I too need help with loss of battery storage.

LndSchneid

I am completely off-grid, and I am dependent on my handyman for putting my system together. He has not done one before. It's all set up, and during the day there is usually a surplus running, and within an hour of the change in the sun it's already down to 75% and then by dark it's in the 60's% when it's been at 100% all day. I have no appliances other than a converted small chest freezer that's running on very little wattage, and 2 to 4 LED low-watt bulbs.  Plus charging my cell phone.
The setup is 8-100 watt monocrystalline and polycrystalline panels, mostly mono, putting out 100 to 400 watts. 10 6-volt l16 batteries paired together for a 12-volt system, which goes into a 60 amp pure sine wave controller, which then goes through a 3000 watt inverter. We have an 8 gauge ground wire +  6 gauge positive battery wire.
Any ideas I can pass onto my handyman?
Thank you in advance.

Photowhit

Kind of difficult to imagine this system. Has it been up and running for a while?

5 strings of batteries would be difficult to keep balanced. When they start aging I suspect you will have some strings pulling down others.

"...by dark it's in the 60's% when it's been at 100% all day"
This sounds like a voltage based 'State Of Charge' meter. All they can do is measure the current 'system voltage' Because to charge batteries the system voltage, that generated by the solar array and charge controller (CC) must be higher than the batteries resting voltage.

Could you tell use what type and model of charge controller you are using?

Your system isn't well 'balanced' 10 - L-16 batteries would be a huge battery bank. Standard L16's are 360 - 370 amps, So 5 strings would represent 360x5=1800 amp hours at 12 volts. In general we would like to see 10% -13% charging capacity from your system for a battery bank that size if the system is in daily use. 10% would be 180 amps. Your 8 - 100 watt panels if using the more expensive MPPT type charge controller, could possible put out about 600 watts ÷ 14 (minimum charging voltage for your batteries) = 43 amps max and you are saying they are producing less than that.

To give you an example, I have about a 1300 amp battery if it was 12 volt and use a 4000 watt array.

I'm worried your batteries are suffering from chronic under charging. It might seem odd, but having an over sized battery bank can often create problems.  

If we could get the age of your batteries, the type and model of your charge controller, and if you have alternate means of charging the battery bank, such as a generator or the grid, we could do a better job of offering constructive help.

BB.

Welcome to the forum Lnd S,

It does not sound like things are working correctly... But the first question is "how do you know" the state of charge is going from 100% to 60% overnight.

Let me start with a few basics... Tools to start with. A DC current clamp DMM (digital multimeter). You use the DC Current Clamp to measure current in your system. How much current is coming from the charge controller in middle of day, how much current is your AC inverter + DC loads drawing at night. How well are your batteries sharing current (one open cell or wire connection can kill 1/5th of your battery bank capacity).

https://www.amazon.com/gp/product/B019CY4FB4 ($105 -- pretty nice AC/DC current clamp DMM with other features)
https://www.amazon.com/gp/product/B07546L9RT ($46 -- "good enough" for our needs)

And you should also have some sort of specific gravity tool, if you have Flooded Cell Lead Acid batteries (vs AGM or other sealed type battery). Always remember to rinse your hydrometer with distilled water before putting away:

https://www.solar-electric.com/search/?q=hydrometer (standard float type)
https://www.amazon.com/s?k=refractometer+acid&i=tools (refractometer/optical specific gravity meter--Random search results)

A Kill-a-Watt meter is handy for measuring your 120 VAC loads and understanding their energy usage (plug one appliance into meter at a time, and see how many Watt*Hours or kWH per day the appliances use).

https://www.amazon.com/s?k=kill+a+watt+meter

The above are just suggested starting points for your search about tools. Feel free to ask questions.

The above are basic tools you should learn how to use (or your handyman needs to maintain your system).

Before we get too deep into debugging a new system (that does not have a history of "working" for your needs), let's look at the design.

I am going to make some (many) guesses here, and please feel free to correct me when I am wrong.

