12 kWatt off grid system + Lithium Battery Bank

Jake48

sorry if this is off topic. but i would like some tips.
i'm thinking on getting in inverter for back up power,
but this seems to be very expensive from what i'v read and i would like to ask the pros on this site!.

the first thing is the inverter. its a beast! wopping 12 kw plus a 36 kw surge for 20 seconds. and it is going to be used mainly for a back up power as noted above.

and what well power this inverter are one:

1: one 48v deep cycle lithium 200 ah/500 ah discharge i think.
2: 440 amp charge controller for wind.
3: the loads/ how much more battery would i need for it to run.
but these lithium battery says 10 kilowatts and im planning on buying 1 for the 12 kw inverter.

and what are GOING to run are:

1: hot water boiler at 4500 watts start up.
2: 1/2 hp 1500 watts water pump.
3: fridge at 1000 watts.
4: 500 watt furnace.
5: 400 watt light (small lights)
would this be a go? or would i need more batterys of the same type.
even tho it says 10 kwh battery?.

BB.

Welcome to the forum Jake.

I have moved your post to its own thread--Should be much easier to follow your questions/needs.

First, I like to start with your loads and conservation, then design the system based on your power needs.

1: hot water boiler at 4500 watts start up.
2: 1/2 hp 1500 watts water pump.
3: fridge at 1000 watts.
4: 500 watt furnace.
5: 400 watt light (small lights)

There are three basic properties we need to know about the loads. They are:

1. Peak Watts--Starting surge typically for motors (well pumps, refrigeration pumps, etc.).
2. Average Watts--Once the load is running, what is the average power consumed (this is a rate, like gallons per hour for pumping water)
3. Hours of Use per day--Now you have the loads "running", take the Watts and multiply by hours per day of use (this is an amount, like gallons of water used)

And solar power (and generator power too) tends to be pretty expensive. It is not unusual for it to cost something like $1.00 to $2.00+ per kWH or about 10x that of grid power when you take all costs into account (buying/installing the system, replacing batteries every 5-8 years or so, new electronics every 10+ years, etc.). Some people here have gotten their cost lower (less than $0.50 per kWH for off grid power)--But that takes a lot of work and living a good/sunny location.

Lithium batteries are really good at outputting a very high current for their size (and good for receiving high charging current too). However, they tend to be expensive and store, roughly, a similar amount of power for use as Lead Acid Batteries. This is the Watts*Hours per day energy usage question.

Your numbers above are 1/2 of the basic information we need. Average Watts. But the hours per day is unknown. Just to make some numbers up for discussion:

• 4,500 Watts * 2 hours per day = 9,000 Watt*Hours per day (water heater)
• 1,500 Watts * 1 hour per day = 1,500 Watt*Hours per day (water pump)
• 120 Watts * 12 hours per day = 1,400 Watt*Hours per day (refrigerator--1,000 Watts does not make sense unless large industrial cooler or something)
• 400 Watts * 8 hours per day = 3,200 Watt*Hours per day (lights)
• ==============================================================
• 15,100 WH per day (or 15.1 kWH per day)

That is, typically, a lot of energy usage per day for an off grid system. A very efficient off grid cabin/home may use around 3.3 kWH per day (lights, refrigerator, well pump, washing machine, laptop computer, clothes washer) and use Propane/Wood/etc. for heating (water, cabin, cooking).

In some cases, people have used Air Conditioning and Heat Pumps (heating, hot water) for their off grid homes--But you need to look for very efficient solutions (a heat pump water heater can be 2x or more efficient vs a resistance type heater).

Anyway, back to battery design. A typical off grid power system will have a battery bank that can store energy for two days of poor sun and 50% maximum discharge for long battery life (this for flooded cell lead acid battery design):

• 15,100 Watt*Hours per day * 1/0.85 inverter eff * 2 days storage * 1/0.50 maximum discharge * 1/48 volt battery bank = 1,480 AH @ 48 volt battery bank

For various reasons, you may get away with a smaller Lithium Battery bank--Something in the ~800 AH @ 48 volt range--But this gives you an idea of what such a battery bank may look like.

