Enecsys micro inverters - AC Coupled to SPPro

I have a 10kw 240v Enecsys micro inverter grid tied system split into 3 strings
(44 micro inverters with 14x235w solar modules and 30x215w solar modules) AC array
and also a stand alone 3.44kw DC array stand alone power supply using 16x215w solar modules,
2 x outback /flexmax 80's, 24 x 2v Haze tubular OPzV+Solar 800 Batteries feeding a
5kw Selectronic SPPro SPMC481 box of tricks

I say box of tricks because this inverter/ charger can be used in many configurations
grid tied, stand alone, UPS, Mobile (ships),standby(generator controller)
Batteries can be charged from grid,from generator,from solar,from ac couple,from wind or hydro

I am in Tropical Cyclone country so it is handy that I can export to the grid or be independant of the grid or both

The reason I am telling you all this that we have many days with 90% cloud cover and no grid power
specially following cyclones and we can have 6 cyclones come past in a wet season

I want to ac couple the 6kw of the 10kw Enecsys micro inverter grid tied system to the sppro on the days
when we have major cloud cover as trialing this has brought the batteries up to float by 9am (2.5Hours)
when it normally takes 5 to 10 hours from my east/west facing 3.44kw DC array

The problem I have is that for AC coupling usually a KACO inverter is coupled the sppro with fully controlled
regulation.
Because I want to use the Enecsys micro inverters there is no voltage control
I used solid state relay to connect the 6kw array to the normal AC couple area of the sppro and once the batteries got to float the battery voltage rose above the preset 61.7 hi batt voltage alert limit the inverter resets quite violently
so I had to turn off the SSR manually.
I can control the SSR by letting the relay turn off once the float light comes on but all this leaves me with
two problems ( I was told once that you can never solve a problem - just change it)

when the array is wired to the SSR to enable an AC couple then it is disabled from normal exporting to grid
So I decided that to get the best of both worlds i need a changeover SSR (NO-COM-NC contacts) to switch it back to grid export after the 2 hour charge each morning (the earlier I get the batteries topped up the more time to allow exporting)
Well solid state change over relays rated at 240v 50amps are like rocking horse poo to find - non existent

and at this stage problem number two presents it self

the first time I tried to make a change over relay out of 2 x SSR's switched by a normal change over relay (one switches off as the other switches on)
I got sparks and fire
It seems that the enecsys side is still loaded (7v across active and earth) even though it is not connected - I thought the zero switching of the SSR's would stop any sparks, I cooked an SSR in the process, I was hoping the sparks might have been from a loose connection or something
until I discovered the voltage (7v)

I beg you experts now to enlighten me - do I need a change over system that switches loads
or can I do it with SSR's and maybe a timer to click in after a certain amount of time has past to connect the micro inverters back to grid

I was going to test first with a normal 63amp changeover switch in the relays place Mains-off-Aux but my birthday is coming up in 3 days and I dearly would like to be at my party - the sparks have un-nerved me

Comments

  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Enecsys micro inverters - AC Coupled to SPPro

    Never came across that inverter before but it looks like a beast, similar in specs to the 5kW SMA Sunny Island... and they're both yellow.

    Interesting approach they've taken with AC coupling the Kaco by using its comms port... never seen that before either :) The other inverter/charger manufacturers typically change the output frequency to bump the grid tie inverters offline when a preprogrammed batt voltage is reached.

    For the problem of switching from the grid to the output of the SPPro maybe the Victron solar switch could help: http://www.victronenergy.com/upload/documents/Brochure%20-%20Solarswitch%20-%20SAL064122020%20-%2002%20-%201103%20-%20EN_web.pdf it will autoswitch based on whether the grid is there or not.

    For the over-charging problem, I see the SPPro has 4 relay outputs(!), so could you attach 1 or a few of these to dump loads, like resistance heaters and then program the SPPro to dump at specific voltages? E.g. if you could use 3 relays, you could dump power in increments, e.g. at 60V turn on dump number 1, at 60.3V number 2, etc.

    Alternatively you could use some PWM dump load controllers to direct the DC power to a resistor... will have to be able to handle 6kW though!

    I believe the enecsys come with a web based interface too, could you by any chance turn them off using this?
  • ISO-tericISO-teric Registered Users Posts: 5
    Re: Enecsys micro inverters - AC Coupled to SPPro
    stephendv wrote: »
    Never came across that inverter before but it looks like a beast, similar in specs to the 5kW SMA Sunny Island... and they're both yellow.

    Interesting approach they've taken with AC coupling the Kaco by using its comms port... never seen that before either :) The other inverter/charger manufacturers typically change the output frequency to bump the grid tie inverters offline when a preprogrammed batt voltage is reached.

    For the problem of switching from the grid to the output of the SPPro maybe the Victron solar switch could help: http://www.victronenergy.com/upload/documents/Brochure%20-%20Solarswitch%20-%20SAL064122020%20-%2002%20-%201103%20-%20EN_web.pdf it will autoswitch based on whether the grid is there or not.

