getting ready to pull the trigger. What do you think?

DKMA · April 2013

Hi all,
I have been lucking in this forum for some time but still am a novice and need some advise. I am ready to pull the trigger in purchasing a small off-grid system for my home. Not interested in a grid-tie, and the primary motivation is for fun, learning, and a little backup power in case of a power outage. I want to build a system that I can expand later so this is my shopping list.
2 - TSM-PC05 235 Watt panels
1 – Outback 60 charge controller
4 – T-105 batteries
Associated cabling, breakers, fuses, etc..
What I want to do, I think, is set up a small 24V system that I can add additional panels and batteries to as time goes on to increase my power production.

Two questions up front.
1) The TSM-PC05 235 panel spec sheet says that the Vmp = 29.3. Is this enough to effectively charge a 24V battery bank?
2) is this a decent “starter” system that I can learn with and later expand.
Thanks for all the great explanations and this forum, I am learning and having fun doing it.

Cariboocoot · April 2013

Re: getting ready to pull the trigger. What do you think?

Welcome to the forum.

DKMA wrote: »

Two questions up front.
1) The TSM-PC05 235 panel spec sheet says that the Vmp = 29.3. Is this enough to effectively charge a 24V battery bank?

Good question. One panel would not be as it could barely make enough Voltage for charging a 24 Volt system. However two panels in series on the proposed Outback 60 would.
What you will have for a battery bank is 220 Amp hours @ 24 Volts. To get the minimum charging for that you need about 11 Amps which would require at least 264 Watts of panel. With two 235 Watt panels you should be able to achieve 15 Amps, which is about a 6.8% rate so it should work.

2) is this a decent “starter” system that I can learn with and later expand.
Thanks for all the great explanations and this forum, I am learning and having fun doing it.

Yes, as for one thing you've left yourself plenty of room for adding panels (parallel another string of the same 235 Watt type for example) and the battery capacity is only slightly less than I use to run my cabin. So you may want to add more panel, but not necessarily more battery.

One missing component: inverter. How are you planning to use that stored power?

DKMA · April 2013

Re: getting ready to pull the trigger. What do you think?

Thanks for the quick reply. That is exactly what I was looking for. Since you asked…. I have more questions.. I am still looking/researching inverters. I have two possible uses for the power I generate, and I think I would need two types of inverters, so I am a little confused in this area. I live in the country and we have a 220 Well pump for our water supply. I was wondering if I could use this system as a backup power source for my well when the power goes out. Not to run it continuously but to be able to fill a tub and flush a toilet.

On a regular use type of day, I would want to convert my power to 120V and power a few small loads in my home. Laptop, cell phone chargers, small TV for a few hrs, radio, etc. My general plan was to set this up and see how much power I could pull off daily and not discharge my batteries below 30%. I have ordered a meter to test my loads but have not received it yet.

Thanks again for the good info. : ) By the way, I am located in sunny Florida.

BB. · April 2013

Re: getting ready to pull the trigger. What do you think?

While we suggest a 5% to 13% rate of charge and your 6.8% rate is fine--It is a bit on the low side if are going to really "exercise" your system.

If you have the money and room (it is all about money in the end

), I would suggest getting 3 panels in total (and run them in series). That would give you ~10% rate of charge for your system--A very nice/healthy amount of panel to battery ratio. And would recharge your battery bank from 50% to 90%+ on a nice sunny day (winter, not so much).

235 watt * 3 panels * 0.52 system derating * 4 hours of sun (~9 month of year minimum) = 1,466 Watt*Hours of 120 VAC power per day nominal

That is almost enough power to run an energy star refrigerator (a useful amount of power per day).

And, as Marc asks, what are you looking at for an inverter... For a small system, I would seriously look at staying at 12 volts and get a MorningStar 300 Watt TSW 120 VAC inverter. They are tough, reliable, and have a couple of features (remote on/off, search mode, even a digital computer interface--probably not needed) that you cannot touch at that price (cost you almost 5-10x as much to get those options in any other larger AC inverter).

But to run a refrigerator, you usually need a 1,200 to 1,500 watt inverter minimum and about a 2x larger array+battery bank.

