Matching battery's, panels, and charger to my inverter

j4ray

Ok so I bought a aims power 6000w 24v inverter for an off the grid small cabin/house. I'm in the middle of the build and don't want to do things twice. I've been researching and researching on what and how to match everything else to that inverter. I have 6 100w renogy panels to start with and just got a 40amp mppt charger. I'm having second thoughts about the charger, maybe I could get another one and run them parallel(if I do that will they have to be synced)? Because I started looking at the amount of battery's I will need to make it work. Also still not sure what size and how many battery's. Or what size charger I need.
Please help me

Thank you

j4ray

It's also for everyday use 

vtmaps

Welcome to the forum.

The purpose of the system is to provide for your electrical needs... in other words, your loads.

When designing a system we need to know what are we designing it for, in other words, your loads.

It's very similar to buying a pickup truck... if you asked my advice on what truck to buy, I would ask the weight of your load and the weight of your trailer. 

After you tell us about your loads, we can choose a battery size that can handle the load.  The final step is to buy enough solar panels and controllers to charge the battery.

By the way, we need the peak load in watts, and the daily energy use in kilowatthours. 

--vtMaps

BB.

Also solar power systems are "expensive"... If you are building a cabin, your best bet may be to continue with a genset for powering your tools. And have a smaller solar power system for evenings/night time lighting/radio/cell phone charging/etc.

If you design a system to power your air compressor+saws+etc. for construction--It may be "too large" for your daily needs when construction is completed.

What is your system design? Type of batteries, Amp*Hour rating of the battery bank (or how many batteries, and voltage/Amp*Hour rating of each battery)?

A 6,000 Watt AC inverter on a 24 volt battery bank is a bit of miss-match... That is a lot of current to pull from a 24 volt battery bank.

-Bill

j4ray

The building is complete, so construction is no longer a plroblem. So pretty much small a/c unit 12000btu. Led lights, 2 flat screens, 1/2hp water pump, refrigerator, and other little stuff not to much more. Everything else is gas.I don't know how to convert all of that in watts. Was looking at some 200ah battery's, maybe 2-4 of those.

vtmaps

j4ray said:

The building is complete, so construction is no longer a plroblem. So pretty much small a/c unit 12000btu. Led lights, 2 flat screens, 1/2hp water pump, refrigerator, and other little stuff not to much more. Everything else is gas.I don't know how to convert all of that in watts. Was looking at some 200ah battery's, maybe 2-4 of those.

I think that when you figure out your loads, you will be looking at a much larger system then you expect.   2-4 of those 200 ah batteries is a small system.  The fridge moves you from a small to a medium sized system.  The a/c will make it a large system. 

Will there be any laundry machines, clothes dryers, hair dryers, microwaves, laser printers, or irons?

--vtMaps

BB.

I will do a really quick (nominal) design for a quick 3,300 WH (3.3 kWH) per day system--Good enough for most of your stuff, except A/C--Which could double the system capacity if done "wrong" (lots of discussion about A/C to make sure you have an efficient design and good hardware).

For A/C, if you only use it during hot summer afternoons (lots of sun), you might get away with a smaller system (running system all day and into the night is a real power draw).

But, before I do that, can you let me know (very roughly, nearest major city) your cabin is located. I would use something like this (look at list of cities) to figure out how much sun per day you have, by season.

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

-Bill

j4ray

The closest city to me is Lafayette La facing directly south. And yes I forgot about the washer.  My dryer is gas. No to the hair dryer and microwave iron or printer. I was planning on getting a mini split a/c and only running it during the day. But I haven't bought it yet.  I was kinda putting it off. Maybe you might have a suggestion? Oh and it's 500 square foot thank y'all 

vtmaps

j4ray said:

I was planning on getting a mini split a/c and only running it during the day. But I haven't bought it yet.  I was kinda putting it off. Maybe you might have a suggestion? Oh and it's 500 square foot thank y'all 

Running it only when the sun is strong can reduce the size battery you need.   There's a lot of info on this forum about minisplits... Most mini splits require 240 volt AC... what voltage does your well pump work at? 

By the way, where will your batteries be kept?  Hopefully in a cool place.

--vtMaps

j4ray

That was my plan. Having the a/c run at my peak power during the day  I'd have it on a timer. My parents have a cabin similar to mine, but run on the grid. They're a/c runs maybe 3 hours total during the day and comes on once at night.  Oh also my inverter is 120/240vac so maybe that helps with the mini split? and the pump is 120vac. The battery's will be kept inside my laundry room. It's an outdoor type laundry room connected to my cabin, it will be well ventilated. No direct sunlight. No moisture.

vtmaps

OK.  It's all about numbers now.  We use formulas to design a system and formulas need numbers.  Give me your overnight consumption in kwh and I will give you a battery size and array size.  The array will be sized to charge the battery AND power the a/c.

--vtMaps

j4ray

So I'm not sure if I've got this right but I'm guessing 2.3kwh. Really not sure though 

BB.

