Multiple different panel size connection

bgu1982

Hi.. im trying to figure out what to do with 8 25 watt 1 amp and 2 100 watt 5.5 amp solar panels. Im off grid so im presuming im going for max amps not volts. I was thinking i could rig them all together into a 40 amp mppt controller and be fine. Is it better to get rid of the 25 watt panels all together? My aim is for a 400 watt total system.

mike95490

here's 2 rules of thumb

1)  Panels in series should be rated for the same Imax  ( current through the string will be limited to the lowest amp panel)

2) Panels in parallel should be rated fro the same Vmp ( volts will be limited to the lowest voltage spec panel

BB.

To add to Mike's rules... The Vmp/Imp/etc. should match within 10% or better (i.e., Imp/Isc = 5 amps and 4.5 amps, or Vmp=17.5 and 19.25 Volts) for "near optimum results".

-Bill

bgu1982

Question..if 4 of the 25 watt panels are run parallel would they they equal 100 watts at 4a? Would that be close enough to the 100 watt single panel that 5.5?

BB.

Yes, 4x panels in parallel, then you have 4xImp or 4xIsc (current max power; current short circuit max).

What you also need to look at is your battery bank voltage/AH rating... And the type of solar charge controller...

For example, a PWM (pulse width modulated) solar charge controller... You need around Vmp~35-40 VDC rated solar array. And the mix and match would be:

• 4x 25 Watt panels in parallel in series with 1x 100 Watt panel (assuming the Vmp for each panel is ~17.5 volts Vmp, and Imp for the 4xImp of the 25 Watt panels is approximately equal to the Imp of the 100 Watt panel). So you have a reasonable 100 Watt array

If you have an MPPT (maximum power point tracking) Solar charge controllers--The rules are somewhat different. For example, that same 5 panel array (Vmp~35 volts) can drive a 12 volt battery bank very nicely (MPPT controller can "down convert" the voltage of the solar array to the battery bank voltage, and it will increase the charging current for the battery bank... I.e., 35 volts @ 5 amps array will (roughly) produce 17.5 volts Vbatt and 10 Amps--I.e., P=V*I=17.5v*10a=175watts).

So--It is a better choice to tell us what you have (panels Vmp/Imp, type of solar charge controller, battery bank V and AH, etc.)--It is not always possible to mix different panels into a "useful" array).

Many times, it works out better to just sell the older (and typically smaller wattage panels) and replace with a matched array of larger wattage panels (i.e., 1x 200 Watt panel vs mix/match of 4+1 panels for 200 Watt array).

Typically, 140 Watt and less panels are something like 2x or more expensive (per Watt) vs the 200 Watt or larger panels.

But it is easy for me to say that--It is not my money.

-Bill

bgu1982

I actually have 8 25 watt harbor frieght panels which are the poly ones 2 100 watt microcrystalline harbor freight panels. Again we are total newbies and started with the 100 watt kit then started to add on. Im still using the controller it came with but i know its junk and already ordered a mppt 40amp cc. It should be here in a couple days. Im rly hoping to use all the panels so i dont have to spend more money. The 8 45 watt panels are in parallel in sets of four. Its Ill hooked up to two deepcycle batteries. The setup doesnt have to be perfect but i want it as good as i can so im not spinning wheels.

bgu1982

2 deepcycle 12 volt 135 ah batteries
2 thunder bolt monocrystaline 100 watt 18v (typical) 22v (open circuit) max 6.2a( it says 5.5a on the box,online it said 6.2a max)
8 thunderbolt( parallel sets of 4) 25 watt 18 volt 1 a

HQST MPPT 40 amp
Max input 100 volts
Max onput 600 watt 12 volt
Max input 1200 watt 24 volt

 Also let me add that i thank you guys very much. This place is awsome. Im Im really learning alot. Thanks for the help and knowledge

bgu1982

Ill add that i have a small generator and im im getting a smart battery charger to help keep the batteries healthy. Ive ordered a multimeter so i can check all the panals individually. Aswell as everything else

BB.

With Harbor Freight, you have kind of a mix bag of available panels...

