Charge Controller - Bulk Float Charge?

tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
I just installed a new Xantrex Series C Controller. Now for the first time I am getting some real time information as to the current and voltage my solar panels are feeding into the battery bank.
However along with these new found facts has come a bit of confusion. The manual that came with the controller has a chart that suggests a bulk charge voltage setting of 29.2 volts, a float charge rate of 26.8 and an equalizing charge rate of 31 volts for my generic lead acid batteries. The factory setting was 28 volts bulk and 27 float.
I have attached the tag information for the solar panels.
I can not see how these values can be obtained. The panels have a Voc of 30.8 volts and a Vmp of 24.4 volts.
So far,(one day) the controller has remained in the bulk charge mode. I have the bulk charge rate set at the factory preset of 28 volts. The panel voltage of course varies with the movement of the sun but I have never seen 28 volts yet. Even though the voltage is below the threshold for bulk charging there is little to no current moving from the panels into the batteries.
What has experience taught you all. On a 24 volt system what should I set the controller at and what should my expectation be.
Thanks!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?
    bp solar
    www.bpsolar.com

    Model SX3200B
    Part # 5213.0123
    Serial # F30802157399200

    Electrical Rating
    Peak Power (Pmax) 200 W
    Warranted Minimun Pmax 182 W
    Voltage (Vmp) 24.4 V
    Current (Imp) 8.16 A
    Open Circurt Voltage (Voc) 30.8 V
    Short Circuit Current (Isc) 8.7 A
    Minimum Bypass Diode 10 A
    Maximum Series Fuse 15 A

    Product data sheet
    Electrical Characteristics2 SX 3200
    Maximum power (Pmax)3 200W 195W
    Voltage at Pmax (Vmp) 24.5V 24.4
    Current at Pmax (Imp) 8.16A 7.96A
    Warranted minimum Pmax 182.0W 177.5W
    Short-circuit current (Isc) 8.7A 8.6A
    Open-circuit voltage (Voc) 30.8V 30.7V
    Temperature coefficient of Isc (0.065±0.015)%/ °C
    Temperature coefficient of Voc -(111±10)mV/°C
    Temperature coefficient of power -(0.5±0.05)%/°C
    NOCT (Air 20°C; Sun 0.8kW/m2; wind 1m/s) 47±2°C
    Maximum series fuse rating 15A
    Maximum system voltage 600V (U.S. NEC rating)

    RHW-2 AWG# 12 (4mm2), cable with polarized weatherproof DC rated Multicontact connectors;
    asymmetrical lengths - 1250mm (-) and 800mm (+)

    Yes, that is a problem... Warm panels (normal day, full sun) don't even output Vmp at standard conditions...

    You need another solution (different panels, more panels+MPPT controller, or something).

    On a 95F, windless, day--those panels could have a Vmp as low as 19.5 volts... And not much better than 20.5 volts on a 77F day...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Wow! That's now exactly the response I had hoped for.
    I kind of inherited this system and the learning curve has been straight up ever since.
    There are 4 panels total 800 watts, and 16 - 6 volts configured into a 24 battery bank.
    You mean to say that I can't ever expect to obtain a full charge.
    Why on earth would BP sell a 24 volt solar panel that's not capable of maintaining a 24 volt battery bank?
  • Solar GuppySolar Guppy Solar Expert Posts: 1,987 ✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Those are not 24V nominal panels, there 18V nominal panels, typically used in series strings for Grid Tie applications. FYI, 12V nominal has a VOC of ~20V
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    seeing sg has posted before me i will confirm what he says is true. to charge a 24v battery bank you would need to have the pvs in series of 2 and paralleled. a pwm charge controller will work, but the vmp will be so high that there will be losses in using the pwm charge controller. it would be advisable to use the mppt style of charge controller.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    Which Cxx controller do you have? Depending on Voc (cold) and the controller's maximum Voc panel input voltage--you may have to (for now) do what Niel said--just put two panels inseries, then combine into two parallel strings.

