Total newbie from UK

Cariboocoot wrote: »

Right, lass; the first thing you have to answer is "what do I need to keep running when the power goes out?" And if you answer "the telly" you'll never make O levels.
As it is, you've bought stuff with no goal in sight and it may none of it do you any good once you figure out what that goal is.

Cariboocoot wrote: »

Hmm. I always think the think to keep running during a power outage is the refrigerator. That way you avoid having to throw out several hundred pounds of food. Must be a Canadian thing, eh?

Your two 40 Amp hour batteries together need about 62 Watts minimum for charging. Regrettably the HF panels tend to under perform, but perhaps you can just make it with the one you've got. Your looking at around 4 Amps output maximum here. The 20 Amp controller is kind of overkill.
What can you do with 80 Amp hours @ 12 Volts?
Well that's up to 480 Watt hours DC. It's a bit less when converted to AC (inverter consumption and conversion efficiency), say 400 Watt hours. A laptop @ 20 Watts would run for about 20 hours. A TV @ 100 Watts would run for 4. A refrigerator @ 150 Watts would run for maybe three (depending on the duty cycle).

Understand from the start that this stuff does not scale up easily. Your "next system" will likely utilize none of the present components, and it's almost inevitable that there will be a next system; it's addictive.

niel wrote: »

i'm a bit late chiming in here so if this was covered already then ignore me, but what meter are you going for to measure things? i also admit i don't know the voltage used there, but some meters here can't measure higher voltages like 230v.

the peak power demand that you need is only part of the answer for it is also for how long that power is to be used too.

BB. wrote: »

Not too far off in expectations--Except we need to know how many hours per day you would like to run them.

In general, if you have another way of heating water (propane, wood, etc.), it is generally a better use of your money (electric PV power is "expensive").

But, with a 60 watt set of panels, assuming sunny weather (at least 4 hours of sun per day):

• 60 watts * 0.52 system derating * 4 hours of sun = 125 Watts*Hours of 230 VAC per day (if using inverter)

Your 15 watt TV would run:

• 125 WH per day / 15 watts = 8.3 hours per day

A 200 watt heating element (yes, I know it is 12 volt, but close enough to keep the math easy):

• 125 WH / 200 watts = 0.625 hours = 37.5 minutes per day

So, you can watch the telly for 8 hours, or have a cup or two of tea per day -- But not both.

-Bill

BB. wrote: »

In the end, it is best to design a "balanced" system... Too much solar panel, you can use the most power when the sun is up... Too large of battery/battery bank, and they usually die an early death (months/year) because of under charging.

LED lights, cell phone chargers, small radio, etc. do not use much power. Heating devices, mechanical/motors (pumps, refrigerators, etc.) all really suck down the power--and need quite a bit of solar panel (+battery bank if needed) to get a "useful" amount of work.

With your current system--stick with small electronics/LED lighting/etc. You may be able to use small pumps (like for small fountains) for a few hours per day (lift water over to garden rows). You will not be able to connect to a hose with nozzle/sprinkler and use like a normal domestic water source (that take quite a bit of power).

Before you start buying a lot of equipment--Learning some of the basic electrical equations and how to use a couple types of meters is the best place to start.

Electricity for Boaters - BoatSafe.com

is a good place to start.

Solar power has never been cheaper--but it is still not "cheap". Just cheaper than a genset+petrol in the long haul (genset or even a long extension cord is still the best bet for short term power usage).

-Bill

BB. wrote: »

Sorry Shella,

I did not intend to sound condescending.

A UPS system is really just like the solar power system you are designing (inverter + AC battery charger + Battery). But they tend to be designed to supply a lot of power for a short period of time (inverter/electronics are "cheap and light", the batteries are "expensive and heavy). Some companies will take a UPS and connect up solar panels+charge controller to the side of the UPS and call is a solar generator.

The problem with solar power (and off grid power in general), it is very difficult to start out small and "grow a system"... Once you grow past a certain size, you need more batteries (mixing old and new batteries can be a mess), and you want a higher voltage battery bank (batteries in series) with new higher voltage inverter, etc...

We try to push the math up front (what are you loads, design the system... Or if you have some components, design the balance of the system around those components so that it will function to the best of its ability).