    For the over-charging problem, I see the SPPro has 4 relay outputs(!), so could you attach 1 or a few of these to dump loads, like resistance heaters and then program the SPPro to dump at specific voltages? E.g. if you could use 3 relays, you could dumap power in increments, e.g. at 60V turn on dump number 1, at 60.3V number 2, etc.

    Alternatively you could use some PWM dump load controllers to direct the DC power to a resistor... will have to be able to handle 6kW though!

    I believe the enecsys come with a web based interface too, could you by any chance turn them off using this?

    Thanks for the link to that switch
    I dont want to dump any excess

    What I want is to turn half my array that is normally exporting over to (ac couple) help charge the batteries
    and once they are up the float stage then turn the array back to exporting
    as an example the enecsys AC solar array would be the common contact of a change over switch or relay
    the Source (grid AC) is the normally open contact and the house load on the sppro inverter is the normally closed
    contact.

    having this would mean when the grid goes down the array is always switching the array to help charge the batts
    when the grid is up the relay/switch switches the array to the grid to export power

    I can use the outputs in the sppro to turn the relay once the batt SOC reaches FLOAT to avoid over voltage hopefully. I have already had the SSR switch to AC couple and charge the batts, I know that works
    I have not tested with a relay to see if it switches the relay once float is acheived but I have seen the relay light come on at the right time

    my problem is switching the relay/switch back to grid export after charging batts
    the first and last time I switched the relay back we had fire and smoke
    it seems there is voltage still on the line - we are switching under load
    there is 7volts ac across active and earth/neutral even coming from nowhere

    I want to try out using a change over switch with off in the middle before I cook anymore relays but as I said before - my birthday is coming up in 3 days and dearly want to be at the party - not my funeral
    having sparks and fire and smoke unnerved me - but at the same time I need to know if using the switch will work

    do I need to wait a certain time before switching to the enecsys
    ac couple - off for 5 minutes - enecsys exporting
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Enecsys micro inverters - AC Coupled to SPPro

    This is purely a guess at the cause of the smoke/fire when you first tried switching over with the SSRs: grid phase was out of sync with the inverter phase, so the SSR may have released at the zero crossing point, but then switched over into full current. I don't claim to know how SSRs work internally, so I'd be inclined to use a mechanical switch over relay instead.

    I didn't notice that your batts are gel, they are VERY sensitive to over voltage and the specs say they shouldn't go over 2.4V per cell. The main problem with AC coupling is precisely how to prevent over-voltage on the batts, so you should be very careful that the changeover happens reliably. You could end up destroying those batts should they sit at more than 2.4V for an extended time. And on that subject you should disconnect the enecsys array as soon as the batts hit the absorb voltage, don't wait till float! If you wait till they reach float voltage it would mean that they go through a full absorb charge with no voltage control. Unless you're not doing a full 3 stage charge, but just charging at float permanently?

    The other issue with those batts is the maximum charging current, the specs say 10% of the C24 capacity. http://www.hazebattery.com/OPzV%20Solar/default.htm C10 is 910Ah and C100 is 1000Ah, so C24 is somewhere in between, let's say 930Ah, which means a maximum charging current of 93A, x 48V = 4.4kW. Since you're already charging them with a 3.4kW DC array adding another 6kW to the mix could tip the current far over that limit.

    Sorry I can't really help with the SSR's, as I said too unknown about what's going on in that black box, a normal mechanical change over relay with some time spent in the disconnect position should be fine.
  • ISO-tericISO-teric Registered Users Posts: 5
    Re: Enecsys micro inverters - AC Coupled to SPPro

    I only switched the active wires when I got the smoke and fire, I wonder if maybe I should have switched
    actives and neutrals.
    Its funny, I said before it measured 7vac across the active and earth even when circuit was open well
    today I installed a changeover switch and the reading I got before doing it was now 4vac
    We will find out tomorrow if its all good or bad. if I can start in the morning on ac couple the two hours
    later throw the switch to off for a while then over to export for the rest of the day. fingers crossed no
    flames

    This is the main reason for AC coupling is to charge the batteries on really bad days and to get the
    charging done first thing in the morning so that the SPPro then has a chance to do some exporting as
    well - the 3.4kw DC array lies 1.7kw east and 1.7kw west so it acts like 1.7kw all day and not 3.44 for
    half a day and I have a choice of which string out of 3 or how many strings I want to AC Couple.
    Tomorrow is another day like today, 90% chance of rain, 80% cloud cover and I need ac coupling to get
    the batteries charged on these days where on a great day I can charge the batts to full and export up to
    64kwh - today took 10 hours to get batteries up to 95% leaving no time for the sppro to export and the
    enecsys arrays only exported only 14kwh. all time worst day I exported 2.5kwh. none of the 13kw of
    solar modules available to me are in ideal situations. so I am not too worried about too much current
    available to charge the batts.The most I have acheived so far is 70amps.

    I am more worried about treating the batteries properly with correct voltages
    haze say the max float current is 20% of C20 , so what do you calculated that at?
    I want the float voltage to be 55.2max - but at what current?? there is no c20 in their charts and some
    charts say c100=1000 and c10 is 912 and some say c100=964 and c10=810
    I cant get a straight answer from haze, so what do you think my max float current should be??

