Which battery question?

[gimpyhauler]

Referring to my 2007 GMC Sierra Classic 2500HD Duramax.

Which battery under my hood is which? For what?

Which one should I hook my winch to?

Driver's side v passenger's side, which is for what?

[DmaxMaverick]

The batteries are wired parallel, with no bias. Neither is primary, nor secondary, and they are not isolated. It doesn't matter which you connect your winch, but I do recommend upgrading the Batt+ connector cable between them. The only load bias is the impedance of the connector cable, and upgrading it will improve the balance. This is not normally critical, as starting duties are momentary. A long session of heavy winching can really show it, though.

[gimpyhauler]

Thank you. That takes a weight off my chest.

As for the connector cable you refer to. Is there a part number or something of both/either the OEM and the recommended replacement.

Again, very cool to have you as a resource.

[a5150nut]

I don't know the part number for the Battery + cable but if he is talking the hot lead between the two positive cables I would get some welding lead and make my own.

[DmaxMaverick]

The only GM cable part number will be what you already have. It's a harness with the "jumper cable" eye in the middle of it.

You don't have to replace the OEM cable. Just add a pass-across cable from one Batt+ post to the other. Or use an OEM-style cable from a 90's single-battery truck (eyes at both ends, with nothing in the middle). If you have aftermarket batteries, such as Optima, they may also have top post terminals. If that is the case, you can just use a cable between each Batt+ post, with traditional terminal ends. I use Optima Yellow-Tops, which have this feature. I currently have a pair I installed in about 2004, and one quit this summer. I haven't yet replaced them, and am running on one Yellow-Top now. It's a little slow to start (winter), but it starts. I'll replace the pair when it's convenient (or maybe not when it's convenient, if the other quits).

[gimpyhauler]

Always willing to overbuild, I'll have to add a cable between the two.

I need to run power into the bed. I have a transfer tank. I'm going to install two back-up cameras (inside bed), perhaps will need a 12v power plug or two for accessory needs at times.

I bought an automotive fused power panel with 6 stations (for boats). Because it needs to be weather/water tight, I'm considering mounting it inside the rear of the cab, toward the corner.

Now I need to go through the rear wall of the cab with wires to the device needing power. Which probably means thru the bed wall also. Since there are waterproof 12v accessory plugs, they solve that problem. But I still need to run wires to the fuel pump unit and cameras.

How would you go about going through (cab & bed) walls with 12v wire and still keep it watertight and not chafe?

[DmaxMaverick]

I wouldn't go through the rear wall of the cab, then through the front wall of the bed. I would go through the cab floor (easily concealed and protected), then up through the bed floor (perhaps using a drain hole). You can use some flexible conduit with bulkhead fittings, for ultimate integrity, if you wish.

[gimpyhauler]

I'll have to look it over and re-think my path.

I was going to hook the fuse box up to a fused wire directly from the battery to the fuse box.

Now I'm going to have to see what I can do.

But it's going to have to wait for a bit. Too much snow on the ground and too many days of snow ahead.

But I'll be thinking.

[gimpyhauler]

I am going to install a new cable between the batteries out of #2 welding cable. Wouldn't it be a good idea to add an isolator while I'm at it?

If I add the isolator, which would be the starter battery and which would be the accessory battery?

As for my prior question, I've decided to run a power wire to the bed inside the frame and into the bed via a drain hole. I'll put a multi fused fusebox inside my Toolbox. I can mount anything I need in the box like 12v receptacles for accessories. I can also add a converter. I'm also installing a couple of cameras in the bed to make 5th wheel attaching easier. So now I'll have fused power in the bed.

[DmaxMaverick]

I am going to install a new cable between the batteries out of #2 welding cable. Wouldn't it be a good idea to add an isolator while I'm at it?

If I add the isolator, which would be the starter battery and which would be the accessory battery?

As for my prior question, I've decided to run a power wire to the bed inside the frame and into the bed via a drain hole. I'll put a multi fused fusebox inside my Toolbox. I can mount anything I need in the box like 12v receptacles for accessories. I can also add a converter. I'm also installing a couple of cameras in the bed to make 5th wheel attaching easier. So now I'll have fused power in the bed.

Still neither/both. They should be left connected parallel. There's no reason to isolate them, such as is OEM in a gasser with an "aux" battery option. Unless you are replacing (removing) the OEM crossover cable, it's still parallel. Why allow for the weaker connection? If you add an additional battery(ies), isolate that. Otherwise, forcing only one battery to perform cranking duties will be more load on the starter and electronics.

[arveetek]

The reason there are two batteries in a diesel is that the diesel engine has much higher compression, and takes a lot more effort to crank over than a comparable size gasoline engine. The two batteries are wired together in parallel, meaning the voltage stays the same, but the amperage is doubled. This gives more power, in a sense, to the starter so it can crank over the diesel engine quickly and efficiently.

Think of the two batteries as one big battery. You don't want to isolate or separate them.

In a gasoline truck, when there are two batteries, usually one battery is for starting the engine and the other battery is for running heavy loads, like a winch or snow plow. This is not the case in a diesel setup.

