I need a smart person to help with inverter configuration

bellisesmbellisesm Registered Users Posts: 4
Hi all,

I need some help with an inverter parameter configuration to get the best out of our system.

I have an off grid home/ working farm which we have recently purchased. The system is 4 years old but has not been maintained well and as such I had to purchase a new generator recently and have spent a lot of time getting the batteries up to a good level.

System information... 2000W solar array, with 3KW 48 volt Selectronic (RAP-3-48-1) invertor, 48 volt 1380Ah battery bank (Raylite mte21s) and a autostart linked 8kVA diesel generator.

Usage.... the big users - We have a pool with a 1100 Watt pump which needs to run for 3 hours a day in summer (1 hour in winter), a dishwasher, and a coffee machine in the mornings.... these items currently automatically turn the generator on when they are used....

We have a TV (3 hours a day in evening), fridge, washing machine, iron, lights etc.

Selectronics have a couple of manuals which don't make much sense to me and I am wondering if a smarter person than I can guide me in establishing what are the correct parameters settings for my system. http://www.selectronic.com.au/documents/AppNotes/PSA/RAP%20Operation.pdf and http://www.selectronic.com.au/documents/AppNotes/PSA/PSA%20Inverter%20Programming%20Example.pdf

I am keen to maintain the batteries - it has taken me a bit to get the cells back to an acceptable capacity and one cell has already needed to be replaced. Current SG readings are in the range of 1250-70 and rising (were 1140 when we took over the place).

Cheers Brett

Comments

  • bellisesmbellisesm Registered Users Posts: 4
    Re: I need a smart person to help with inverter configuration

    To assist here are the settings i need help on. The setting descriptors below give the default setting and the range with which they can be set.


    |BatSize Ah 400|
    | > 20, < 3000|
    This is the size of the battery in ampere hour. The value set should be the capacity of the battery at the typical
    discharge rate expected in the system.

    |GenMax kW 6.0|
    | > 1.0, < 15.0|
    This is the maximum power which will be held on the generator for any sustained time. It must be set at less than 80% of the nominal KVA rating of the generator to ensure the generator is not overloaded. In a system supplied from the grid it is the maximum power which will be drawn from the grid.

    |MinStrtDis % 5|
    | > 4, < 80|
    This is the minimum depth of discharge which will start the generator at the preferred charge hour.

    |GenStrtDis % 20|
    | > 4, < 80|
    This is the depth of discharge which normally starts the generator except during the lockout time. It is expressed as a percentage of the battery size. For example a battery of 200Ah would be discharged by 66 ampere hour if the GenStrtDis was set to 33%.

    |NiteStrtDis % 30|
    | > 4, < 80|
    This is the depth of discharge expressed as a percentage of the battery capacity which will start the generator during the lockout time. Normally it is set to a higher value than the standard depth of discharge to help keep the generator off during the lockout time. However if it doesn't matter when the generator runs or if the system design is such that the generator has to run at night it should be set to the same value as the standard discharge.

    |GenStartV 117.0|
    | > 111.6, <125.4|
    GenStart V is the battery voltage averaged over 15 seconds which will start the generator independent of the state
    of battery charge.

    |GenHoldOn % 32|
    | > 20, < 50|
    If the two minute average power level power produced by the generator is above this value, which is set as a percentage of the generator maximum rating, the generator will be kept running. A high value can cause the generator to start and stop more frequently. A low value can be used to keep the generator running provided the load is high and only revert to inverter o only operation when the load is low. It should not be set to too low a value or the generator will run for extended time at low load and low fuel efficiency. The generator power must be below this value and below the minimum charge power set below before the generator is shut down.

    |MinChrgPwr % 4|
    | > 2, < 9|
    If the battery charge current is above this value, set as a percentage of the nominal energy storage capacity of the battery, the generator will be kept running. For example if a system had a 400Ah battery at 120V the nominal storage capacity is 48kWh, 4% of this is 1.92kWh, so the generator would be kept running until the charge power had fallen below 1.92 kW. It is used to ensure that the battery has reached a good state of charge before the generator is shut down. The charge time can also be used to ensure that the battery has reached a good state of charge.



    |NomAc Volt 240|
    | > 210, < 260|
    This is the nominal ac output voltage. Changing this value adjusts the output voltage. The potentiometer RV4 should be used to adjust the actual output voltage to correspond to this value. This ensures that the actual value corresponds to the indicated value and that the generator voltage is correctly displayed.

