The Once And For All On Batteries...

doghead

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Based on the thread title, I must thank you. Finally done with all battery threads after this one. Finally!
 

Ronmar

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So, I'm going to go with two batteries. Four just doesn't seem to make any sense; financially or otherwise.

How do I identify the 24V vs 12V cable? Maybe it will be obvious when I look at it, but the only cables I recall being obvious are the NATO plug wires.
The 12V cable is the one that has 4 battery terminal connectors on it:) the others y0u can kind of determine by their length. The ground linees need to be long enough to reach the front of the tray, while the 24V lines are fairly short as the 24V terminals are all the way in by the frame...
 

GTR0419

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Based on the thread title, I must thank you. Finally done with all battery threads after this one. Finally!
And it's been a good one! Some good info. I had no idea about the Alt/Generator charging issue. That aspect of how to set up your vehicle never occurred to me and it's kind of a big deal.
 

Third From Texas

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What year truck?

If an AO (facing truck) there are two cables coming in inboard/forward (top/left). These are your 24v (on the AO's the two are paired together, on the A1R it is a single cable (I've never owned an A1).

Then one single inboard/middle (center/top). This is 12v

And one that reaches all the way to the outboard/aft (closest/right). This is ground.

If you make a single jumper between the + and - , then you can save the takeoff cables incase you or next owner wishes to revert to quad bats.

20190724_141553.jpg
 

GTR0419

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What year truck?

If an AO (facing truck) there are two cables coming in inboard/forward (top/left). These are your 24v (on the AO's the two are paired together, on the A1R it is a single cable (I've never owned an A1).

Then one single inboard/middle (center/top). This is 12v

And one that reaches all the way to the outboard/aft (closest/right). This is ground.

If you make a single jumper between the + and - , then you can save the takeoff cables incase you or next owner wishes to revert to quad bats.

View attachment 825008
It's a 1997. I thought all the cables came in from the upper left. I'll have to look closer.
 

Ronmar

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On my A0 all the cables come in from the upper left. On mine the 4 connector 12v cable was made up of bolt together 2 terminal units. I reused one of these for my 12-24 jumper between the 2 batts...
 

GTR0419

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OK folks. Two 31s installed and the beast is alive. I will be modifying the box a little and will probably make some new cables. I feel good about it.

Funny little side note - I buy my truck batteries from a local small business that sells blems, used, and reconditioned batteries. I always get the new and their warranty is just as good as the big boys. The only real issue would be having a problem while traveling since they only have two locations.

Anyway, take look! Appropriate labeling!LMTV Battery.jpg
 

GTR0419

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On my A0 all the cables come in from the upper left. On mine the 4 connector 12v cable was made up of bolt together 2 terminal units. I reused one of these for my 12-24 jumper between the 2 batts...
I did the exact same thing. Yes, all the cables come from the left on mine as well. It was actually fairly easy to figure out once I was looking at it.
 

coachgeo

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ok..... so now question in a different direction (literally) since previous conversation has a logical lean to the "starter" batteries

scenario one- Not my case but it may be for others building Poo Man's campers.
> Oem 100amp 28/14 Niehoff<
. what about 24v "House" batteries charged via a battery isolator connected to alt and the two different banks of starer and house. Isolator; once the "starter" batts are charged then sends juice to House batts.
? AGM still a no- no for house bank here?

scenario two- my case Hummerized alt
>200amp 28/14 Niehoff<
. Again- 24v "House" batteries charged via a battery isolator- once the "starter" batts are charged and Islolator is sending juice to House batts.
? AGM still a no- no here?

sure would be nice to have AGM for house. Yeah true; sure would be nice for lithium...... but lets leave this out of conversation for now cause does not meet the "poo mans" criteria.
 
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Awesomeness

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ok..... so now question in a different direction (literally) since previous conversation has a logical lean to the "starter" batteries

scenario one- Not my case but it may be for others building Poo Man's campers.
> Oem 100am 28/14 Niehoff<
. what about 24v "House" batteries charged via a battery isolator connected to alt and the two different banks of starer and house. Isolator; once the "starter" batts are charged then sends juice to House batts.
? AGM still a no- no for house bank here?

scenario two- my case Hummerized alt
>200amp 28/14 Niehoff<
. Again- 24v "House" batteries charged via a battery isolator- once the "starter" batts are charged and Islolator is sending juice to House batts.
? AGM still a no- no here?

sure would be nice to have AGM for house. Yeah true; sure would be nice for lithium...... but lets leave this out of conversation for now cause does not meet the "poo mans" criteria.
The fact that the batteries are AGM is not what was being debated. AGM are always better batteries than conventional flooded lead-acid. It was the size that was being problematic.

Each 6TL is 100 Amp-Hours (AH), and so with four you have a total of 400 AH. Even at 100% efficient, (which it is NOT), the 100A alternator would take 4 hours of constant running at peak RPM to charge those batteries (400Amp*Hr / 100Amp = 4Hr). Then take into account that the 12V side of the alternator doesn't make the full 100A, and that when at low/idle RPM it doesn't make the full 100A either, and it basically means you need to run the engine a lot.

Better would be a small generator with dedicated charger (e.g. NOCO Gen4). Solar can help, but since you can only get about 200W/sq-yd at high noon, you're probably not going to get quite enough (12'x8' box roof = 10.6 sq-yd total, times 200W equals 2133W, divided by 24V equals 88A peak). But you only get peak sun for a couple hours each day (if at all), so if you average it across a whole 24Hr day it's probably like 5-10A average, which is less than idling the engine.
 

coachgeo

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The fact that the batteries are AGM is not what was being debated. AGM are always better batteries than conventional flooded lead-acid. It was the size that was being problematic.

