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Battery bank placement and questions  RSS feed

Posts: 1421
Location: SW Missouri
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Battery bank placement and questions

A list of questions for wise folks to help with. I have read enough to confuse myself pretty well, so I give up, and ask. If you know of threads or links that might help with any of this, please toss them at me, I’d love to know. The things I ask, I need to know good or bad, and if it’s bad, WHY it is, so I can understand this.

I’m building our house soon, will add solar and wind generators later, but I need to know where to put my battery bank so I can make sure I have all my construction plans correct. The batteries will be car or marine types, whatever I can afford and work in as I get them.  

The BEST placement for me, for ease of maintenance, is in the basement. The room above the place I am considering is a bedroom, and there is airflow that goes between the floors. If I put it there, would I need to put it in a cabinet with a vent to the outside? I can do that.

Other options for placement are the garage, and there’s a mudroom/dogtrot room, like a long hall, that is an option. I don’t like the garage because it’s too easy for them to get damaged and way too easy to forget to do maintenance there. All the other systems that need maintaining are in that same basement area. It’s a good place because some of the input wires might possibly be shorter, and the output wires might be too. The shorter wire length is the only good thing about placing it in the dogtrot, that’s a high traffic, very busy space, I don't want it there if there is any other option. But it’s very close to the breaker box area.

So if we decide where it goes, then I have secondary questions...
1.  I have no real clue of where my best areas for generators will end up being (depends on several factors,) how long is too long for wires to the batteries? For wires to the breaker box?

2.  Is there such a thing as a breaker type switch to just swap a breaker in the breaker box over to the batteries? I plan to put the stuff I want to stay running in a power outage on a breaker circuit or two, and little to nothing else on those circuits. I’d love to be able to say “power’s out, just switch onto the batteries.” I could also do a separate small breaker box if that would work better.

3.  Until I get generators running, can I get away with putting a battery float charger onto the batteries, keep them charged off the grid? If so, then can I get away with making those circuits ALWAYS bouncing through the battery bank, so when the power goes out, it just draws straight off the batteries, no switch required?

4.  If I have it either switching or always bouncing through the batteries, do I need it all surge protected? I’m thinking yes. The main grid power in will be on a full house surge protector, this area has REALLY grubby power. Brownouts and flickering, short blackouts, and long blackouts are all par for the course here. My desktop computer is on a UPS at this rental, I still unplug it off the wall anytime I’m not actively using it, it’s that unstable. I plug in the UPS and power it all up if I need to use it. I want the house to be MUCH more stable.

5.   Right now I’m only worried about things that need to be built into the house, not the panels or wind generators, can you think of anything I’m possibly missing? I know where the breaker box is, where the wires go, where the circuits I want battery-able are, what kind of power draw I’m expecting, etc. Anything else in the structural design I need to have planned out now?

Thank you for your input!!

Posts: 83
Location: The Ozarks
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Hi Pearl,

You have a load of good questions, but let me ask you one or two before I begin to jump in.  I am an electrical engineer, now mostly retired, with 35 plus years work experience on a variety of rocket, satellite, airborn, shipborn, and handheld systems.  As for solar etc., I am no expert, but i do have some hands on experience at my home with a solar system and a backup generator.  I will help walk you through some wiring options, but first the question or questions.  

Do you plan on having a generator in addition to your off-grid generation?  This will affect how you wire the system and is a good first step to protecting yourself quickly form power outages.

Solar and especially wind are far more construction intensive and take longer to get all the bugs worked out.  Most importantly, however, is that in the winter you don't have a great deal of sun and the angles of incidence are not so friendly unless you opt for an expensive mounting and/or tracking system for the panels.  Also wind generators do not put out a lot of power except in mid to heavy winds.

The beauty of a less than off-grid (because you still need to buy propane) propane generator is that you can run it for a few hours and recharge your battery bank when the batteries are low.   This also provides a step by step path to off-grid power security.  

Your first step after installing the generator would be to add the battery bank and the inverter /charger system.  This gives you the ability to run off batteries until they need to be charged.  Then the generator would kick on and the house would run off the generator while the batteries charge.  This means that the generator may only have to run 2 to 4 hours a day depending on the size of battery bank, power load you are using, and size of the generator.  Also since you are drawing power at the same time you are charging the batteries, the net efficiency of your system is better.  This would greatly extend the life of your propane reserve in an extended power outage.  The other item which would be accomplished as part of this phase is the power to your house would all be routed and wired to automatically switch between, grid, generator, and battery power modes.

