Dual Battery Question

[chubbusket]

I'm working on improving my 97 K2500's electrical capacity. I used this truck for plowing for the first time last year so I bought an Optima Deep-Cycle battery and ran 0awg wire for everything. The battery did well but it had a hard time keeping up with the constant hard draw from the plow. When I started the season I had installed a high-output alternator but I am fairly certain that the AGM Optima battery killed the voltage regulator in it. I've now read that the AGM battery does not accept voltage as readily as other batteries so my best guess is that when the truck wasn't using all of the power it had nowhere else to go and toasted the alternator. I asked the alternator manufacturer and they said it should be compatable with AGM batteries. Anyway, the alternator only lasted all of about 100 miles and it stopped charging. I had it replaced under warranty but then I put the old alternator back on the truck to get through the plowing season. So now I have a new, unused HO alternator. So here is my plan for what to do this season:

I want to install a second battery to use in parallel, a regular lead-acid one. Since the second battery location in the truck is already taken up by my plow hydraulic pump, I am going to have to put the new battery in the truck bed in a new box. Since I am mixing battery types, I read that those batteries could discharge each other so I am planning on getting an automatic battery disconnect that will be hooked up between the two batteries to take away the connection when the voltage in the system drops below a certain amount. And that way the starter battery will always have voltage to start the truck even if I use my other accessories too much with the engine shut down. And I would like to install the high output alternator again. If I hook it directly to the normal lead-acid battery I think this would give the voltage a place to go even if the AGM battery won't accept voltage as fast as the alternator wants, right? Anyway, I made a diagram of what I am thinking which I attached. I'm not an expert in this by any means but I think this setup will do what I want. Thanks for any feedback you have to offer.

 

[Erik the Awful]

I've now read that the AGM battery does not accept voltage as readily as other batteries so my best guess is that when the truck wasn't using all of the power it had nowhere else to go and toasted the alternator.

Nope. You had a bad alternator. AGM batteries have some quirks, but they're not that finicky.

I have a lot of experience with AGMs, and the Optimas aren't as good as they were when they first came out. They're definitely built cheaper now. They are exceptional if the vehicle gets parked for months at a time with the battery disconnected. Just reconnect and it fires up. Sitting is less harmful to an AGM than it is to a lead-acid battery.

They absolutely do not tolerate being completely drained. Do it once and the battery loses about half its cranking capacity. Do it again and you have a doorstop.

 

[RichLo]

I'm running an E60H on my plow truck (most powerful pump Meyer offers) with a huge, heavy straight blade. I run two alternators and two batteries to power that monster, I have the second battery's positive going directly to the top post on the first battery. I run a marine dual battery manual cutoff/selector switch in the cab (pictured below) running through the ground cables. With this setup I can run whatever battery's I want without worry of them draining each other. I really don't think an automatic cutoff switch would work with a snow plow application because it draw so much power that every time you lift or angle it would drop voltage and cut out the second battery, lol.

Here is a thread I made with my plow in action:

Snow Plowing HEAVY Snow...Pic heavy for your enjoyment

I was taking these pics for a truck of the month thread but after taking more and more, I figure I would just show them off in its own thread. Some of you might appreciate the difficulty in pushing this is, notice how lumpy and hard the snow is in some of these pictures.

www.gmt400.com

There are some in-cab pics that I think shows this switch and my dual ammeters to monitor the health of each alternator.

You must be registered for see images attach

 

[1998_K1500_Sub]

They absolutely do not tolerate being completely drained. Do it once and the battery loses about half its cranking capacity. Do it again and you have a doorstop.

Is that mostly relevant to the "starter" type batteries, e.g., Optima "red top"?

OP states he's got a "deep cycle" but he didn't say Optima "yellow" or "blue". Even then, it's better not to completely drain them, but my belief is they're more tolerant.

 

[1998_K1500_Sub]

There are some in-cab pics that I think shows this switch and my dual ammeters to monitor the health of each alternator.