• 10x 6 volts @ 390 AH L-16 flooded cell lead acid battery bank configured in 2x series (12 volt bus) by 5 parallel strings (5x390AH= 1,950) AH battery bank
• 8x 100 Watt Vmp~18 volts x Imp~5.6 Amp panels (x series by y parallel connections?)
• 60 amp pure sine wave Controller... Not sure what this is. 60 amp MPPT solar charge controller?
• 3,000 Watt 12 volt (TSW/PSW or MSW?) 120 VAC inverter (brand/model/link to inverter?)
• Location--Don't know... Start with San Francisco SFO airport (decent amount of sun on average)
• LED lights -- 4x 13 Watt lamps * 5 hours a night = 260 Watts of lighting overnight
• Chest Freezer/Refrigerator conversion -- Assume 350 Watt*Hours every 24 hours (per day).
• AC Inverter -- Assume 55 Watts * 24 hours per day = 1,320 WH per day

The "heart" of your system is the Battery Bank. So I like to start there and see how it is configured/what is "ideal" for your needs. For a typical cabin/off grid home, we like to see 2 days of storage (no sun; 1-3 days storage typical range of options) and 50% maximum discharge (for longer battery life). So, typically, we would like see the battery bank 4x your daily loads (or you use 1/4 of your battery capacity) in normal usage.

• 1,950 AH * 12 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 maximum discharge = 4,972.4 WH per day "ideal" energy usage per day

Your (guesstimated) system usage is:

• 260 WH lighting + 350 WH refrigerator * 1,320 WH AC inverter "tare losses" = 1,930 WH per day estimated AC loads

Or you are using about 1/8 (or ~12.5%) of your battery capacity... Seeing it go down to 60% by the next morning indicates your loads are much higher, or your charging was incomplete, or wiring issues, or your State of Charge estimates are wrong, or your battery bank is "bad"...

For the battery bank, review this website for proper bank wiring of parallel battery strings (lots of detailed information in their technical section):

http://smartgauge.co.uk/batt_con.html

Next, there are two solar panel calculations we need to make. One is based on the size of your battery bank (larger battery bank, needs more charging current). And the second is based on the amount of sun vs loads for your locations.

First, solar + charging: Generally, we suggest around 5% to 13% rate of charge for solar charging... 5% works OK for weekend/summer cabin charging. 10%+ is recommended for full time off grid (>9 months of system usage):

• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 Rate of Charge = 1,836 Watt array minimum
• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 Rate of Charge = 3,672 Watt array nominal
• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 Rate of Charge = 4,774 Watt array "cost effective" maximum

Your present 800 Watt array, based on the size of your battery bank is way too small (as I understand your system).

Based on loading (my guesses), your battery bank is ~2x larger than you need--A 1/2 size battery bank should work fine and be easier to charge/maintain.

Also, I would suggest that a 1,950 AH @ 12 volt battery bank is too large of AH capacity for easy wiring/charging/operation (very heavy copper cabling required). Roughly, I would suggest that any battery bank >~800 AH should go up to the next sizes--Rewiring your battery bank would be 4 x 6 volt batteries in series (24 volt bus) by (2x parallel strings of 390 AH = ) 720 AH battery bank (you would have 2x L-16 batteries we cannot use--unless you buy 2x more batteries for a 3rd string). Generally, 1 string of batteries are ideal, and I would suggest that you avoid more than 2-3 parallel strings for "typical" configurations.

Next, there is sizing the solar array based on your loads and location. Picking San Francisco, fixed array, 800 Watt array, you would get:
http://solarelectricityhandbook.com/solar-irradiance.html

San Francisco
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 52° angle from vertical :
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.77	4.26	5.46	6.07	6.21	6.07
Jul	Aug	Sep	Oct	Nov	Dec
5.49	5.34	5.40	5.05	4.19	3.69

An 800 watt array would (on average) produce:

• 800 Watt * 0.52 off grid AC system eff * 6.07 hours of sun (June) = 2,525 WH per day

Now, you would only use somehthing like 50% to 65% of your solar power system for base loads (loads that you need to run everyday, like LEDs and Refrigerator--Washing machine, well pumping, etc. only done on sunny days)... So, 1,930 WH of daily AC base loads, would require roughly:

• 1,930 WH per day load * 1/0.52 off grid system eff * 1/0.50 max base load uses * 1/6.07 hours of sun = 1,223 Watt array "recommended for June"....
  

Of course, if you are up there in winter and using solar power, you would probably pick 4.26 hours of February sun and use a genset at times during the winter... Or even look at using Decemeber at 3.69 hours of sun (use very little genset)... These are your choices.