The amorphous panels, the ones that look like a solid black cell with lines through them--These panels do not really last long (may be as short as 6 months before they start losing output:

https://www.harborfreight.com/merchandising-promotions/hot-buys/100-watt-solar-panel-kit-63585.html

And there are poly/mono-crystalline panels--These (in general) are the type (with glass cover) should last 10-20+ years. These panels, you (generally) will see separate black "cells"--Something like 36x cells for a Vmp~18 volt rated panel:
https://www.harborfreight.com/100-watt-monocrystalline-solar-panel-57325.html

You have a MPPT type solar charge controller... Which  has Vpanel input max voltage is 100 VDC. Tipcally, you would want Vmp-array to be about 2/3rds of Vmax (or Vmp-array no more than ~66 volts Vmp which would be 3x Vmp-18 volt panels in series (if you are in a warmer climate (non-freezing) you may be able to put 4x 18 volt Vmp panels in series (in this case, match Imp for each panel in series).

With an MPPT controller, you generally want Vmp-array to be something like 2x Vbatt (2x15 volts charging = 30 Volts minimum) for "optimum" MPPT operation. You can go over 2x Vbatt--And the MPPT charge controller will be slightly less efficient (generally not worth worrying about).

When you put panels in parallel--If you have (typically) 3x or more panels in parallel, each panel (or series string of panels) is supposed to have a series protection fuse (or breaker). This is to protect (for example) one shorted panel being fed too much current from the 2 or more other panels in parallel and starting a fire. The series protection fuse should be listed in the panel specifications--Or you can (roughly) use 1.5xIsc panel current rating for the fuse value.

The need for series protection fuses are one drawback to wiring a bunch of small solar panels in parallel (cost and complexity of adding a combiner box/fuses/series fuse holders/etc.).

For your 100 Watt:

• Pmp=100 Watts
• Imp=Pmp/Vmp= 100 Watts / 18.0 volts Vmp = 5.56 Amps Imp (6.2 amps sounds like Isc--sort circuit current rating)

You have a 40 Amp controller... It does matter what the battery bank voltage is... For example, rough maximum array (use max array wattage in manual--Just an example of how the calculations work):

• 40 amps * 14.5 volts charging * 1/0.77 panel+controller deratings = ~753 Watts max suggested array for MPPT controller @ 12 volt bank
• 40 amps * 29.0 volts charging * 1/0.77 panel+controller deratings = ~1,506 Watts max suggested array for MPPT controller @ 24 volt bank

A higher voltage bank--Same controller manages 2x larger array (same current, 2x voltage = 2x more power). Also the minimum Vmp-array is dependent on battery bank voltage (~Vmp=35 volts for 12  volt array; 18 volts for 12 volt battery bank--minimum array voltage).
Optimum minimum array voltage is roughly (at least) 2x Vbatt-charging:

• 14.5 volts charging = 29 volt nominal Vmp array.
• 29.0 volt charging = 58 volts nominal Vmp-array.

If you put 3x 18 volt panels in series (matching Imp per panel) = 54 volts... Will work for 12 or 24 volt battery bank even in very cold weather.

You can mix the 25 Watt arrays in 3x series and 3x 100 Panels in series, then put the two (or more) strings in parallel as Vmp-array is ~54 volts (close enough for solar).

-Bill

bgu1982

So the 4 25 watt panels that are connect in series,then the 2 sets  are connected together afterwards in parallel?
 So im thinking 4 x 25 watt in series x2 connected in parallel
Then 2 100 watt panels in parallel. 
Would that work?

mike95490

bgu1982 said:

So the 4 25 watt panels that are connect in series,then the 2 sets  are connected together afterwards in parallel?
 So im thinking 4 x 25 watt in series x2 connected in parallel
Then 2 100 watt panels in parallel. 
Would that work?