    At least you will begin to properly charge that battery bank....

    An estimate of power into your battery bank while charging would be:
    • 2*8.16 amps Imp * 29.2 volts Vbatt-charge =477 Watts on a bright sunny day
    Check how much current you are currently inputting to your battery bank while charging (and what is the bank voltage)... If the input current is below ~10-14 amps with the 1x4 array--you will be better off doing the 2x2 array instead with the PWM Cxx controller.

    Next Step: If you can justify a MPPT controller, you will have to purchase one for use with this panels. At least a 30 amp--perhaps 45+ amp if you are in a cold region (get lots of bright sun, snow, and sub freezing temperatures).

    -Bill

    I guess you are somewhere in Texas--so no snow for you.

    Again, sorry about the miss-configuration. No "cheap way" to fix it 100%. :cry:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    An education can be expensive.:cry:
    I had nothing to do with specifying or purchasing the actual panels in this installation.
    What I am hearing from you all is that these panels are not actually designed to be installed in parallel as a 24 volt system.
    Reconfiguring them into a series parallel configuration is certainly an option. Summer temperature down here are typically 100 + and can reach 115 or so. In the winter it is seldom below freezing although this winter seemed to be a real exception with a couple of day time temperatures right at the freezing point.
    It seems to me I would get better performance this way even though it seems strange to run 50 or 60 volts on top of a 24 volt system.
    Here's the current dilemma for me. The controller I just purchased is the C60 model.
    It's input voltage is limited to 55 Vdc. So close but I guess there is the possibility of these panels actually producing 61.6 Vdc under perfect conditions even though I have never seen anything close to that. The C40 controller is limited to 125 Vdc. In hine sight this would have been a better choice. Do you think these panels will ever under real world conditions exceed the limits of the C60? Do I need to purchase another controller for this solution to work?
    I do have perhaps one other option.
    I have six more small panels rated as follows:
    @ 25 C
    55 watt
    I @ max power 3.13 amps DC
    v @ max power 17.6 Volts DC
    Short circuit current 3.29 amps
    Is it acceptable good practice to configure panels with different outputs into the same array?
    Thanks so much for all your input. It's not exactly what I had hoped to hear but it good to have individuals such as your self to lean on.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    No, you cannot use those SX320B panels with the C60 at all with a 24 volt bank at all... In parallel, they will not charge the bank. 2x in series will be too high of voltage (2xVoc is too high).

    The 55 Watt panels, 2x series and then put the 3x strings in parallel will work OK.

    If you want to use both set of panels--but the C60 on the 55 watt panels. An get an MPPT for the 200 watt panels. Connect both to the battery bank (each through their own set of short/heavy cables to the battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Well it seems as though I got a real can of worms here.
    From what I can make out of all the comments is that the problem started with the wrong panels. The SX3200B panels are a 16 volt nominal panel and I need a set of panels with a 24 volt nominal rating. Strange no where on the tag is the nominal voltage rating listed. I was only able to confirm what Solar Guppy posted by doing a little internet research. I also looked at a number of other panels rated at 24 nominal volts and the average Voc was 41.32 with an Vmp of 33.53. If only I had those panels!

    So where do I go from here!!!

    I have three ideas and would appreciate your input.

    New panels rated at a nominal voltage of 24
    Could use all the existing hardware
    Perhaps I could find a buyer for the SX3200B panels and off set some of the cost
    Would get the approximately 800 watts output

    Reconfigure the panels into a series parallel setup
    2 groups of 2 panels in series with an output of Vmp 48.8 Voc 60.6
    This is considerably more voltage than is required for a 24 volt system and it would require a new voltage controller. The Xantrex C60 has a maximum PV array open circuit voltage of 55 volts. The Xantrex C-40 has a maximum open circuit voltage of 125 volts and could be used
    Then take the 2 series set and configure them in parallel to achieve approximately 400 watts maximum output.
    Cost a new controller and a compromised array.