But so far, your basic system design is not really "balanced". You have a way to large battery bank (need about 1/2 size), may want to look at 24 volt battery bank (smaller wiring, fewer 24 based charge controllers). Your solar array is probably way to small for your present battery bank and AC loads. And look at a 1,500 Watt or so AC inverter (12 or 24 volt). The 3,000 Watt AC inverter is very large for your present needs (as I guess them), and that makes the Tare Losses for the inverter the major load on your system (and not your loads--Not a great starting point).

Assuming that this is one of the best months for energy production--You should, at least, sort of OK right now (during sunny weather). And your battery bank discharge behaviour is not making a lot of sense. So--You may be having some other issues and you need, at least the proper tools (DC Current Clamp DMM, hydrometer) to figure out what is happening.

Anyway, making lots of guesses here to shorten the discussion and hopefully focus on what needs to happen next.

The battery battery bank is something you have to pay attention to. It is the one thing that can be damaged or ruined if they are not properly charged/maintained. So checking the charging battery voltages during the day to get an idea what is happening (you may start at 12.2 volts before sunrise, charge to 14.75 volts (slowly rising voltage or "bulk charging"--maximum current from solar controller) and then hold 14.75 volts for 2-6 hours of "absorb charging" (deeply discharged flooded cell battery, need closer to 4-6 hours of "absorb" charging). After that, the charge controller may fall to roughly 13.6 volts "float charge" (until sun goes down/your loads exceed panel power capacity).

Some light reading:

Deep Cycle Battery FAQ
http://lib.store.yahoo.net/lib/wind-sun/Pump-Inverter.pdf

-Bill

Photowhit

Also please let us know what brand and model inverter you have. 3000 watts is ill-advised on a 12 volt system. Some of the people who make inverters like this expect them to be used in mobile applications when they are turn on only for a short time so they may have higher idle drains than inverters intended for 24/7 use.

LndSchneid

i am really grateful for the replies.  I have to pass them onto my handyman tomorrow because my head is swimming with my inability to comprehend some of this.  In the meantime. the batteries are about 3-5 months old, the inverter is a new YueQing Reliable Electric, and the Renogy Controller is a new 60A MPPT. Thank you again.  Will follow up again when he returns.

LndSchneid

P.S.  I am reading the display on the controller to determine what percentage of battery charge I have.

BB.

Meters are, at best, only guesses at battery state of charge. Some are better than others, and others are worse. Some meters also need to be programmed with the battery bank type/capacity for them to have a better estimate of capacity... Others just monitor the battery bus voltage and time (under charge/discharge/etc.).

And don't feel bad about asking questions and learning more. The math is usually not too bad--And I try to write the equations like a simple sentence (read right to left).

I try to break things into pieces... Like sizing the battery bank for your loads. Then sizing your solar array based on A) battery bank size, and based on your loads and hours of sun per day.

Even if you are not doing the work, you will learn a lot just from the math and discussions and you can help your installer better understand your needs and the system.

Watts is a rate of energy flow (like gallons per minute at 100 PSI)
Amps is a rate of current flow (like gallons per minute)
Watt*Hours is an amount like 100 allons pumped at 100 PSI.
Amp*Hours is an amount like 100 gallons pumps

Watts and Watt*hours are "complete units".

Amps and Amp*Hours are not complete units... We also need the voltage to figure out Watts and Watt*Hours (WH).

Sort of like pumping water... If I pump water from a bucket up 5 feet in the air, that is little pressure and energy needed to move the water.

If I have to pump the water a 1,000 feet up a mountain, it takes a whole lot more energy to move it up the mountain.

Amps * Volts = Watts
Amps * Volts * Time (hours) = Watt*Hours
Watts * Time (hours) = Watt*Hours

The math around here does not really get much more complicated than that.

-Bill

BB.

I am guessing this is your inverter:

https://reliableinverters.com/products/wzrelb-3000w-power-inverter-pure-sine-wave-inverter-white

I do not see any details/manual... So the Tare Loss is a guess at this point.

-Bill

icarus

What is the current draw of the chest freezer?  Could be more than you think?

Tony

Photowhit

BB. said:

I do not see any details/manual... So the Tare Loss is a guess at this point.

It does say 

"...No Load Current Draw

1.5A"

So figure 1.5x24= 36 amps at 12 volts or 432 watt hours and 

"...Efficiency

85% -- 90%" assume 85% peak for 12 volt...

BB.