2 thunder bolt monocrystaline 100 watt 18v (typical) 22v (open circuit) max 6.2a( it says 5.5a on the box,online it said 6.2a max)
8 thunderbolt( parallel sets of 4) 25 watt 18 volt 1 a

4,  25 watt panels that are connect in series = 72v 1a
paralleled with
2,  100w   panels in parallel = 18V 11a
    NOPE

try :
2,  25 watt panels that are connect in series = 36v  2a
paralleled with
2,  25 watt panels that are connect in series = 36v  2a
paralleled with
2,  100 watt panels that are connect in series = 36v  11a

The 2 strings of 25W panels, each string needs a fuse in series with it, likely around 2-3A
  This should work, but it "feels wrong" :
 
So voltages match now. adding amps up in parallel, 15A @ 36v to your MPPT controller   
That's 540 watts, which does not compute since you only have 300w of panels.

 calculating backwards

25W @ 18V  = 1.388888888888889 amps   ( 5.55A total )
100w @ 18V  =  5.555555555555556 amps   ( 11.1A total )

 Either I'm having a bad day, or HF uses new math

Update, I left out an additional 4, 25w panels.  So there's another 2 series strings of the small panels, another 100w,

BB.

From Mike:

You have 8x 25 Watt panels--So 2x in series times 4 parallel strings os you can use all 200 Watts worth of 25 Watt panels. Each string of panels needs its own fusing... ~2-3 Amp fuse for 25 Watt panels (4x fuses). And 1x 8 amp fuse for the 100 Watt string

2,  25 watt panels that are connect in series = 36v  2a
paralleled with
2,  25 watt panels that are connect in series = 36v  2a
paralleled with
2,  25 watt panels that are connect in series = 36v  2a
paralleled with
2,  25 watt panels that are connect in series = 36v  2a
paralleled with
2,  100 watt panels that are connect in series = 36v  11a

That will work well for charging your battery bank--Assuming it is 12 volt bank (2x 12 volt @ 135 AH batteries in parallel for 12 volt @ 270 AH battery bank). Wired per:

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

And, not knowing your loads and amount of sun for your location(?), the typical starting point is 5% rate of charge for a standby/weekend/sunny weather system--Minimum rate of charge. And 10%-13% rate of charge... More or less, the approximate array wattages:

• 14.5 volts charging * 270 AH * 1/0.77 panel+controller deratings * 0.05 rate of charge = 254 Watt array minimum
• 14.5 volts charging * 270 AH * 1/0.77 panel+controller deratings * 0.10 rate of charge = 508 Watt array nominal
• 14.5 volts charging * 270 AH * 1/0.77 panel+controller deratings * 0.13 rate of charge = 661 Watt array "typical" cost effective maximum

And your array is:

• 8 * 25 Watts = 200 Watts 
• 2 * 100 Watts = 200 Watts
• 200+200 Watts = 400 Watts total
• 400 Watt array * 1/14.5 volts charging * 0.77 panel+controller derating = 21.2 Amps typical "best" harvest current (few times a year into a discharged battery bank around solar noon on cool/clear day)

Your array is "OK..."... But if you have lots of loads expected and/or issues with sun--You could certainly justify a larger array.

-Bill

bgu1982

Thank you. Im starting to get the hang of this thanks to you guys. Thisis only the primary power source till next year then we will be on grid. But will still use solar for other applications. Because of the investment i wanted it to be as good as possible while be capable of some more investment if needed. Going to have a cabin farther out on the property and i want to have this solar system moved to that area. I will probably replace the poly panels with mono panels in the future.

bgu1982

(question) i have 8 25 watt in 2 groups of 4

If you advise i wire a certain way ill listen to you

Sorry if the way i described my setup was confusing

You say connect 2 25 watt in series then parallel them. Is it different than connecting  4  25 watt in series then connect them parallel?

 Im Isking because the 8 harbor frieght panels come with wiring to wire them in series 4 at a time..then connect the 2 sets in parallel. I understand that it might not be ideal but if itshould be 2 25 watt panels connected in series instead of 4 ill have to rewire it. Which is doable.

bgu1982

Im rereading multiple time what you guys said..and i think i understand. Im just asking because of the wiring the 25 watt panels came with. Which is 4 25 watt panels in series. Then the wire goes to a hub( not sure the proper name) so the 2 sets of 4 25 watt panels and the 2 100 watt panels all go into a hub(included in the harborfrieght kit) this hub i presum is bringing all the panels together in parallel. Then to the cc. Is the hub ok? I cant find any info on the hub online as far a power limits or anything. Im thinking of reduing it but its extremely convenient. Should i get rid of it. It comes with the harbour frieght kit

BB.