The next step would be to add the solar panels and solar charging circuit and work out those bugs.

Final step would be installation of the wind generator, charging circuit and a dump load for excess power when the batteries are charged.  This may include adding a second water heater inline with and in front of the primary water heater to store the excess power from the wind generator.

I guess that is probably enough food for thought in a single post.

We are neighbors as I am in NW AR.
Posts: 2115
Location: Cincinnati, Ohio,Price Hill 45205
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Let me touch on 2 and 3.
If you are feeding a few devices from battery power during power outages,  they will either need to be DC devices or the power will need to be converted to AC via an inverter.

If you always run that power through the batteries you will be coverting it at least twice, each conversion making the process less efficient.

I would want a sub panel for the power critical circuits,including the trickle charger, equiped with a transfer switch.
Posts: 2295
Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even Soil:SandyLoam pH6 Flat
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Grid/Generator Powered Charger $400 24kWHr/day

DC(battery) to AC Inverter 4000W (8000W surge) cost $1,200

Battery $2,000 4.6kWH 24V (8X3.2V),  180AH with 80% DOD comparable to 9.2kWHr car battery with 40% DOD.

Solar Charge Controller $300 3.5kW (* the usual 4hr of sunlight for 14kWHr per day)

12 Solar Panels $2,000 for 3500W ($0.52/Watt) and (14kWH/day assuming 4hrs)

If you wanted to do radiant floor heater.
Thermal Battery (Floor) $2,000
Heating element ($1/sqft) $1,000

Controller $600

24 Solar Panel $4,000
(the solar controller will interface with the house battery to give 6kWH/day on top of the 14kWH/day for 20kWH/day)
[Thumbnail for solar.png]
S Bengi
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Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even Soil:SandyLoam pH6 Flat
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I prefer LiFePO4 batteries they last at least 5 times as long, with twice as much usable power. no problem with motor surge. They don't need maintenance/fumes/acid/lead or extra weight.

How much power do you see yourself using per day?
My above system assumes 10kWH/day
Lighting =0.5kWH (10x LED (10w) for 5hrs)
LED TV/Tablet-PC/Phone = 1kWH (4x 50W for 5hr)
Appliance/etc = 9kWH

What is your peak usage?
I assumed just 4000W thus only one inverter rated for 4000W and about 4600WHr in LiFePO4 battery.

I would just put my system about in a laundry room.

Going with your lead batteries.
I think the basement is perfect.
Wires from battery to inverters and chargers should be at a max 6ft.
When it comes to wires from solar/wind to charge controller they can be pretty far away esp as the DC voltage goes or if the amperage is kept below 10amps and the wire is reasonable thick. You could run all the solar strings wire to the house independently and then combine then there.

When it comes to wind expect 1/5th of whatever it is rated for 1000W becomes 200W at best but you do get 24hr production so 4.8kWHr per day.

I think you might like this.
Inverter $4,400 8000W. With Battery Input+Generator Input+Grid Input. So Two AC input and One DC input. It will charge the battery too, and also automatically switch between and combine power sources to match load. And in the future you can connect whatever solar charge controller you like to the battery.

or https://www.wholesalesolar.com/2550550/outback-power/inverters/outback-power-sbx5048-120-240-inverter
[Thumbnail for inverter.png]
Posts: 388
Location: Michigan
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I like your path of making infrastructure considerations before shoe-horning equipment in or having to walk around it. Retrofit integration is usually the main challenge of installations.

If you like your ups function for the computer you will absolutely appreciate a whole house version.

A transfer switch is a nice device, manual or automatic.

Automatic transfer switches are available as an add on or even better, integrated into the inverter.

I like Ralph's suggestion of having a battery based inverter system in place first (large UPS system), it will get the panel work and battery enclosure in place and integrated into the building electrical and is the hub of the system, no matter what order new energy sources are added.

Midnite solar has a manual transfer switch enclosure that is compact and inexpensive. Samlex makes an auto transfer switch that can be added to most any 120v inverter, inexpensive also. There are others.

Aims inverter/chargers are probably the most capable amd reliable low cost inverter charger option and come about 800$ for 2000w-3000w and have auto transfer.

Its hard to beat an outback fx series or radian for this but they are 1800$ for an fx, mate and temp sensor. Worth every penny.

An inverter/charger with a good (4 milisecond) transfer switch will detect poor power quality on the utility line and disconnect from the grid while switching to inverted battery power without you even knowing, usually. This function is highly under-rated.
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