One last question for today, dual batteries

[JIMs70GMC]

The K30 I bought has the "auxillary battery" option. How was that wired in with the alternator? I looked at some saved wiring diagrams i have and no luck. thanks,

Jim

[100%Chevy]

I have 3 trucks with dual batteries.2,82's and a 95.The 2,82's have a winch ( the car-hauler actually has 3 batteries) and the 95 is a diesel.
They're no different than the wiring on a single battery except there's a positive cable connected between both and each battery has a ground cable to the engine.
The alternator will keep 2 batteries charged if they are within range.Not so much for dead batteries!
I don't know how your truck should be wired,but will work wired the way I've described.
Mike.

[JIMs70GMC]

Thanks. Didn't know if it was anything special.

[hatzie]

Is the truck equipped with Option TP2, is it a converted diesel, or did someone add a diesel style LH battery?

The diesels have both batteries wired in parallel to double the starter amperage. The grounds go to the block and there's a jumper lead from battery to battery with a longer positive clamping bolt on the RH battery to accommodate both the Jumper and the Starter hot lead.

The TP2 option isolates the Aux battery from the primary start battery when the ignition is switched off for add-on equipment loads like camper lights. This avoids killing your primary battery with the camper lights. There's a relay to connect the AUX battery to the alternator with the ignition in the RUN position and a power distribution stud on the AUX battery hot cable.

AUX battery option TP2 does not have provision for start current from the AUX battery. You could conceivably jump the primary battery from the AUX battery with plain old jumper cables if you ran the Primary battery down and the AUX battery was charged.

[wilkin250r]

There's a bunch of different ways to do it. Some just wire them in parallel like 100%Chevy posted, others use an isolator. The isolator allows your alternator to charge both batteries, but keeps them otherwise isolated (hence the name).

If they're wired directly in parallel, problems with one battery will affect the other, like a bad cell, or even an electrical problem that drains your battery. If one goes dead, the other will follow. The isolator protects them, so one might go dead and the other is perfectly fine.

I've also heard of people wiring a large switch (like a battery cut-off switch, but with multiple positions) to allow a variety of configurations with just the turn of a switch. You can install your isolator and keep the batteries protected, but with a quick flip of a switch, wire them together for a winch pull, extra starting power, or instant jump-start without cables.

[cjthompson]

Originally Posted by hatzie

Is the truck equipped with Option TP2, is it a converted diesel, or did someone add a diesel style LH battery?

The diesels have both batteries wired in parallel to double the starter amperage. The grounds go to the block and there's a jumper lead from battery to battery with a longer positive clamping bolt on the RH battery to accommodate both the Jumper and the Starter hot
Attachment 1551031

? V=ir so cranking amperage wouldn't double when wired in parallel, right? As you still only have 12 volts. This would work like adding another tank on a compressor system. it just keeps you at pressure longer without voltage drop right?

[wilkin250r]

Yes and no.

The problem is that Ohm's Law is just a basic guideline, rarely can the real world be simplified to such a simple mathematical expression. There are a whole slew of real-world parameters that come into play, like internal resistance of the battery, voltage drop along the battery cables, ect ect. If Ohm's Law was a perfect expression of the real world, I could start my car with eight AA batteries.

So IF you were starting something small, like a lawnmower, then adding another battery in parallel wouldn't provide any additional benefit because a single automotive battery has plenty of power to do the job alone. In that respect, you would be correct, it's all 12V.

However, since your starter pulls such a huge draw against your battery, adding another battery in parallel can often give you a significant increase in cranking amperage.

[hatzie]

Originally Posted by wilkin250r

Yes and no.

The problem is that Ohm's Law is just a basic guideline, rarely can the real world be simplified to such a simple mathematical expression. There are a whole slew of real-world parameters that come into play, like internal resistance of the battery, voltage drop along the battery cables, ect ect. If Ohm's Law was a perfect expression of the real world, I could start my car with eight AA batteries.

So IF you were starting something small, like a lawnmower, then adding another battery in parallel wouldn't provide any additional benefit because a single automotive battery has plenty of power to do the job alone. In that respect, you would be correct, it's all 12V.

However, since your starter pulls such a huge draw against your battery, adding another battery in parallel can often give you a significant increase in cranking amperage.

A normal starter minimum draw is somewhere between 300 and 500 A.
Eight AA batteries do not have the amps to do the job... AA batteries are 2.4A each so even if they were 12v per cell eight would only be 22.4A
The problem is the size of a pack of AA that would be needed. In an ideal world you would need more than 1,500 AA batteries wired in mixed series and parallel to make 500A output power at 12V and more than 3,000 AA batteries to provide 1,000A... This is not taking any losses from internal resistance of the AA cells into account among other things. It's probably more like over 4,000 AA cells. I'm not including the heat generated by sucking a large slug of juice in a short time period from these batteries...

Lead acid batteries are a much denser power source with capacity to move a lot of electrons in a short time period. The two group 78 batteries in my GMC are 1700A of capacity at 0°F. Two Group 78 batteries are much smaller than a 4,000 cell brick of AA batteries.
Folks have been experimenting with Hybrid Super Capacitor and smaller Lead Acid battery and Lithium battery configurations for weight and size savings. They are real good for short bursts of power and quick re-charge. Not so good for long runtime.

The rule of thumb is batteries in Parallel doubles your amperage and in series doubles your voltage.
You can mix Series and Parallel in a battery pack to give the desired volts and amps. Cordless drills and electric forklifts are examples of mixed series parallel configurations.
http://batteryuniversity.com/learn/a...configurations