It is (usually) to make a larger system out of smaller system components (i.e., expanding by 2x may be cost effective--But expanding by 4x or more--Generally a higher voltage battery bank, new AC inverter for new battery bank voltage, probably a larger than 40 Amp charge controller, new batteries--larger AH, and probably will go with 200+ Watt solar panels for best $$$/Watt results).

More or less, 200+ Watt panels are 1/2 the cost ($/Watt) of 140 Watt or smaller panels (2x more solar for same price).

And with >200 Watt panels and larger arrays, you generally are looking at MPPT type charge controller--Which are usually most more costly than simple PWM controllers (MPPT controller with "higher voltage" solar arrays use smaller copper wire for same wattage--So can make wiring much more cost effective if you choose a higher voltage array).

If you tell us the nearest major city, we can estimate your daily harvest (by month)--And give you an idea of how much power you have available. If you are "up north", your winter harvest is going to be poor. If you are in the south west, you have more sun (on average).

For an example:

• 500 WH per day (500 WH * 30 days = 15,000 WH = 15 kWH per month)--Cabin--For lights, cell phone charging, RV water pump
• 1,000 WH per day (30 kWH per month)--Add running a laptop computer, more lights/RV water pumping.
• 3,300 WH per day (100 kWH per month)--Add clothes washing machine, LED TV, "solar friendly water pump", full size energy star refrigerator+freezer (aka a "near normal" electric existance)
  
• 10,000 WH per day (300 kWH per month)--Enough power for a family with a couple of refrigerators, some irrigation, central heat (propane for heating) etc.
• 30,000 WH per day (900 kWH per momth)--Much more electric appliances (electric stove, some A/C, etc.).

The "north american average" power usage runs around 500 to 1,000 kWH per month. Living in Texas with electric hot water, stove, full A/C, etc. -- You can get to 3,000 kWH per month or more.

For a reasonably sunny area, guess around 3 hours per day of sun for Winter... And 5+ hours of sun per day for non-winter months. 

http://www.solarelectricityhandbook.com/solar-irradiance.html

Pick 3,300 WH per day loads. You can use a 24 or 48 volt battery bank (i.e, 400 AH @ 48 volts = 800 AH @ 24 volts--Same energy storage). More or less, if your "battery bank AH" gets >800 AH--Then suggest jumping to next higher voltage (keeps wiring and controllers "reasonable amount of copper" and costs).

To size the battery bank--Suggest 2 days of storage and 50% max discharge (flooded cell lead acid) as a starting point:

• 3,300 WH per day * 1/0.85 AC inverter losses * 2 days storage * 1/0.50 max discharge * 1/24 volt battery bank = 647 AH @ 24 bolt battery bank suggested

Two calculations for solar array... One based on rate of charge (5/10/13% from previous post). Suggest 10%+ for full time off grid:

• 647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,218 Watt array minimum
• 647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 2,437 Watt array nominal
• 647 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,168 Watt array "typical" cost effective maximum

And sizing the array based on loads and hours of sun per day... For the moment, assume 3,300 WH per day in winter with 3.0 Hours of sun per day:

• 3,300 WH * 1/0.52 off grid end to end AC system eff * 1/3.0 hours of sun (good winter sun) = 2,115 Watt array "winter break even"

We suggest that you plan on using around 50% to 65% of your predicted solar power (if solar only) to allow for bad weather, occasional heavy loads, etc... A refrigerator uses 1.5 kWH per day... If you need a laptop for work, you would add its daily loads too. Say another 750 WH per day for cell charging, lighting, RV water pump:

• 1,000+750 WH of "base loads" = 1,750 WH per day minimum for "life"
• 1,750 WH base load * 1/0.52 system eff * 1/3 hours of sun * 1/0.65 base load fudge factor = 1,725 Watt array base load @ 65% fudge factor
• 1,750 WH base load * 1/0.52 system eff * 1/3 hours of sun * 1/0.50 base load fudge factor = 2,244 Watt array base load @ 50% fudge factor

So--Looking at the above... Such a mythical installation would look pretty reasonable at 2,437 to 3,168 Watt array (10% minimum array, fudge factor loads are smaller array than 10% rate of charge, and 3,168 suggested max cost effective array).

