How much voltage is needed to start my truck?

everytime i've had jumpstart me or someone else. it's always been at least 12 volts. if batteries get too weak. you might crank but no power to the ecm.

i know if it had ignition. it has to be at least 12 volts or you don't get power to the igntion system. and maybe the ecm.

with trucks. all we gotta worry about is enough power to the ecm while cranking. which probably isn't happening if the crank is slow.

a technician might come along to know the exact answer. and post it

 

Folks, look at Maxwell Ultracap battery capacitor for semi trucks you would never worry about cold weather starts. I worked with a research scientist Dr. Kent Davey utilizing this on a project.
http://www.maxwell.com/products/ultracapacitors/applications/cold-starting

 

Most will start with slightly less than 12 VOLTS , my last PETE would crankover nicely with 10.8 Volts ( had digital meter for Bat output )

 

Voltage drop is a function of Ohms Law... E=I*R

E=Volts
I=Amps
R=Ohms /Resistance

If your is voltage is dropping below an acceptable level when introduced with a load, then this would indicate a deficiency in either the available amperage(battery capacity) OR an unacceptable amount of resistance in the wiring OR a load that is not rated for the circuit OR all three combined.

Most trucks use parallel wiring for the electrical system. If 4ea 12VDC 100 amp hour batteries are wired in parallel, the output capacity is 12VDC @ 400 amp hours and inversely if wired in series the output is 48VDC @ 100 amp hours.

You can increase load performances by increasing the amp hour ratings on the power plant (batteries), keeping in mind that they should all be of equal amp capacities & voltages.

This being said, it is more likely that a faulty ground, bad connection,improper wire size or bad wire(s) is the root cause of a voltage drop since starting circuits (induction) are designed to provide adequate power.

Most common place of corrosion is the parallel wiring between posts on the battery, and the output connections from the battery. These should be kept clean and tight to assure all available capacity is available when a large load is introduced.

Batteries should also be individually checked for specific gravity and charge. One or more poorly performing batteries in a combined power plant can significantly reduce the output capacity especially when under high loads.

 

basically as above, you could have 14 volts, but if you don't have the amperage the truck won't crank.

And what I learned the expensive way is that if you are dragging your batteries down into the 10-11 range with a load, you are dramatically shortening their life cycle. I have a TRiPac which was originally programmed to kick on to charge when the voltages fell this low, and was replacing batteries about every year and a half. Now have it set to start charging when it only falls to about 12.0, and on 3rd year with these batteries.

Of course if you were using deep cycle or AGM batteries it would be different.

 

The minimum at the starter is 9 volts if you have Delco Remy 42MT and are checking the wiring. 9V=OK!

What the volt gauge shows is at the battery. What counts is what gets to the starter.

 

Don't recall exact figure, but I believe Mack folks told me '02 E-7 needs to see 10.2 volts to the ECM or it won't start (won't fire injectors).
Other motors - ???

 

I always thought my CELECT+ would fire the injectors on 9v, but if I have 10v showing on the voltmeter in the cab, the engine will crank till the starter smokes, without so much as a cough. This is with a voltmeter that reads from the starter (FLD Freightliner with battery box in the rear) and a Cummins ECM that draws directly from the batteries. A thousand amps along 12 feet of 2/0 cable can cost you an entire volt.

10v cutoff sounds way too low for the inverter.