Ok, lets go through the numbers... A very efficient off grid home (full size energy star fridge, well pump, led lighting, washing machine, computer, etc.) around 3,300 kWH per day in Lafayette La. For the moment, lets assume that you may use 2-3 kWH per day for A/C during the day/late afternoon (direct from solar, not so much from batteries in the summer months) and see what happens.

Battery bank--Assume 2 days of storage and 50% maximum discharge (typical "optimum" off grid system & for maximum battery life), 48 volts (larger system if you bump up system size for more A/C loading later).

• 3,300 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge * 1/48 volt bank = 324 AH @ 48 volt battery bank

Then there is sizing the solar array for charging the battery bank. 5% to 13% is typical for solar charging. 5% for seasonal/weekend usage... 10%+ for full time off grid. 13% plus perhaps for your afternoon solar powered A/C.

• 324 Ah * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,241 Watt array minimum
  
• 324 Ah * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 2,483 Watt array nominal
• 324 Ah * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,227 Watt "typical cost effective" maximum

Then there is sizing the array based on amount of needed energy... Using this link (fixed array):
http://solarelectricityhandbook.com/solar-irradiance.html

Lafayette
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 60° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.40	3.93	4.75	5.22	5.34	5.06
Jul	Aug	Sep	Oct	Nov	Dec
5.14	5.10	5.01	4.83	4.01	3.53

Use November as the "break even" month for 3.3 kWH per day:

• 3,300 WH per day * 1/0.52 off grid system eff * 1/4.01 hours of sun per day = 1,583 Watt array for "Nov" break even month
  

So--just for day to day usage--even a "small" array could work pretty well. Now let us look at what a 13% array could do for you.

• Jan: 3,227 Watt array * 0.52 AC system eff * 3.40 hours of sun per day = 5,705 Watt*Hours per day (typical January)
  
• Nov: 3,227 Watt array * 0.52 AC system eff * 4.01 hours of sun per day = 6,880 WH per day (typical November)
  
• Summer: 3,227 Watt array * 0.52 AC system eff * 5.0 hours of sun per day = 8,390 WH per day (min-typical summer)
  

So if you use a 13% array and a 3.3 kWH "per night" battery bank (324 AH @ 48 volts), for summer you could have:

• 8.4 kWH summer capacity - 3.3 kWH night time loads = 5.1 kWH per day available for "day time" A/C (minimum)
  

Seems like a possible solution--Run it for a few years with a minimum battery bank and see how it works?

-Bill

j4ray

So I need to get a 48 volt inverter? Or is there any way it can work with the 24 volt I have now? Also would it be better to get a dc mini split or is that even an option? 

vtmaps

j4ray said:

So I need to get a 48 volt inverter? Or is there any way it can work with the 24 volt I have now?

System design is about compromise.... both 24 volts and 48 volts will require compromise because each has advantages.    If your peak loads are under 2000 watts you can make 24 volts work.  But the battery bank that BB suggested above (324 ah at 48 volts) will have to be 648 ah at 24 volts.  If that forces you to put batteries in parallel (never optimal design), then that is another compromise.   You can build a 648 ah bank at 24 volts with a single string of batteries, but you won't be able to use the cheap, mass produced batteries like L-16 or golf cart batteries. 

Also, consider that you don't really know what your needs are... you will be in much better position to expand the system at 48 volts.

One more thing... you haven't mentioned how far the panels are from the charge controller.  Longer distances work better with a 48 volt system.

--vtMaps

j4ray

there should be no more than 30 ft of wire between panels and chargers. And at the most 10ft of wire from chargers to battery's. What size wire should I use from panel bank to charger, is 10awg ok? Running 4 battery's in series/parallel to get 24volts is a bad idea? When you say single sting of battery's, you mean 2 battery's in series to get 648ah? I just want to make sure I'm understanding. I had my eyes on a 12v 200ah solar power mighty max battery, is this a good or bad brand? 

j4ray

Would 4 vmax 225ah 6 volt be a better option? 

BB.

Don't get too much into wiring issues at this point--We have to settle on loads, array size, and lengths (note, you want to keep charger and inverter wiring very short/heavy--10 feet may be a bit on the long size for your system).

Note that Power = Voltage * Current... So if you choose a 24 volt battery bank, the current is 2x higher.

For example, lets say you have 8 batteries: 6 volt @ 225 AH "golf cart" batteries. You can arrange them as:

• 4x 6 volt batteries in series = 24 volt string; 2x parallel strings for 24 volt @ 450 AH battery bank
• 8x 6 volt batteries in series = 48 volt string @ 225 AH battery bank

They both store the same amount of energy:

• 24 volts * 450 AH = 10,800 Watt*Hours
  
• 48 volts * 225 AH = 10,800 Watt*Hours

However, for example, when charging (say 10% rate of charge), the current on the same bank:

• 24 volt bank: 450 AH * 0.10 = 45 amps charging
• 48 volt bank: 225 AH * 0.10 = 22.5 amps charging

Both are the same power (same size solar array, same size AC genset, etc.)--But the wiring has to be heavier and instead of using a 30 amp solar charger, you need a 50+ amp solar charger (more expensive solar charger for "same job").