A 2,437 Watt array would need a MPPT charge controller of (minimum):

• 2,437 Watt array * 0.77 panel+controller deratings * 1/29.0 volts charging = 65 Amp minimum rated MPPT controller.

The nominal to maximum AC inverter rating (max continuous loads, with 2x starting surge support):

• 647 AH battery bank (at 24 volts) * 500 Watts * 1/100 AH @ 24 volts = 3,235 Watt max suggested AC inverter (and max suggested solar array for that battery bank)
• 3,235 Watt Inverter "Maximum" / 2 = 1,618 Watt inverter (good nominal size)

To run a very efficient Cabin/home on that battery bank--Somewhere around 1,618 Watt to 3,235 Watts--And keeping closer to 1,800 to 2,400 Watts for this "cabin/efficient" home on this battery bank (larger inverters "waste" more power, and cost more--Keep everything "balanced" in power usage/requirements).

If you live in a location with less than 3 hours of sun per day--Then you may have to use a genset during bad weather and possible shading from trees/mountains/etc. in winter--Obviously, keeping loads low saves fuel. And conservation in general saves you more money (larger solar systems/genset fuel usage costs money every day--Conservation is once out of pocket--Then saving you money for years on).

Don't get me wrong... 3,300 WH per day for a family... You need to be very energy efficient/conservation minded. It is easy to double that power usage if not careful (look at your present utility bill and see how many kWH per month you use).

Your thoughts?

-Bill

bgu1982

One other question..should i add another 100 watt mono? Would that top off my 40amp mppt controler? So 500 watts in total from panels. It would be the same one as the other 2 harbourfrieght panels.

bgu1982

I think ill be happy with what a 40 amp mppt cc can do. I just want to maximize what it can accomplish. I live near oklahoma city so really i feel we get fairly ideal amount of sun light.

bgu1982

Oh and thank you Bill for your help

bgu1982

The 100 watt..which is 25 watt x 4 hf kit came with the hub.

Ive upgraded to a 40 amp mppt cc and added the 2 135ah deepcycle batteries.

The kit originally came with a tiny pwm cc

Do you think that hub is usable when ive added all the other panels

I found some info on the hub..its 400 watt max and 33.3 amp max

UPDATE.. my mom told me the 400 watt hub was not in the kit and she bought it extra..sorry..still ot is very convenient lol

BB.

From the ealier post:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Oklahoma City
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 54° angle (from vertical):
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.97	4.23	4.98	5.47	5.38	5.59
Jul	Aug	Sep	Oct	Nov	Dec
6.03	5.70	5.32	4.79	4.05	3.71

So... 3.0 Hours of sun is even less than your average (these are ~20 year averages--It is very easy to get a week of bad weather and lose 1/2 or more of your "predicted" harvest).

You presently have a 400 Watt array... And if you tilt the array to 54 degrees from vertical (or 36 degrees from horizontal--What most normal people use to measure):

• 400 Watts * 0.52 off grid AC system eff * 4.79 Hours of sun per day (October for example) = 996 WattHours per day October "average"
• 996 WH per day / 12 volts = 83 Amp*Hours per day @ 12 volts

Of course, some days will be more and other days less...

For solar panels... a 100 Watt panel is something like $110 from my local HF. $110/100W = $1.10 per Watt... Not a bad price for a smaller panel.

