Getting into solar ...

[CountryGent]

Well, I want to get us set up with some solar power systems and I could use some advice. I've done a bit of reading on the topic, talked to some folks, and got some quotes, but I'm still looking to make sure we do it right.

A bit of background first: our family is preparedness-oriented and we are heavily invested in being as self-sufficient as possible. I couldn't be more thankful that both me and the Mrs are on the same page. Our main backup electricity is a whole-house generator backed up by a smaller, portable unit. Our backup heat and cooking source is a wood stove and many acres of timber. For short term disruptions, this setup has worked and worked well. However, I am looking for another backup and, should it really hit the fan with a long term situation, a source of juice that isn't dependent upon fossil fuels, parts, etc.

Solar would seem to fit that bill. That said, we don't live in an area known for a ton of sunlight. The lay of property also doesn't provide a lot of direct sunlight to the house area. And I've found solar power to be redonkulously expensive, even with all the tax breaks, compared to other sources. But at the end of the day, I've got to make it work.

So here's the question, what amount of equipment (panels, batteries, etc.) should I acquire to:

1. Power the smallest of the SunDazer refrigerators.
2. Power some comm equipment (e.g., amateur radio, CB, et al.).
3. Recharge various small devices (e.g., notebooks, cell phones, mobile radios, et al.).
4. Recharge batteries.

Thanks all for any advice, links, lesson learned, etc.

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[Joe13]

You can get a lot of government rebates on the panels - even on cloudy days they will produce, but not at 100%.

You will need an inverter to switch from 12v to 120v.

Deep cycle batteries are the biggest cost by far. The more you have the more you can store.

You will need a transfer switch if you want to use it for household power.

It's a big upfront investment but great for long term.

 

[Kruel J]

Solar panels, whether portable or permanent mount are all DC suppliers (20-50 volt nominal). You need an inverter to make AC voltage (wall power). Yes, low light has a huge effect on most panels, although some are Amorphous and work better in low light. Think of solar panels as not much more than a battery charger (household panels can run alongside an inverter without batteries in peak daylight). A typical small-scale system would be a couple of panels, a charge controller (to regulate the output power as to not pop battery tops), a battery bank and an inverter to make AC voltage.

And at the end of the day, I always recommend a backup power supply to solar such as a generator. Being 100% off grid via solar takes some money and roof real estate and isn't always feasible for a small off-grid dwelling.

My short, abridged answer.

 

[Camelfilter]

IMO skip any conversion to AC, stick with DC. All of the applications you list should not require conversion to AC. Maybe convert initially to AC to recharge some stuff until you can figure a way to charge via DC (ie you can make your own USB & "12V" outlets appropriately stepped down as need be).

--not much info on solar-- (I left my flexible panel on the roof of my truck and drove to work one night...)

Anyways-

There are a bunch of 12V fridges/freezers, I'm really not familiar with the on you listed. Sorry.

I have a portable fridge/freezer for camping, if I recall it's about 35liter sized. It'll run 48 to 72 hours on my "house" (camper) battery before low voltage cuts it out-about half power remaining in the battery. My house battery is pretty good sized though. Depends if I run it freezing, 4C or 6C, and how much I open/close it...and if it's really hot out--like above 90. I'll have to take a look at it and get back to this thread at a later time, probably Saturday morning.

Mind that my portable doesn't appear anywhere near as well insulated as the one in your link, but I did make an extra insulated cover for mine, which markedly improved the run time before recharge.

There is an equation you can use, just determine the AMP draw of that fridge and divide it into half of the AMPs of your proposed battery (or battery bank). That would give you a general idea of how "big" of a battery/bank you would need. ie, do you want the option to run it for 1,2,3,4,5 days before needing recharging?

For example, my fridge has a Danfoss compressor which draws 3-3.5A/hour if running continually, which doesn't happen in fridge mode. On a really hot day I figure it runs 1/4-1/2 of the time to maintain 4C, at night if its cooler it runs much less the time (dependent on outside temp). As an example--simplistically & theoretically, if it were to run continually for 24 hours I would need about 72A of available power, so my battery should be rated for about 144A.

