The 6.7L Cummins is a high-compression diesel that asks a lot of its starting batteries. Ram 2500 and 3500 trucks run a dual battery setup in BCI Group 65, and both batteries have to deliver serious cold cranking amps to spin a heavy diesel over on a freezing morning. A weak or undersized battery shows up fast on a Cummins as slow cranking, hard cold starts, and grid heater strain.
We focused on real Group 65 batteries that physically fit the 6.7 Cummins tray and terminal layout, then sorted them by cold cranking amps, reserve capacity, vibration resistance, and how they hold up to deep accessory loads. Below are seven batteries we trust for this truck, ranked best first, with honest notes on where each one falls short.
| Photo | Product | Score | Buy |
|---|---|---|---|
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Odyssey 65-PC1750T Extreme Series Best Overall Group 65 AGM, 950 CCA, 1750 cranking amps, TPPL construction |
9.5 | 🛒 Check Price |
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XS Power D6500 AGM Best High Output Group 65 AGM, 1070 CCA, sealed spiral-free flat plate design |
9.2 | 🛒 Check Price |
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Optima RedTop 34/78 Best Vibration Resistance SpiralCell AGM, 800 CCA, dual SAE and GM-side terminals |
9.0 | 🛒 Check Price |
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ACDelco 65AGM Professional AGM Best OEM Replacement Group 65 AGM, 850 CCA, 100 minute reserve capacity |
8.8 | 🛒 Check Price |
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DieHard Platinum AGM Group 65 Best Reserve Capacity Group 65 AGM, 850 CCA, high reserve capacity, sealed |
8.6 | 🛒 Check Price |
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NorthStar NSB-AGM65 Best Longevity Group 65 AGM, 930 CCA, TPPL pure lead construction |
8.4 | 🛒 Check Price |
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Delphi BU9065 MaxStart AGM Best Balanced Value Group 65 AGM, 850 CCA, 160 minute reserve capacity |
8.2 | 🛒 Check Price |
1. Odyssey 65-PC1750T Extreme Series: Best Overall
The Odyssey 65-PC1750T is the battery we reach for when a 6.7 Cummins owner wants the strongest possible cold start and the longest possible life. Its Thin Plate Pure Lead AGM construction packs more plate surface into the Group 65 case, which is why it puts out 950 cold cranking amps and a 1750 amp cranking figure. On a high-compression diesel sitting outside in single-digit temperatures, that headroom is the difference between a confident start and a slow, straining crank.
The honest weakness is weight and charging demand. This is one of the heaviest batteries in the group, so installing a pair is a workout, and the TPPL chemistry really wants a charging system that holds proper voltage. If your alternator is tired or your truck sits for weeks between drives, you will want a maintainer to get the full rated life out of it.
- Thin Plate Pure Lead AGM design for maximum cranking current
- Rated for up to 400 charge cycles at 80 percent depth of discharge
- Tolerant of heavy vibration and deep accessory draws
Pros: Massive cranking power for cold diesel starts; Long service life compared to flooded batteries; Handles deep cycling from winches and inverters
Cons: Heavier than most Group 65 options; Demands a healthy charging system to stay topped up
2. XS Power D6500 AGM: Best High Output
The XS Power D6500 is built for 6.7 Cummins owners who pile on the electrical load, whether that is a big stereo, light bars, an inverter, or a winch. Its AGM construction and low internal resistance let it dump a lot of current fast and then bounce back, which keeps voltage stable while the diesel cranks. As a starting battery in a dual setup, it gives you a generous cushion of cold cranking amps over the factory unit.
The trade-off is that the D6500 is somewhat overkill for a bone-stock truck used only for commuting. You pay for output you may not fully use, and like any high-output AGM it performs best when the charging system keeps it near full state of charge. For a modified or heavily accessorized Cummins, though, it is hard to beat.
