Duramax Diesel Question?

[lungslicer]

Can anyone tell me exactly why I have 2 batteries under the hood of my Diesel. Do both batteries actually crank the motor? What do they each do? Does anyone know of a good HSOforum to learn more about Diesel motors? Thanks guys!

[Valv]

Diesel motors have much higher compression than gas, that's why there is no spark plugs.

To start a diesel motor you have the compression and speed of motor to achieve the combustion necessary, that's why 2 batteries are needed, 1 will not have enough power to spin motor fast and long enough.

They are both charged by the alternator, follow the positive cables from each battery, you'll see they are bridged.

Which truck do you have ? If you do a Google search for your brand name forum you will get a lot of results. Check which one has most poster and you'll find the best ones out there.

[LMITOUT]

To add to what Valv already said, the engines have glow-plugs which require a fair amount of power before the engine even fires, so add that plus the high compression ratio (18:1) fighting the starter and you need that extra battery for easy starting.

[Whoaru99]

Yup, one battery MIGHT do in the summer, but come cooler weather when oil viscosity throws in another factor, both are necessary for the reasons mentioned.

Believe me, if GM thought you could get by with one battery, there would be only one battery there.

[Jeremy airjer W]

Quote:

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Believe me, if GM thought you could get by with one battery, there would be only one battery there.

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I'll second that!

[hawkeye43]

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[iffwalleyes]

You always will find a 2 battery set up under a diesel way more power required to start. Not so much now but wait till Dec-Mar that 15-40 oil is stiff. You will notice a hugh difference on colder mornings if you have it plugged in but that isn't always possible. Mine started last winter one day when it was -30 and wasn't plugged in. It wasn't happy but it did start . Your going to love that truck I sure like mine.