    |RevPwr kW -1.00|
    | >-10.00, <-0.20|
    RevPwr kW is the reverse power which is allowed to flow into the generator before disconnection takes place assuming that the generator has run out of fuel or the generator has been turned off manually and the inverter must disconnect to prevent it being driven as a motor.

    |Hi Lim Hz 55.02|
    | < 65.00, >50.10|
    This is the maximum frequency at which the inverter will synchronise to the generator or stay synchronised to the generator. Values above 55Hz are not recommended as they may cause overloading and overheating of compressor loads such as refrigerators and air conditioners. If the generator frequency is excessively high it should be adjusted if possible.


    |Lo Lim Hz 45.00|
    | < 49.90, >43.00|
    This is the minimum frequency at which the inverter will synchronise or stay synchronised to the generator. Values below 45 Hz are not recommended as they may cause saturation and overheating in motors such as refrigerators.

    |ShutDisch % 60|
    | > 0, < 90|
    This is the battery depth of discharge at which the inverter will shut down to prevent over discharge of the battery. If renewables are providing charge current to the battery and there is no renewable shunt a value of zero should be used to disable shutdown on depth of discharge. Shutdown will then only be based on battery voltage. In systems without renewables and where a renewable shunt is fitted a typical value would be 60% of battery capacity.

    |ShutDwnV 111.0|
    |> 102.0, < 111.0|
    ShutDwnV is the battery voltage averaged over 15 seconds which will shut the inverter down to avoid over discharge of the battery. After such a shutdown the battery voltage must recover to above the nominal battery voltage (by renewables charging the battery) or there must be AC power present from the generator allowing the inverter to synchronise and start to charge the battery.

    |RenFloat V 136.2|
    | > 126.6, <144.0|
    This voltage is used to monitor the effect of renewables charging the battery particularly if there is no renewable shunt present. If this voltage is exceeded for the RenFloat hr the battery is considered charged, the battery ampere hour is adjusted and boost charging is deferred for half a day.

    |RenFloat hr 2.0|
    | > 0.3, < 12.0|
    See RenFloat V description above.

    |Shunt A/mV 1.00|
    | > 0.20, < 5.00|
    This is the calibration constant for the renewable current measuring shunt. The default value is 1.00 A/mV which corresponds to a 50mV 50A shunt or a 100mV 100A shunt. A 50mV 100A shunt would require a value of 2A/mV. If large currents are being measured a 100mV or even 150mV shunt is preferred as this minimises errors in measurement.

    |In Chrg V 139.8|
    | >126.0, < 144.0|
    This is the initial charge voltage, which is applied when charging starts, at full charge current. Once the charge current has fallen below the boost current setting the final charge voltage is applied, the current is reduced to the boost current setting. The final charge is competed at the charge voltage and boost current. It is held at the charge voltage until the charge time and minimum charge power conditions are satisfied. This allows maximum charge rates to be applied at high efficiencies as many battery manufacturers allow higher charge currents while the battery voltage is low.

    |Float V 139.8|
    | >126.0, < 144.0|
    This is the battery voltage maintained after the battery has reached charge condition and while it remains connected to a source of ac power such as the generator or mains. In systems with mains supply permanently available a lower float voltage should be set.

    |Charge V 144.0|
    | >132.0, < 147.0|
    This is the battery voltage maintained in the charge condition provided the battery current is below the charge current limit and while the charge time described below has not been satisfied. The battery is brought to this voltage and held for the charge time set below and until the charge power has fallen to less than the minimum charge power set above.

    |Chg Time hr 0.3|
    | > 0.3, < 12.0|
    This is the time that the inverter holds the battery at the charge voltage before shutting the generator down provided the charge power is below its setting and the generator load is below its shutdown level.

    |Boost V 147.0|
    | >132.0, < 147.0|
    This is the maximum battery voltage during a boost or equalise. This voltage is set after a normal charge is completed. Boost charges occur when the specified number of days has elapsed but also depend on how often renewables charge the battery. The battery must be at this voltage for the boost time value set below.

    |Charge Amp 30|
    | > 10, < 35|
    This is the maximum battery current supplied while the inverter is charging the battery. The value should be set to hold the charge current within the battery manufacturers ratings. Lower values can be used to prevent the inverter shutting down on over temperature during periods of sustained charging and at high temperatures. In a three phase system this figure applies to the master phase, and the total current charge current is three times this value.

    |Boost Amp 20|
    | > 5, < 30|
    This is the maximum battery current supplied while the inverter is boosting or equalising the battery. The value should be set to keep the boost current within the battery manufacturers recommendations, particularly if the battery bank is small. In a three phase system this figure applies to the master phase, and the total current charge current is three times this value.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I need a smart person to help with inverter configuration

    Welcome to the forum.

