Two Batteries Instead of Four - Issues?

[Kevin Means]

Our M1083 has the typical four-battery setup, with 12 and 24 volt circuits. I've noticed that many people have switched to two batteries instead of four. I'd like to switch to two larger batteries, and then move them a short distance to help with outside storage. Any issues/problems when you do that in these rigs?

Kevin

 

[Mullaney]

Our M1083 has the typical four-battery setup, with 12 and 24 volt circuits. I've noticed that many people have switched to two batteries instead of four. I'd like to switch to two larger batteries, and then move them a short distance to help with outside storage. Any issues/problems when you do that in these rigs?

Kevin

.
No problem at all - unless you are in the far north. And even then, with a block heater you should be fine. As a matter of fact you will make your alternator a lot happier as well...

 

[MarkM]

Just use large batteries with high CCA ratings.

Mark

 

[Ronmar]

None at all. Cat specced a pair of group 31 batts for these engines, and that is really all they need. A pair of group 27’s would also work well IMO.

4 batts is too much for the alt as when 12v is fully loaded it puts out around 1/3 less energy than a straight 24v@100A alt does.

a pair of conventional wet 6t batts is still an acceptable match for the 100a dual volt.

I would not recommend a pair of 6t in AGM or anything larger than a pair of 6t wet cell batts for the dual volt alt.

AGM batts when thirsty/worst case dead battery recharge conditions, are looking for nearly twice the charge current out of the alt than a conventional wet cell lead acid does. 45% of the AH rating in amps vis 25% of the AH rating for wet cell batts. Plus the truck loads of course…

 

[Ronmar]

The truck was saddled with this monster 4 battery bank to meet some cold crank mil-spec at a very low temp. Unfortunately the bright lights at S&S didn't size the alt properly to support it, so these trucks have been plagued with charge and battery issues as they typically do not run enough hours to keep the battery charged fully. And when they do run, the alt is coping with an overload trying to top off the low batts and probably never succeeds before it is shut down. The biggest killer of batteries is low state of charge and the resulting sulfation...

They also have a 12v vampire on the A0 trucks that tends to pull that half of the battery bank down, which doesn't help... The A1's got manual and automatic battery disconnects(LBCD) to help bandaid the issue but they didn't truly deal with it until the 260A alt on the A1R, but that was an absolute necessity with the fielding of AGM batts...

Throwing amp hours(and ether) at cold is probably the simplest way to try and cope, but the proper way to deal with cold starting is to apply heat...

 

[MarkM]

Boy you need to be careful with the ether. I've seen some real carnage when too much is used. As far as heat I always liked the waffle iron magnetic heaters. Super simple and you can't beat the ease of install. I used them all the time in the material handling equipment world.

Mark

 

[Ronmar]

Boy you need to be careful with the ether. I've seen some real carnage when too much is used. As far as heat I always liked the waffle iron magnetic heaters. Super simple and you can't beat the ease of install. I used them all the time in the material handling equipment world.

Mark

Ether itself is not the problem, as it is simply a combustible fuel with a lower ignition temperature than the diesel that is also being injected during a normal cold startup. It is its misuse that causes the problems...

Diesels don't have throttle plates and use governors to control fuel. When you fill the entire air filter and intake pathway with a combustible air-fuel mix, when it does finally fire, the engine tends to runaway as you have no control over the engine using that fuel-air mix. So you take a cold engine from crank RPM to redline and beyond, and depending on the length of the intake, hold it there for a bit.

Since the governor is commanding idle fuel, as soon as the RPM goes over idle, it then cuts the diesel being injected so no top end lube either... Its that cold high rev that does the damage, causes the wear that brings on difficult starting, and "ether addiction", and under extreme cases, bends/twists cranks and throws rods, thus giving ether its bad rep. It is not the ether itself...

Direct injection into the manifold like the LMTV uses, is the proper way, it is metered and can be completely controlled, so no runaway, no governor fuel cut and no damage, just the chemical "spark plug" cold starting aid it is intended to be...

 

[Kevin Means]

Thanks everyone. Helpful as usual

Kevin

 

[coachgeo]

If you will be in AZ most of time.. go to two battery as suggested. Weather there you wont need four. If you upgrade significantly your alternator as suggested.. AND end up with her in cold country (with no ether start esp.) then go to four battery.