    Finally and this one I don't even know if it's possible.....
    I have 6 Arco Solar Inc. :confused:Model M55
    Max Power 55 watts Imp 3.13 amps Vmp 17.6 Short Circit amps 3.29 Voc 24 volts
    Configure each of the four Model SX3200B panels is series with one of the M55 to create a cell producing Vmp 42 volts Voc 54.8 volts
    Each of the four series grouping would produce approximately 255 watts
    Then configure the four series grouping in parallel to form an array with an output of approximately 1020 watts.
    If this can be done I could use the current C-60 controller but it would require some extensive modifications to the solar array mounting.

    Any way you shake it I'm not a happy camper but once you jump in it time to swim.

    Thanks again for all your help.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?
    tkc100 wrote: »
    Well it seems as though I got a real can of worms here.
    From what I can make out of all the comments is that the problem started with the wrong panels. The SX3200B panels are a 16 volt nominal panel and I need a set of panels with a 24 volt nominal rating. Strange no where on the tag is the nominal voltage rating listed. I was only able to confirm what Solar Guppy posted by doing a little internet research. I also looked at a number of other panels rated at 24 nominal volts and the average Voc was 41.32 with an Vmp of 33.53. If only I had those panels!
    Solar panels are nowhere near "ideal batteries"... In the end they need temperature "correction" in the environment for where they are to be installed, and laid up against the battery bank charging voltage (i.e., 24 volt bank needs ~29-32 volts) and the type of charge controller (the PWM vs MPPT discussion).
    So where do I go from here!!!

    I have three ideas and would appreciate your input.

    New panels rated at a nominal voltage of 24
    Could use all the existing hardware
    Perhaps I could find a buyer for the SX3200B panels and off set some of the cost
    Would get the approximately 800 watts output
    I have no reason to assume that the BP 200 watt panels are anything but very good panels (and relatively price competitive $$/watt).

    I have 20x BP 175 panels on my roof right now running my Grid Tied system.
    Reconfigure the panels into a series parallel setup
    2 groups of 2 panels in series with an output of Vmp 48.8 Voc 60.6
    This is considerably more voltage than is required for a 24 volt system and it would require a new voltage controller. The Xantrex C60 has a maximum PV array open circuit voltage of 55 volts. The Xantrex C-40 has a maximum open circuit voltage of 125 volts and could be used
    Then take the 2 series set and configure them in parallel to achieve approximately 400 watts maximum output.
    Cost a new controller and a compromised array.
    Not a good idea to choose any PWM setup with existing panels--lots of wasted power.
    Finally and this one I don't even know if it's possible.....
    I have 6 Arco Solar Inc. :confused:Model M55
    Max Power 55 watts Imp 3.13 amps Vmp 17.6 Short Circuit amps 3.29 Voc 24 volts
    Configure each of the four Model SX3200B panels is series with one of the M55 to create a cell producing Vmp 42 volts Voc 54.8 volts
    Each of the four series grouping would produce approximately 255 watts
    Then configure the four series grouping in parallel to form an array with an output of approximately 1020 watts.
    If this can be done I could use the current C-60 controller but it would require some extensive modifications to the solar array mounting.

    Not a possible solution as you proposed... You could take 3x 55 watt panels in parallel and connect that in series with one 200 watt panel...

    But you have 4x 200 watt panels and would need 4x3=12 of the 55 watt panels--which you don't have.
    Any way you shake it I'm not a happy camper but once you jump in it time to swim.

    For the 800 watts of panels--your only practical solution is an MPPT charge controller.

    Put panels in a 2x2 series/parallel array and connect behind a Morning Star Tri-Star 45 amp MPPT charge controller for $411 or so.

    If you plan on a larger array in the future--you could look at the 60 amp Tristar (and that even has an Internet Webserver included).

    I don't see any practical/cheaper solution for you... Each panel is worth ~$500 each--to "toss" some amount of that energy away with a PWM controller is difficult to justify... Of course, spending $400 for yet another controller hurts too.