Casey

[gimpyhauler]

Something happened. I'm guessing I left something on. Both batteries tested zero.

Now I need to replace the batteries.

The isolator doesn't disconnect the batteries until you turn the ignition off. It only allows one battery to drain in the event of a problem.

I believe the dead battery would be the "accessory" battery. The starting battery will not drain. When the vehicle is started, it charges the main battery first, then charges the "accessory" battery. Both are now at full charge.

When both batteries are charged (as normal), both batteries are still used like OEM to start.

[DmaxMaverick]

Something happened. I'm guessing I left something on. Both batteries tested zero.

Now I need to replace the batteries.

The isolator doesn't disconnect the batteries until you turn the ignition off. It only allows one battery to drain in the event of a problem.

I believe the dead battery would be the "accessory" battery. The starting battery will not drain. When the vehicle is started, it charges the main battery first, then charges the "accessory" battery. Both are now at full charge.

When both batteries are charged (as normal), both batteries are still used like OEM to start.

I know how battery isolation works, but that's not what you have. If one battery is dead, and the other is not (OEM), then one battery is bad and the other is very short to follow (count on it). This is why we generally consider batteries as "pairs", requiring both to be replaced as pairs. When wired parallel, there is no "primary" and no "secondary", regardless of which is wired closer to the starter, and which is wired closer to the alternator. They crank equally, and charge equally, with the only difference being the impedance of the crossover wire itself. Isolation would prevent both batteries from being drained, but as soon as you key-on, your truck wouldn't start, normally. The dead battery, once un-isolated, would pull a lot of amps from the good battery (as much or more as the starter will demand), leaving you too little current for a start (Diesel). GM V8 Diesels need 2 batteries in parallel for effective, reliable starting, or GM would not include them in all V8 Diesel vehicles (they are cheap that way, ya know). Battery isolation with a manual override (to prevent un-isolation during a start with one dead battery) may allow a successful start under ideal conditions with a very healthy battery. Deep winter in cold country, forget it. Been there. Done that. Doing that now, still. My 2001 won't start once the overnight temp gets down to about 20F without a boost (and it starts REALLY easy and quick, compared to many D/A trucks). 20-30F is a coin toss. Above 30F and it'll start, but not if it sits for more than one overnight. I'm not driving it much lately, so it's not much of a priority right now. I just keep the charger handy, and put it on every few days if I don't drive it. Isolation would not help my situation one bit, as I only have one good battery to work with. Fortunately, it's a really good battery.

[gimpyhauler]

Okay. Now I'm starting to see the trees through the forest.

BTW, both batteries zeroed out. These were not old tired batteries. I just screwed up big time. I'm able to repeat my mistakes.

It is often that I don't drive my truck for a couple of weeks. Add to that, repeated nights from zero to 30, it does give batteries a challenge.

What about a battery shut-off switch? For extended periods of non-use?

Eventually, I'll have access to cover and a constant electrical source for maintenance but for now, I need to figure out an alternative.

What say you? Will my truck suffer if I cut all power? Then when needed, I'd flip the switch and have power again? Any issues other than the clock?

PS: I will be making a new positive cable between the two out of #2 welding cable with crunched (Copper?) ends.

[DmaxMaverick]

No problems, other than the clock. It may take a few seconds longer to "boot up", but no issues, with a disconnect.

Adding an additional crossover cable will never hurt, but it's only relevant during the cranking cycle or other high load condition dependent on that end connection. If you aren't adding additional battery(ies) in the circuit, it won't help much, if any, unless your current cable is compromised in some manner.

[gimpyhauler]

Basically, I screwed up somehow and killed my batteries. Get over it and just replace them and leave things alone. The only real extra thing I can/could do is the shut-off switch.

I will add an additional connection cable out of the #2 cable just to make myself feel better and at the very least, help equalize.

Heck, for a couple of bucks from Amazon, I can get cut off switches that mount on each battery. Get home, raise the hood, unscrew knob and close it down. Next time I need the truck, I raise the hood and screw the knobs. Close and get in the truck.

I use my car regularly and never have issues. But the truck, it gets lonely.

I do really appreciate what you do to help when I (just me) have questions. I also appreciate the "don't go crazy" stance. Smile

The other thing I've been learning along this particular journey, 2-3 times per year, put things on a tender for 24 hours.

[DmaxMaverick]

The "Amazon disconnects for a couple bucks" are cheap junk. I've used these (same as Harbor Freight or JC Whitney stuff, same Chinese/Taiwanese supplier), and they are underrated junk for anything greater than a lawn mower. They won't carry the current, and will fail. If you're lucky, they won't set your truck on fire (seen it happen). What you need is the marine switches, and they aren't cheap at $40+, each. Also note that, although disconnecting the batteries is a good idea for extended periods, most methods (especially on a budget) of connecting/disconnecting will not only get old after a while (relative to your patience), they will wear, then fail, with no warning (or a fire). If you want to disconnect for short period storage (long unused periods), just keep the system healthy, and trickle it once in a while. The batteries won't last longer (or fail sooner, to be fair), if you disconnect them, in an otherwise healthy system. Regardless of your course, the batteries will need to be maintained, or they will die an early death.