 

[Camelfilter]

Oh & never run anything directly off Solar panels, preferably run thru a SOLAR controller, or secondarily to your battery bank if properly protected, but it's simpler/safer just to use the solar controllers outputs.

 

[CountryGent]

Thank you all for the thoughts and guidance. I appreciate the responses.

Couple follow ups for those that got into solar:

• Did you go with a particular vendor or installer? I'm thinking of DYIing a lot of this, but am open to other options.
• If I may ask, how did you set it up in your home for ease of use and safety?

Thanks much.

 

[tc556guy]

I'm going solar this fall. I'm not going with battery banks, at least initially. It's purely to offset my utility bill. The solar rep says the panels are designed to cut off the solar if theres a power outage, even with the cutoff panel I use with my generator. There goes the idea of using the panels to power the house during a prolonged outage. Guess I'll still be relying on the generator for that

 

[teflon6string]

What simple device would you guys recommend for charging a deep-cycle 12v battery using solar energy?

I see a lot of inexpensive devices that keep small (motorcycle, mower) batteries topped off between uses. But that's not enough.

Very specifically, I'm thinking about an extended power outage, and running CPAP with an inverter at night off a boat/RV battery, and then charging back up in daylight.

Ideas appreciated.

 

[mjbskwim]

Everthing that I have read or heard from folks in the know say it's OK. Especially if power lines aren't an option.
Well one friend who was a super for a big construction company had friends who did solar for big 'green' building projects
He said buy the time the solar is paid off things need replaced. His claim is it just ain't what it's all fracked up to be ,efficiency wise,by the manufacturers of solar gear.
With my limited math x electrical knowledge,wind seemed a better bargain.
There is always some wind movement
Maybe some of both?

 

[Joe13]

What simple device would you guys recommend for charging a deep-cycle 12v battery using solar energy?

I see a lot of inexpensive devices that keep small (motorcycle, mower) batteries topped off between uses. But that's not enough.

Very specifically, I'm thinking about an extended power outage, and running CPAP with an inverter at night off a boat/RV battery, and then charging back up in daylight.

Ideas appreciated.

You should only need a voltage regulator if your just using the panels to recharge your batteries.

If you want to convert that power to AC from DC then you need an inverter to feed a dedicated circuit.

If you want it to power your house during the day (or night of the batteries), during outages then you need a manual or automatic transfer switch.

 

[ChiefStealth]

What simple device would you guys recommend for charging a deep-cycle 12v battery using solar energy?

I see a lot of inexpensive devices that keep small (motorcycle, mower) batteries topped off between uses. But that's not enough.

Very specifically, I'm thinking about an extended power outage, and running CPAP with an inverter at night off a boat/RV battery, and then charging back up in daylight.

Ideas appreciated.

The calculations depend on what percentage of the battery charge, in how much time. If you use say 10Ah of the battery at night, you need to charge 10Ah back into the battery during the day. In general, in the PNW, I plan on 100 watts of solar panel for every 3Ah of battery, per day. Wanna charge faster... ya need more panel watts. Charge more amp/hours... more panel watts. Figure $150 dollars per 100 watts of panel. The more panel, the bigger the charge controller.
So, figure out how much power the CPAP uses, per day, in amp/hours. Calculate from there.

 

[Camelfilter]

What simple device would you guys recommend for charging a deep-cycle 12v battery using solar energy?

I see a lot of inexpensive devices that keep small (motorcycle, mower) batteries topped off between uses. But that's not enough.

Very specifically, I'm thinking about an extended power outage, and running CPAP with an inverter at night off a boat/RV battery, and then charging back up in daylight.

Ideas appreciated.

