winter man is here,this year my truck is a little harder to start.I'm thinking replacing the batteries,what is the best battery for these cummins (reserve cap & cranking) I'm thinking we need some reserve for the grit heater,then cranking to start,the new style round cells are they any good ?

Was that with the block heater plugged in? Sometimes they go out or the cord goes bad. You can tell if it's working when you plug in since you can hear the very low sizzling sound it makes.I'm currently using two deep cycle batteries in my truck. Works great but about once a month I top off with the charger since deep cycles are a little different charge needs than the voltage regulator sends out from the truck.

Not always the batteries that make a difference. Remember I'm one of the few that ran on 10 year old OE batteries into winters down to -25*F.Sometimes your hard start could be starter contacts and brushes, battery cables and connections, or may a mixture of the above. Now as for batteries they are a weird animal. If a battery is discharged below 11.5 volts for a extended period then the battery takes on damage from the discharge and loses a good chunk of either Amp/Hour rating (Deep cycle) or cold cranking amps (starting batteries). Then beyond that, any battery that is a maintenance free is not a good choice. There is no way to maintain electrolyte levels in each cycle this is why I'm not sold on AGM or Optimas. They tend to have a shorter life span because of this flaw.

I'm currently using two deep cycle batteries in my truck. Works great but about once a month I top off with the charger since deep cycles are a little different charge needs than the voltage regulator sends out from the truck.

I have used deep cycle batteries in vehicles before, but I wouldn't do it in one of these truck and especially in the winter. Deep cycles aren't designed for the rapid flow needs of cranking, and there is a reason these trucks come with a pair of 750cca batteries. What voltage needs doesn't the vehicle provide?

Not always the batteries that make a difference. Remember I'm one of the few that ran on 10 year old OE batteries into winters down to -25*F.

Lot's of folks do that these days, the OEM's are a good piece. I replaced mine at 6 years because I wanted to. That was in 2010, and they are still going strong in my buddies Ford.

Then beyond that any battery that is a maintenance free is not a good choice. There is no way to maintain electrolyte levels in each cycle this why I'm not sold on AGM or Optimas. They tend to have a shorter life span because of this flaw.

I 100% disagree. I have seen sealed batteries go much longer than any of the non-sealed. When they are sealed there is no where for the electrolytes to go, and they don't use a liquid battery acid. Good batteries are MUCH better than cheap serviceable batteries. The OEM's in my 05 were maintenance-free, and IIRC that's the same battery that was used in 02 that you got 10 years out of. While I wouldn't buy an Optima anymore, as their quality has seemed to gone downhill, I had an Optima that was amazing. I bought it in 1999, it has been the display model for 2-3 years but I needed a battery that day. I used it in that truck for 2 years. I then put it into my new rig (95 4runner) where I used it for winching often. I also let it die several times, one time with a light left on for 6 weeks and the voltage was 0.010v, that was in 2004. In 2005 I put it into yet another rig and used it for winching/driving until 2006 when it got parked for about a year while I was deployed. It was down around 11.5 when I got back and put a charge on it, it worked for 2 months while I got the truck ready to sell. I sold it in summer 06 and the last time I saw the guy who bought it he was still using it, that was in 2010-2011. I would like to hear of a non-maintenance free doing that. My dad also has some 11 year old 6 volts AGM's that he uses once a year and they work like new, where the non-sealed versions only last about 4-5 years with similar use.

The truck wasn't plugged in wasn't quite ready for the cold but I had done the switch to 10w30.So 750 cca would be good enough what about res cap?

Remember that's 750 per battery (or 1500 CCA for both). The reserve capacity also doubles too.The old school rule of thumb was to have double the CCA worth of batteries for the highest amperage draw your starter could draw. Accordding to FSM the starter draws 450-700 Amps so 700 CCA batteries would be the bottom line.

750's are factory, but I really like how my 930's crank the truck over!What 10w-30 are you running?

When I bought my new batteries, I got them from WallyWorld. For $75.00 each, and with the warranty good at all stores, and with WallyWorlds everywhere.........except by Michael.........it was a "no brainer" for me.There are only about 3-4 battery manufacturers around............and one of them makes the WallyWorld ones!!!

I've been using Deep cycles in both my ctd's for around 14 years now without problems. The reason I do that is because of all the stops I can make in a day, I sometimes leave my lights on for too long which will damage a starting battery in a hurry. With the deeper batteries I can wait for a bit after shutting off the lights and they recover enough to start the truck again.My deisel book says running deep cycles are a good idea and is a misconception that people say you can't do that. I do know that starting batteries throw more juice up front when cranking. I really don't know, I just do it Mainly because of the extra places/ studs on top of the batteries for wires and the stronger plates inside.

I am not sure why it would say it's a good idea, it's not that it won't work it's that it doesn't work as well. It certainly is not the preferred method. A dual purpose would probably be your best bet. The Odyssey's are dual purpose and are amazing batteries. You can also get them with extra posts.

Yeah I'm not sure either John. I just started doing the deep cycles because of the book I have. I haven't really seen any problems. They are not as expensive as an AGM is one thing

Shell Rotella T 10W30 diesel engine oil is what I switched for.

Here I figured the dual 750s were due to the heater grid demands, not the starter.. I've started my old CTD with a cheap jump box with not a single battery in the truck.. Of course it was a mid-summer morning.

Having a ford, I have put all batteries to the ultimate test. That thing took a lottt of cranking to get it to start. I used a pair of red top optimas and they sucked. The initial 5 seconds were fine but then they went downhill quick. Then I had a pair of everstart maxx's and they would crank and crank forever. So my opinion is that for pieces of crap, use lead acid batteries.. But for everything else I don't see the problem. I mean you only need a few cranks to get the thing to start which the dry cells do fine and I have yet to see either of these red tops go bad yet. I have one in my jeep now. Plus there is no corrosion issue. The maxx is now in my dodge and now has a dead post so I switched to the other post and noticed the other day that it has all kinds of build up on it. It's done for. Do dry cells have the same derating in winter? I only remember seeing one rating.

Do dry cells have the same derating in winter? I only remember seeing one rating.

Yes. The battery's I run are rated at 930 CCA's at 0°F, 1070 MCA's at 32°F, and 1350 HCA's at 80°F.