[gimpyhauler]

You do understand I appreciate this.

I will just keep it OEM (except the batteries) and just except that the extension cord out the front door, through the porch, out the door, out the gate, across the driveway and hooked to the truck every so often.

All this meaning I gotta get out of here and get my house and out buildings built.

Thanks again my friend.

I hope this new year is prosperous for you.

[a5150nut]

CAT used to use disconnects on the ground cable. Takes a key looks like a ducks head. They are rated for 24 volts and plenty of amps.

Weak batteries left in the cold will freeze and break the plates and connections internally. Keep them charged to get through cold weather.

[DmaxMaverick]

It's my pleasure.

I understand the extension cord thing. It seems everything I do on my property requires power, and is almost always as far away from an outlet I can get. I have a lot of extension cords, all of them HD outdoor type, and of the correct gage (16g to 10g, 100'ers), depending on what I'm doing and how far. I also have a brilliant solution for those times it's too far, or I just don't want to drag out an extension cord. Harbor Freight had generators on sale some time ago, and I got a 700/900 Watt little suitcase-thing that weighs less than 30 pounds. It runs the power tools, small air compressor, and battery charger/booster. That little "handy as a pocket on a shirt" thing cost me less than $80. It starts easy and works well. So far, it seems reliable and should last, at least as long as the warranty.

Anyhoo, I have a lot of family in Klamath Falls and the area. Beautiful country, and too long since my last visit. My aunt and (late) uncle were Mounted Posse members there.

Thanks for the New Year Cheer, and I hope the same for you and yours.

[gimpyhauler]

We have some similarities. Many good extension cords. I have a 7-800 Honda pocket generator. I forgot about it. It has lugs on the end for 12v charging, 8.5 amp.

When I get my equipment under cover and with power, I'll have tenders on each battery I have. Till then, more attention means longer life.

I'm wondering if I have a problem draw. Can't I put a test light between the negative cable and post and pull fuses until I find a draw? Do I have that correct?

PS: You ought to see the area. Less and less but mostly still white.

[DmaxMaverick]

These trucks are rolling supercomputers, meaning, they never sleep. No matter how you do it, if the batteries are connected, they will draw current. If one, or both batteries are weak, it will pull them down very quickly. With 2 good batteries and a healthy system, it should last at least 2 weeks before a drain is noticed. Yours is recovering from 2 questionable batteries, so give it some time before you make a judgment. If you have stray voltage going somewhere, new batteries will give you some time to figure it out before causing any new damage. One weak battery will cause all kinds of havoc, to be sure.

[gimpyhauler]

This is a first, I actually have something/info for others.

If you've read through this thread, I've recently had a challenge with my batteries. They are only 2 yo Optimas. Somehow, over just a couple of days, I drained the batteries to zero.

Spent a bit over $400 on two new Optimas. While I was waiting for delivery, I started my compulsive researching. I believe it was on the Optima Website where I read an interesting tip. A possible fix in my situation.

I tried numerous times to charge the batteries. They would cut the charger off at 7v. Repeated three times. Always cut off at 7v. Battery toast?

I have one of the largest Optima Batteries I used for various projects and needs. So here we go.

My journey:
24 hours ago - Take the old batteries out of my truck getting ready for replacements. Take one bad battery inside. Jumper cables between my extra good big battery (11.8v) and the garbage battery (5.6v). Let them sit for 24 hours.

This morning, cables off. Garbage battery is now 11.7v and holding. Hooked it up to the charger, away it goes with no issues. My charger does diagnostics and it has no more problems with the garbage battery. It's charging away like normal.

Braving the cold rain and wind, I just removed and brought the second "garbage" battery inside and the jumper cables are hooked up. Big battery still reads 11.8v. The second battery was reading 6.5v when the cables were attached.

This may have just cost me just over $400 but it might end up leaving me with enough good "extra" batteries for use on other projects and needs. Not as disappointed with the results as I expected.

I will report back with updates. Both when I get to test out the "garbage" batteries and perhaps a month or two after installation to see how they are holding up.

While I'm at this, I bought extra #2 welding cable. Enough to route front to rear to finally install Quick connectors front and rear for jumper cables. Plus I need power to the bed. So I'll get all this done while we enjoy the weather. The snow is melting today.

I cannot say enough about this site or the great people that take their valuable time to help us lesser mortals. Gracias

[DmaxMaverick]

That's excellent information! All my chargers are old-school (dumb), so it never occurred to me. Your charger is too smart for you, and your dumb batteries....

Now, to figure out what drained those batteries???

[gimpyhauler]

This is crazy stuff.

An hour ago I went out to find the first "bad" battery fully charged. Charger indicated it was ready.

Disconnected the second "bad" battery (battery cables to a better charged battery) and it was at 11.8v.

Charger running as it should. Just went out to verify the charger was still cranking away.

I'll see what the voltage is on the first to charge "bad" battery tomorrow morning.

Starting installation tomorrow. I still say this is crazy chyt.