Morningstar / pro star charge controller.

https://www.amazon.com/Morningstar-...t_3?ie=UTF8&psc=1&refRID=EC9QHMD78YV481G965Y8

Cruddy cell pic of mine, a similar model. Looks almost exactly like that one above linked in Amazon, but my cell flash washed it out.



Caution! Look around a bit & they (or similar models) can be found anywhere from $110-$200. Depends on if you want multi battery type recharging (lead acid/gel etc) or not --- and I recommend that you do get a multi battery type, even if you will initially only be using wet cells.

Also my version has the realtime voltage / power display (like the one in the Amazon link). I like that feature, because I can see at a glance the battery voltage as well as Amp draw when I have it in use.

 

[PaulB47]

Panels must be getting cheap as you see them everywhere these days.

The problem with something like this is that there are so many questions and so many answers.

I'm getting to the point where I am just going to get a kit like this:
900 Watt Solar Kit, 4- 225 Watt Topoint Solar Panels
...just to get into it, without worrying too much about details other than how to site it and put it together. Then if SHTF I will at least have *something*. Maybe not enough to run the refrigerator I have now, but that would be taken care of with later iterations to the system.

Do you have water taken care of? You need power to pump it from a well. City water, good luck...

I couldn't be more thankful that both me and the Mrs are on the same page.

Hell, that's half the battle. You are luckier than a lot of us.

 

[CountryGent]

Has anyone experience with Wholesale Solar? Their prices look interesting. They appear to be based in Northern Cali.

Thanks.

 

[Gunwheeler]

I have a 5.2kw grid tie system (no batteries) (very infrequent power outages). I heat with a combo of propane and electric. I spend appox $350 a year for propane (heat, cooking). I also spend about the same for power. Thru the Washington State incentive program I receive an annual check from the power company for $1200 to $1600.

My last house (built in 1984) was a hybrid solar ( oriented to sun and HWT panels) super insulated house. Hot water floors heated the place. Solar worked very well except for the coldest of months. Then we used a woodfired boiler and upgraded to a propane boiler. That house qualified us for a $10,000 Jimmy Carter tax credit.

 

[ATCclears]

I thought this was a good read.

The state of residential solar power

 

[AMProducts]

This is a pretty complicated question, and there's a lot of things you'll have to do to make things work for you.

A few things:

Most of the "bigger" panels are 24V, some have a 36V open-circuit voltage (not connected to any load), if you connected something like this directly to a battery bank without a charge controller, you could quickly boil your batteries dry.

From an electrical perspective, a 24V system is easiest to maintain, as the higher your voltage, the lower your currents will be. However all of the components for a system like this will be more expensive (except for the panels).

6V Lead-acid deep cycle "golf cart" batteries are the cheapest/highest capacity batteries you can get, you will need at least 4 to make a 24V bank, in most cases you will have a mix of series and parallel, meaning you may have 3 parallel banks of 4 series batteries for a total of 12 batteries.

You can still have a 12V output using buck down type voltage converters, these are not really practical for having a single unit, but you can use them to convert 24V to 12V at point of use (radios?) and they're available fairly cheaply ($5-10 for a 3-5A unit on ebay/amazon)

AC is still good to have, as it's hard to find a 12-24V power saw. AC has one major advantage: you don't need to run large wires to support large loads. A 12V system will need wires twice as thick to deliver the same amount of power as a 24V system, and a 110V system can be even thinner. (this isn't totally precise, look at the discussion here on wire gauges vs amps capacity: American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies and wire breaking strength) The important equations are:

1) Watts = Amps * Voltage
2) I = V/R (current = Voltage/Resistance)
3) P = I^2 * R (Power = Current^2 * Resistance)
4) P = (Va - Vb)I (Power (thermal) = (Voltage initial - Voltage after) * Current)

What you need to be aware of, is if you have a conductor, if you are drawing a lot of current across it, and you get a voltage drop (as a function of the earlier table I posted) you will heat the wire according to equation 4. In the case of equation 2, you can calculate what the maximum useful current over the conductor is. In most cases, a temp increase of 10F/hr is usually acceptable as the system will usually be able to equalize and dissipate that heat.

