Critique my System. Help wanted!

ayurtdweller · August 2014

Long time lurker, first post.Thanks for the great forum!
I thought I had it all figured out, but real experience is teaching me otherwise.

I would like some suggestions to help keep my batteries from going to the scrap yard prematurely. They are 1 year old now.
Measured by Kill A Watt, my usage is 800 watt hours/day.

Here's my system:
2 x 250 watt mono Vmpp 31.1, Impp 8.05a. Wired series. http://www.altestore.com/store/Solar...0-Frame/p9879/
6 Trojan T105re @ 12v, 675 ah
TRACER 3215RN mppt Controller 30A 12V 24V
* Maximum Battery Voltage: 32V
* Max. Solar Input Voltage: 150VDC
* Max. PV input power: 12V/ 390W 24V /780W http://www.amazon.com/TRACER-3215RN-.../dp/B008KWPGAE

I am having difficulty keeping the batteries above 12.3 by the AM. I feel this is too deep and I am wondering if they are truly getting a good charge during the day. They seem to drop down to 12.5 right after sun down with an 80 watt load on them for 15- 20 minutes. Is this normal or OK?

I face South, 190* and the panels are unshaded 100% for about 5-6 hours/ day this time of year.

Area Code 03601. Acworth, NH

Batteries routinely get up to 14.2 , but I can't seem to obtain 14.6 for very long.

I believe my controller can handle another panel but I don't want to throw more PV at it unless it will help.
This controller has never run an equalize charge as far as I know. I am not even sure how it decides when to run equalize. I have not tested with hydrometer.
I currently have no other means of charging.

Whaddyathink?
More PV? More Battery? Better Controller?
Thanks for suggestions and questions.
Attachment not found.

mryimmers · August 2014

Re: Critique my System. Help wanted!

Looks like your system is similar to mine. But I only have 4 x 105re batteries. I think you don't have enough PV to keep that bank charged up, do you use your system every day?
Mine is already at a the low end of the preferred 6-13% rate of charge, but my system is pretty lightly used, so it stays charged up pretty easily. I'm also sure you will be cautioned on using 3 parallel strings of batteries and the problems that can cause. I have never heard of that charge controller, but maybe someone on here has some insight.
You came to the right place, there is a lot of knowledge and help here, good luck!!!!! PS cool cabin, I like it!! PPS, get a hydrometer

Cariboocoot · August 2014

Re: Critique my System. Help wanted!

Welcome to the forum, yurt system #6.

Well 800 Watt hours per day on 12 Volts is roughly 78 Amps hours. So the battery bank would probably be around 314 Amp hours for 25% DOD.

You've got 675. And on three parallel strings. But the real problem is you've only got 500 Watts of panel. And to make it worse a 30 Amp charge controller. The panel is capable of 32 Amps and the battery bank wants 67.

Right now, separate those three strings. Check the SG on each and every cell and try to match up pairs. Put the best one in place and know that it will be drawn down more than 25% to supply that 800 Watt hours.

You might get along fine on 225 Amp hours: it would be about 35% DOD daily. Somewhat shorter life than at 25% but not unreasonable.

Trouble is, you've got more batteries which will sit around and die from lack of use & charging. Easiest solution is to go up to 24 Volts and add more PV, making use of four of the six batteries. If you must stay at 12 Volts and need all those batteries ... you will need a much bigger charge controller (80 Amp MPPT) and a lot more PV (1050 Watts total).

ayurtdweller · August 2014

Re: Critique my System. Help wanted!

Thanks for the input.
Is there any feelings that the batteries might be sulfated? They have never been lower than 12.3, and are almost always at 12.7 after sundown before a load is put on them.

So if I get this straight, if I use a 24v 225ah bank, then my 30a controller will be sure to supply enough to charge at the recommended 10% rate? And I would need more pv? Been thinking about adding one more.

I don't need to stick with 12v. That's what I went with because I could only afford 2 t105 at the time. Added 4 more after 3 months.
I suppose I could eBay the 12v inverter. And maybe I could find a buyer for the 2 t105s.
Any recommendations on 24v Inverters? I prefer one with a "smart" fan that I don't have to listen to 24/7.

Another recommendation I received from a pv dealer was to add another 500 watts pv and another 30a controller on my current bank. Is this a decent option?
Thanks for walking me through this.

Photowhit · August 2014

Re: Critique my System. Help wanted!

ayurtdweller wrote: »

Whaddyathink?
More PV? More Battery? Better Controller?

Buy a hydrometer, use a hydrometer, get some real idea of where your batteries are at...

Once you have a hydrometer, you can measure the Specific gravity (SG) of the cells and figure out the needs of the battery bank, you may need to equalize, you may have some batteries that are toast. you could find that the bank is in pretty good shape. You need this information before you make choices in changing your system.

Then pretty much follow 'Coot's advice, if you have 4 batteries that have lived with this charge regime and are still in good shape, you might consider doing 2x2 12 volt battery bank with the array you have now, but you will be below Trojan's minimum charge rate and charging at a minimal rate generally. If you find all 6 are in good shape, I personally would add 2 more panels now and plan on switching to a 24volt system when the batteries fail, hope fully in 4-5 years.

Grinnin · August 2014

Re: Critique my System. Help wanted!

I also had too much battery for my array. My loads are small enough that I could keep the batteries at higher voltaves than you see, but they did eventually succumb to underuse after 8 or so years.

You said you didn't want to "don't want to throw more PV at it unless it will help". It will help.

The other way to help is cutting the size of your battery bank. A hydrometer can help.