Thank you Photowhit,

Not that bad of tare losses at (1.5ampsx24hours= 36 Amp*Hours) -- But still a lot for the overall systems loads (maybe somewhere around 250-350 Watts for a converted chest freezer per day--Vs (36 Watts * 24 hours per day = ) 864 Watt*Hours per day Tare losses...
36 AH per day * 12 volt battery bus = 432 Watt*Hours per day Tare losses
 
Still 2x or slightly more energy to run that AC inverter vs the chest refrigerator (again, lots of guesses).

If the power usage is "this simple", then using a 1,500 Watt inverter (with closer to 20 Watt Tare) that has "search mode" (generally 8 Watts or much less in "auto-standby") could really save a lot of Tare Losses... Of course that is at the expense of a much more expensive AC inverter with search mode...

-Bill

PS: Corrections: I am not doing very good at math the last couple of days.... Sorry. -Bill

Photowhit

BB. said:

Not that bad of tare losses at (1.5x24= 36 amps Watts) -- But still a lot for the overall systems loads (maybe somewhere around 250-350 Watts for a converted chest freezer per day--Vs (36 Watts * 24 hours per day = ) 864 Watt*Hours per day Tare losses...

I'm bad about showing my work, but at 60, I'm not likely to change...

1.5 amps x 24 hours = 36 amps x 12 volt system = 432 Watt hours.

Though how reliable a number that is, is very suspect. they list 1.5 amps for 12, 24 and 48 volt systems.

BB.

Oh boy... I am not paying attention at all... 12 volt, not 24 volt system, so you are correct at 432 WH.

My excuse .... Well, probably should not say more.

-Bill

Estragon

A couple of additional possible issues:
- with 5 strings of batteries wired in parallel (problematic in itself, as noted above), each string should be fused, in addition to the breakers/fuses on the other dc circuits to/from the bank.  
- not sure if "8 gauge ground wire and 6 gauge positve battery wire" means yor negative battery wire is 8 gauge.  The positive and negative DC wires should be the same size on a given circuit.  Anyway,   depending on length, 6-8awg could be pretty marginal for the controller to battery circuit, making the controller think it's charging at a higher voltage than it really is.  It's also far too small for a 3000w 12v inverter.  Although you aren't doing so now, you could potentially draw 3000÷11v (with sag) = ~270a sustained (with surge to maybe twice that).  To accomodate that kind of current needs ~4/0 (about thumb sized) wire. 

In any case, I certainly hope you have fuses/breakers on the controller and inverter circuits appropriate for the wire size actually used.

LndSchneid

Thank you.  After reading all of your comments, Kevin, my helper thinks we should go back to the 1500 watt inverter, still with the 60 Amp controller.  What do you think?  Okay also, all these fittings don't seem to accommodate the fatter wire.  Is there some way that even though the controller has these little mini ports to attach it to that a bigger wire could be used?

Thanks again.

Linda

BB.

What 1,500 watt inverter do you have? 

It should help. 

• A 60 amp mppt controller should work nicely with a "cost effective" maximum array of:
• 60 amps * 14.5 volts charging * 1/0.77 panel+controller derating = 1,130 Watt array typical maximum

As always, check the controller manual... That is always the definitive answer.

That is still not the minimum 5% array charging current that I would suggest (you have a very large AH battery bank). From my post near the 

First, solar + charging: Generally, we suggest around 5% to 13% rate of charge for solar charging... 5% works OK for weekend/summer cabin charging. 10%+ is recommended for full time off grid (>9 months of system usage):

• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 Rate of Charge = 1,836 Watt array minimum
• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 Rate of Charge = 3,672 Watt array nominal
• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 Rate of Charge = 4,774 Watt array "cost effective" maximum

A 5% minimum rate of charge for your bank is:

• 1,950 * 0.05 rate of charge = 97.5 Amps minimum

And that would be an array supplying 5% charging current (97.5 amps):

• 97.5 Amps * 14.5 volts charging * 1/0.77 panel+controller derating = 1,865 Watt array minimum

As you can see--That would be 2x 60 Amp charge controllers just to meet the minimum rate of charge for a flooded cell lead acid deep cycle battery bank. Generally 5% is about the absolute minimum rate of charge I have ever seen--And most FLA battery mfgs recommend 10% rate of charge minimum (of the battery's 20 Hour rated capacity)...

An 1,865 Watt array + a second 60 amp controller (up to 1,130 Watt array per 60 amp controller) would be required...

