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  • Trying to understand Data Sheets

    Hi,

    Trojan batteries seem to be well respected as a quality product. I'd like to understand the Data Sheet that is found on their website regarding their different batteries.

    I'd like to use this particular battery for no other reason than we're all talking apples.

    http://www.trojanbattery.com/product/31-agm/

    What is this telling me?

    I undestand dimensions and won't drop this brick. But what about the first three columns

    Capacity minutes/ Capacity Amp=hours/ Energy (kWh)

    And how do these numbers correspond to the proper use of this battery. In other words using it like it should be but not beating it like a rented mule.

    Thanks, mj52

  • #2
    OK first thing you need to know, is this is a SLI (Starting Lighting & Ignition) battery which is not designed for deep cycle applications. If you would have looked at the Spec sheet you will see a CCA and CA rating which means it is made to crank an engine.

    First column is RC (Reserve Capacity) Minutes and is BCI standard for the amount of time in minutes the battery can deliver 25 amps until the battery voltage drops to 1.75 volts per cell or 10.5 volts for a 12 volt battery. When you see RC Minutes means you are looking at a Hybrid Battery meaning a cross between a SLI and Deep Cycle battery.

    Capacity Amp Hours is th eAmp Hour rating of a battery at various discharge rates measured in Hours. They are usually published at the 20 hour discharge rate. This battery 20 hour Amp Hour capacity is 100 AH. That means if you discharge the battery at 5 amps, it should last 20 hours until the battery voltage drops to 1.75 volts per cell or 10.5 volts for a 12 volt battery. However if you discharge the battery at say the 5 hour rate of 20 amps, it is only a 82 Amp Hour battery. Amps = Amp Hours / Hours. Example a 100 AH battery discharged at the 20 hour rate 100 AH / 20 H = 5 amps.

    The Kwh they list is fudging numbers a bit to make it look better than what it is. To determine the watt hours a battery has is Battery Voltage x Amp Hours = Watt Hours. What they have done is used the 100 Hour Ah rating of 111 AH or 1 amp. 12 volts x 111 AH = 1332 watt hours or 1.32 Kwh. At the 5 hour rate the battery only has 12 volts x 82 AH = 984 Watt Hours or .984 Kwh.

    The Datasheet gives you more useful information. When you see a battery with a part number like 31, 24, 27, etc is a BCI case code for a standard automotive battery. Look up any battery that is 31 size will be exactly the same demensions as the Trojan 31-AGM. Deep cycle batteries do not usually use BCI dimensions. This battery is not a candidate for solar applications unless you need extremely high charge and discharge rates. Put it into cycle service and you are only going to get a few hundred cycles. A good deep cycle battery should get you around 1000 cycles or more.
    MSEE, PE

    Comment


    • #3
      Sunking,

      Thank you for the lesson.

      To be honest I just went to the Trojan site and picked a battery with things I recognized, they were 31, AGM and deep cycle.

      I'll reread your reply and try to remember what you've told me.

      mj52

      Comment


      • #4
        What is important to take away is there are 3 types of lead acid batteries.

        1. Is SLI aka Cranking Batteries. As the name implies they are designed to crank engines with brief extremely high currents, then be recharged very quickly. To do this the batteries must have very low internal resistance. To have very low resistance the battery lead plates must be constructed with many very thin sponge like texture to maximize surface area. Press them into cycle service with deep discharges and those plates end up in the bottom of the battery jar in a few cycles. Each cycle removes lead from the plates. SLI batteries will only have CCA and CA ratings. There will be no Amp Hour rating.

        2. Deep Cycle batteries are designed to be deeply discharge many times. To do this the manufacture makes the lead plates very thick and massive. However there is a trade-off. The internal resistance will be much higher thus limiting how high of a charge/discharge current they can handle. Typically no higher than C/8 Where C = the Amp Hour at the 20 hour discharge rate, and 8 is the hour charge rate. So if you have a 80 amp hour battery the 8 hour rate is 10 amps max. Amps = Amp Hours / Hours. Deep Cycle batteries will never have a CCA, CA, or MCA rating. Some larger Deep Cycle (larger than 200 AH) batteries may have a RC Minutes rating

        3. Hybrid Batteries tries to be both Deep Cycle and SLI. They have thicker plates than SLI, but not as heavy as deep cycle. Again it is a trade-off. They can deliver higher charge discharge currents than Deep Cycle, but not as much as SLI. They have more cycles than SLI, but not as many as Deep Cycle. Hybrid batteries have Marketing Names like Golf Cart, Floor Machine, RV, Leisure, Marine Deep Cycle, ect.... Dead Giveaway you are looking at a Hybrid battery is when you see specs of CCA, CA, MCA, RC, and Amp Hours. You may not not see all of those but it will always list AH and RC. If it is a Marine Deep Cycle you will see MCA, RC, and AH Hours

        Some examples using Trojan. Look at the Data Sheets and you will see this clearly

        Trojan T-105 is a hybrid Golf Cart 6 volts 225 AH battery. Look at the Data Sheet. You see RC Minutes (minutes @ 25 amps) and AH rating at the 5, 10, 20 and 100 AH rates. The dead giveaway it is a golf cart battery is the Minutes at 75 amps which is run time standard for golf carts. There is no CCA, CA, or MCA spec.

        Trojan T-105RE is a pure Deep Cycle 6 volts 225 AH battery. All you see is AH ratings. No RC Minutes, although they could because it is over 200 AH, and absolutely no CCA, CA, or MCA specs. Note the difference between the T-105 and T-105RE. The RE has 5 more pounds of lead in it in the same GC2 case. That is the thicker heavier plates.

        Trojan 31-AGM is another hybrid as Trojan does not make a pure SLI battery. But look it has CCA, CA, RC Minutes, and AH ratings. It is the only automotive battery Trojan makes in a BCI 31 case. This would be used by vehicles with 160 amp alternators using high power accessories like winches, competition stereo systems, and low riders with hydraulic pumps to make the car dance.
        MSEE, PE

        Comment


        • #5
          Excellent summary, SunKing. I'm going to save this to refer new people to when I'm training them. Nice job.
          Solar Queen
          altE Store

          Comment


          • #6
            Originally posted by Amy@altE View Post
            Excellent summary, SunKing. I'm going to save this to refer new people to when I'm training them. Nice job.
            The hybrids do have a place in solar applications as do AGM's. The hybrids and AGM's have fairly low internal resistance making them suitable for high current applications. A few examples:

            • Less than 3 Sun Hours or applications requiring charge rates in excess of C/8.
            • High discharge rates. A deep cycle 12 volt 100 AH battery can only handle an inverter of about 150 watts (12.5 amps @ C/8 discharge). Go beyond that and you will encounter false low voltage disconnects or pre-mature disconnects from under voltage. A hybrid and AGM can go up to 300 to 500 watts depending on manufacture. How many idiots use a 12 volt battery on a 1000 watt or more inverter? Don't be caught dead being that idiot.
            • AGM's are useful in extreme cold environments (in excess of -40 degrees F), mobile environments where spills are likely to occur with FLA, or tight quarters where hydrogen gas build up is a concern.


            Hybrids are usually a little less expensive, but long term cost more due to shorter cycle life. AGM's cost roughly twice that of FLA Deep Cycle and last half as long making them some 400% higher long term cost. So before you use Hybrid or AGM, you really need to justify the cost and have a reason to use them.
            MSEE, PE

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