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325 ah Trojan L16s: how much charge current is too much

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  • 325 ah Trojan L16s: how much charge current is too much

    Trojan recommends between 10 - 13% of the C20 rating which for my L16RE-A batteries is between 32.50 and 42.25 DC charging amps. Using my 5kw diesel generator I can get right at 42.25 amps by setting my XW5545 inverter/charger to 29% charge rate. If I set my charge rate to 100% my batteries will see 75 to 85 DC amps when bulk charging at about 80% SOC. I haven't let them charge at these high rates for more than ten minutes or so but the battery temps didn't go above 55 degrees Fahrenheit. I rarely have to use a generator in the summer and would only consider these higher rates when it is cold out, assuming I'm not shortening the life of my batteries.

    The RV boondockers believe in high charge rates to reduce generator run time.

    So my question: is it OK o bulk charge at these high current rates as long as I don't let the batteries get above 55 to 60 degrees Fahrenheit? Is there any benefit? I have read that deep cycle batteries actually charge more efficiently at lower current. Just trying to maximize fuel efficiency from the diesel generator.

    I called Trojan and the tech told me I could go up to 20% as long as the batteries don't heat up. That would be 65 amps.

  • #2
    Originally posted by hammick View Post
    I called Trojan and the tech told me I could go up to 20% as long as the batteries don't heat up. That would be 65 amps.
    That would seem to be your answer right there. Always trust the manufacturer over advice you get from the Internet.

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    • #3
      You can charge them as fast as you want if you stay below gassing voltage of 2.4 volts per cell. Once you reach 2.4 vpc should be no higher than 10 to 15% of C Trojan recommends.

      Here is the problem. The faster you charge, the quicker you will arrive, and longer you will stay at the Constant Voltage stage of charging. Marketers call this ABSORB. The Constant Voltage or Absorb stage is at and above Gassing Voltage where water loss and damage occurs. Example if you charge at say C/2 (50% of Capacity) you will arrive at Gassing Voltage when the battery is at approximately 60 to 70% SOC. Which means you are going to spend a lot longer time at Gassing Voltage which corrodes plates and electrolysis on water turning it into Hydrogen and Oxygen.

      Charge at a Slower Rate like 10 to 15% of C, and you reach Absorb or Saturation phase when the battery is 80 to 90% SOC and thus significantly less time gassing, corroading, and warping plates and grids inside the battery.

      Having gone all through that, Trojan Batteries are hybrids and can be charged faster than what Trojan lets you know. Then can be charged at C/6 without any fuss. At C/6 you will hit Saturation CV stage at 80 to 90% SOC. If you were to take your batteries to a Trojan Authorized Dealer, they charge batteries less than 200 AH at 50 amps, anything above 200 AH charges at 75 amps.

      So in a Nut Shell normal routine charging is done at C/10 to C/8 to maximize battery life. EQ and emergency can be done at much higher charge rates like a generator when you want to minimize fuel burn and run times without any significant side effects. Just do not make it a habit.
      MSEE, PE

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      • #4
        Originally posted by Sunking View Post
        You can charge them as fast as you want if you stay below gassing voltage of 2.4 volts per cell. Once you reach 2.4 vpc should be no higher than 10 to 15% of C Trojan recommends.

        Here is the problem. The faster you charge, the quicker you will arrive, and longer you will stay at the Constant Voltage stage of charging. Marketers call this ABSORB. The Constant Voltage or Absorb stage is at and above Gassing Voltage where water loss and damage occurs. Example if you charge at say C/2 (50% of Capacity) you will arrive at Gassing Voltage when the battery is at approximately 60 to 70% SOC. Which means you are going to spend a lot longer time at Gassing Voltage which corrodes plates and electrolysis on water turning it into Hydrogen and Oxygen.

        Charge at a Slower Rate like 10 to 15% of C, and you reach Absorb or Saturation phase when the battery is 80 to 90% SOC and thus significantly less time gassing, corroading, and warping plates and grids inside the battery.

        Having gone all through that, Trojan Batteries are hybrids and can be charged faster than what Trojan lets you know. Then can be charged at C/6 without any fuss. At C/6 you will hit Saturation CV stage at 80 to 90% SOC. If you were to take your batteries to a Trojan Authorized Dealer, they charge batteries less than 200 AH at 50 amps, anything above 200 AH charges at 75 amps.

        So in a Nut Shell normal routine charging is done at C/10 to C/8 to maximize battery life. EQ and emergency can be done at much higher charge rates like a generator when you want to minimize fuel burn and run times without any significant side effects. Just do not make it a habit.
        I am curious about the Trojan batteries. I have a golf cart with 6 x T-605 in my 36V system. The cart comes with a charger and I wonder what the charge rate is and if it fast or slow.

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        • #5
          Thanks for the details Sunking. Next time I am up at our place I will take some notes on the what the batteries are showing for charging amps when at 2.4 vpc. Pretty sure the current is down to safe absorb levels when I reach that state.