    You can look at other configurations and their limitations (48 volt battery bank)--but those would even include more costs (new inverter).

    In the end, how much power do you need per day... Will a PWM system with existing panels give you the energy you need, or will you need the MPPT controller?

    And do you have any expansion plans (panels, batteries, bank voltage change, etc.) in the future?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    just thinking here, you may not be as out on the limb as you think. now i think you still need to get a good mppt controller to utilize the 200w pvs and i believe the better move is to get a new controller than replace all of the pvs. pvs with those odd voltages really are set up to be utilized in straight gt systems and they just don't try to optimize the pvs for battery voltages. the saving grace is the abilities of the mppt controller as it allows more versatility for battery based systems. one other plus is the higher voltages sent by the pvs will help to overcome the wire resistive losses up to the mppt controller.
    so what to do with the c60? use it with the arco pvs with 3 strings of 2 in series. those pvs were optimized for battery voltages.
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Niel, I am assuming you are proposing an MPPT controller with the SX3200B panels configured as 2x in series and then the 2 series modules in parallel.
    In my way of thinking I need approximately 28 volts to reach a full charge in the 24 volt battery bank and somewhere in the neighborhood of 31 volts to equalize the bank. The SX3200B panels will never see that kind of output and though I do not completely understand the MPPT concept I don't think it has the ability to boost voltage. So I guess a straight parallel set up would be out.
    Now as I'm thinking I have not played with the PV voltage loss due to heat yet but there maybe some measure of reason in this type set up.
    I'm wondering if a 24 volt nominal panel would produce adequate voltage through out the summer with day time temperature routinely in the 100+ range. That would be 100 degrees air temperature in the shade. Of course these panels are going to be in the full sun and running at a considerably higher temperature.
    This series parallel setup would certainly have adequate head room to work with even on the hottest days even thought it would not produce the most wattage.
    I have got to go and try to make some money but tonight I will play with the figures.
    The 48.8 Vmp produced by two SX3200Bs in series may in fact be just about where I would want to be on a hot summer day.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    The 200 watt panels will be around 18-19.5 Vmp on very hot days...

    And even 24 volts is not enough to charge your battery--a 24.00 volt lead acid battery is around 50% charged... You need probably at least 27.5 volts (or a bit more) to even really charge the 24 volt battery bank.

    Regarding MPPT charge controllers... The vast majority of them can only efficiently "down convert" or drop voltage (Vpanel should be at least 1-2 volts above Vbatt-charging) for proper operation.

    You can read about PWM and MPPT charge controllers from NAWS' FAQs:

    All About Charge Controllers
    Read this page about power tracking controllers

    There are no real drawbacks to MPPT charge controllers vs PWM--except that they are 2-3x as expensive (which is an issue).

    If you had Vmp=17.5/35.0 or so panels--PWM would be fine for you--But you do not...

    And yes, the two panel in series will charge your bank just fine--just not using all of the wattage your expensive solar panels are capable of providing. But, you are left with a C60 controller which cannot handle the Voc (open circuit voltage).

    You could wire the C60 as a "Dump Controller" (the solar panels are tied directly to the battery bank as series/parallel with a series blocking diode) and attach some sort of electrical resistance heater(s) to the C60 for now--but this is really only a poor second choice solution... And I am not sure how much money/hassle it saves you in the long term.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Yes I think you are correct.
    Given my current situation the choices look like this:
    1) Get the right PV panels. 24 volt nominal
    2) Purchase a new MPPT controller and configure the panels into a 2x series - 2x parallel system
    3) Purchase another PMV controller one capable of handling a Voc of 60+ volts and again configure the panels into a 2x series - 2x parallel system
    4) Do nothing, which is of course unacceptable as the battery bank would never reach a full SOC.