Since I am spending your money anyway--I would also suggest:

Battery Monitor
Hydrometer
DC Current Clamp meter (this is an AC/DC DMM type meter for $60)

-Bill

Cariboocoot · April 2013

Re: getting ready to pull the trigger. What do you think?

Bill, I don't think he was planning on using it as a constant power source at this point. If he were to do so, doubling the panels up solves the issue in one step.

DKMA, there are inverter that output 240 VAC directly (with the ability to provide the split-phase 120 VAC common to households in North America) and there are also transformers that can step Voltage up from 120 to 240 for individual items. My own system uses a 120 VAC Outback VFX3524 and a transformer to supply 240 for the one pump that requires it.

However, there are a lot of inverters available. Some off-grid types from our host: http://www.solar-electric.com/inverters.html

If you look through those listings you'll see they also come in a wide variety of features and prices. One of the options being with or without a built-in battery charger (takes power from AC mains to keep batteries up). In that realm you are looking at roughly $2,000 just for an inverter.

So this is one of those "think carefully about what you want to do with it in the future" issues.

DKMA · April 2013

Re: getting ready to pull the trigger. What do you think?

Great advise and info guys. Thanks a bunch. I will check out the inverters you mention and think I will bump up my panel purchase to three.
Boy BB, you are almost as good at spending my money as my wife is : )
I do sincerely appreciate the advice. Like I said in the beginning, my primary driver in all this is to have fun and learn a little. If I can pull off some back-up power and use a little of what I produce daily all the better. I just have to throttle my spending curve to keep the wife from going ballistic on me. : )

westbranch · April 2013

Re: getting ready to pull the trigger. What do you think?

keep in mind that you may have to do some rewiring of the house circuits to another load center (box) or 2 if you go 2 different inverters.
I would consider 4 panels 2x2 rather than 3 in series the less difference in input voltage to output voltage the more efficient the CC is.
hth

DKMA · April 2013

Re: getting ready to pull the trigger. What do you think?

OK guys need a sanity check. I changed panels and purchased 3 yesterday. Want to order my Outback 60 today but would like a sanity check before I do it. Here is what I purchased, and plan to purchase at a later date:
I purchased: 3- Sanyo 210N panels. (210 W, Vmp – 41.3, Imp = 5.09A)
Want to order an Outback 60 charge controller (for 24V up to 1800W, 60A, Voc= 150VDC Max)
4 – T-105 batteries in 24V config = 220 A/hr of bank capacity
Inverter - still researching
So my thoughts are to run these 3 panels in parallel ckt to produce a V= 41.3 and I = 15.27A
Question : Is this a good match of current and Voltage to the Outback 60 to charge my 24 V battery bank?
Later, to expand the system, I think I could purchase 3 additional panels and run an identical parallel string (for a total of 2 strings of 3 panels) I think this would work out to V = 41.3 and I = 30.4. If this is correct, is the Outback 60 still a good match for this array set-up?
Very excited about building my first solar setup. Learning a lot and I think I have found my new Hobby

: )

Photowhit · April 2013

Re: getting ready to pull the trigger. What do you think?

I might check out the Midnite Classic Charge controllers. If you must have a display, I think Northern Arizona Wind and Sun has a The Classic at $610 and Monday they have a 10% off sale. The Classic Lite, most of the features of the Classic without a display (if your computer literate the info is available via network cable) is $500 and Monday $450.

The Classic is designed by the people who designed the Outback 10+(?) years ago. and has features that truly make it a classic, ability to start loads dependent of charge status, ability to measure charging at the shunt so loads don't confuse the charging, etc.

Cariboocoot · April 2013

Re: getting ready to pull the trigger. What do you think?

A 24 Volt system needs an array Vmp of at least 35 for proper charging. 41.3 Vmp will work fine.
The Outback would have no trouble handling six of these panels on a 24 Volt system. It could in fact handle eight. You could also change it to two panels in series for Vmp 82.6 without suffering noticeable efficiency loss. The advantage would be reducing the array current.

If you're planning expansion, size the wire for the full current now; no sense having to take it out and replace it later. Much easier just to connect up the additional panels.