    Let's see if I have this straight: you have a 48 Volt system with 1300 Amp hours of battery and a 2000 Watt array? If so, the generator must run a lot. That would be the first issue I'd address.

    Otherwise I can see why you're having trouble: some of those parameters do not make sense. Float Voltage of 139? On a 48 Volt system? :confused: I guess it is controlling the battery stage based on AC output Voltage or possibly some arbitrary rating system, which is a very odd way to do it and in my opinion not a good way either.

    It appears that this is an inverter with built-in charge controller. These appear to be popular outside of North America, but for the life of me I can't think why because they nearly always have limitations which get in the way of optimization and adaptation.

    Make sure your system has the shunt required to measure battery SOC. Most of the parameters seem very straight forward. But you could be having trouble based on the "BatSize" alone if it is set to 400 and you actually have 1300 Amp hours. Plus, if this has been chronically undercharging (30 Amps won't do much for a 1300 Amp hour battery bank and it seems 35 is maximum) then they will be sulphated to an unknown capacity and probably don't function well.

    My advice would be to start by double-checking the battery capacity. I also would suggest you consider replacing this unit with one that follows Off Grid system conventions.
  • Texas WellmanTexas Wellman Solar Expert Posts: 153 ✭✭
    Re: I need a smart person to help with inverter configuration

    Why not invest in a pool pump that is solar ready? Sun Pump and Lorentz both make DC pumps. You are wasting energy converting the power to AC and then to a possibly energy hog AC motor.

    Try a DC motor that has permanent magnets (brushless type) or at the very least consider going to a 2-speed motor that will use 1/8th the electricity. You can easily shave 50% off your electricity usage by going to a 2-speed AC motor that should cost around 2-300$.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: I need a smart person to help with inverter configuration

    not sure, but i think the inverter is rated at 24v. at least the link you provided shows this. could it be it was a 24v battery bank and you mistook it for 48v?

    also be very sure the batteries are not being fed with voltage in the hundreds area as that would fry your batteries. be very sure of the electrolyte levels and give the batteries only distilled water using a good hydrometer to determine their charge. check with the battery manufacturer for the specific gravity and charging parameters as well as maintenance your batteries need. during the time it was not occupied while being sold could be too long of a time and they may be down in their capacity and in need of replacing.
  • bellisesmbellisesm Registered Users Posts: 4
    Re: I need a smart person to help with inverter configuration

    Thanks everyone for the information.

    On the back of your advice I have worked out some of my confusion.... the parameters in the manual are not consistent with the parameters in the system.

    The battery bank is definitely a 48Volt 1380Ah system (Raylite MTE21s) http://www.battery.co.za/download/dl/M%20Solar.pdf

    I have copied across the parameters settings as they are in our system currently. The system is 48v (the manual obviously covers a range of systems.) I need advice on what they should be to make the system work a bit more efficiently.

    Current Configuration setting:

    BatSize Ah 1320
    GenMax kW 6.0
    MinStrtDis % 20
    GenStrtDis % 29
    NiteStrtDis % 45
    GenStartV 45.6
    GenHoldOn % 32
    MinChrgPwr % 9.8
    NomAc Volt 240
    RevPwr kW -1.00
    Hi Lim Hz 55.02
    Lo Lim Hz 45.00
    ShutDisch % 60
    ShutDwnV 42.0
    RenFloat V 54.4
    RenFloat hr 4.0
    Shunt A/mV 1.00
    In Chrg V 60.1
    Float V 57.1
    Charge V 58.3
    Chg Time hr 0.3
    Boost V 61.0
    Bst time hr 1
    Charge Amp 30
    Boost Amp 20
    BstFrqDay 14
    PrefGen hr 17
    Lockgen hr 23
    Unlock hr 6

