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what is the impact of an underpowered solar charger on agm batteries?

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  • what is the impact of an underpowered solar charger on agm batteries?

    i have 4 fullriver DC150 AGM batteries http://www.fullriver.com/products/ad...e/DC150-12.pdf in our van with a xantrex freedome 3000 inverter/charger and a set of 4 lensun panels and a tracer controller. in full sun the panels don't seem to produce enough power to charge the batteries. my voltage will hover at 12.7-12.9. before i added the solar i would drain 30% of my batteries on a hot day (powering the fridge, etc) but now i pretty much hold my own or gain a little during the sunlight hours. what i am finding though that is odd is that after a couple days i might be down to 12.4 volts on my batteries but if i plug in the xantrex charger (which i have on a relay to cut out the solar panels) it takes many hours to recharge. i plugged in this morning and 7 hours later i am still bulk charging at 25A (charger can put out 150A) and voltage is up to 13.3. in the past i have seen the batteries recovered from this level of depletion much faster.

    i am concerned that i am doing some kind of damage to my batteries with the underpowered solar charging. can anyone help me understand what might be happening?

    greg

  • #2
    Originally posted by indygreg View Post
    i have 4 fullriver DC150 AGM batteries http://www.fullriver.com/products/ad...e/DC150-12.pdf in our van with a xantrex freedome 3000 inverter/charger and a set of 4 lensun panels and a tracer controller. in full sun the panels don't seem to produce enough power to charge the batteries. my voltage will hover at 12.7-12.9. before i added the solar i would drain 30% of my batteries on a hot day (powering the fridge, etc) but now i pretty much hold my own or gain a little during the sunlight hours. what i am finding though that is odd is that after a couple days i might be down to 12.4 volts on my batteries but if i plug in the xantrex charger (which i have on a relay to cut out the solar panels) it takes many hours to recharge. i plugged in this morning and 7 hours later i am still bulk charging at 25A (charger can put out 150A) and voltage is up to 13.3. in the past i have seen the batteries recovered from this level of depletion much faster.

    i am concerned that i am doing some kind of damage to my batteries with the underpowered solar charging. can anyone help me understand what might be happening?

    greg
    Based on the extended time to recharge your batteries I would also say that they are getting sulfated and losing their ability to get back to 100% nameplate SOC.

    When it comes to solar panels you might never get out of Bulk charge stage unless you have a rate faster then a C/10. If you have 4 of those 150Ah batteries wired in parallel to build a 12volt 600Ah battery system you need at least 60 amps or more of charging.

    So the question is do you get that many amps from your solar panel / CC system? If not then you are slowly depleting those batteries and shortening their life.

    Comment


    • #3
      Chronic undercharging causes sulfation, ruining the batteries.

      It sounds like your PV is undersized, either not matched to the load or not getting the exposure projected.

      Any idea how much energy you actually use in a day? Want to share more details about the PV system?
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

      Comment


      • #4
        thanks SunEagle. i am not getting 60 amps from solar. more like 20 most of the time.. i decided that solar was really more of a backup when i realized that it could not fully charge the batteries so i added a relay that cuts the solar out when the van is charging off of wall current and i plug in most nights. i regularly see that xantrex deliver 100+ amps during bulk charging off of wall current. then if my van is running i have a second inverter powered off the vehicles charging system which supplies 110VAC to the xantrex so it effectively thinks it is plugged into the wall. so much of the time i am plugged in or running the engine thus my charger thinks it is plugged in. i was hoping to use the solar as just a range extender. i would estimate the van draws 4-9 amps at idle depending on what is running so my solar supplies enough to cover what i am using and if the sun is full i probably have 10 or so left over for charging. i am pretty careful to get back up to fully charged by plugging in at night but yesterday i didn't plug in and today i find it is taking many, many hours to charge and does not seem to be taking on much current. i would have thought that getting sulfated would take more than a day or two.

        greg

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        • #5
          It might be worth breaking the bank down and charging each of them individually, or at least verifying that the bulk charge is going equally to each of them.. 4 AGM's in parallel is very hard to balance, and the odd charging you are seeing might be a consequence of that.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

          Comment


          • #6
            Originally posted by sensij View Post
            Chronic undercharging causes sulfation, ruining the batteries.

            It sounds like your PV is undersized, either not matched to the load or not getting the exposure projected.