    It is easy for me to disconnect the enecsys array as soon as the batts hit the absorb voltage
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Enecsys micro inverters - AC Coupled to SPPro
    ISO-teric wrote: »
    I am more worried about treating the batteries properly with correct voltages
    haze say the max float current is 20% of C20 , so what do you calculated that at?
    I want the float voltage to be 55.2max - but at what current?? there is no c20 in their charts and some
    charts say c100=1000 and c10 is 912 and some say c100=964 and c10=810
    I cant get a straight answer from haze, so what do you think my max float current should be??

    The difference between the two values isn't that great, I'd take the worst case value say midway between C10 and C100, which is 956Ah for the first set and is the larger answer, so pick this one to be safe. 20% (which is double what their manual says BTW), would be 191A, so you should be ok. Assuming that 20% is in fact the correct limit ;)
  • ISO-tericISO-teric Registered Users Posts: 5
    Re: Enecsys micro inverters - AC Coupled to SPPro

    I think you misunderstood me
    I already have my MAX charge current set to 96amp

    I need to work out from the misleading haze data sheets what there "FLOAT" current is at 55.2v

    For When I switch the system over to an UPS situation and float the batteries

    I was told by a salesman float current is 20% of C20
    There is no C20 in their charts
    my thinking is 964 is C, 192 is 20%, 20% of 192 =38.4 amps

    and yet when I have the batts floating at 55.2v whatever I set the current to
    (I can set the float current to 50amps but it drops down and hovers around 6 amps naturally
    So I think 38.4amps is way too high and it cant be 3.84amps because set at that the voltage changes to 52v

    I need to know the proper setting before I ruin my batteries for good

    quote
    I am more worried about treating the batteries properly with correct voltages
    haze say the max float current is 20% of C20 , so what do you calculated that at?
    I want the float voltage to be 55.2max - but at what current?? there is no c20 in their charts and some
    charts say c100=1000 and c10 is 912 and some say c100=964 and c10=810
    I cant get a straight answer from haze, so what do you think my max float current should be??
    unquote
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Enecsys micro inverters - AC Coupled to SPPro
    ISO-teric wrote: »
    I think you misunderstood me
    I already have my MAX charge current set to 96amp

    I need to work out from the misleading haze data sheets what there "FLOAT" current is at 55.2v

    For When I switch the system over to an UPS situation and float the batteries

    I was told by a salesman float current is 20% of C20
    There is no C20 in their charts
    my thinking is 964 is C, 192 is 20%, 20% of 192 =38.4 amps

    and yet when I have the batts floating at 55.2v whatever I set the current to
    (I can set the float current to 50amps but it drops down and hovers around 6 amps naturally
    So I think 38.4amps is way too high and it cant be 3.84amps because set at that the voltage changes to 52v

    I need to know the proper setting before I ruin my batteries for good

    quote
    I am more worried about treating the batteries properly with correct voltages
    haze say the max float current is 20% of C20 , so what do you calculated that at?
    I want the float voltage to be 55.2max - but at what current?? there is no c20 in their charts and some
    charts say c100=1000 and c10 is 912 and some say c100=964 and c10=810
    I cant get a straight answer from haze, so what do you think my max float current should be??
    unquote

    For a conventionally designed charge controller, the Float stage is strictly constant voltage, with no time limit and no current limit IF the batteries are in good condition.
    For a charge controller which tries to regulate a Float current, but with a maximum voltage setting overriding that current, then it may make some difference what that current is, and there will be a corresponding maximum time in Float after which the CC shuts down.

    There can also be a maximum current drain which will break the controller out of Float and back into Bulk. Not sure how one would want to set that though and it does not seem that it should be specific to a battery type but rather to the charging environment.

    I think the constant current based Float is more likely to be found in an internal charger in a UPS where quick recharge is valuable. But it would still have to go back to constant voltage for the long haul.
    SMA SB 3000, old BP panels.
  • ISO-tericISO-teric Registered Users Posts: 5
    Re: Enecsys micro inverters - AC Coupled to SPPro

    Thanks, I can set the short term float stage voltage, current as a percentage of max charge current and the long term float voltage.
    When I put a random figure into the short term current selection (50amps) it works its way down and settles at about 6 amps, So I assume it is constant voltage - so why have a current choice
    There is no current selector for long term float
  • BB.BB. Super Moderators, Administrators Posts: 29,344 admin
    Re: Enecsys micro inverters - AC Coupled to SPPro

    With a "hefty" current for long term float--It allows you to have DC loads that are sustained by the "battery charger" rather than cycling the battery bank.

    May or may not make sense for a UPS type system... But for a solar power system where you have charging current available (solar array + sun), and variable loads--The ability of the charger to keep the battery >~12.7 volts keeps the battery bank from being cycled while there are other power source(s) available.

    More or less how the "RV Converters" work (supply DC power to RV/Inverter while connected to shore power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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