Unless you plan on using a genset/utilty power during poor weather (or when the RV is parked at home), I highly suggest you install a larger solar array (5% minimum for weekend/summer usage, 10% minimum rate of charge for full time off grid).

Generally, a larger solar array is better than running your genset longer number of hours... 

Note the number for system design, solar array size, etc... I am using the "exact" number like 1,836 Watts for a 5% rate of charge array... In solar power system, anything within 10% (1,836 +/- 10% or +/- 184 Watts) is basically "the same".

I am using these "full numbers" so you can follow my math and not get a bunch of roundoff error as I go through the various steps.

-Bill

LndSchneid

Thank you for being so helpful.  Would it work for us to add a second 40Amp controller and 2 or more panels, while keeping the 3000 inverter?  4 batteries would be hooked to the 40 Amp and 6 to the 60 Amp?

Estragon

According to the specs for a Renogy  "rover" 60a mppt CC (may not be the same model as yours though), 4awg is the max wire size.  That's likely solid wire though, stranded wire actual size is a bit bigger for a given awg size, and can be tough to fit without using a crimp-on ferrule.  6awg is probably ok if the distance from CC to bank is just a few feet.  If the negative is 8awg, or distance is longer, that may be an issue.

Assuming these are flooded lead acid batteries, I'd have the handyman check and record the specific gravity of the electrolye in every cell in the bank, and also water levels.  This is an important part of routine (FLA) battery maintenance, and will help determining what, if any, remedial charging measures are needed.  As the bank is underperforming, this should be done ASAP, as the underperformance is likely to worsen.

BB.

LnDS,

I am really concern that I (we) can give you technically correct answers, and you will still not have a "working towards you needs" system.

I have made a lot of guesses (where the system is installed, off grid, available generator/unity power, your power needs, what equipment you have, etc.).

Without some more answers and what you are looking for from the system (full time off grid or summer only, you have a clear of shade southern exposure vs bottom of a valley/trees/chimney & vent stacks on roof--all possibly shading panels somewhere around 9am-3pm, etc.).

We really do not know if the system is working the best it can--Or if there are other problems that need to be addressed.

At this time (assuming you are in the northern hemisphere)--You have some of the best "hours of sun" per day at this time of year (unless you are on the coast and have a problem with Marine Layer 4 days out of 6). When you head into fall and winter, your harvest will probably be a lot less (again, depending on where your system is installed, local trees/valleys/etc. shading your property). The closer you get to the North/South Poles, the greater the changes in available solar energy between summer & winter.

-Bill

LndSchneid

Thank you both again so very much.  I am grateful.   I am in Fort Bragg, Northern California. I am by the ocean on 17 acres of open pasture.  The panels are facing south, with just a very slight turn to the east.  I am in a location that can get foggy and gray because of the ocean, but we also have a fair amount of summer sunlight.  The reason I want to have a system that's up and working correctly is I have a Steinway grand piano in my converted Chicken Barn. It is my pride and joy, a treasure that I have actually renovated an entire room for, reinforced it with extra insulation and all sorts of things to keep it protected. Underneath te piano is a bar to keep its heat and humidity consistent.  I just moved it in this week, and I know when fall and winter arrive, there will be considerably less light and I want to be able to keep that heater going.  Right now, with the existing set-up, when I run the piano heater 24/7 the percentage on the controller reads 57-59% in the morning.  That is with full-sun days. I also like to be able to see, but I don't really need very many appliances or much other use than a little bit of light.  I do like to run my water pump when I need to. That's for brief periods and I usually run it when there's a surplus of power, or if all else fails on a generator.
Thank you again.
Linda

BB.

Thank you Linda.

The piano heater--That is probably a very significant load---Guessing at ~37 Watts:

• 37 Watts * 24 hours per day = 888 WH per day

Or possibly 2-3x the load of your chest refrigerator... 

Using PV Watts to estimate your energy harvest @ Fort Bragg, south facing, ~45 degree tilt (roughly best year round harvest). Use these numbers for your Solar Array "hours of sun" energy production equations:
https://pvwatts.nrel.gov/pvwatts.php

Month	Solar Radiation ( kWh / m2 / day )
January	4.00
February	3.94
March	4.85
April	5.86
May	5.88
June	5.93
July	5.62
August	5.45
September	5.59
October	5.10
November	4.18
December	3.23
Annual	4.97`

That "extra 37 Watts", if 24 hours per day (no timer), that is a very significant load.