This is bit in the "weeds" where you are at in the process right now. We still do not know how much power/energy you need to "be happy". Normally, we would start with your loads and figure out your daily loads, then size the rest of the system.

If, however, you have other limits (most people do not have an unlimited bank account)--Perhaps you only want to spend $xxx money on batteries at this time--We can use that and size the system based on the limited amount of batteries. And if you need more power, you can use your genset (to power saws, fill a cistern once a week with a genset, etc.).

Note refrigerators and well pumps can make a system "much larger". And add A/C, that can make the system even larger.

We just need to figure  out what your needs/limits are, and then size the system to mee those needs.

-Bill

j4ray

So did a home wattage calculator.  Peak running 4900w continuous (that's everything running all at one time). That wouldn't happen much and only on the weekend
2200w continuous during the day while I am at work. That's with the a/c on. 600w continuwith the a/c off. 

So im guessing 4.9kwh peak, 2.2kwh daily, 0.6kwh daily with out the a/c on. 

j4ray

So 4.9kwh is a lot. But I will never be running the a/c, clothes washer, and dryer all at one time.  The most I would do is washer and dryer at once if needed. That would put me at 3.4kWh peak rarely. And only during the day. So let's go with that 3.4kwh 

BB.

• 4x 6 volt @ 225 AH batteries series = 24 volt string @ 225 AH
• 2 strings in parallel = 24 volt @ 450 AH (8 batteries total)
• 8 x 6 volt @ 225 AH batteries in series = 48 volts @ 225 AH

Note that 8 batteries (2s strings @ 24 volts vs 1x string at 48 volt) stores the "same amount of energy". (no difference to above energy usage calculations).

Just that 24 volts take 2x current (heavier wiring, heavier charge controllers, etc.)...

• 450 AH battery bank (24 volt) * 0.10 rate of charge = 45 amps
• 225 AH battery bank (48 volts) * 0.10 rate of charge = 22.5 amps

-Bill

j4ray

So the 48 volt system looks like the best way to go. But I have to much invested in this inverter I have now.  I have to do with the 24 volt set up. Will 450ah be enough for my needs? 

BB.

450 AH @ 24 vdc battery bank is really only good for around 2,400 to, maybe, 3-4,000 Watts maximum. A 6kW inverter is pretty big/oversized for that bank.

Is your inverter TSW our MSW? What is its taste load (power usage just turned on)?

If the inverter is a MSW unit and/or uses >>20 Watts tare, you may want to think about a different inverter.

It all depends on your energy needs, or you adapt your energy usage to what you can afford. And maybe 2-5 years in the future, you revisit your setup.

1kWh power day=led lighting, rv water pump, laptop, radio, cellphone, internet.

3.3 kWH power above + fridge + well pump + washer + a few fans (near normal electrical life with lots of energy conservation).

Power usage is a highly personal set of choices. My suggestions as a starting point are just suggestions. What works for me or others may or may not work for you.

-Bill

j4ray

AIMS Power (PICOGLF60W24V240VS) 6000W 24V DC to 120/240V AC Pure Sine Inverter Charger

• 6000 Watt continuous pure sine power
• 18000 watt peak power for 20s
• Built in 85A smart battery charger with 7 selectable battery type settings
• Auto gen start feature
• Marine and industrial grade 

i have no idea if it is tsw or msw. 

BB.

True Sine Wave = Pure Sine Wave

So yours is a PSW/TSW type inverter--Better for running all of your AC loads (MSW--Modified Square Wave can cause issues for some devices/loads).

Just an FYI--Many folks here have had less than ideal function/reliability with AIMs inverters--Others have been pretty happy. (I will offer no opinion other than some of the much more expensive/better brands of inverters do tend to be more reliable).

A 6,000 Watt inverter with 18,000 Watt surge draws a lot of current at 24 volts:

• 6,000 Watts * 1/0.85 inverter eff * 1/21 volts cutoff = 336 Amps (max load, minimum input voltage to inverter)
  
• 18,000 Watts * 1/0.85 inverter eff * 1/21 volts cutoff =1,008 Amps (max surge load)
  

Those levels of current are very difficult to get from a 24 volt battery bank--Probably around 200 Amps maximum (perhaps close to 300 Amps for a couple second surge) are more realistic "maximum" currents.

I would suggest ~2,400 to perhaps 4,000 Watts as the maximum AC inverter for a 24 volt battery bank with "reasonable size" wiring and lead acid batteries.

Not to say you cannot do more--But I would not suggest it unless you are willing to experiment to confirm you get 6/18kWatts from the inverter.

-Bill