The Outback is a perfectly good controller. It is about $100 less than the MidNite, but slightly more expensive than the MidNite Lite (which has no display). Either would work fine here.

BB. · April 2013

Re: getting ready to pull the trigger. What do you think?

Before you buy--I would suggest pick the inverter too... Inverter types/options/power are different across the 12/24/48 volt range and I would hate for you to decide on XX volt bank and finally settle on an inverter that did not match your bank voltage and support equipment (backup AC battery charger, fusing/breakers, wiring, switches, DC direct loads, etc.).

HAM radio should be your next hobby after solar. Other than a boat (a hole in the water in which you dump money).

-Bill

kellylipp · April 2013

Re: getting ready to pull the trigger. What do you think?

I would also emphasize a meter to help keep track of what's going on with your system. Trimetric is probably the best IMHO. While you can gather a lot of information from the CC if you have either a panel or a network connection to it, the Trimetric measures the inputs and outputs better due to the way it is wired into the system.

All that said, I surely wish the Trimetric provided better access to all of the information it collects and stores!

Kelly

PS The system you are building is very similar to the one I put on my RV. I have the same battery bank but in a 12V config and have a 2000W Magnum inverter. If you search on my name on this forum you will find a diagram of my system. Or PM me and I'll send it to you.

Photowhit · April 2013

Re: getting ready to pull the trigger. What do you think?

kellylipp wrote: »

I would also emphasize a meter to help keep track of what's going on with your system. Trimetric is probably the best IMHO. While you can gather a lot of information from the CC if you have either a panel or a network connection to it, the Trimetric measures the inputs and outputs better due to the way it is wired into the system.

I wonder how far boB will get with the battery module, boB are you out there? Likely it could be as functional as the Trimetric, if the Classic has enough processing capacity. Just an information tidbit Midnite has a battery module planned for the Midnite Classic, which should be out this year. They've stated it should be very reasonably priced, @$60, and will measure the current passing through a shunt to the battery bank.

Panamretiree · May 2013

Re: getting ready to pull the trigger. What do you think?

Photowhit wrote: »

I wonder how far boB will get with the battery module, boB are you out there? Likely it could be as functional as the Trimetric, if the Classic has enough processing capacity. Just an information tidbit Midnite has a battery module planned for the Midnite Classic, which should be out this year. They've stated it should be very reasonably priced, @$60, and will measure the current passing through a shunt to the battery bank.

I heard from the Forum that MidNite was working on a module for battery monitoring. I guess my question would be how does one manage the power from the solar array so that the batteries get the requisite charge each day? Bill mentioned in one of his posts that the power from the array during the day goes to the batteries and the loads. How this can be managed is probably beyond my understanding, and maybe i cannot be done as we know it; however, I would think that the current from the CC will take the path of least resistance and this would be to the loads as it is more difficult to push the charge into the batteries then it is to use it up as a load. Having stated all this, I surmise that having a "smart" CC hooked into a Battery Monitoring tool would allow the CC to increase the amount of charge current (up to the amount coming in of course) to try and top up the battery bank - conversely, decrease the charge current if applicable.

Was searching the internet for info on battery monitoring, temp-etc, and came across articles that mentioned the best way to measure the SOC is with an amp meter, second is individual battery voltage. Marine industry has some very nice units to choose from, only problem is that the cost can be high because of that big "M" (for marine) at the beginning of the units. I often found similar products and less expensive at RV shops. These products would be a stand-alone installation, but could give you some good information I think.

Here is a web site with lots to choose from:
http://www.nauticexpo.com/boat-manufacturer/battery-monitor-17432.html

Found a web site that has does a DIY Solar Battery Monitor. Don't think I have the want to make one but it would be easy to connect a ready-made into the system.
http://www.virtualsecrets.com/build-solar-battery-bank-monitor.html

Here is a web site about marine battery monitors, good explanation with pictures - especially the hook-up:
http://forums.sbo.sailboatowners.com/showthread.php?t=125606&styleid=1

Had an analog system on our last boat that measured the 4-house batteries, 2 engine starting and one for the genet. Used this in parallel with the Trimetric.