Our host:

https://www.solar-electric.com/rec-solar-rec330np-n-peak-series-330-watt-module.html

$213 / 330 Watt panel = $0.65 per Watt

You have to really look around... Price of panel is one part... But price of packaging (if you are buying 1 panel vs a pallet) and shipping (typical >140 Watt panels need to ship truck/on pallet where a 140 Watt or smaller panel can ship post office, UPS, etc.).

It is not unusual when buying a single large format panel to have shipping+insurance cost more than the panel itself... Looking around your area for panels (over run from jobs, local supplier/no shipping charges) can save money.

And when looking for panels--You have to look at the Vmp/Imp to make sure they mix and match correctly... The above panel is a "60" cell panel which is somewhere (typically) 30 volts (this is 34 volts--seems a bit high)... You want the panels to "match" your Vmp-36 volt array... 34 volt single panel in parallel with 36 volt Vmp-array should work OK.

Your charge controller is rated for 550 Watt array (@ 12 volt battery bank):

https://hqsolarpower.com/40a-mppt-solar-charge-controller/

Note, if you wire your panels in series (for Vmp-array~36 volts)--You would need 2x more 100 Watt panels so your total array will be 400+200=600 Watts...

For good quality MPPT charge controllers, "over-paneling" is a normal thing--The MPPT controllers will limit their output current to rated current (or less if they start getting hot) safely and as normal operation. I cannot speak for the brand you are looking.

Your 25 Watt groups of panels (8x 25 watt = 200 Watt)--They generally will not last long--And replacing them with 200 Watts of crystalline panels would be a good thing long term (more than 1/2 a year of use???).

So, now you look at getting 2x more 100 Watt panels later--Or simply get 4x 100 Watt crystalline panels now and replace the 25 watt amorphous panels.

You have lots of options here... But try not to "cheap out" on your solar hardware--You can get into issues with "mis-matching" components, components with poor life/reliability, etc.... And end up spending time (and more money) fixing things down the road.

Do you have any tools? An AC+DC Current Clamp DMM (digital mulitmeter) is really nice to debug--And just understand how your system is running (check the current for each solar panel--To make sure panel and wiring is correct and such).

Also having a hydrometer of some sort (good quality) helps you ensure your batteries are kept "happy".

https://www.amazon.com/gp/product/B00O1Q2HOQ (good enough inexpensive Clamp DMM)
https://www.amazon.com/gp/product/B019CY4FB4 (example of a mid-quality/price Clamp DMM)
https://www.solar-electric.com/search/?q=hydrometer

Note that "glass hydrometers" will roll of tables and hit the ground & break... Be careful with them--And always rise with distilled water at the end of day. The dried electrolyte will cause the float to stick.

-Bill

bgu1982

I just ordered a new mppt cc it was $100. I figuered for our setup that should be adequate considering we had a  tiny 10 amp pwm cc we started with. The amount  of AH You said for 400 watts was disappointing. Thats less than half of my two 135 ah batteries.i orded a DMM comes on tuesday with a bunch of other stuff. I will be checking every panel individually and everything else.

As far as replacing the amorphous panels now im willing but they are still producing power so id rather use them instead of just get rid of them. Id Id rather inigrate them now and replace them as they wear out. You know what im saying? There brand new, when they crap out theyll get replaced the way i see it. If i buy more larger mono panels i i want to add them on top of all the other ones, and if the amorphous ones fail then ill replace them.

bgu1982

I ordered a smart charger AC for generator..it says it can test,repair,maintain and charge deepcycle batteries. I will use this on cloudy days or when batteries are over used

bgu1982

Would it be better to take away one of my 135ah battiers for my set up instead of 2? Therfore im asumming the one battery would charge more fully then the 2 batteries.

I will definitely in the future only by mono panels for upgrades or replacements

BB.

You also want to "match" the charger to the batteries (ideally, 10%, 5%-20% works). And also match the genset to the charger/battery draw.

For a "typical" gasoline genset--You want to draw around 50% -80% of rated power (below 50%, the genset will draw about the same gallons per hour at 50%/25%/0% power). Over 80% loading on genset with battery charging--Discharged batteries can take hours of "max charging current" and if you are near/over 100% of genset wattage rating, you can overheat the motor and/or alternator+wiring.