Each 6TL is 100 Amp-Hours (AH), and so with four you have a total of 400 AH. Even at 100% efficient, (which it is NOT), the 100A alternator would take 4 hours of constant running at peak RPM to charge those batteries (400Amp*Hr / 100Amp = 4Hr). .....
thanks...... math makes since but figures dont?. Am I wrong to see it i as the 100amp OEM 14/28v is not 100amp.... it is instead in more simplistic terms only up to 50amp for each 24v and 12v? If so then the Hummer one would then be in simplistic terms be 150amp 24v & 50amp 12v?

Also in scenario questions is asked 12v is irrelevant.... that won't be hooked to the battery isolator.
 
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Awesomeness

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thanks...... math makes since but figures dont?. Am I wrong to see it i as the 100amp OEM 14/28v is not 100amp.... it is instead in more simplistic terms only up to 50amp for each 24v and 12v? If so then the Hummer one would then be in simplistic terms be 150amp 24v & 50amp 12v?

Also in scenario questions is asked 12v is irrelevant.... that won't be hooked to the battery isolator.
I think the subtlety not coming across is that none of this stuff ever works at 100% capacity. So I was using the simple numbers, and came out with 4 hours, but the reality is that you may only be getting 1/2 that AT PEAK, because the alternator is old and not delivering it's 100%, the batteries are old and not taking the charge 100%, the length of cable has a lot of resistance cutting it down further, etc. When idling, you may only be getting 10-25%.

Same with the solar. You're crazy if you're calculating off 200W/sq-yd. That high noon, with the best panels available (e.g. not Harbor Freight), panel pointed straight at the sun, high efficiency converter, batteries right next to converter with no/short cables, etc. Reality is probably 100W useful power into the batteries, and as the sun moves it drops quick.

Overall, this is why these trucks are so overbuilt with everything. In order to meet the government specs, it has to do it on the worst day, in the worst conditions. That's the opposite of civilian spec stuff, where it claims on the package "up to XXX performance!" and you can only get that in a lab, under ideal conditions, etc., and then you actually get way less.
 

Third From Texas

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Am I wrong to see it i as the 100amp OEM 14/28v is not 100amp.... it is instead in more simplistic terms only up to 50amp for each 24v and 12v?
I don't think so...

My 260a on my truck makes 260a on the 28v side and 140a on the 14v side. Now whether it alternates that thru the magic smoke contained within or if it does it at all the same time, I've no idea (I suspect the former).

If memory serves, the 100a OEM 28/14 puts out 100a/40a respectively...grossly underpowered.
 

Awesomeness

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I don't think so...

My 260a on my truck makes 260a on the 28v side and 140a on the 14v side. Now whether it alternates that thru the magic smoke contained within or if it does it at all the same time, I've no idea (I suspect the former).

If memory serves, the 100a OEM 28/14 puts out 100a/40a respectively...grossly underpowered.
I think that may be the max from either leg at once, not the combined.
 

JD4044M

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Glad I read more on this post. I am ready to tryout 2 battery's for my 95 1078-A0 even tho I have 4 installed. Run 2 and have the other 2 for back up. Don't run mine much right now and checking them gives me something to do. It starts so easy 2 should do it no problem. There Group 27s and I just need to swap cables around. Thinking of setting up Disconnects or Relays later I can switch from inside the Cab. They seem to stay charged better just not hooked up to the truck? Be nice to have a 24 volt set up to jump start it if needed. Wind chills down to -5 below zero so kind of nippy outside right now.
 

Awesomeness

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Wind chills down to -5 below zero so kind of nippy outside right now.
Wind chill temp doesn't matter, just the actual temp. Wind chill temp means that the wind is blowing heat away as fast as if it were that temperature, but you still will not actually drop below the real outside temp under any circumstances.

Two batteries is probably ok for most people. The 4 batteries are mostly to retain Cold Cranking Amps (CCA) and reserve capacity when the batteries are at -30°F, plus the redundancy of being able to have a battery fail and still get power. Personally, there is space for 4 and I like retaining all the cool capabilities these trucks have to offer. If you keep the batteries on a tender, and/or use the truck regularly, you're fine with 4 batteries... it's not a "design deficiency" that you should feel the need to correct.
 

JD4044M

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I was watching the 4 New Batteries I just put in. Found that one 12 volt was dropping and not the other? It was not tied into the other 12 v. Charged all 4 at 24 volts they did not charge equal for me. To get them all floated even I had to do one at a time at 12v. The 12 v part is going down slowly over a few days? It did the same thing with the 4 Red Tops that were in it. Pulled them out and found only one was bad out of the group. I still have them. Going to put a amp meter on the cable to see where it is bleeding off to. The Cold Temps I was talking about was me freezing my butt off. I did not have gloves. It is blowing 23+MPH and 39 MPH Gusts at 19 degrees. Did not take long unhooking my batteries to get my fingers froze! Will be dropping down to 1 degree real soon here.
 

Awesomeness

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I was watching the 4 New Batteries I just put in. Found that one 12 volt was dropping and not the other? It was not tied into the other 12 v. Charged all 4 at 24 volts they did not charge equal for me. To get them all floated even I had to do one at a time at 12v. The 12 v part is going down slowly over a few days? It did the same thing with the 4 Red Tops that were in it. Pulled them out and found only one was bad out of the group. I still have them. Going to put a amp meter on the cable to see where it is bleeding off to.
If one is bad, all kinds of goofy stuff can happen.

The NOCO Gen4 charger that I have actually hooks to each of the 4 batteries individually. It checks them, desulfates them, charges and maintains them, at 40A max. It's also fully submersible. They just came out with a newer version, too, that can charge lithium ion batteries.
 
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