Heaters (and Air Conditioning, etc.) can be very energy intensive. Putting on timer (run at night/damp weather) can help--But when you get into winter, it is cold and damp all the time.

Generally, water pumping for household use, it not much energy... Depending on what your source is (deep well, surface water into holding tank, etc.)--Lots of details to work out. Running a genset 1-2x a week to run a "large well" pump to cistern, then use a 12 or 24 volt DC RV Pump for house pressure (and some sort of pressure/holding tank to reduce pump cycling). --- Lots of options.

You really need to measure your loads (Kill-a-Watt type meter for 120 VAC loads), a DC AH/WH meter for 12 VDC loads (or use a DC Current Clamp to at least understand the current being used and estimate number of hours per day, if not 24 hours per day operations).

Here is a sample link for a DC Watt*Hour meter (for smaller DC loads). I know nothing about the meter or supplier:

https://www.amazon.com/bayite-6-5-100V-Voltmeter-Multimeter-Amperage/dp/B013PKYAV6

Things like heavily insulating the room and making it water tight (Tyvac house wrap or similar), shading on windows to prevent direct light on piano, and avoid large temperature swings. Some of this may be easy, or it may be difficult--Depending on if you are going to remodel the house/room and construction methods.

I would highly suggest getting your solar array to a total of ~1,836 Watts minimum (with 2nd controller) for 5% rate of charge.

What you "really need", need to total up your loads (both minimum/base loads every day, and possibly seasonal loads).

What 1,500 Watt brand/model of AC inverter do you have that you can reinstall?

Again, just an first pass, I would suggest (with your present 1,950 AH battery bank)--5% to 10% rate of charge:

• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 Rate of Charge = 1,836 Watt array minimum
• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 Rate of Charge = 3,672 Watt array nominal
• 1,950 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 Rate of Charge = 4,774 Watt array "cost effective" maximum

And based on, lets say (note: DC loads are technically more efficient because it does not use the AC inverter--But treat everything the same (as AC loads) for now (keep math simple):

888 WH = heater per day (120 VAC)
350 WH = chest refrigerator (120 VAC)
325 WH = 13w * 5 LED * 5 hours LED (AC or DC)
96 WH = 8 Amps * 12 volts * 1 hour water pumping (AC or DC)
================================================
1,659 WH base per day (call it AC loads on inverter)

Your battery bank can handle upwards of  4,972.4 WH per day very easily (2 days of no-sun, 50% maximum discharge).

And lets say you have other variable loads (running clothes washer, fan on hot/cold days and wood stove), TV, Laptop Computer, etc. of ~1,659 WH per day (i.e., 2x your base loads).

Total of 3,318 WH per day design for December @ 3.23 Hours of sun per day (long term average--Some days more, somrse days less).

• 3,318 WH per day (50% of that are every day base loads) * 1/0.52 off AC system eff * 1/3.23 Hours of sun per day = 1,975 WH "break even for December" Array...

Again, my suggestion (not my money, this is yours) is something around 1,836 to 1,975 Watt array is very easy to defend as needed for your system. (no change to battery bank, 2nd charge controller, more solar panels, need to define genset and AC battery charger).

If costs are a big hit for you... Changing to a 24 volt battery bank, can save money (only 1x mppt charge controller required). And, drop 2 batteries (8 total) for 24 volt bank (slightly less storage). Or add 2x batteries for 12 bank total (4x series by 3 parallel strings)...

And if you have a genset+AC Battery charger--You need to get the batteries to 100% State of Charge and equalized (check specific gravity, if cells are >0.030 sg units between "high and low cell", equalization is generally required to bring the bank back into balance (controlled overcharge, to bring all cells to near equal SG readings).

If the battery bank is not getting fully charged (>90% state of charge at least 1-2x per week, avoid going below 50% state of charge -- Using a hydrometer to measure your cells), need to get them back up--"Deficit Charging" -- charging less than full charge every few days, but slowly going lower and lower SoC -- A good way to kill a battery bank).

Your system is not what I would have suggested--But you have what you have--At this point, getting more solar panels (and mppt charge controller) on the battery bank is the first place to start. You want to "save your bank" -- That is a lot of $$$ to die an early death.

Going with the 1,500 Watt AC inverter should be a better fit for you needs (depending on brand/model of inverter). So I would go back to it until you get the rest of your system debugged/increased array wattage/verify that all is working correctly.

After that (and that is a lot), then can look at what to do next.

