?
Last question: Who the heck is tall enough to pull out one of those batteries! (ok, just kidding).
Newbie question: Why does the 6.7PSD have two batteries?
Second newbie question: Since all batteries eventually die, how do you know when one is bad? No start? Slow start?
Last question: Who the heck is tall enough to pull out one of those batteries! (ok, just kidding).
Super Moderator
Joined: Aug 2008
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From: Frederick, MD
Easy stuff first, step stool!
Two batteries as it take alot of amps turn turn that motor over. You also have glow plugs to heat the chambers when cold. Diesels work on compression.
You change both at the same time. (batteries)
Two batteries as it take alot of amps turn turn that motor over. You also have glow plugs to heat the chambers when cold. Diesels work on compression.
You change both at the same time. (batteries)
Freshman User
Joined: Nov 2010
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A tremendous amount of current is needed to crank an engine that has a 16:1 compression ratio. The starter alone weighs about as much as a small engine. Secondly the glow plugs will eat up a few amps and the reserve capacity is necessary to crank the motor.
Starwarrior
Starwarrior
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Elder User
Joined: Mar 2011
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From: Maryville (Mur Vul), TN
Trust me, if your truck did not need two batteries Ford would not have put two in. Neither would GM or Dodge. Once one needs to be replaced you can change one but you SHOULD replace both....
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Freshman User
Joined: Nov 2010
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Dual batteries in a parallel circuit
It is a 12vdc system not 24vdc meaning the batteries are hooked up in parallel and 2 batteries simply doubles the current capacity. Since there is no diode isolation between them the system will draw power from both batteries at the same time. That also means that the bad battery can and will draw the energy from the good one. It is always best bet is to have both batteries at the same potential. (same age, same current capacity) Suggest replacing both of them.
Super Moderator
Joined: Aug 2003
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From: Isanti, MN
A tremendous amount of current is needed to crank an engine that has a 16:1 compression ratio. The starter alone weighs about as much as a small engine. Secondly the glow plugs will eat up a few amps and the reserve capacity is necessary to crank the motor.
Starwarrior
Starwarrior
It takes a LOT of power to complete all the tasks to start these engines up. Glow plugs can draw as much as 35 amps each, the injectors take much more power to fire than a gasser, the engine controls are far more complex, and the thicker oil requires more power to pump in cold weather.
Freshman User
Joined: Nov 2010
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Ever try to turn a Diesel engine by hand? Good Luck. Why do you figure they need a starter motor the size of a Honda engine to crank the sucker over, just to yank the owners crank? 4 cycle 8 cylinder engines have a fixed ratio between cam and crank timing and the higher compression ratio makes a big difference.
Elder User
Joined: Aug 2010
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From: Ft. Worth, TX
Not following this... each cylinder that is decompressing is not 'helping' the engine turn over, it is merely not hindering it. If it's the electronics that take so much juice to start, why do Dodge trucks (without glow plugs) have two batteries? What about 80's and 90's model diesel trucks that are fully mechanical (injectors, oil pumps, etc)? Modern gas engines have just as much electronics on them, but they only have one battery.
If you think that a motor with a compression ratio of 16:1 is no harder to turn over than a gasser at 9:1, you should try doing it be hand!
If you think that a motor with a compression ratio of 16:1 is no harder to turn over than a gasser at 9:1, you should try doing it be hand!
Freshman User
Joined: Nov 2010
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Great, you got it only glow plugs have nothing to do with combustion other than to warm up the cylinder so combustion can take place when heat is transfered in colder weather. And yes my friend, I have cranked enough cranks in my day, both gassers and oilers.
There are 8 TDCs in 1 revolution not 1
There are 8 TDCs in 1 revolution not 1