    Thanks for your advice on the pump Tex. I will do some further research.... I have been using a smaller secondary pump 750W which is better on the power supply but it doesn't have efficient power to push the quantities of water through the filter and chlorinating system. Its a 100,000 litre pool (10ft deep) and I am finding it needs to process at least 50,000 litres a day to stay at correct Chlorine levels (will need to process more during the peak of summer when the pool is being used)
  • upa123upa123 Registered Users Posts: 17
    Re: I need a smart person to help with inverter configuration

    Looking at the battery manufacturer's spec sheet it would appear the 1380 amp/hr capacity rating is based on a 100 hr discharge. A 20 hr discharge rating is a little more typical and realistic on a solar based application. I would speculate your 20hr capacity is closer to 1100 ah, still an impressively large battery.
  • Texas WellmanTexas Wellman Solar Expert Posts: 153 ✭✭
    Re: I need a smart person to help with inverter configuration

    I had to do a quick conversion. 100,000 liters is about 26,000 gallons. Pretty sizable pool. Mine is about 20K gallons in comparison.

    For any residential pool you need to be turning the water over at least once per day. So figuring 100,000 liters/24 hours you need to be pumping about 4200 liters per hour or about 70 liters per minute, which in American units is about 18 GPM. The trick is for you that you need to be able to do this in about 6-12 hours (when the sun is up and charging your system).

    My 2-speed 1 HP Pentair pump runs about 50-60 GPM at about 8 amps and 3450 rpm. Cut the rpms in half and the flow drops in half, about 20-30 GPM but the electricity drops by 1/8 to about 1 amp. I can cut my pumping by 1/2 but my electricity falls by 8x.

    bellisesm wrote: »
    Thanks for your advice on the pump Tex. I will do some further research.... I have been using a smaller secondary pump 750W which is better on the power supply but it doesn't have efficient power to push the quantities of water through the filter and chlorinating system. Its a 100,000 litre pool (10ft deep) and I am finding it needs to process at least 50,000 litres a day to stay at correct Chlorine levels (will need to process more during the peak of summer when the pool is being used)
  • Texas WellmanTexas Wellman Solar Expert Posts: 153 ✭✭
    Re: I need a smart person to help with inverter configuration

    So given that you need to turn your water over in say about 10 hours you are going to need about 40ish gallons per minute, or about 166 liters per minute. That's a lot of water movement using solar.

    If you take your 50,000 lpd (which I'm not sure is enough) you can knock that requirement in half to about 20 gpm. I would strongly suggest looking into one of the Lorentz or Sun Pump pool pump set-ups that utilize permanent magnets that are much more efficient than regular induction motors or go with the 2-speed (much cheaper option) that will do the same and leave you with the ability to run on high flow.

    Also I have found that keeping the water moving for a longer period of time has a much better effect on the water than just simply circulating a pre-determined amount and then letting it sit stagnant until the next cycle. This is where a 2-speed pump really shines.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I need a smart person to help with inverter configuration

    You should separate the parameters into those that affect the battery charging (such as Amp hour capacity, charging Voltage and current) and those that affect the generator connection (anything starting with 'Gen" for example). It will be easier to understand that way.

    You will immediately see a problem of 30 Amps into a 1000+ Amp hour battery bank. That isn't even remotely close to being an effective maximum charge current. In fact if that is the limit from all sources (solar and gen input) the batteries are doomed.

    So at that point you have to re-evaluate the whole system, starting with the loads. If you can't reduce the need for that large a battery (you're looking at 250 Amp hours+ for 25% DOD or 12kW hours) you will have to increase charging. A 2kW array is not going to do it. It may appear to be working, but that could be on a basis of having a massive battery bank that simply has so much capacity that its diminishing size through premature sulphation does not obviously affect operation - yet. One day it will.
  • solar_davesolar_dave Solar Expert Posts: 2,362 ✭✭✭✭
    Re: I need a smart person to help with inverter configuration
    Also I have found that keeping the water moving for a longer period of time has a much better effect on the water than just simply circulating a pre-determined amount and then letting it sit stagnant until the next cycle. This is where a 2-speed pump really shines.

    I agree, I have a VFD pump and instead of shortening the time of run I slow the pump down in the winter months leaving the run time at about 4 hours. Our pool is about 20,000 gallons as well.

    BTW I just moved to back to run on peak to help burn some excess on-peak kWh. We are now in to cooking freezer meals to do the same during the day.
  • bellisesmbellisesm Registered Users Posts: 4
    Re: I need a smart person to help with inverter configuration
    You should separate the parameters into those that affect the battery charging (such as Amp hour capacity, charging Voltage and current) and those that affect the generator connection (anything starting with 'Gen" for example). It will be easier to understand that way.