-Bill

LndSchneid

Right on Bill.  I will pass all of this on to Kevin on Monday and reconnect witj you then.  You are very helpful.

.Linda

LndSchneid

Bill,
One more question please.  How many more panels?
Once we dig out the 1500 inverter we will provide.
Linda

BB.

I would be suggesting a total array of ~1,836 to 1,975 Watts... You presently have 800 Watt array on a 60 amp MPPT controller that can (check manual) cost effectively support around 1,130 Watts of solar panels maximum (see above calculations).

For various reasons, to add to your present array, you should find solar panels that are roughly equivalent to what you have... Which are probably Vmp~17.5 to 18.0 volts or so. These are "12 volt" solar panels. And for this controller on a 12 volt battery bank, you should have 2x panels in series by 4x of your present 100 Watt panels (Vmp~17.5 x  Imp~5.71 amps).

So, if you, for example can find some other "12 volt" panels that are more cost effective (here is an example):

Solartech SPM130P-S-N 12V (roughly $1.73 per Watt)

• With 1,130 Watt controller max - 800 Watts of current panels = 300 Watts
• 330 Watt headroom / 130 Watts per panel = 2.5 panels ~ 2 panels more on first controller
• 800 Watt original panels + 2*130 Watt additional panels = 1,060 Watt array

For the second controller:

• 1,975 Watt array - 1,060 watt upgraded #1 controller = 915 Watt second controller.

If you want "more cost effective panels", since you are already using/looking at MPPT charge controller, 

AXITEC 330W poly (~$0.66 per Watt)

• 915 Watts / 330 Watt per panel = 2.7 ~ 3 panels
• 3 panels * 330 Watts = 990 Watt array (round up or down, your choice)
• 990 Watt array * 0.77 panel+controller derating * 1/14.5 volts charging = 52.6 amps current (~60 Amp MPPT controller)

There are lots of things to consider here... Is the wiring heavy enough for controller #1 to carry the higher current--Or does wiring need to be made heavier (there are other options too).

Configuring a solar array is actually a bit on the complex side. The battery bus voltage, the Vmp and Imp of the panels, the input voltage range of the charge controller, and its rated output controller, MPPT vs PWM controller (PWM are much less expensive), how to fuse/breaker the parallel connected solar panels, choice of wiring type and AWG, how far from array to Charge controller, etc... All require a lot of thought, and many times, adjustments as you find you (may) not be able to find 100 Watt "12 volt" solar panels for a reasonable price to put in series/parallel with your existing panels (note the 130 watt and smaller panels can be shipped by regular carrier. The >200 Watt panels usually need to be palletized and shipped by truck). This stuff is easy to get in trouble with the first time a system is designed and built... By the 3rd or 4th system, you will be a pro. 

If you agree with me to add another ~990 Watt array and 2nd controller, you would need the #2 controller to be 60 amp rated MPPT controller too (notice that the larger/non-12 volt panels are much cheaper per Watt--A good reason to use MPPT controllers, which more more expensive, with cheaper large format solar panels).

Can you use the 3,000 Watt inverter with the "new solar array"... I don't know, but you can try it. In general, we try to get the minimum loads possible (most efficient use of energy)--That allows us to design the smallest/most cost effective system. If the smaller inverter saves 200 WH per day--It is not the end, but that is getting close to the energy your chest refrigerator consumes.

Also, it is pretty difficult to get much more than 1,800 Watts of power (maybe 3,600 Watts surge to start a pump motor) from a 12 volt battery bank. That is one reason we suggest higher voltage battery banks when working with >1,200-1,800 Watt 12 volt inverters (less voltage drop, less current, cheaper copper wire, etc.).

My whole point here is to get your system to an ~5% minimum rate of charge--Any less, and your battery bank will probably not be very happy at all. 

-Bill

LndSchneid

Okay.  You are a wealth of information and help.  Will need to pass along to Kevin on Monday to start implementing.
Thank you again ever so much.
Linda

BB.

Linda,

You will probably want to do several "paper designs" and then check them against the MPPT Controller specifications, solar panels specifications, wire run requirements, possible series protection fuses/breakers (generally required when there are three or more solar panels (series strings) in parallel), and other issues (availability of the solar panels you want to use, MPPT charge controller limitations, etc.).

-Bill

mike95490

A workaround for the water pump, is to have it's own large inverter and have the inverter be controlled by a relay from the pump switch.  And the inverter has to be able to start up with a large load on it.