            Any idea how much energy you actually use in a day? Want to share more details about the PV system?
            i would estimate i consume 150AH of of my 12V batteries on a hot day (when the fridge and cooling fan are running a lot). less when it is cool. the inverter burns 4A at idle (seems like a lot) and the fridge draws 4 when the compressor is running. i checked my notes from a fairly sunny day in the fall and i was seeing about 16A coming out of the controller.

            Thanks for the great read on sulfation. I know i am underpowered but i would estimate i have been plugged into the wall 5-6 nights a week for the 2 months that i have had the solar system so it is not that often that i dont fully charge. on the days i don't plug in the batteries are down to 12.4 or so.

            greg

            Comment


            • #7
              Originally posted by sensij View Post
              It might be worth breaking the bank down and charging each of them individually, or at least verifying that the bulk charge is going equally to each of them.. 4 AGM's in parallel is very hard to balance, and the odd charging you are seeing might be a consequence of that.
              thanks for that thought. you know the expression you live, you learn...? these 4 are mounted in a steel frame under the van and are not very accessible. i figured batteries were a once every few years thing. i do have 2 sets of cables coming up from under the van to a switch so i can select 2 batteries at a time but i cannot isolate each one.

              greg

              Comment


              • #8
                Hopefully dumb question: I thought the symptoms of sulphation were a battery presenting full charge very quickly, but having no capacity.

                Is that wrong? Is it right for FLA but different for AGM?

                Comment


                • #9
                  Originally posted by AzRoute66 View Post
                  Hopefully dumb question: I thought the symptoms of sulphation were a battery presenting full charge very quickly, but having no capacity.

                  Is that wrong? Is it right for FLA but different for AGM?
                  I read the OP's post and initially interpreted that the battery was transitioning to absorb (becoming current limited) much sooner than normal and therefore taking longer for the charge to complete, which is why my first suggestion was sulfation.
                  CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                  Comment


                  • #10
                    Originally posted by AzRoute66 View Post
                    Hopefully dumb question: I thought the symptoms of sulphation were a battery presenting full charge very quickly, but having no capacity.

                    Is that wrong? Is it right for FLA but different for AGM?
                    yeah that is definitely not what i am seeing. it just never takes a lot of current and charges for a really long time. i would normally see it go to well over 100 amps in bulk and be charged in a couple hours but after i have been on solar for a while it will read as if it is 80-90% charged but never get over 25 amps in bulk and today it stayed in bulk for 8+ hours. does this sound like sulfation? it is like the internal resistance is really high and it is like the battery is more depleted than it measures since i can multiply the current by the hours and it would appear the battery took far more AH than it should have.

                    greg

                    Comment


                    • #11
                      Originally posted by indygreg View Post

                      yeah that is definitely not what i am seeing. it just never takes a lot of current and charges for a really long time. i would normally see it go to well over 100 amps in bulk and be charged in a couple hours but after i have been on solar for a while it will read as if it is 80-90% charged but never get over 25 amps in bulk and today it stayed in bulk for 8+ hours. does this sound like sulfation? it is like the internal resistance is really high and it is like the battery is more depleted than it measures since i can multiply the current by the hours and it would appear the battery took far more AH than it should have.

                      greg
                      It sounds like you do not have enough charging amps from the solar pv system to get that battery bank over 90% SOC.

                      Comment


                      • #12
                        i figured it out. sorry this was my bad. i turned on gen support on my inverter so that i would limit the draw on my vehicle electrical. i was plugging in a large load last weekend and since my van has a smaller inverter powered by the vehicle that feeds 110V to my charger/inverter when i am running, i thought i would test the feature that allows me to augment the AC from my van with the batteries. i forgot that when i am plugged into the wall this same feature will apply so the house inverter/charger was limiting it' s draw even when i was plugged into a 20A circuit. i turned off gen support and was suddenly charging at 120A.

                        so i definitely have an underpowered solar. i can't add more panels and i can't see removing the solar since it adds so much to my run time. i will definitely plug in and do a proper charge as frequently as possible but i wonder if i should tell my solar charger to just output a consistent voltage that is low enough that it won't try to charge the batteries but it will supplement them during the day? or maybe put a diode between the solar and my batteries? as it stands now i might lose 15% overnight and put 5% of that back during the day with the solar powering the van. is it better to do that or to just use solar to power my load when it can and never try to apply the excess to the house batteries?

                        greg

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