I find the easiest way to explain a solar power system... The battery is the "heart" of your system. To a large degree, everything that hangs off the battery can be treated as a completely separate black box.

The loads (and inverter if used) drain the the battery bank. Volts, Amps, Amp*Hours/Watt*Hours and the capacity of the battery (typically given in Amp*Hours as some 5, 10, 20 hour discharge rate). Get that section of your system defined/designed... Then move on.

The charging system--You may have several. Your solar panel(s) + charge controller--Enough solar to both replace the power you use in a day or two, and enough current to properly "condition" the batteries back to full charge (and do it quickly).

Another charging source may be an AC battery charger--To recharge the battery bank when the system is put away for the winter--And/or as a backup with a petrol generator set.

So--anyway--I probably have gotten a little lost what I can help you with... Do you have some components you want hook up (XXX watts of solar panels as an example)--Or are you looking to getting more information about your loads before we try defining your system?

It tends to be much easier if we focus on your needs vs trying to conduct a general education call on solar. Once you have designed/built your first system, then the rest of the "big picture" discussions make more sense. Many of the answers depend on the size of solar system you want to have--so real numbers and real hardware are easier to discuss/less confusing in the end.

-Bill

BB. wrote: »

If I understand correctly, you really just need a 12 volt battery... Using the standard 5% to 13% rate of charge and 0.77 panel+charge controller derating:

• 60 watt array * 1/14.5v batt charging * 1/0.77 panel+charger derating * 1/0.05 rate of charge = 107 AH battery maximum recommended
• 60 watt array * 1/14.5v batt charging * 1/0.77 panel+charger derating * 1/0.10 rate of charge = 54 AH battery "nominal"
• 60 watt array * 1/14.5v batt charging * 1/0.77 panel+charger derating * 1/0.13 rate of charge = 41 AH battery minimum recommended

So, now you can do some math on the battery bank. Say your section of sunny old England is 4 hours of sun per day (that is "noon time" solar energy of ~1,000 Watts/M²).

For a small system, you can probably cycle down to 20% state of charge (use ~80% of the stored battery energy). For a 80 AH battery:

• 80 AH * 80% use = 64 AH

An 80 AH battery is typically rated a C/20 hour rate), that means:

• 80 AH * 1/20 discharge rate = 4 amps for 20 hours
• 64 AH usable energy / 4 amps = 16 hours for 20 hours to 20% state of charge

If you have an AC load--Say it is 30 watts for a small pump or charging a laptop computer. Then:

• 30 watt (at 230 VAC) * 1/0.85 AC inverter efficiency = 35.3 watts from DC side of inverter

Then the battery will support:

• 64 AH * 12 volt battery bank * 1/35.3 watts = 21.8 hours of run time

To recharge your 80% used battery assuming 4 hours of sun per day:

• 64 AH * 14.5 volts recharging * 1/0.77 panel+controller losses * 1/60 watt panel * 1/4 hours of sun per day = 5 days to recharge bank

Anyway... The other stuff to look for. A DMM (digital multi meter), inexpensive hydrometer (if flooded cell battery), a battery monitor would teach you a lot--however probably not cost effective your smaller system...

-Bill

BB. wrote: »

Yes... But I highly recommend that you do this in a "balanced manner".

For example, large or small battery bank, your 60 watts of panels will output around (60 watts * 0.52 system eff * 4 hours of sun per day = ) 125 Watt*Hours per day.

You can have a very large battery bank, or a very small battery bank, your panels will still supply (roughly) the same amount of usable power.

On the other had, a very small battery bank will "fill up" quickly, and may not store enough power to carry you through 1 night (or a day of bad weather).

You could start with a 107 AH battery and a 60 watt set of panels... And later add another 60 Watts or more panels with the same battery--And you will get more WH per day, and recharge the battery faster.

It is very difficult to "grow" a solar system in a cost effective manner... More or less, you can grow a system by about 2-3x in power/storage/panels. Past that point, you almost have to get rid of what you have and start over (higher voltage battery banks, larger charge controller, higher wattage/input voltage inverter, etc.).

Since you are experimenting, a 50-80 AH battery bank would be a good fit. And see what it does for you. If you kill the battery by accident--not a big loss (about the size of a normal car battery).

-Bill