Diehard AGM Batteries (lacks 'marine' markup)

Discussion in 'OnBoard Electronics & Controls' started by papabravo, Sep 30, 2014.

  1. papabravo
    Joined: Sep 2012
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 11
    Location: Northern Virginia

    papabravo Junior Member

    Research:

    Diehard AGM Auto Group 34 775 CCA: $153

    Diehard AGM Marine Group 34 880 CCA: $250

    West Marine house brand "Dual Purpose" Group 31 $310

    Mastervolt (via West Marine) Group 31: $320

    Assume (I know it's hard to do) a fairly generic recreational boat setup of starter bank and house bank.... I'm thinking the "auto" AGM battery is fine for both banks. It's a sealed system afterall. I don't see what 'marinizing' would bring to a AGM battery, except a higher price.

    ..and what is this "Dual Purpose" label on the West Marine house brand. Wouldn't your generic AGM battery be good for dual purpose?

    Will an accredited surveyor give me demerit points for using auto batteries?

    I thinking of going with Diehard automotive AGM.. unless people here smarter in these matters convince me otherwise.
     
  2. 7228sedan
    Joined: Nov 2009
    Posts: 327
    Likes: 9, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    My family owns a battery warehouse distributorship. The West Marine labeled batteries are manufactured by East Penn Manufacturing (Deka batteries). The only real difference between marine & auto is primarily the terminal. Threaded studs with lock nuts are routinely used in group 24-group 31 batteries. 4D, 8D & other commercial batteries tend to have posts and other custom terminals specific to the application. Autos tend to use the posts. The "Dual Purpose" label would be used to identify a battery that is not a true deep cycle, nor is it a high calcium content cranking battery. An AGM lends itself very well to being a true dual purpose as it has significantly higher cranking amps then a gel cell (in the same size or class). In addition you will get reserve capacity that is closer to a traditional wet cell deep cycle of the same size. The West house brand AGM 31 should have a manufacturers part number of 8A31DT or 8A31DTM. The difference is the terminals offered. That is a quality AGM battery with very good specs... you can find it for a hell of a lot cheaper than 310.00 though ;-) West gets a pretty penny for their batteries.
     
  3. papabravo
    Joined: Sep 2012
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 11
    Location: Northern Virginia

    papabravo Junior Member

    Very helpful insights.

    So far, my impression is, if auto terminals work for me, the Diehard AGM is a viable option.

    Your part nuimbers were helpful. I google/shopped them and found prices in the 230-250 range.
     
  4. 7228sedan
    Joined: Nov 2009
    Posts: 327
    Likes: 9, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    The DieHard AGMs are manufactured by EnerSys. They're the same manufacturer of the Odyssey brand AGMs. A group 34 battery is the same length & width as a group 24 so it will fit in the same battery tray or box. It is a few inches shorter however. What is your application (engine, accessories, etc.)? Generally speaking, a group 24 AGM will have better specs than the 34 equivalent due to the taller case. Make sure you select a battery with a sufficient CCA rating and reserve capacity for your application.
     
    2 people like this.

  5. papabravo
    Joined: Sep 2012
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 11
    Location: Northern Virginia

    papabravo Junior Member

    The engine is a 75 HP diesel. The manual says minimum battery: 180Ah, 1200 CCA. I plan to exceed that minimum quite a bit.

    70 Amp alternator.

    Will run the engine 2-3 hours a day on longer trips. So I want to size a house battery for that. Only big draw on house battery would be a 4 AMP drawer fridge. Other stuff on the house circuit would be LED lights, plotter etc.
     
    Last edited: Oct 3, 2014
    1 person likes this.
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.