    You will immediately see a problem of 30 Amps into a 1000+ Amp hour battery bank. That isn't even remotely close to being an effective maximum charge current. In fact if that is the limit from all sources (solar and gen input) the batteries are doomed.

    So at that point you have to re-evaluate the whole system, starting with the loads. If you can't reduce the need for that large a battery (you're looking at 250 Amp hours+ for 25% DOD or 12kW hours) you will have to increase charging. A 2kW array is not going to do it. It may appear to be working, but that could be on a basis of having a massive battery bank that simply has so much capacity that its diminishing size through premature sulphation does not obviously affect operation - yet. One day it will.

    Thanks for all the feedback it is helping....... I understand that the the 2kW array is not meeting our needs, the question is how big do i need to go?.... there is $15K of ridiculously big batteries and a $10K Kubota diesel genset in the shed (We also have a 6kva lister backup). Panels prices are coming down here in OZ as the gov rebates disappear and serious competition in the market starts. So would your advice be to up size the panels and the inverter or hold out until the batteries die and revisit the lot...?

    As background...We have done the sums on getting mains power to the farm and it in the tune of $200K.... so not really an option....plus i don't really want to be on the mains... . we would be at the end of the line, so it is more than likely we would have regular blackouts, plus maintaining 1 km of private powerlines in a high bushfire risk area comes with its own expenses too.... the house is not your average house, two storey with a 600 sq metre foot print (6500 sq feet) - I think the original owners built it to be a guest house. As discussed it has a big pool but also has other things like a big spa (heated on gas but has three electric pumps), sauna etc. We have numerous shedding and run air compressors and welding gear irregularly. We are also planning to build a small cool room to store our produce before sale which will also be a power sucker.... so i know i need to go bigger... what are my options and what is going to have the best outcome are the things i am working through. Any advice is greatly appreciated...

    Back to the inverter settings.....On the back of the advice received (and a little more research into the batteries) I have changed the current setting of the inverter..... can anyone see any problems here? do the setting sound ok? Have I interpreted all your comments correctly? The settings I am most unsure about are Min Charge Power (was above 9% now 4), Charge Amp and Boost Amp...

    BatSize Ah 1100
    GenMax kW 6
    MinStrtDis % 20
    GenStrtDis % 40
    NiteStrtDis % 50
    GenStartV 45.6
    GenHoldOn % 40
    MinChrgPwr % 4
    NomAc Volt 230
    RevPwr kW -0.5
    Hi Lim Hz 55.02
    Lo Lim Hz 45
    ShutDisch 60
    ShutDwnV 45.6
    RenFloat V 57.6
    RenFloat hr 4
    Shunt A/mV 1
    In Chrg V 54
    Float V 55.92
    Charge V 58.8
    Chg Time hr 0.3
    Boost V 62.4
    Bst time hr 2
    Charge Amp 100 (this is the maximum Amp)
    Boost Amp 48
    Best Freq Day 14
    prefgenhr 18
    lockgen 23
    unlockgen 6

    Regards

    Brett
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: I need a smart person to help with inverter configuration

    I'd question this, Chg Time hr 0.3, Is this 3/10's of a hour ?? It would be on my Inverters. Mine would be from 1.5 to 3.0 hours depending on the system when using generator power. This does work in conjunction with Min Charge power, but on most inverters the time overrides that setting.
  • BB.BB. Super Moderators, Administrators Posts: 30,511 admin
    Re: I need a smart person to help with inverter configuration

    Good quality solar panels should last 20-30+ years... Your batteries and fuel costs are now--So getting "enough" solar panels to run your loads and keep your batteries happy is probably the best investment of time and money right now.

    If you have a need to "day time" water pumping (irrigation/pumping to tank/storage), I would highly suggest looking at Solar to VFD (variable frequency drive) to 3 phase AC pumping... If you can avoid the battery bank, you will save A LOT OF MONEY for your pumping power (1/2 to 1/4 the cost with no-battery system vs one that uses a battery bank off grid solar power).

    Syed has found China is producing VFDs designed for this application:
    Sorry Bill for responding too late. Regarding to your question yes we modify VFD to some extent but now a days many Chinese are producing pumping inverters without battery support. These inverters are also basically new form of VFD please visit the site for more information
    http://www.sacredsolar.com/index.aspx?menuid=12&type=introduct&lanmuid=87&language=en

    I hope it will help you. I will try to help you in this matter.