          I'm also considering buying an Iota 48v charger so I can use my little 1,600 watt Wen inverter (Yamaha clone) for absorption charging. The Iota puts out a max of 13 amps which should be fine for the finishing stage which takes forever.
          Last edited by hammick; 10-16-2018, 09:44 PM.

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          • #6
            Originally posted by SunEagle View Post
            I am curious about the Trojan batteries. I have a golf cart with 6 x T-605 in my 36V system. The cart comes with a charger and I wonder what the charge rate is and if it fast or slow.
            Must be an older Club Car? All cart manufactures quit using 36 volts and moved to 48 volts some time ago, and Club Car back then and today are the only manufacture I am aware of that comes in with buit-in charger controller. So I am assuming an older CC. Golf Cart Chargers are pretty much standardized. 36 volt chargers will be around 15 to 20 amps because 200 to 230 AH capacity at 36 volts. 48 volt chargers a little less current around 12 to 15 with capacities of 150 to 190 AH batteries. Neither fast or slow, around C/10 or a little less.

            Some of the smarter chargers can do any algorithm you can dream of, but the currents do not change. One good change I have seen is you can add a Float Charge after a normal CC/CV charge, or even better just a Float Charge if you got 24 hours before your next ride. Will really extend the life of your battery. Just be sure to keep an eye on Specific Gravity to make sure you are Floating at 100%, and cells are equal. You will have to EQ charge periodically. At Float Voltage the batteries never gas.

            MSEE, PE

            Comment


            • #7
              Originally posted by hammick View Post
              Thanks for the details Sunking. Next time I am up at our place I will take some notes on the what the batteries are showing for charging amps when at 2.4 vpc.
              I can tell you exactly what the current will be. It will be exactly Bulk current or less all the way down to 0 amps. The only thing current will tell you is when Bulk ends and when Absorb starts and finish. Just how it works.

              Your charge voltage will equal gassing voltage. So if you have a 12 volt battery will be as low as 14.4 volts up to 15 volts depending on temperature. When you connect a discharged battery to a charger with the voltage of say 14.6 volts to a discharged battery of say 12 volts, you are not going to see 14.6 volts for several hours. Your charger will be operating in Constant Current Mode and the voltage will see will be greater than 12 volts and less than 14.6 volts. The charger can only supply a finite amount of current, or else it would burn up. To limit current the voltage must Fold Back to Current Limit aka Bulk Charge Current. of say 20 amps. `

              As the battery charges up, the voltage will rise. When the voltage gets high enough, both the charger voltage and battery voltage are becoming more equal. When the Battery Voltage gets at the set point, you will see the current start to Taper. Say 20 amps to 19.9999 amps starts the Constant Voltage aka Absorb Stage. At that point you will now see the voltage at 14.6 volts set point. As the battery Saturates, current will continue to taper down toward 0 amps. When it tapers down to 3% of C, the battery is fully charged. At that point terminate charge or lower the voltage to 13.8 volts aka FLOAT.

              Point of the drill is to learn, the faster you charge, the longer you gas. The battery manufactures recommend a charge rate that is fast enough without issues. It works best for them and their lawyers.

              Now there is a way to charge very fast but takes a long long time and is the best way to charge your battery. You can charge at 1C if you got the money. But it wil take 24 hours to fully charge. But will not gas the batteries. Charge with a Float Charge Voltage of 13.8 volts. At 1C you wil charge at 1C for 10 or 15 minutes and quickly taper off, and some many hours later will finally trickle down to 0 amps when fully charged If fully discharged would take 24 hours to saturate.
              Last edited by Sunking; 10-16-2018, 09:17 PM.
              MSEE, PE

              Comment


              • #8
                Sorry meant current. Corrected.

                Comment


                • #9
                  Originally posted by Sunking View Post
                  Must be an older Club Car? All cart manufactures quit using 36 volts and moved to 48 volts some time ago, and Club Car back then and today are the only manufacture I am aware of that comes in with buit-in charger controller. So I am assuming an older CC. Golf Cart Chargers are pretty much standardized. 36 volt chargers will be around 15 to 20 amps because 200 to 230 AH capacity at 36 volts. 48 volt chargers a little less current around 12 to 15 with capacities of 150 to 190 AH batteries. Neither fast or slow, around C/10 or a little less.

                  Some of the smarter chargers can do any algorithm you can dream of, but the currents do not change. One good change I have seen is you can add a Float Charge after a normal CC/CV charge, or even better just a Float Charge if you got 24 hours before your next ride. Will really extend the life of your battery. Just be sure to keep an eye on Specific Gravity to make sure you are Floating at 100%, and cells are equal. You will have to EQ charge periodically. At Float Voltage the batteries never gas.
                  It is an EZ-GO TXT model that is about 8 years old. The charger is not built in but it did come with the used cart. I can use a 15amp outlet and it charges the batteries in about 3 hours depending on their SOC.