I like some marine products because they are generally waterproof, and made for a harsher environment.

Cheers

Ernest

DKMA · May 2013

Re: getting ready to pull the trigger. What do you think?

Hi folks,

Back working on my little off grid solar backup project again. Wife distracted me with her To-Do list (kitchen remodel). I have received my 3 - 210 W panels, and MC4 cables, and my combiner box. I am waiting on my Morningstar MMPT controller to come in. (ordered online).
I have yet another newbie question. I have been working on my mounting HW for the panels to go up on the roof and was going to put them on this week and run the cabling to the combiner box, then the heavier 10AWG wire from the box to where my controller, inverter, and bat bank will reside. Then I got to thinking if it would hurt my panels to be on the roof, in the sun, and not connected to a CC? Is there any harm in this? With the wife making me serve my time on her projects (kitchen remodel), It may take me a week or two to get the CC in, The Battery bank set up and all of it hooked up.

Thanks again. Still learning …..

DKMA

Cariboocoot · May 2013

Re: getting ready to pull the trigger. What do you think?

DKMA wrote: »

Then I got to thinking if it would hurt my panels to be on the roof, in the sun, and not connected to a CC? Is there any harm in this?

Nope; won't hurt a thing. No circuit = no current.

BB. · May 2013

Re: getting ready to pull the trigger. What do you think?

Unconnected solar PV panels in the sun is no problem... Just keep the unconnected connectors out of the weather (clean and dry).

By the way, did not get a Male/Female MC4 cable so you can cut it in 1/2 and connect to the +/- open ends of your array? You don't want to cut the connectors off the panels and just two connectors is not worth buying the tools to make the proper crimps.

8 Foot MC4 Extender Cable Male/Female
Disconnect Tool for MC4 Connectors (set of 2)

Technically, you don't need a combiner box at the moment with one series string unless you are planning on having 3 or more parallel strings later. Although, a combiner box with breakers in nice if you want to turn off the array while working on the controller.

And don't make/break the MC4 connectors under load. DC Current is really good at being an arc welder and those connectors do not tolerate hot plugging under load (current flow) well.

-Bill

DKMA · May 2013

Re: getting ready to pull the trigger. What do you think?

Thanks BB and Cariboocoot,

I purchased 3- 30ft MC4 cables and cut them in half for 15ft lengths. Plan is to put these 3 panels on the upper portion of my roof (~12 feet up) and run the longer MC4 cables down to the porch (under the roof and out of the weather) to meet my home made combiner box.

Combiner box – I purchased a water tight box from Home Depot, a 6 connection fuse panel from Advanced Auto, and a buss bar. I mounted the fuse panel in the box and installed 3- 15A fuses. Plan to run the Hot leg from the panels to a fuse and then out of the box with 10 AWG. Plan to run the Negative panel cables to the buss bar and then out of the box. This little fuse box has 6 separate fuse slots so I figure I can use it to expand to one more string of 3 panels down the road some time. I know I will have to upgrade down the road but figured this would give me a 15A fuse protection for each panel and it was cheap. Built the entire little box for around $22.
If I did my homework correctly (probably not) then I should be able to add one more string of 3 panels and not have to redo the combiner box or upgrade the wiring. I think 10 AWG will handle the added panels.

What do you think?

DKMA · May 2013

Re: getting ready to pull the trigger. What do you think?

Forgot one more thing. I found a battery disconnect switch at Advanced Auto also. I was planning on using this between my combiner box and the CC so that I could break the circuit if I need to. Think this will work?

BB. · May 2013

Re: getting ready to pull the trigger. What do you think?

slow down a moment...

What is the battery bank voltage? Originally, you were looking at 24 volts... One panel did not have high enough voltage (ideally, Vmp-array should be around 35-38 volts minimum for a 24 volt battery bank).

So, the reason you got a TS XX amp MPPT charge controller was so you could put three panels with Vmp~30 volts in a single series string to properly recharge your battery bank (two-three panels in series with Vmp~30 volt panels should work well).

