Cold cranking amps vs Amp hours

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • baileyem
    Senior Member
    • Jun 2006
    • 175

    Cold cranking amps vs Amp hours

    This is not an A-4 question, but it is closely related:
    When shopping for a new battery I find that non-marine suppliers only list Cold Cranking Amps and don't have the faintest idea how to calculate Amp Hours......but then neither do I. How does one calculate Amp Hours for a battery?
  • rigspelt
    Afourian MVP
    • May 2008
    • 1252

    #2
    I use Cold Cranking Amps (CCA) to tell me about engine start batteries (lighter and smaller), and amp-hours to tell me about deep cycle batteries (heavier and larger) used for house loads. CCA indicates how much voltage a start battery can deliver to an engine starting motor in a very short period of time, while Amp-hours tells me how much amperage can be drawn from a deep cycle battery for a certain period of time. Start batteries do not get deeply discharged in regular use, unlike house batteries. If a battery is not rated by amp-hours, then it may not be designed for frequent cycles of slow deep discharging.

    Basically, amp-hour measures the maximum number of amps that can be drawn from a battery until the battery is dead (about 10.5 volts) over a fixed time period, say 20 hours or 100 hours. Not all amp-hour statistics are apples and oranges, because there are different ways to calculate and measure amp-hours while controlling for variables like temperature in different ways.

    Compromise economy batteries, often labelled "marine", have mixed features: both cranking and deep cycle. This type of battery is a compromise for certain types of boating. They may provide enough cranking amps to start lower demand engines, but usually don't provide sufficient deep cycle capability for serious cruising. The term "Reserve Capacity" is another measure used to describe batteries: number of minutes a battery can maintain a useful voltage at a certain amperage discharge rate. Some of these economy batteries are also rated using Marine Cranking Amps (MCA), which is not the same as CCA. See http://www.exide.com/faq/faq_marine.html.

    These might be of interest:





    The books by Calder or Wing are useful in understanding how to design a boat battery system for house loads.
    Last edited by rigspelt; 03-29-2009, 08:07 AM.
    1974 C&C 27

    Comment

    • msauntry
      • May 2008
      • 507

      #3
      For what its worth, I've been using a pair of deep cycle Trojan 6v batteries for years. I only have one bank and this does it all. For my long cruise, I threw in a second "bank" which consisted of a cheap lawn tractor battery. That was rated 300 cca and it turned the A4 over just fine, but I've since yanked it and am back on the Trojans.

      Comment

      • baileyem
        Senior Member
        • Jun 2006
        • 175

        #4
        Cold Cranking Amps vs.....

        Thanks, rigspelt and msauntry, for the responses. It looks as though I have some reading to do. Thanks again.

        Mike

        Comment

        • rigspelt
          Afourian MVP
          • May 2008
          • 1252

          #5
          Originally posted by msauntry View Post
          For what its worth, I've been using a pair of deep cycle Trojan 6v batteries for years. I only have one bank and this does it all. For my long cruise, I threw in a second "bank" which consisted of a cheap lawn tractor battery. That was rated 300 cca and it turned the A4 over just fine, but I've since yanked it and am back on the Trojans.
          I've heard others talk about just equipping a small sailboat with deep cycle batteries when the auxiliary is a relatively low starting current engine like the A4, roughly 135-150 amps, from what I can tell reading the net. It's an interesting thought. A cruiser wants lots of house electricity when sailing/anchoring, and the suggestion is that perhaps A4s may not strain deep cycle batteries with that kind of starting motor amperage. I haven't found any technical discussion of this option. Weight becomes a factor for the Monday-Wednesday racer who cruises less than races and can't stand being down the results page.
          1974 C&C 27

          Comment

          • msauntry
            • May 2008
            • 507

            #6
            You can certainly add a lot of complexity and money to the charging system, but I had to go with something cheap and simple.

            For race weight, I'd probably avoid the double Trojans. Each one is a slipped disk waiting to happen. I think a decent single 12v deep cycle will survive the starting loads of the A4 just fine. Its such a low compression engine that its easy to turn over. If you really want light weight, a motorcycle battery will start this engine.

            Comment

            • Mephisto, a C&C 29 Mk. 1
              Frequent Contributor
              • Apr 2007
              • 9

              #7
              Cold Cranking Amps Required by an A4

              Can someone tell me the cold crank amp requirements of a late model Atomic 4, please? I cannot find that in any of the specifications that I have in hand. I ask because I'm about to replace my two existing batteries - 1 starting battery and one deep cycle battery - and I'm wonder if the CCA requirement is low enough that two deep cycle batteries in parallel would do a sufficient job of turning over the engine. Thanks very much!

              Comment

              • RobH2
                Senior Member
                • Dec 2009
                • 346

                #8
                @Mephisto, a C&C 29 Mk. 1, did you ever determine what CCA requirement is needed for a late model A4? I have the same question and it's difficult to determine even 15-years later.
                Rob--

                "Who is staring at the sea is already sailing a little."

