Mixed panel wattage/voltage dileamour!

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  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Mixed panel wattage/voltage dileamour!

    You want to adjust so that none of the controllers will over volt/over charge the battery bank.

    They will never transition at the same time/exact voltage. Don't try for that. It will drive you crazy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BajaSunBajaSun Solar Expert Posts: 72 ✭✭✭✭
    Re: Mixed panel wattage/voltage dileamour!

    I believe you! In just checking, the C40 is indicating charged but the FM60 is back in bulk! So now what do I do??!! The water pump,is due to come on again very soon which might affect the C40's status.
    The battery voltage seems to be holding steady at float value but the FM 60 is still in bulk pumping in 10A at 55V, C40 still solid green.
    Yup, confused.......
    Just think if things were so easy, nothing would be fun!
  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Mixed panel wattage/voltage dileamour!

    I would presume a system would enter bulk/absorb if the temperature corrected battery voltage falls below ~12.7 volts (12 volt reference).

    Add temperature correction issues and how long below 12.7 volts--Is all going to serve to confuse each other... But, in the end, if the Outback is holding the bank at your chosen Vabsorb voltage (say 14.5)--Then there is no need for the other controllers to come out of float (and since they see>12.7 volts--they are still happy in float).

    In the end, see if the voltage required to recharge your battery bank back to 100% full is being met--You really don't really care if 50% of the current comes from (solar charge) controller A and 50% from controller B, or if 100% comes from A. It is all the same as the battery is concerned.

    More or less, the controller with the highest Vabsorb/Vfloat voltages will "win". As long as the other controller(s) kick in and help charge when needed (battery below ~80-90% SOC), then all is well.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BajaSunBajaSun Solar Expert Posts: 72 ✭✭✭✭
    Re: Mixed panel wattage/voltage dileamour!

    'morning.
    Sorry to be such a pain, but I'm really confused now.
    I witnessed the system attempting to wake up this morning.
    C40 was blinking (once) away. FM60 was straining to get to 66V tried to wake up and went back to snooze. I decreased snooze to 0.2A and woke up the controller. It has not gone over 1A for hours and the C40 is still at one blink. SO to test further, I fired the generator. FM reported a change in Voc to 68V out at 28.5V 0A but was ex-absorb from the generator and the C40 was flashing four times!
    Shut down the genny and instantly back into bulk at 1A on the FM 60 and one flash on the C40 26.1V out.

    What have I done wrong? This makes absolutely NO sense to me now...

    Help??!!
  • BajaSunBajaSun Solar Expert Posts: 72 ✭✭✭✭
    Re: Mixed panel wattage/voltage dileamour!
    BB. wrote: »
    I would presume a system would enter bulk/absorb if the temperature corrected battery voltage falls below ~12.7 volts (12 volt reference).

    Add temperature correction issues and how long below 12.7 volts--Is all going to serve to confuse each other... But, in the end, if the Outback is holding the bank at your chosen Vabsorb voltage (say 14.5)--Then there is no need for the other controllers to come out of float (and since they see>12.7 volts--they are still happy in float).

    In the end, see if the voltage required to recharge your battery bank back to 100% full is being met--You really don't really care if 50% of the current comes from (solar charge) controller A and 50% from controller B, or if 100% comes from A. It is all the same as the battery is concerned.

    More or less, the controller with the highest Vabsorb/Vfloat voltages will "win". As long as the other controller(s) kick in and help charge when needed (battery below ~80-90% SOC), then all is well.

    -Bill
    Hi guys,
    Not sure why I'm not getting any answers now? Do I need to start a new thread? Sorry if I'm not so smart as to understand everything being said-kinda why I asked the forum for help, oh well..
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Mixed panel wattage/voltage dileamour!
    BajaSun wrote: »
    Hi guys,
    Not sure why I'm not getting any answers now? Do I need to start a new thread? Sorry if I'm not so smart as to understand everything being said-kinda why I asked the forum for help, oh well..

    Strangely enough I'm not on here 24/7. :p

    You're not necessarily seeing anything wrong.
    1). If there's not enough light falling on the panels they won't produce power. Ignore Voc; it means almost nothing for charging purposes. If the FM60 doesn't get enough power on the panels it won't wake up and try to charge.
    2). The generator does not charge through either controller (at least it had better not). So if you start the gen it will push the battery Voltage up via the charger through Bulk to Absorb, et cetera. At that point the FM60 will see Absorb Voltage on the battery and register "Absorb"; it doesn't care where the Voltage is coming from.
    3). If battery Voltage is at 26-ish without the gen running and neither controller is putting out current you either have insufficient daylight or a bad connection in the wiring which is preventing connection between arrays and batteries.
  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Mixed panel wattage/voltage dileamour!

    And it is perfectly OK to "bump" the thread...

    We try to answer questions when we see them--But the forum is getting busy enough that we cannot see/respond to every question.

    Regarding Cariboocoot/Marc's details... In dark weather, it is very easy to get down to ~5% current on the array (or even less). My GT system with 3.5 kW array was drawing 0.4 amps at 330 volts (~132 watts) in and driving about 12 watts out (the rest was used to run the electronics).

    So--When you are back to good sun, see what the controller reports on the input and outputs... On the inputs you want to see Vmp-array (+/- 20% depending on temperatures) for the MPPT controller, and ~Vbatt+a couple volts for the PWM input--Assuming both are in Bulk mode (i.e., battery was discharged down by 10-20% and needs recharging (battery voltage in the 24.x to low 26.x volts... Once the battery hits ~29.0 (or whatever is your absorb voltage), the Vmp-array will start going up (and current start going down) as the charge controllers try to hold ~29.0 volts for 2-4 hours or so (depending on controller firmware), then drop back to around 27.6 volts (float voltage) until the sun goes down (or there is enough DC loads to pull the battery lower than the charge controllers can keep the float voltage).

    In the mean time, check the voltage at the array, and at the battery bank and compare that to the terminals on the controllers/what they report... You do not want a very big voltage difference--or that could indicate too small of wire and/or a poor electrical connection.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BajaSunBajaSun Solar Expert Posts: 72 ✭✭✭✭
    Re: Mixed panel wattage/voltage dileamour!

    Thanx Bill and Mark,
    Wanted you to know that it appears everything is working well now! Interestingly it is possible to use the potentiometers on the C40 to adjust the battery readout/SOC on the FM60 which helps to balance the two controllers! What now happens is that they both charge simultaneously. The C40 starts to flash more as the FM60 shows batteries over float charge (as in absorbing). This is where adjusting the charge potentiometer seems to help balance. When the FM60 floats, not long after the C40 floats too and we're all happily floating along together! HOWEVER, IF a major load kicks in during absorption, the FM60 goes back to bulk/absorb and the C40 will float. The FM60 sees this as an external charge input, ie ex-absorb and quits charging, but I believe the system is charged up.
    Anyway, interesting stuff, proving it can be done with some patience and help from our moderators (who we know are not available 24/7 :-). )
    It's a little,disconcerting not knowing if the batteries (AGM's) might be getting overcharged as one controller might be floating and the other still in bulk, but does it really matter if the batteries are subjected to bulk for a few hours a day even though they should be floating?
    Onwards...
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