 

[olly hondro]

I concur with the 2 battery solution here in A Z

 

[Ronmar]

In the case of the 3116, There were a whole lot of GM trucks(box and small dump) produced with this engine. In fact, other than what cat decided to use in it’s own production equipment and configure as marine propulsion, nearly all these engines went to GM(Some found their way into ag equip also). I suspect that is why HP and torque graphs for the road engines are not available as GM kept that info to themselves… Now these trucks found their way to everywhere between AK and FL, and there are still quite a few of the road Operating just fine in all kinds of climates… I have yet to see one or any spec for one with 4 batteries…

The 3126 was a little more openly marketed by cat and also found its way into the medium truck and marine markets, but at least cat published the road engine curves for it… also never seen one of these, or a spec for one with a 4 battery config…

weird crap happens in the mythical land of milspec

 

[GeneralDisorder]

I personally stick with four. One simple reason. Two is one, one is none. With four you can drop to two. With two (one failed, punctured, destroyed, lost in a boating accident, etc)...... you can walk

 

[Priapism]

Does anyone have a wiring diagram for 2 batteries? Watched this video (

) but he doesn't have a schematic?

 

[GeneralDisorder]

It's pretty simple - it's just a pair of batteries in series providing 24v (for the PPD/LBCD, and the starter leads) with one extra lead that happens to come from the middle of the pair to provide 12v for the PPD/LBCD 12v stud that feeds the 12v subsystem. A two battery system is the simplest setup and really anyone that owns one of these trucks should commit that much electrical knowledge to memory if they are going to work on the truck themselves.

For an overland application though, there is zero reason to prefer two over four except in terms of cost. Four gives you more reserve in case of alternator/charging system deficiency and redundancy in general. But I'm that guy that carries a spare starter and drags half the Motorpool tool cage along for the trip.

You can also switch to four smaller batteries to free up some space in your tray. Sprinter batteries are what I would look at. Those silly things are EVERYWHERE and the batteries are in stock everywhere and frequently on sale. They have studs also so they are quite convenient to hook up. I run two of those in my CUCV.

Never had to tow my truck yet..... Knock on wood.

 

[Ronmar]

look under the battery box cover, there is a diagram there... Remove either the pair of batteries towards the front of the truck, or the pair towards the rear of the truck and any unused connections and jumpers...

 

[sue]

Been running two 12v batteries for years.

 

[GeneralDisorder]

Been running two 12v batteries for years.

It's simply a matter of choices in terms of packaging and pricing. If money was zero object I have no doubt that everyone here would be running four 6T-AGM's and the 260A or 300A FMTV alternators. But that's a $4500 to $8500 alternator and $2800 in batteries.

But make no mistake - you are giving up range with a charging deficiency, and you are losing redundancy by eliminating two batteries. With these trucks being automatic and HEAVY there is ZERO ability to get that big paperweight under the cab spinning without that 24v starter. You are absolutely and completely hosed without a backup plan for starting the engine.

 

[Ronmar]

If I were going to run 4 batts, I would isolate them with an isolation switch and charge them with a small DC-DC charge controller or a BIRD relay, like a house battery. That way they would not overload the 100A alt if they should somehow become discharged. but would still receive a charge when the engine ran/once the main batts are mostly charged. They could then be a true backup, not affected by something that say inadvertently discharges the main service battery...

 

[GeneralDisorder]

Usually a drain will only affect either the 12v or the 24v bank and it's often the case that a truck which will not start can be started by swapping the inner and outer battery pairs.

Protecting the 100A alternator.... For me that's easy. Throw it away - can't hurt itself or my batteries from the inside of a scrap metal dumpster (or more likely just downrange into some other poor fellas truck so it can continue to victimize our community). It was always too small. That's a design flaw given what we know today.

And yeah I get that the path of least resistance is to keep that awful thing and try to work around it. Life is better post-100A I assure you. Just get rid of it. Upgraded alternators are WAY cheaper than class 8 tow trucks. Most people have NO CLUE till the nice lady at the tow company wants a $2500 down payment over the phone before any hardware goes downrange.

I agree that improvements could be made in the isolation department. Setup like an old school RV where a momentary rocker switch will pull in the extra battery bank as a booster with the flip of a switch.