    I did do a little of the math and I know it's not entirely correct as I didn't figure in the relationship between voltage, amperage and wattage but here what it looked like.
    SX3200B Temperature coefficient of Voc -(111±10)mV/°C mV
    120mV for each degree C above 25 C
    So if I am figuring right this panel would lose 4.87 volts with an operating temperature of 150 degrees F or 65.55 degrees C
    If I started out with an Vmp of 24.4 volts at 25 degrees C I would not have 19.53 volts at 150 degrees F or 65,55 degrees C
    Two of these panel configured in series would have an Vmp of 39.06 volts
    24 volt nominal panel with average Vmp of 33.53 under the same conditions would have an Vmp of 28.66

    150 degrees is kind of a worst case scenario.
    I ran across a study done down here in the south west and here are their figures.
    Panel temperature was monitored during a solar-AC water pumping experiment by the USDA-Agricultural Research Service, Bushland, TX. Using 6 years of average monthly panel temperature data, the solar panel performance during winter was estimated to be at rated power, but the solar panel performance during the summer was estimated to be only 93.5% of rated power.

    With these figures and or my figuring there is no real justification for all the extra overhead generated by the SX3200B panels in a series parallel configuration. It's only a stop gap measure. A 24 volt nominal panel has enough room to even accommodate summer down here.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?
    tkc100 wrote: »
    I did do a little of the math and I know it's not entirely correct as I didn't figure in the relationship between voltage, amperage and wattage but here what it looked like.
    SX3200B Temperature coefficient of Voc -(111±10)mV/°C mV
    120mV for each degree C above 25 C

    So if I am figuring right this panel would lose 4.87 volts with an operating temperature of 150 degrees F or 65.55 degrees C
    If I started out with an Vmp of 24.4 volts at 25 degrees C I would not [not not, you would have?] have 19.53 volts at 150 degrees F or 65,55 degrees C

    Two of these panel configured in series would have an Vmp of 39.06 volts
    24 volt nominal panel with average Vmp of 33.53 under the same conditions would have an Vmp of 28.66

    To be clear--a panel (or pair of panels) designed to charge a 24 volt battery bank would have Vmp~35-38 under Standard Conditions (STC nameplate) to optimally charge with a PWM controller.

    You are not the first, nor will you be the last to get bit by the Vmp=24 volts must be for charging 24 volt batteries...

    If I recall correctly, Xantrex uses a rise of 35C (63F) above ambient for their string calculators... A lot of worst case design limits (very hot panels mounted flush to roof, battery bank in below grade cold cellar, while equalizing the bank, and long cables from solar array to charge controller, and no remote battery temperature sensor, etc.) can difficult to meet with a simple PWM controller.

    But, the reality is that you should not be equalizing often (once a month of less if all else is OK) and not every day is a record setting summer day...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    I understand the "To be clear" part.
    But to be fair, to the uninitiated, no where on the tag does it say 16 volt nominal panel. I'm not trying to duck the issue or avoid taking responsibility. I own all $4k of it.
    It's just you would think with all the other figures posted it would be a simple matter to list what the intended system usage is.

    To come up with the figures I posted for a 24 volt nominal panel I took the ratings for 6 different panels made by BP.
    What I came up with is:
    Sample of 6 panels with a nominal voltage of 24 volts
    Voc 36.2 to 43.6 average 41.32
    Vmp 29 to 35.7 average 33.53

    You can bet the farm on the fact, should I decide to change these panel out, now or in the future, I will go with the highest Voc - Vmp rating.

    I have got to see what the budget will allow for now.
    All of the figuring I did for kwh used and or needed was based on getting somewhere between 700 to 800 watts out of the array. Now I'm looking at half that, perhaps a little more if I spring for the MPPT controller. That's a big WTF mate.

    Once again thanks to you, niel and solar guppy for all the input. You have made it very clear to me where the error lies and what needs to be done. It's not what I wanted to hear when I started this thread but then again what I needed to hear was how to make this thing right.
    Thanks!
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    tkc100,

    Sorry--sometimes I get repetitive if something is a bit unclear to me and there may be a misunderstanding somewhere...

    I am sure you "got it"--but others reading down the road may miss the point if not reading closely.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    No need for apologizes, no offense taken!
    I was just having some fun.