-Bill

Cariboocoot · May 2013

Re: getting ready to pull the trigger. What do you think?

DKMA wrote: »

Forgot one more thing. I found a battery disconnect switch at Advanced Auto also. I was planning on using this between my combiner box and the CC so that I could break the circuit if I need to. Think this will work?

As to the switch, what is it rated for? It's got to be able to handle the expected maximum Voltage and current DC.

DKMA · May 2013

Re: getting ready to pull the trigger. What do you think?

Yep 24V system is my design choice based on info I read on the forum

OK OK sorry.. I left out a few updates along the way. My original panel purchase fell through and I ended up purchasing 3 Sanyo 210 W panels. (Vmp = 41.3, Imp = 5.09). spec sheet says fuse rating = 15 Amps.

So.. My math. These 3 panels in parallel V=41.3ish and I = 15.3ish. With this setup I figured the little combiner box with the 15A fuses would work. (from the panel spec sheet “fuse rating = 15).

My thoughts were that if I later purchased 3 more of these panels and ran a second parallel sting like above, then combined them in series to the CC I would end up with
V=82ish I = 15.3ish.

Am I confused? I get that way easily. I ordered the Morningstar 60 amp MPPT controller. Spec says it can handle up to 150V. Please tell me I did not order the wrong CC……
All this still going to 4 T-105 6V batteries.

Cant remember what the battery disconec switch said but it is BIG. I will look at it when I get home tonight.

as always thanks for all the help!

Cariboocoot · May 2013

Re: getting ready to pull the trigger. What do you think?

You're only a little confused. We all are.

Nomenclature: each panel in parallel would be a "string" even if it's a "string of one" So you have 3 strings already, and yes each one on a 15 Amp breaker because they are in parallel. With a six breaker combiner box you can add three more later.

210 Watt panels on a 24 Volt system: 630 Watts / 24 = 26 Amps (short math). Add three more and you should have about 40 Amos peak (long math). So a 60 Amp controller should handle it. Just be sure the wire from combiner to controller and controller to batteries is sized for the big number now rather than having to change it later.

If you had an even number of panels now you could make a 2 x 2 array and use no fuses, but you'd have to add them later if you add panels and the higher Vmp would decrease the controller's efficiency.

Oh and just because the switch is big doesn't mean it will handle the 50-ish Volts from the panels. It is probably meant for high current @ 12 VDC.

DKMA · May 2013

Re: getting ready to pull the trigger. What do you think?

Thanks again Cariboocoot. One more question while I have your attention.
You said:
“Just be sure the wire from combiner to controller and controller to batteries is sized for the big number now rather than having to change it later.”I thought (I know that is dangerous), that the current from the combiner box to the CC would be at 15.3 A.

So I was planning on using 10 AWG wire from the box to the CC. and then from the CC to the Battery bank using heavier gage wire that could handle the larger current that my MPPT CC would produce as otput to my BB.

Is this correct or do I need to use a hevier gage wire from the box to the CC as well. I am looking at a distance of around 52 feet from the combiner box to the CC.

thanks

Cariboocoot · May 2013

Re: getting ready to pull the trigger. What do you think?

DKMA wrote: »

Thanks again Cariboocoot. One more question while I have your attention.
You said:
“Just be sure the wire from combiner to controller and controller to batteries is sized for the big number now rather than having to change it later.”I thought (I know that is dangerous), that the current from the combiner box to the CC would be at 15.3 A.

Right now with 3 panels it will be. Add three more panels in parallel to the box and it will be 30+ Amps.

If you add a panel in series with each of the first three then the current will remain the same but the Voltage will go up. This presents no wiring difficulty, but will decrease the controller's efficiency slightly.

So I was planning on using 10 AWG wire from the box to the CC. and then from the CC to the Battery bank using heavier gauge wire that could handle the larger current that my MPPT CC would produce as output to my BB.

10 AWG would work either way as it can handle 30 Amps continuous. Just check it for Voltage drop over the distance @ Voltage and current.

Rough estimation: 40 Volts, 30 Amps, 10 AWG good for about 20 feet with minimal V-drop.

getting ready to pull the trigger. What do you think?

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