And there is the solar array. Without knowing where you live and other needs, in a reasonably sunny location you may average ~4 hours of "useful" sun per day for 9 months of the year (more in summer), the solar array would be around:

• 15,100 WH per day * 1/0.52 overall system efficiency * 1/4.0 hours of sun per day = 7,260 Watt solar array "break even" for ~February

You would presumably need to run a genset during November through January to make up for poor sun, and possibly sometimes in February and October depending on actual weather.

Anyway--That is what a system could look like given the numbers you have provided so far. For most people, this size of system is too large for their famliy budget (solar+generator power is expensive), and I would suggest looking closer at your loads/needs and see if you can, through conservation, use of solar thermal for hot water/heating, and alternative fuels (cooking, heating, hot water) to greatly reduce your electrical energy needs.

If you are way up north (something like Iqaluit, Nunavut, Canada), winter is going to be a killer for you--Diesel genset/fuel for heating & cooking time?

-Bill

Jake48

yes, thank you for your reply. in the summer here is nice for sun. the sun rise's at 5 in the morning tell like like 5 in the after noon. but those storm here are killers!. and the city lights to go back on some times take 2 hour (power out) and gets so cold here in winter time.
about your comment:

• 15,100 WH per day * 1/0.52 overall system
efficiency * 1/4.0 hours of sun =
7,260 Watt solar array "break even" for
~February.
1. thank you for the sums. i am planing on getting 5 more of these.
2. i will not be using solar for this project,
3. since i will not use solar i can use this amount
for the same price for some more battery for back up power. because here in winter it (now days )reaches -60 in wind chill and your question on a generator (propane generator im thinking). i dont like to use a LP gas or Propane but a gasolene generator is less efficient and very heavy.

yes, im ahwere of the over all costs, the inverter i have is a, aims corp 12 kw pure sine wave inverter/charger.
and i dont have any batterys yet, i was planning on getting lead acid battery's to power the system (15 deka 8g8d's), but the amout put in getting them to run would charge more then less for the hole unit to run at say half hour to 3 hours. plus cabin trips sorry to mention this a day after.but during winter i can use the inverter plus 6 batterys to run some high watts heaters insted of using a propane fuel for heat.
cause i seem to be clumsy at the LP gas/propane..
:~p bit scary.

now to charge the battery would be city power i am not going to be in off the grid, i just seen my next door with in inverter for back up.

and taking off battery and put in cabin take off again put back. so it would not be light when traveling with a skidoo on lead acid battery. so instead i will go with 6 lithium deep cycle batterys.

thank your for your replys very helpful. .

have a nice day.

BB.

Jake48 wrote: »

since i will not use solar i can use this amount for the same price for some more battery for back up power. because here in winter it (now days )reaches -60 in wind chill and your question on a generator (propane generator im thinking). i dont like to use a LP gas or Propane but a gasolene generator is less efficient and very heavy.

Propane at -60F(?) is pretty iffy... I don't have propane and I am in a very moderate climate--But you should probably talk to others (hopefully some cold weather folks will post here too) about using it, or not.

One person ended up using a gasoline Honda em4000sx (note, "sx" has an electronic engine controller--May be easier to auto/remote start, no choke needed) for his cold weather needs. Just put a 70-100 watt flood lamp with the engine (in small doghouse) to preheat for a couple of hours--He also found gasoline was his "ideal" fuel--Easier to start, does not gel, does not "lose pressure" with cold tank, etc.

yes, I'm aware of the over all costs, the inverter i have is a, aims corp 12 kw pure sine wave inverter/charger.

AIMS inverter... What is the battery bank voltage? It sounds like 12 volts (15x 12 volt Deka batteries)?

AIMS has some very large inverters that run at (what is usually) considered to be pretty low voltage. Although, it looks like their 12kW (MSW/PSW) inverter is 24 volts (MSW) and 48 volt (PSW).

AIMS does not have the best reputation--But there are some folks that have been happy with them.

Since you are looking for battery backup power vs solar--What are your expectations? Just enough power to carry you through a 2 hour outage (and start the genset at that point)? Or do you want to run your loads for 2 days, then start the genset if needed?

Would, for example, you be OK with running reduced loads (emergency backup) from the inverter (lights, water pump, computer, TV, radio, refrigerator) and start the genset for the big loads (electric water heater, sustained water pumping, etc.)?

and i don't have any batteries yet, i was planning on getting lead acid battery's to power the system (15 deka 8g8d's), but the amount put in getting them to run would charge more then less for the hole unit to run at say half hour to 3 hours. plus cabin trips sorry to mention this a day after.but during winter i can use the inverter plus 6 batteries to run some high watts heaters instead of using a propane fuel for heat.
cause i seem to be clumsy at the LP gas/propane..
:~p bit scary.