I copied one of your pictures, below, that shows your instrumentation.

 

[Erik the Awful]

OP states he's got a "deep cycle" but he didn't say Optima "yellow" or "blue". Even then, it's better not to completely drain them, but my belief is they're more tolerant.

We have the blues in some equipment, but I think they're about "1%" better. A lead acid will always be superior for deep cycling.

 

[baxterday]

I am running two 1000cca batteries after using the second tray. I have a big amp in the back that draws a lot of power, but have the factory hi out put alternator. So far it's working great. I did have a battery go, which drew down the good battery, quick trip to Wally world solved that problem. I have never used the Optima type batteries, as they are not cheap. Did not know they don't tolerate a drain down.

 

[1998_K1500_Sub]

We have the blues in some equipment, but I think they're about "1%" better. A lead acid will always be superior for deep cycling.

For the reader’s benefit:

I assume you mean to say a “flooded” lead acid is superior, yes?

An AGM is also a lead acid battery.

 

[Erik the Awful]

Yes.

 

[chubbusket]

Nope. You had a bad alternator. AGM batteries have some quirks, but they're not that finicky.

I have a lot of experience with AGMs, and the Optimas aren't as good as they were when they first came out. They're definitely built cheaper now. They are exceptional if the vehicle gets parked for months at a time with the battery disconnected. Just reconnect and it fires up. Sitting is less harmful to an AGM than it is to a lead-acid battery.

I guess that makes me both relieved and worried at the same time. If the AGM was unlikely to have killed the alternator then I guess the Q/C of that type of alternator is not very good for it to only last 100 miles. It was a Powermaster, which I now believe (after doing some more reading) isn't that good of a brand anymore, either. The last thing I want is to put it back on the truck and have to replace it again right away. I guess I could always try it out again and see how it does. Thank you for sharing that information.

I'm running an E60H on my plow truck (most powerful pump Meyer offers) with a huge, heavy straight blade. I run two alternators and two batteries to power that monster, I have the second battery's positive going directly to the top post on the first battery. I run a marine dual battery manual cutoff/selector switch in the cab (pictured below) running through the ground cables. With this setup I can run whatever battery's I want without worry of them draining each other. I really don't think an automatic cutoff switch would work with a snow plow application because it draw so much power that every time you lift or angle it would drop voltage and cut out the second battery, lol.

Thank you for sharing your thoughts and experiences, as well. A dual-alternator setup sounds quite complicated. Did you remove the air conditioner to fit the second alternator in there? I don't have a plow that big, just an 8ft Fisher Speedcaster I retrofitted to mount on my '97.

I think your point about the automatic cutoff is a good one, as well. I hadn't thought of it, but the voltage drop of running the hydraulics will (as you pointed out) probably cause the isolator to remove one of the batteries when I need it the most. Something more like what you have suggested is better. Does the battery isolator you use have relays or solenoids or did you have to wire the fat-gauge ground wires for the batteries directly into the interior? I'm thinking of exploring something like this but I know they also make electronic ones that will connect both batteries only when the vehicle is running. That might be something more like what I need.

Is that mostly relevant to the "starter" type batteries, e.g., Optima "red top"?

OP states he's got a "deep cycle" but he didn't say Optima "yellow" or "blue". Even then, it's better not to completely drain them, but my belief is they're more tolerant.

To clarify I am currently running a single Optima Yellow Top. Had I known I was going to end up putting a battery in the bed, I probably would have just stuck with a regular lead-acid battery in the normal place and gotten a huge Odyssey battery for the bed since space wouldn't be an issue. However, the Yellow-Top hasn't been too bad to me so far--the truck started without too much complaining at -20F. Usually at the end of a plowing session I would have to let the truck run for awhile to get the battery back up to full charge. I would like to eliminate that going forward.

Thank you again everyone for the information. I will keep the thread going as I make more decisions and start putting things together. At the moment, though, I am fighting a misfiring issue so the battery will have to wait until it gets resolved.