My coach has always lacked enthusiasm starting. I recently had it at Nacogdoches Motorhome Services to adjust brakes, lube slide pins, check and adjust ride height. Ended up replacing all slide pins and adding helper springs. They also replaced the bearing seal on the front passenger wheel. I was concerned it had a slight leak. Sure enough. Also told them my alternator dash gauge wasn't agreeing with the little 12 volt power adapter. After measuring voltage at start batteries and at alternator, they determined the alternator defective and it was replaced. After starting a couple times, it had to be boosted to start. During the last hour of driving to Nac in the dark the dash gauge was below 12 volts and the 12 volt power adapter was behaving crazy. Drive back was much better.
Once home I decided to load test the start batteries and clean a little bit of corrosion. Both batteries showed good voltage, but one battery failed completely a load test. The batteries are Interstate Group 24, 850 CCA. The battery rack is designed for two to three Group 24 batteries, a Group 27 or 31 will not fit, too long. Stock cabling is for two batteries.
My dilemma is this: The Cummins manual recommends 1800 CCA. I'm not finding any Group 24 batteries with more than 800 CCA, which would put me a little below the recommended capacity, and way below the recommendation of 640 RCA at 32 degrees F. We plan to start full timing December 15 and some cold weather camping will be necessary when visiting kids in Portland and Albuquerque. We will also be doing a fair bit of high altitude camping, and with a mechanical engine the air/fuel mixture at high altitude is not optimal for starting.
I'm leaning towards installing three Group 24 batteries of 800 CCA, which involves some new cabling and the purchase of three rather than two batteries. Or I could just hope the boost switch would make up the difference when necessary.
I read through the long discussion from two years ago with Chuck's decision to install an 8D start battery with the goal of extending his off grid power by combining house and chassis. I'm running out of time and not wanting to make too many changes this close to going full time, but reliable starting in all kinds of weather and places is of great interest to me.
On a side note, Nac was my first trip since discovering my coolant temperature gauge was errant. Pulled the gauge leads at the dash, sprayed the contacts with debrox and it read 180 all the way to Nac and back. Hallelujah!
Most of the coaches of your era have 3 start batteries.
Not trying to influence your decision in any way, but I will say I have been totally satisfied with the starting performance of my single AGM8D start battery. I have never had to use the boost switch on our coach for starting, but then again we have never challenged the starting capability by camping in really cold weather.
I believe Don (Don & Tys) also used a single AGM8D for starting his '99 U270 for a while, although I believe he has since changed to a different starting setup. He may have some experience cranking his 8.3L with the single AGM8D in colder conditions?
Engine Start Battery Options (https://www.foreforums.com/index.php?topic=34528.msg318506#msg318506)
I have two 800 cca batteries and it starts fine, 1996 8.3 . My starter was pulling them down. Replaced starter with a reduction drive and really spins now
Just keep the batteries fully charged when stopped and when it gets cold you can always use the boost switch,when you cleaned the cables did you clean all the grounds where they attach to the frame?
I used these in our U320. The U270 may be different.
https://www.oreillyauto.com/detail/b/fleet---heavy-duty-5000/agriculture-hd-parts---accessories-19818/fleet---heavy-duty-20088/battery---electrical-20106/agriculture-hd---batteries---accessories-19802/fbaa0ce66430/super-start-fleet-heavy-duty-battery-group-size-31/agm31t/4742641?pos=3
925 CCA. Group 31 size. Check your battery tray size, these are 13" wide vs 10.25" wide for a group 24
Clean connections are important.
Easy to add another 24 series to your rack with only a cable modification needed. Good to have a geared starter and a short extra ground cable to the frame close to the battery rack. I've also never used the boost switch. I asked Autozone for a discount when I replaced our three start batteries last year and they gave me 10%. 31 series were a little cheaper and only cost just over $300 for all three out the door. Now have 2850 CCA. Yes, it's work to replace or modify the rack for longer batteries. Here is an old post of mine showing our new rack with a tape measure in case you want to make one like this: How to install group 31 batteries in your coach (https://www.foreforums.com/index.php?topic=31785.msg281706#msg281706)
Pierce
Thanks for the feedback in such a timely matter. I'm gonna go with three group 24 batteries and make the cabling modification. Should certainly be better than what I had.
Your 98 u270 came from the factory with 2 red top batteries.
If you ever went on a cruise ship again, would you sign up for two meals a day or three?
Pierce
How many cca does a 8.3 require?
I think Cummins says 1250 but several RV companies who put 8.3s in their coaches recommend 1800 CCA.
Pierce
So the oem battery fitment was adequate?
Depends on your definition of adequate. Adequate sounds a lot like entry level when you buy a car. At sea level and new batteries, that works well. But in winter when batteries don't crank out as much CCA as in warm weather and there is a lot more temperature rise necessary to ignite the diesel plus not so many oxygen molecules up at 8000 feet makes a lot more load on the batteries. And when the engine is harder to crank, the battery terminals without maintenance build heat and resistance cutting the CCA that gets to the starter.
And batteries along with RVs age. A few years down the road, the diesel may not have had the valves adjusted, the fuel in winter may still be summer diesel in the tank and the owner may not have the batteries at 12.7V.
So, I didn't need 2850 CCA for the Detroit but just like in aircraft accidents, it's not the single event but a combination of things that go wrong that cause the big problem. And 2850 CCA cost me right around $300 for about 10 years of good starting. To me, it's win-win.
Pierce
Good points about cable corrosion reducing current flow.
The red tops do not seem to corrode the cabling.
According to the 2000 Foretravel spec sheets, the U320's had three, but the U295's (like mine) had two. The brackets were the same, so when I replaced my two starting batteries, I used three red tops. At the time, I was also replacing the factory 3/0 cables with 4/0 cables, and a buss bar system. Just as easy (almost) to make three equal-length cable pairs as two equal-length cable pairs. The chassis battery buss bars were fairly straightforward.
My next electrical remodel will be buss bars for the three house batteries. My preliminary design has short positive and negative buss bars in the battery compartment. Then, I can go through the side wall, with a well-protected pair of 4/0 cables, to a secondary pair of buss bars for further distribution. They will be located near the existing electrical panel that contains a lot of circuit breakers (unless someone has a better suggestion??). The new 4/0 wiring will go from there to the charger/inverter and other 12 volt loads. I will share pictures with the forum.
Hope this helps,
Trent
I found 1800 CCA in a pdf Cummins factory manual for my series engine, 6ATC8.3. Two red tops would reach that (if I remember correctly) but my three batteries will come in at 2400 and cost less than two red tops. Also owner reviews of red tops made recently in Mexico indicate they may have suffered some quality issues in the move. There were enough posts to give me pause, some experiencing failure in a year. I will be upgrading to 4/0 cable in connecting the three to parallel. My cabling system will allow me to easily isolate batteries to test them individually. I have no idea when one of my batteries went south. Should have it up and running by Wednesday.
Wire the three batteries as shown. Once a year take the battery from the inner most position and move it to the outside position and move the others toward the inside. Clean all cable ends and terminals at the same time. Figure out what the torque spec for you battery reminals are and use an inch pound torque wrench to tighten appropriately.This should enhance life expectancy of your batteries.
Excellent suggestions. Thank you.
In 19 years of owning the U295 the 2 red top batteries start the engine in a split second after the wait to start light goes out. The last batteries lasted 10 years
Agree with Turbo,immediate start with 2 batteries.