10% of your 270 AH battery bank would be ~27 Amps (nice number for charging FLA deep cycle storage batteries).

And, if you can tilt your panels (say once a month), you can maximize harvest... The solar calculator shows:

Oklahoma City
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel where the angle is adjusted each month to get optimum sunlight.

Jan	Feb	Mar	Apr	May	Jun
4.21	4.31	4.98	5.63	5.76	6.33
Jul	Aug	Sep	Oct	Nov	Dec
6.55	5.99	5.32	4.85	4.25	4.04

You can see that for October (vs standard "middle harvest" angle setting, you can 0.05 more hours of sun or just a bit >1% more harvest... Not even worth doing it right now (in winter, you may get closer to 20% more harvest).

I can calculate the AH a different way...

• 400 Watts * 0.77 panel+controller derating * 1/14.5 volt charging = 102 AH for "average" October day

Or ~83 to 102 AH per average October Day (using 4.79 hours of sun) (using a different set of assumptions. From pesimistic to optimistic assumptions).

In the last few years, there has been a lot of AC and DC metering options... For example, the DC measuring (Battery Monitors are specifically designed to monitor charging current in and discharging current out from the battery bank--And estimate electronically the battery state of charge). DC WH/AH meters may only measure the current "one way" (i.e., just how many AH are drawn by the load)

Lots of inexpensive options out there...

Also lots of "high quality" battery monintors out there too:

https://www.solar-electric.com/search/?q=battery+monitor

And the good old Kill-a-Watt type meters for measuing 120 VAC loads (also good for checking appliance energy usage in the home):

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

Note we have sort of started the "design cycle" in the middle... There are lots of other questions you may have that can help optimize your system for your needs.

-Bill

bgu1982

Im thinking i should add 1 more 100 watt panel that should be hopefully adequate for my needs. I watch the meter alot and see how low the batteries are getting and start shutting things off ect. If it gets to low. I have ordered a decent smart ac battery charger that should keep my batteries safe and healthy. My generator is 6.5 hours on 1.1 gallon. So not unreasonable to supplement the power from solar panels occasionally with the generator.

bgu1982

Also at the moment we move our pannels accordingly during th day for optimum lighting. Not ideal but we have the time to do it( not mounted on roof) 
 We have a 2300 max generator. More than enough i think. We attach everything else(jackery,phones ect) when using generator so the batteries cam charge freely

BB.

Still need to know the charger's Amp rating @ 12 VDC (10 amps, 20 amps, etc.).

If you put two panels in series (optimal for for charging 12 volt battery bank with Vmp-array~35 Volts)--Then you need two panels.

If you mount all panels in parallel for Vmp~18 volt array--Then you can add panels one at a time... However, an MPPT controller running Vmp~18 volt array is pretty much operating the same as a "cheap" PWM controller. For the MPPT controller to "do its magic" and allow the smaller diameter (AWG) copper wiring from the array to the charge controller--You really want (in your case), two panels in series.

For your genset--Ideally for best efficiency, you want your AC loads to be >=~1,000 Watts... Running a 500 Watt AC load, uses about the same Gallons per Hour as running 1,000 Watt load from a 2,000 Watt rated (continuous load) genset..

To charge a 12 volt battery bank "efficiently":

• 1,000 Watt genset load * 0.80 AC battery charger eff * 1/14.5 volts = 55 Amps @ 12 volts (very rough numbers).

Inverter generators, run fairly fuel efficient down to ~25% of rated load.

-Bill

bgu1982

Thanks bill.. i reread all of what you said i think i understand better. Im going to hook up the 8 25 watt solar pannels in series of 2 and then string them all after that parallel for 36v total.. then run the  2 100 watt panels together in series for 36 v. Then run them in parallel with the other ones. Thank you sir for your help

BB.

You are very welcome BGU.

Take care,
-Bill

bgu1982

Ill post some pictures when im done. And ill check everything with the multimeter and report the findings. hopefully it will be a mission success but i know if i have any problems i know you guys can help me trouble shoot. This forum is awsome. Thank you!