                1968 C&C Invader 36' / Late Model Atomic4
                https://www.tumblr.com/blog/sherloch7

                sigpic

                Comment

                • Dave Neptune
                  Afourian MVP, Professor Emeritus
                  • Jan 2007
                  • 5117

                  #9
                  The A-4 only needs about a 120~130 amps to start. I used a Grp 27 deep cycle for start and a pair of Golf cart 6v's for the house. Never an issue. Many will insist on a start style battery but I never found it necessary and if I did drain it down it did not sacrifice the batteries recharge capability. A win win for me.

                  Dave Neptune

                  Comment

                  • joe_db
                    Afourian MVP
                    • May 2009
                    • 4544

                    #10
                    Originally posted by Mephisto, a C&C 29 Mk. 1 View Post
                    Cold Cranking Amps Required by an A4

                    Can someone tell me the cold crank amp requirements of a late model Atomic 4, please? I cannot find that in any of the specifications that I have in hand. I ask because I'm about to replace my two existing batteries - 1 starting battery and one deep cycle battery - and I'm wonder if the CCA requirement is low enough that two deep cycle batteries in parallel would do a sufficient job of turning over the engine. Thanks very much!
                    An Atomic 4 draws about 125-135 amps while starting. You want around triple that or better for the CCA rating. I use this battery as my starting battery: https://www.amazon.com/ML-U1-CCAHR-12V-320CCA-Battery-terminal/dp/B07K6Z3VZ2/ref=sr_1_4?crid=1QMFPLU9E45NN&dib=eyJ2IjoiMSJ9.JAC UPjgbnOIu1lTzP-PxgY-CRbiQoadAgluoogmwISE3XORJUQz2EWK11tti_uKP3JVXLAid0 e8zgSAmMf7VvRt-Qe3zcKSH3g7B9SVYwsE2zQFE4y7FPiiYUaNmw8X-Tsqf5XWbNcj4eMQppuQoAKrYV-T39QK8QX1RlVR_JVLuG8Kv9zvqWI5oLaLMmJ51m20C0DNwJMfJ _YiKi25k_j6549X4BPQ4zQkzGYNJ3K6N6fW4-jB4CM4j2CfDMPjt-g3N51XKQWUChDBGRynGXLtA8HQLAVaLZg15YdslomQ.VbRW0FV h8O-LJjyVLSL8y4KZS_NcSuCbZF4Gsjoo1Vc&dib_tag=se&keywor ds=u1+battery&qid=1717152875&sprefix=u1+%2Caps%2C1 95&sr=8-4
                    It works fine in warm weather and still works in the winter, but I usually parallel with the house battery if the engine is really cold-soaked.

                    Click image for larger version

Name:	fetch?id=219058&d=1714133853.jpg
Views:	33
Size:	75.2 KB
ID:	219239
                    Last edited by joe_db; 05-31-2024, 08:45 AM.
                    Joe Della Barba
                    Coquina
                    C&C 35 MK I
                    Maryland USA

                    Comment

                    • joe_db
                      Afourian MVP
                      • May 2009
                      • 4544

                      #11
                      Originally posted by baileyem View Post
                      Cold Cranking Amps vs.....

                      Thanks, rigspelt and msauntry, for the responses. It looks as though I have some reading to do. Thanks again.

                      Mike
                      CCA (0 F) or MCCA (32 F) is important for starting engines. They need a lot of amps quickly. If they are flooded lead-acid batteries, the designer will use a lot of thin plates. This provides for the most cranking amps from a given size of battery and provides for fast recharging. These batteries are not designed for cycling use. If allowed to run down and then recharge, the thin plates don't last long. Some starting batteries, i.e. most car batteries, can be destroyed by being run down only a few times. For cycling use the designer does the opposite, the same size battery will have fewer but thicker lead plates. You get less CCA from the same size battery and they charge slower, but they can withstand being discharged and then recharged numerous times. This is typical of how a house battery is used on a sailboat.
                      Golf cart batteries are a good example of deep-cycle flooded batteries with rugged thick plates.To use them to start engines you would need a lot more size and weight than if you used a starting battery.
                      This all can vary with other chemistries. Some AGMs are sold as start-only batteries and some do both. I have never seen a gel battery specified as a start battery, they all seem capable of deep cycling. Lithium batteries are a special case, the BMS (battery management system) can be destroyed or at the very least cut the battery off if overloaded. One would need a BMS capable of well over the engine start load for me to try and use one as a start battery.
                      Short version:
                      Start off a deep cycle battery - fine if it is big enough, the worst it will do is not start the engine.
                      Cycle off a start battery - fine if you like buying a lot of batteries, otherwise no.
                      Combination batteries - YMMV here, some like AGMs and Gels may truly be good at both tasks, the "marine start and deep cycle" flooded batteries seem to be just the higher end of the car type batteries with maybe a better warranty. We used to get them from Sears when I was a lad, they had a no questions asked warranty and the things were always dead before the warranty, so it was endless free batteries
                      Joe Della Barba
                      Coquina
                      C&C 35 MK I
                      Maryland USA

                      Comment

                      Working...
                      X