But winter time, unless you are in a unusually sunny spot - you have a lot of coastal fog/marine layer, and should plan on generator run time to keep the batteries healthy.   do you have a backup generator for the main generator ?   Lots of runtime means one may wear out or need service - when you need power.  

mike_s

How and where is the 3000W inverter wired in? If it's via the "8 gauge ground wire +  6 gauge positive battery wire", you're not going to get 3000W, and you're going to see a significant voltage drop even with a short run and low load. If your voltage monitor is at the same end of the wiring as the inverter, it's going to see that drop and think the batteries are at a lower voltage than they really are.

Are the batteries wired with that 8/6 gauge? That's going to kill you, too. A 12V, 3000 W inverter (250+ A @ 12V) will want at least 1/0 gauge (NEC is more like 4/0), and short runs. And the batteries need to be interconnected with the same.

Also, internal resistance of the batteries is going to cause a voltage drop even at the battery terminals, so you'll probably never see anything close to an accurate reading when there's more than a very small load (relative to your system), even with 2x5 L16s.

LndSchneid

Mike,
If the panel wiring, and the controller cannot accommodate a thicker wire because the ports for the wire are small, how do we do that?
Linda

LndSchneid

Bill,
The 1500 inverter is now connected, it's a tiger claw.  What are we looking for to know if that's addressing issues?. Also, what  gauge wire should we use on the batteries, and should we be using smaller gauge wire throughout the system?

BB.

In general, larger diameter wire than needed is not going to hurt anything except in some "corner cases".

For 1,500 Watt inverter, I would suggest:

• 1,500 watt inverter * 1/0.85 inverter eff * 1.25 NEC continuous current wire/breaker derating * 1/10.5 DC cutoff voltage for inverter = 210 Amp branch circuit wiring and fusing/breaker rating.

Your installer should have an NEC (national electric code) book for actual current/AWG calculations, but a good rough guide starting point would be:

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

Or somewhere between 3/0 AWG and 250 kcmill (depending on insulation, ambient temperatures, conduit fill, etc.). NEC with the NEC derating is a pretty conservative cable rating.

If you need to put two cables in parallel, and 1/2 current in each, you could use something like 3 and 1 AWG... However, running cables in parallel is not recommended if it can be avoided.

For the battery interconnects, I would suggest ~2 AWG or heavier cabling. Ideally, with parallel battery banks, each bank should have a fuse/breaker per string of batteries. I.e., 2 AWG cabling from battery string to battery bus would be ~105 Amp fuse/breaker. BlueSea makes some very nice/small terminal fuse holders for this type connections (links to holders only, still need to order fuses):

https://www.bluesea.com/products/2151/Dual_MRBF_Terminal_Fuse_Block_-_30_to_300A
https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

I would be surprised if more than just professional installers fuse/breaker parallel battery connections (suggested for 3 or more parallel strings of batteries).

There is also looking at wiring drop--Longer wire runs to inverters means higher voltage drop. You can use a simple Voltage Drop Calculator, and play with AWG vs one way wire run in feet vs Voltage drop. For example:
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.2028&voltage=12&phase=dc&noofconductor=1&distance=5&distanceunit=feet&amperes=210&x=74&y=15

Example:
210 Amps by 5 feet on 3/0 cable will have:

Voltage drop: 0.13
Voltage drop percentage: 1.08%
Voltage at the end: 11.87

I suggest for a 12 volt system, you have a maximum of 0.50 volts drop--So, 0.13 drop is fine.

I guess this is your Tiger Claw inverter:

https://www.amazon.com/Tiger-1500W-Power-Inverter-DC-AC/dp/B008JGE8LE

Do you have an installation manual? Generally that is where you start for the connection requirements.

Anyway--If the inverter meets your requirements for loading--And the input wiring is correctly done--That side is OK.

Will it "fix" an 800 Watt array on a 1,950 @ 12 volt battery bank... I would still highly suggest increasing your solar array size.

However, without using  a Kill-a-Watt meter to measure each of your 24 hour 120 VAC loads--It would be pure guesswork on my part to say yea or nea for this configuration.

Before you toss a bunch of money at the present system... Measuring and logging battery specific gravity (for each cell ~once per month, then pilot cell for other readings), and understanding your loads/solar harvest--Then you can make some more informed decisions on how to proceed.

-Bill