- Very high cranking output for big diesel and audio loads
- Sealed AGM build mounts in nearly any position
- Low internal resistance for fast voltage recovery
Pros: Exceptional cranking and burst current; Spill-proof sealed design; Recovers quickly under heavy electrical load
Cons: Geared more toward high-draw builds than daily simplicity; Premium battery that rewards a strong charging setup
3. Optima RedTop 34/78: Best Vibration Resistance
Optima’s RedTop is famous for its spiral-wound SpiralCell cells, and that design is exactly why it shines on a work truck. The 6.7 Cummins spends its life towing, hauling, and rattling down job-site roads, and vibration is what kills most batteries early. The RedTop’s tightly wound construction shrugs off that abuse and keeps delivering strong, clean cranking bursts when you turn the key on a frosty morning.
The catch is fitment. The 34/78 is not a native Group 65 size, so on a Ram you need to confirm tray and hold-down compatibility, sometimes with an adapter. Its reserve capacity is also lower than the bigger flooded and TPPL options, so if you run heavy key-off accessories, it is better as a dedicated starter than as a deep-cycle helper.
- SpiralCell design resists vibration on rough roads and towing
- Strong, clean cranking bursts for diesel starting
- Sealed and spill-proof for flexible mounting
Pros: Outstanding vibration and shock resistance; Reliable starting power in cold weather; Maintenance-free sealed AGM
Cons: Not a true Group 65 case, verify fitment and hold-down; Lower reserve capacity for heavy key-off loads
4. ACDelco 65AGM Professional AGM: Best OEM Replacement
If you want a no-drama, drop-in upgrade that fits the 6.7 Cummins tray exactly, the ACDelco 65AGM is the safe pick. It is a true Group 65 AGM with the right terminal layout, so there is no adapter shopping or hold-down guesswork. The AGM chemistry gives you better cycle life and reserve than the old flooded factory battery, which matters on a modern diesel loaded with electronics and a grid heater.
Its cranking numbers are strong and dependable, but they do not match the Odyssey or XS Power flagships, so this is the battery for owners who value perfect fitment and reliability over chasing maximum amps. As always with a dual setup, replace both batteries together and keep them matched so one does not drag the other down.
- True Group 65 fitment for direct factory tray install
- AGM construction for better cycling and life
- High Reserve Capacity for accessory and key-off loads
Pros: Drop-in factory fit with correct terminals; Solid reserve capacity for diesel electronics; Maintenance-free and well-sealed
Cons: Cranking output trails the top high-performance picks; Best paired with a matching second battery
5. DieHard Platinum AGM Group 65: Best Reserve Capacity
The DieHard Platinum AGM in Group 65 is a well-rounded choice for a 6.7 Cummins that sits between commuter and worksite duty. Its strength is reserve capacity, the number that tells you how long the battery can power lights, electronics, and key-off loads without the engine running. On a diesel with plenty of modules and an owner who occasionally runs accessories with the engine off, that cushion is genuinely useful.
Where it gives ground is peak cold cranking, which is good but not class-leading, and overall weight, which is on the heavier side. For most owners that is a fair trade, because the AGM design recovers from deep discharges far better than a flooded battery and tolerates the vibration of truck life well.
- AGM build with strong reserve for heavy accessory loads
- Sealed and spill-proof for any mounting angle
- Good deep-discharge recovery for occasional use trucks
Pros: Generous reserve capacity; Reliable cold starting; Handles deep discharges better than flooded
Cons: Heavier than basic flooded options; Cold cranking trails the dedicated high-output picks
6. NorthStar NSB-AGM65: Best Longevity
NorthStar’s NSB-AGM65 uses the same pure lead TPPL philosophy as the Odyssey, which means it combines high cold cranking amps with the kind of deep cycle endurance most starting batteries cannot match. On a 6.7 Cummins, that translates to confident cold starts paired with the ability to survive the occasional deep draw without permanent damage. Owners who keep trucks a long time tend to love how many years these last.
The downsides are practical rather than technical. NorthStar availability tends to come and go depending on the retailer, so you may have to hunt for a matched pair. And like all TPPL batteries, it rewards a charging system that keeps it near full and punishes chronic undercharging with shortened life.