An easy way to get a 24V inverter is to look for used UPS units, which often run 24-48V internally, most of these units are junked out when the batteries go bad, and 24V units are fairly common. If you're dealing with large loads, you may need a more serious commercial inverter.

In general, any solar system needs to be sized properly for the battery bank, as well as the power utilization at your specific location, usually you will need a battery bank that's about 3-5x your daily power needs, and you'll usually want a solar system that's 2-4x your daily power usage. In winter, you'll usually only get 6 hours of good sunlight per day, so a 4x of panels will allow you to get enough power for 24 hours in the 6 hours of good light per day.

You will likely also want a load-cut off device, if your voltage goes low, for a 24V system, you're pretty much tapped out when your voltage drops to 22V, and at full charge your system will max out at about 28V, any more than that and you risk boiling out your batteries.

Either way, I hope this helps you out. Solar is a very technical undertaking, and the more you know going in, the more money you'll save, and the fewer surprises you will get when you try to roll it out. One thing I suggest you consider is having an emergency load, like a large water pump, or a heater, when your batteries approach full the voltage will get high (unless you're dumping the electricity into another load), if for some reason your load/charge controller breaks, having something like a large immersion heater in the stock pond where you can put all that power will save your batteries.

 

[RVTECH]

This is a pretty complicated question, and there's a lot of things you'll have to do to make things work for you.

Pretty good 'summation' of solar AM - want a 'consultant' job ? !

I occasionally deal with RV solar issues but usually it is after the customer has been 'sold' on a system, it's been installed, or I have to answer questions about it. Unfortunately (with RV solar anyway) is the customer usually gets minimal or incorrect information about just exactly what solar will (or will not do) and winds up dissatisfied with the system. The most common problem is the owner is often led to believe it can 'run' their RV. Reality is they are NOT educated on the simplest aspect of solar I.E. that being the BATTERIES provide the power and the solar system does nothing more than recharge the batteries. These people are shown a bunch of mathematical calculations that purport to show that this combination of batteries, panels and an inverter can provide the NONSTOP amperage and wattage requirements they need. Some of them have residential refrigerators and combined wattage draw of that and other items can easily exceed 3000 watts. RV solar is a great SUPPLEMENT to provide battery recharge but other than for very low wattage/amp draw requirements it will not provide a sustained and continual power source. We do not push the sale or installation of other than basic battery charge systems and if a customer insists on anything with greater output we refer them to a manufacturer of solar products to get more education and an understanding of what solar really is and what it does.

 

[AMProducts]

Pretty good 'summation' of solar AM - want a 'consultant' job ? !

Sure! They'll love my new sun-power Zero Point Module, provides all the power they could ever want for as long as they could ever want it!

But yea, seriously, I do mechanical and electronics design, I've given some thought into designing solar power control electronics. If you got a spec, e-mail me and I can get it designed and made. I use OSHPark for making all my circuit boards (Made in USA in Oregon), and then do all the assembly myself (occasionally when I got overflow I hire out a friend's company who normally assemble audio equipment).

 

[bbbass]

Well, I'm thinkin the OP is long gone. However, I'll throw this out there for others:

IMO DIY solar is a serious undertaking. It's not too bad to tinker around with for hobby/toys/cellcharger/etc, but for real-world applications such as RV or house you gotta know what you are doing or things go bad in a big hurry. Fortunately there is a lot of good info out there, unfortunately there is a LOT of info out there. The learning curve is steep, there are scammers, salespeople, and knowitalls. In Quartzsite AZ, most RVers have theirs done by a qualified solar installer. I think the house offgrid customer typically does the same. I missed out on the tax credits for my RV.

My 36' 5th has three 125W 12V panels, a 30A PWM controller, and six 6V batteries. We have plenty of power for all our needs. BTW, the new connectors and load centers are a blessing.