                  So far I usually measure about 44V when they are charging. After they have been charged and rested the SG in each of the 6 units is around 1.25 - 1.26 and 6.3V to 6.35V so they can't be the original units but in my opinion may be coming to the end of their life. I was just wondering if the charger is doing a good job or slowly cooking them if I leave it plugged in too long.

                  I am not sure how to get the charger to EQ but that is something I will look into when I get ready to replace them next year. Good thing I do play 18 holes a day. The cart is mostly used to make the round trip to my mail box which is about 1200 feet from the house.

                  Comment


                  • #10
                    Originally posted by SunEagle View Post
                    It is an EZ-GO TXT model that is about 8 years old. The charger is not built in but it did come with the used cart. I can use a 15amp outlet and it charges the batteries in about 3 hours depending on their SOC.
                    My bad, Sounded like a Club Car. I know EZGO TXT quite well.

                    Originally posted by SunEagle View Post
                    So far I usually measure about 44V when they are charging. After they have been charged and rested the SG in each of the 6 units is around 1.25 - 1.26 and 6.3V to 6.35V so they can't be the original units but in my opinion may be coming to the end of their life. I was just wondering if the charger is doing a good job or slowly cooking them if I leave it plugged in too long.

                    I am not sure how to get the charger to EQ but that is something I will look into when I get ready to replace them next year. Good thing I do play 18 holes a day. The cart is mostly used to make the round trip to my mail box which is about 1200 feet from the house.
                    Something does not sound right, or you do not discharge too deeply. If the batteries are good, and if they were deeply discharged would take more than 3-hours at 15 amp charge rate. My guess is you just do not use it much and 3 hours is just the Absorb phase to top them off.

                    Golf Cart Chargers run a gauntlet. What you get from the cart manufactures is bare bones, a very simple CC/CV charger with no settings. One size fits all. There is no EQ, Float, or any way to set any parameter. Today you can buy After Market semi-smart, or smart chargers. Semi-smart chargers will have 3 fixed stages of Bulk/Absorb/Float and maybe, maybe not EQ. Pay up a few dollars and you can get a fully programmable charger to any voltage or finish current you want. They come with loaded battery profiles, like Trojan and US Battery, AGM, Gel, Lithium, or whatever you want it to be.

                    If you ever decide to upgrade chargers look for one that will at least give you Float and EQ. Lester Summit, Delta-Q, and Accusense to name a few.

                    Anyway 15 to 18 amps is good for either 36 or 48 volt batteries. Example if you were to buy a Lester Summit charger does both 36 and 48 volt batteries. It charges 36 @ 18 amps, and 48 @ 15 amps. Key to finding a quality charger is they will be rated in watts, not amps because they can charge more than one voltage. They run 600 to 1000 watts.
                    Last edited by Sunking; 10-17-2018, 04:34 PM.
                    MSEE, PE

                    Comment


                    • #11
                      Originally posted by Sunking View Post

                      My bad, Sounded like a Club Car. I know EZGO TXT quite well.



                      Something does not sound right, or you do not discharge too deeply. If the batteries are good, and if they were deeply discharged would take more than 3-hours at 15 amp charge rate. My guess is you just do not use it much and 3 hours is just the Absorb phase to top them off.

                      Golf Cart Chargers run a gauntlet. What you get from the cart manufactures is bare bones, a very simple CC/CV charger with no settings. One size fits all. There is no EQ, Float, or any way to set any parameter. Today you can buy After Market semi-smart, or smart chargers. Semi-smart chargers will have 3 fixed stages of Bulk/Absorb/Float and maybe, maybe not EQ. Pay up a few dollars and you can get a fully programmable charger to any voltage or finish current you want. They come with loaded battery profiles, like Trojan and US Battery, AGM, Gel, Lithium, or whatever you want it to be.

                      If you ever decide to upgrade chargers look for one that will at least give you Float and EQ. Lester Summit, Delta-Q, and Accusense to name a few.

                      Anyway 15 to 18 amps is good for either 36 or 48 volt batteries. Example if you were to buy a Lester Summit charger does both 36 and 48 volt batteries. It charges 36 @ 18 amps, and 48 @ 15 amps. Key to finding a quality charger is they will be rated in watts, not amps because they can charge more than one voltage. They run 600 to 1000 watts.
                      Thanks for the information. I will check out those Chargers.

                      By the way, my existing charger is an EZGO Powerwise QE type for 36v system. It has a 16amp rating but zero ability to change the charge settings.
                      Last edited by SunEagle; 10-17-2018, 05:02 PM. Reason: added last sentence

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                      • #12
                        Sunking thanks for the heads up on the Lester Summit chargers. Was going get an Iota 48v charger until I saw the Lester. The Lester is less than $100 more and has 1050 watts of DC charging at 48 volts. Their specs much more detailed than Iota which give me great confidence my 1,600 watt Yamaha clone inverter/genrator will power it. Plus fully configurable and upgrade-able via Bluetooth. Can also monitor the charging via Bluetooth. Another shiny gadget to play with and should save me a lot of fuel costs vs using the diesel genset for absorb charging.

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