Lead Acid are probably a better choice for extreme cold weather. LiFePO4 batteries usually do not like to be charged below freezing.

In general, it will be much less costly to use propane/diesel/gasoline for heating vs a battery bank. A fuel driven heater will be something like 80% efficient. A gasoline genset driving heater, very roughly:

~114,000 BTU per gallon * 3.412142 BTU/hr * 1 Hour = 33,410 Watt*Hours per gallon
33,410 WH per gallon * 0.80 efficiency = 26,728 Watt*Hours per gallon of "useful heat" from burning fuel

Vs a Honda eu2000i genset:

1,600 Watts * 4 hours * 1/1.1 gallons = 5,818 Watt*Hours per gallon

Or, burning fuel for heat vs genset->electric heat is something like 4.6x more efficient.

now to charge the battery would be city power i am not going to be in off the grid, i just seen my next door with in inverter for back up.

and taking off battery and put in cabin take off again put back. so it would not be light when traveling with a skidoo on lead acid battery. so instead i will go with 6 lithium deep cycle batteriHes.

Hauling batteries for power--Not usually a great plan. For example, a single deka 8g8d battery... 12 volts * 220 AH:

12 volts * 220 AH * 0.50 typical maximum discharge = 1,320 Watt*Hours for a 157 lb battery
1,320 WH "useful" per battery / 5,818 WH per gallon = 0.23 gallons of gasoline (~1.4 lbs of gasoline)

Lithium are going to be much lighter--But not that much lighter. Of course, a Honda eu2000i genset will weigh ~50 lbs--But you can bring a lot of fuel for the weight of the battery bank.

And there is the issue that lithium rechargeable batteries typically do not like sub freezing weather. That Lead Acid batteries, if severely discharged can freeze in sub freezing weather, and those Deka batteries are "GEL" type--They typically do not like to be charged very fast (usually a ~5% rate of charge).

The slow rate of charge may be OK for your since you are not going solar--And can take time to recharge after a blackout (or slowly recharge with your genset).

-Bill

Dave Angelini

If you have the grid, and you need back-up, I would recommend the use of a diesel generator in a very cold climate. I might add a grid tie solar and use a TL series grid inverter that could run during a daytime outage.
I would almost never recommend a battery system unless there was a medical need or some really important reason when you have grid power. I do enjoy reading the info Bill posts. It is really helpful and I wish I had the patience. Thanks for the rain last night Bill !

BB.

Always happy to rain on your parade Dave!

-Bill

Jake48

Hmmm... i'll think of buying a generator.
but also the reduced load.
now to go solar at full house. since it go's -40 to -60 C with wind chill
(some times, for the past 2 years).
i'v read some site providing info on solar panels/inverter/10 plus more L16 battery's all in one. plus the watts a day giving the amount of battery's say, 115 kwh solar supply is ranging to 80 to 125,000,00$. im thinking of spending 46k.
and i just went ahhhhh, still worth the inverter tho.
but!, what battery would i use?!?! lead acid? same one that my next door used???!?!. would it happen to
start dropping the battery volts from 12v to 1.5v?
would it die next 3.5 years???? if i started with just 4 8g8d?. reeeelly is worth the cool future of having not to pay for fossil fuel. but i'll go with the generator for now.. but for the lithium battery, my next door used a 6000 watts inverter and at 8 battery's the first 4 battery's was replaced i think and i dont want to go that far every 3 years... improper discharging i guess 67% discharge mabey(?).
hmmm thank you very much.

yes the aims seems not to have a best reputation.i'v seen a video on youtube about the same inverter i have it was in north of ireland i think.
running on what looks to be 4 car battery's and a random battery at that.
running there hole house!. but improper care can damage the inverter like on the video. and also looks
can be desieving. the aims inverter is a 12kw 48v puresine wave capable of running 12HP that is why i went with just the inverter/soon to have lithium battery' because im planning on using the extra power for personal use aswell. and well use the exta heat in the winter to start the inverter and charge the battery at 30° C im hoping have a nice day.