- Pure lead TPPL plates for long life and high output
- Strong cold cranking for high-compression diesels
- Excellent deep cycle durability
Pros: Very long service life; High cranking amps; Strong deep-cycle endurance
Cons: Premium battery with availability that comes and goes; Needs disciplined charging to reach full lifespan
7. Delphi BU9065 MaxStart AGM: Best Balanced Value
The Delphi BU9065 MaxStart is the quiet all-rounder of this list, and it earns its place by doing everything competently in a true Group 65 case. Its AGM construction delivers dependable cold cranking, a healthy reserve capacity for the 6.7 Cummins electronics and grid heater, and good vibration tolerance for daily work. For an owner who just wants a solid, fuss-free pair that fits the factory tray, it is an easy recommendation.
It will not win a cranking-amp shootout against the Odyssey or NorthStar, and Delphi does not carry the same brand cachet, which puts some buyers off unfairly. Performance-wise, though, this is a genuinely good AGM battery, and the strong reserve capacity makes it a sensible balanced choice for a stock or lightly modified Cummins.
- MaxStart AGM design balances cranking and cycle life
- High reserve capacity for electronics-heavy diesels
- Sealed maintenance-free construction
Pros: Well-balanced all-round performer; Strong reserve capacity; Maintenance-free and vibration tolerant
Cons: Not the highest cold cranking in the group; Less name recognition than the big brands
Frequently Asked Questions
What size battery does a 6.7 Cummins use?
Ram 2500 and 3500 trucks with the 6.7L Cummins use BCI Group 65 batteries, and they run two of them in a dual battery configuration. Both batteries should match in brand, type, and age so they share the load evenly. When you replace one, it is strongly recommended to replace both at the same time, because a mismatched pair forces the stronger battery to compensate and shortens the life of both.
How many cold cranking amps do I need for a 6.7 Cummins?
A high-compression diesel like the 6.7 Cummins needs serious cranking power, especially in cold climates. Aim for at least 750 cold cranking amps per battery, and more is better if you live where winters are harsh. With a dual setup, the two batteries work together, but each one should still be a strong Group 65 unit. The high-output picks on this list deliver 850 to over 1000 CCA each, which gives you confident starts even in single-digit temperatures.
Should I use AGM or flooded batteries in my 6.7 Cummins?
AGM batteries are the better choice for most 6.7 Cummins owners. They handle the vibration of truck life better, tolerate deep accessory draws, recover from discharge more gracefully, and are sealed so they can be mounted without spill worries. Flooded batteries can work and are simpler, but AGM technology generally lasts longer and starts more reliably on a heavy diesel. Just make sure your charging system holds proper voltage, since AGM batteries dislike chronic undercharging.
Do I have to replace both batteries at the same time?
Yes, replacing both batteries together is the right move on a dual battery 6.7 Cummins. The two batteries are wired to work as a team, and a new battery paired with an old, weakened one creates an imbalance. The newer battery ends up carrying more of the load and discharging deeper, which ages it prematurely. Matching the pair by brand, type, and purchase date keeps the system balanced and gives you the longest, most reliable service.
Will a more powerful battery hurt my Cummins charging system?
No, fitting a higher cold cranking amp battery will not harm your charging system. A battery only draws the current it needs, so a stronger battery simply gives you more starting reserve rather than forcing extra load on the alternator. The one thing to watch is that high-output AGM and TPPL batteries want to be kept near full charge, so if your truck sits for long periods, a quality battery maintainer will help you get the full rated lifespan out of them.
Our Verdict
For most 6.7 Cummins owners, the Odyssey 65-PC1750T Extreme Series is our top pick thanks to its enormous cold cranking power, long service life, and ability to shrug off deep accessory draws, making it the most confident cold-morning starter in a true Group 65 case. If you run a heavily accessorized or modified truck, the XS Power D6500 is the runner up, delivering even higher burst output for big audio, lighting, and inverter loads. Whichever you choose, replace both batteries as a matched pair and keep your charging system healthy for the longest possible life.
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