    If I should decide to go the route of configuring the panels in the series parallel manner with a new MPPT controller have you got any recommendations?
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    Depending on eventual size of the array/battery bank... Any of the MorningStar or Xantrex MPPT controllers are very good.

    Rogue 30 amp MPPT is a nice unit too--but I don't think it safely handle your Voc (cold) voltage (controller is rated 60 VDC maximum).

    The Morning Star SureSine MPPT 5 amp 12/24 controller has a maximum Vpanel of 75 volts--your panels are 70 volts or so at 14F. And in any case, is on the small side for 800 watts of solar panel on 24 volts--you would really need two 15 amp controllers.

    So, you are kind of getting down to the 45 amp MorningStar Tri-Star MPPT or 60 amp MPPT... Or the Xantrex XW 60 amp MPPT. And there is Outback too...

    I am sure that others here will have some other suggestions--I am certainly not aware of all the units out there today.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Thanks for the input BB
    I have looked a both the Morining Star and Xantrex models. There are both a bit of a bullet to bit off but certainly my best alternative for now.
    Earlier in this thread you gave me some estimated figures for the 2x2 configuration
    An estimate of power into your battery bank while charging would be:
    * 2*8.16 amps Imp * 29.2 volts Vbatt-charge =477 Watts on a bright sunny day
    This was assuming a new PWM controller such as the C40 that could handle the Voc of this configuration.
    Have you got any speculation as to what the output might be with the MPPT controller?
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    The best case output of a MPPT charge controller would be:
    • 800 watts * 0.95 conversion efficiency = 760 Watts (pretty cold/clear day)
    The typical maximum output would really be closer to:
    • 800 watts * 0.77 panel + controller derating = 616 Watts
    And because the MPPT controller convert's to the battery's voltage--From the (conservative 616 watts), you could see:
    • 616 watts / 24 volts = 26 amps (batteries are near 50% charge)
    • 616 watts / 29 volts = 21 amps (batteries are >80% charged and will start to accept less current as they continue to fill)
    Note that the same amount of Watts is going into the bank in each case--but the MPPT controller is "adjusting" to the optimum input current based on current battery bank voltage.

    And note, that once a battery bank is over 80-90% full, it will naturally accept less and less current until it is fully charged. During this period, a MPPT basically enters a type of PWM mode as maximum power is no longer needed from the solar array (during the Absorb/Float charging stages).

    In your case, once the PWM mode of the MPPT type controller reaches:
    • 2*8.16 amps Imp = 16,.3 amps
    Or so--there will be no difference in the power transferred into the battery bank between a MPPT or PWM controller (because maximum power from solar array is not needed).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    If ever there was a good case for an MPPT controller then this, my unfortunate situation has got to be one.
    I guess I will have to shift a few lines in the budget.
    Prior to all the late breaking news I was hoping to purchase a good system monitor but it will have to wait.
    It's not the best solution but one that will have to work for now as I really don't have the money for four new panels right now.
  • tkc100tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    Yes there is a Santa Claus.:D
    Armed with all the information I gained from everyone I approached the company that sold these panels in the first place.
    After considerable negotiations they agreed to give me an MPPT controller. Not only did they give me the controller but they gave me a very nice one.
    Xantrex XW Solar Charge Controller
    Yesterday I got it physically hooked up and tomorrow I will put it into service. There is a bit more to setting it up than the old PWM C-60 but if I take my time and work through all the menus I think I will be OK.
    So as it all turn out I think I'm better off than if they had sold me the 24 volt nominal panels to start with.
  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Re: Charge Controller - Bulk Float Charge?

    Or an Easter Bunny. :D

    Congratulations!
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    glad to hear of your good fortune. mighty nice of them to do that for you and let us know what you think after you see all of that power being produced.:D:cool:

    ps i was thinking the next significant day would be april 1 so let's call it a late Christmas present.
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Charge Controller - Bulk Float Charge?

    O your gonna love that MPPT Boost ;)
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