    Regarding your solar array size... Based on just your battery bank, we normally suggest around 5% to 13% rate of charge to keep the batteies "happy"... For your system (48 volt 1380Ah battery bank), the math would look like:
    • 1,380 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 5,197 Watt array minimum
    • 1,380 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 10,395 Watt array nominal
    • 1,380 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 13,513 Watt array "cost effective maximum"

    This is assuming your battery bank is sized "correctly" for your loads (a good, balanced design--Works out to a battery bank about 4x larger than your daily loads--2 days of "storage" and 50% maximum discharge for longer battery life).

    Assuming it is "sunny" where you are--You should have a minimum of 4 hours of sun per day for at least 9 months of the year. A "nominal array" would generate around:
    • 10,395 Watt array * 0.52 end to end AC system efficiency * 4 hours of sun per day = 21,622 Watt*Hours = ~21.6 kWH per day

    If you do not know your daily loads yet--I would suggest getting a couple of used utility meters (or some nice industrial kWH meters, or a consumer type whole house monitor--like this US version) and start logging your kWH per day from the AC inverter and your generator(s).

    A decent Diesel Generator installation should get somewhere around 1-1.5+ kWH per 1 liter of diesel (wild guess)... If you are running the gensets as less than 40-60% of rated power, you can end up with wet stack/carbonization/cylinder wall glazing), and poor fuel economy.

    You may also want to look at your AC battery chargers (I assume you are using these a lot)... You should be looking at 5-13% rate of charge minimum for your battery bank from genset power. You can go as high as 20-25% -- But watch your battery bank temperatures during charging (don't overheat) and keep an eye on fuel economy (the last few hours of battery charging do not draw much current and a large genset will be loaded very lightly).

    There is also the option of running the batteries on a 50-80% (state of charge) daily charge/discharge cycle and charging back >90% once a week. Batteries should stay good (not sulfating) and it is much more efficient charging cycle (>90% efficiency with <80% SOC charging; less than 80% efficiency when >90% SOC charging (and near zero efficiency when over >95% SOC).

    Note that my numbers are within 10% type numbers--Just carrying the digits so you can repeat my math and see where the numbers are used in the next calculations. Getting >5% rate of charge on your battery bank from solar would be my first goal (in my humble opinion) to keep batteries healthy and reduce generator usage. 10% rate of charge would be very nice if you are using a fair amount of power from your battery bank daily.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I need a smart person to help with inverter configuration

    I'd reevaluate the whole system now, starting with measuring load demand and testing batteries. If the batteries are still good then upping the array to provide sufficient charge power from solar would be the best investment, just as Bill said.

    It appears your existing built-in controller can not handle the amount of PV needed for that size battery bank. With 1100 Amp hours (assuming that adjustment to 20 hour rate is correct) you would want 110 Amps of peak charge current or roughly:

    110 A * 48 V = 5280 Watts / 0.77 (typical array efficiency) = 6857 Watt array.

    Basically you are looking at the need for two 60 Amp MPPT controllers with 3500-ish Watts of panel each. That is a lot of array which is why I suggested looking at the loads first to determine if you really need that much battery.

    Since this is an 'inherited' system it was likely designed "the old way" with lots of battery capacity and very little PV because batteries were cheap and PV wasn't not too long ago. As such the design is probably not as efficient as it could be.

    And I think that the central inverter-charger-controller unit is a poor design in and of itself. It clearly was never meant to handle large battery and PV capacity.
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: I need a smart person to help with inverter configuration

    Rememeber that with midnite / outback controllers you can put more (sometimes quite a bit more) panel into them than rated. I know a guy is has just installed 10.5kW of pv into two fm80s. You just set them to current limit the peaks off, and is a cost effective way to run an array that size. The reason this can make sense is that the peaks are often short lived, equinox, clear and cool days, when batterys still charging at mid day sort of thing,
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • NorthGuyNorthGuy Solar Expert Posts: 1,925 ✭✭
    Re: I need a smart person to help with inverter configuration
    zoneblue wrote: »
    Rememeber that with midnite / outback controllers you can put more (sometimes quite a bit more) panel into them than rated. I know a guy is has just installed 10.5kW of pv into two fm80s. You just set them to current limit the peaks off, and is a cost effective way to run an array that size. The reason this can make sense is that the peaks are often short lived, equinox, clear and cool days, when batterys still charging at mid day sort of thing,

    This is also a good way to limit current into batteries during peaks and still have good power in between.

    The drawback is that it limits all the current (batteries + loads). If some big loads come on they limit battery current even further.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: I need a smart person to help with inverter configuration
    NorthGuy wrote: »
    This is also a good way to limit current into batteries during peaks and still have good power in between.

    The drawback is that it limits all the current (batteries + loads). If some big loads come on they limit battery current even further.

    Not sure I'm following you on this??:confused:

    I use the Midnite Classic charging amp limit to limit input to my inverter during cloud edge or very cold, very sunny periods which might cause my inverter to try to sell more than its continuous rated output.

    This has absolutely no effect on the potential amp output of my inverter. It still spits out very high surge amps when my septic pump comes on for example.
  • NorthGuyNorthGuy Solar Expert Posts: 1,925 ✭✭
    Re: I need a smart person to help with inverter configuration
    mtdoc wrote: »
    Not sure I'm following you on this??:confused:

    I'm talking about battery charging.

    During absorb and float, the current to batteries is naturally limited, but during bulk stage they can take more than you may want. If, say you have 400AH bank, you may decide that you do not want more than 80A to go to batteries (C/5). So, you set the amps limit on CC to 80A, and you buy an 80A CC, even though your array is capable of 100A.

    At this point, if a big load, say 30A, comes up, 30A go to the load and only 50A to the batteries. If you had no limit, you would get full 100A - 30A to the load and 70A to the batteries (still below the 80A limit).
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: I need a smart person to help with inverter configuration
    NorthGuy wrote: »
    I'm talking about battery charging.
    .

    Ok got it. You're only talking about CC output not load/inverter current -that makes sense. Thanks.
  • SolInvictusSolInvictus Solar Expert Posts: 138
    Re: I need a smart person to help with inverter configuration
    Since this is an 'inherited' system it was likely designed "the old way" with lots of battery capacity and very little PV because batteries were cheap and PV wasn't not too long ago.
    The old way, according to the inverter manufacturer's recommendation, was to size the battery array at the 20 hour rate of discharge to the continuous power rating of the inverter. bellisesm has a 3,000 W inverter which I assume is its continuous rating. Assuming he has 12 Raylite mte21s (2 cells/battery, 4 V battery) in series with a capacity of 1,130 Ah at the 20 hour discharge rate (from the yellow chart in the spec sheet), the batteries can source:

    1,130 Ah / 20 h * 48 V = 56.5 A * 48 V = 2,712 W for 20 hours which is reasonably sized for his inverter.

    His average daily power consumption is needed to assess whether his PV array is too small, but I suspect from his list of high powered devices (especially 3.3 kWh/day to run a pool pump) that his PV array is likely undersized. His 2 kW PV array is fully able to keep his battery array charged and allow his batteries to last 20 years, but the farm would have to use less than 4.5 kWh/day (possibly less depending on insolation at his site and excluding the power from the generator) and minimize power consumption at night and on cloudy days to achieve it. The farm is or was likely using more than 4.5 kWh/day on average and deep cycling the batteries.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I need a smart person to help with inverter configuration

    Nope.

    Daily power consumption in Watt hours determines battery bank capacity.
    Maximum load at any given time determines inverter size.
    Battery bank capacity determines array & controller sizing.

    Any other way ends up with someone like me doing a lot of work to fix it 'cause it's wrong.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: I need a smart person to help with inverter configuration
    Charge Amp 100 (this is the maximum Amp)
    Boost Amp 48

    It's not clear which charging parameter will be applied during boost charging. Make sure that during boost while the battery voltage is below 61V and the gen is on, that you're getting the maximum 100A charge.

    Also, you mentioned at the start that turning on the coffee maker or the dishwasher causes the gen to come on. This should not be the case as neither of those draw 3kW (I would hope). Is there another setting on the inverter that causes it to start the gen when it sees a certain current draw? If the consumption of those two loads is less than 3kW then you could modify that parameter to turn the generator on later, e.g. at a 2.8kW draw.
    But it sounds like you'll be adding even more and bigger loads, so I'd consider increasing the inverter capacity to avoid the gen coming on so often. Goes without saying that you'll need more panel to support additional loads; and given the price of PV, this is a worthwhile investment compared to the cost of diesel.
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