I started here with 4 L16HC (high capacity) batteries for about 780Ah at 12V. For years I used only the top 10% of these with occasional dark weeks going down toward 50%. I probably used half the batteries 6 or 8 times in 8+ years. But the fastest charge rate was C/30, or only a third of what it should be. Even with these abuses, the batteries worked fine for years.

I am much happier with the 2 J305 battries (about 300Ah) that I've had the past 5 or 6 years. I use far more of the batteries, getting to 50% dod far more often. On the other hand I can charge at C/11 now, pretty close to the recommended C/10. The smaller battery bank also cost far less and I'm more comfortable knowing that they're not permanent.

Skyko · August 2014

Re: Critique my System. Help wanted!

I have started thinking about batteries as consumables. Going with two instead of four and pushing them a little harder, you will still be ahead even if you only get 3 years out of them instead of 5 because you only have to buy two batteries at a time.

Based on this I am not against pushing my Lifeline AGM to 50% and occasionally 60% DoD.

Cariboocoot · August 2014

Re: Critique my System. Help wanted!

Deep cycle batteries should be cycled. Otherwise they are a waste of money. If you look at the 78 Amp hours 'used' as a percentage of the 675 Amp hours total you see the DOD is only 11.5% - about half what is normally used for economic value (25%).

You can not add batteries without adding charging capacity.

Your 30 Amp controller is maxed out on 500 Watts of panel with a 12 Volt system.

Adding an additional controller & PV is one way, but in reality you don't need all that battery capacity to begin with. Plus it is better to avoid multiple charge controllers if possible.

The most efficient thing to do would be to go up to 24 Volts using the existing controller and adding PV (about 185 Watts) if you can find matching panels.

It all hinges on finding out first if you've still got any good batteries, and that means getting the hydrometer and using it.

ayurtdweller · August 2014

Re: Critique my System. Help wanted!

Cariboocoot wrote: »

The most efficient thing to do would be to go up to 24 Volts using the existing controller and adding PV (about 185 Watts) if you can find matching panels.

It all hinges on finding out first if you've still got any good batteries, and that means getting the hydrometer and using it.

hydrometer is on the way.....

I now plan to go up to 24 and add panels. Are you meaning 2 x185, or 185 ÷ 2?

Cariboocoot · August 2014

Re: Critique my System. Help wanted!

ayurtdweller wrote: »

hydrometer is on the way.....

I now plan to go up to 24 and add panels. Are you meaning 2 x185, or 185 ÷ 2?

185 Watts total.
You'd have 220 Amp hours @ 24 Volts.
You'd want 22 Amps peak charging current @ 24 Volts, that's 528 Watts.
Under average output conditions panels are 77% efficient so 528 / 0.77 = 685 Watts approximately.
You've got 500 so the difference is 185 Watts.
Of course this needs to be adjusted to suit the panels available, and that's where it gets tricky.

Right now you've got two 250 Watt panels with a Vmp around 30. As-is they'd be in series to have enough Vmp to charge a 24 Volt system; 30 will not do. That means the next panels you add have to have the same Vmp as that string: 60.
So you would not be adding one 185 Watt panel but rather two panels that will give you at least 185 Watts more. Given the necessary Vmp you will more likely go up by 400 Watts. It all depends on what you can find in panels.

ayurtdweller · August 2014

Re: Critique my System. Help wanted!

Cariboocoot wrote: »

185 Watts total.

Right now you've got two 250 Watt panels with a Vmp around 30. As-is they'd be in series to have enough Vmp to charge a 24 Volt system; 30 will not do. That means the next panels you add have to have the same Vmp as that string: 60.
So you would not be adding one 185 Watt panel but rather two panels that will give you at least 185 Watts more. Given the necessary Vmp you will more likely go up by 400 Watts. It all depends on what you can find in panels.

Thanks so much for the help!

I can get 2 more of the same panels. Around a dollar a watt and only an hour drive for pickup. From the same warehouse I can also get midnite kid controller. http:// http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Midnite-Solar-Charge-Controllers/Midnite-Solar-The-KID-30A-MPPT-Charge-Controller-150V-Black/p11138/ to charge 24 volt 225 ah bank. Is this a reasonable solution?
Yall rock!

westbranch · August 2014

Re: Critique my System. Help wanted!

If you are even remotely thinking you might expand the system in the future, get some extra panels now and store them... finding 'matching ' panels can be a real pain...

ayurtdweller · September 2014

Re: Critique my System. Help wanted!

Update:

I pulled 2 strings offline last week. They have been sitting at about 12.4 since. Still have one string online. Here are my hydro readings:
For the 12 cells that are offline, 1.23 give or take a smidge on each cell.
For the 6 that are in use- 1.22 give or take a smidge. These batteries were under charge when the reading was taken. These are also the first batteries purchased and put into use. The next two strings were added 3 months later.
Ideas?

Cariboocoot · September 2014

Re: Critique my System. Help wanted!

Sounds like a bunch of nearly dead batteries.
It also sounds like the ones still connected aren't getting enough charging. This is where you need to check the Absorb Voltage and time, as well as contemplate running a corrective equalization charge. They are not completely dead so it may be possible to revive them somewhat.

ayurtdweller · September 2014

Re: Critique my System. Help wanted!

Cariboocoot wrote: »

Sounds like a bunch of nearly dead batteries.
It also sounds like the ones still connected aren't getting enough charging. This is where you need to check the Absorb Voltage and time, as well as contemplate running a corrective equalization charge. They are not completely dead so it may be possible to revive them somewhat.

Please pardon me as I am new to this. I am hoping you could explain what clues you in to the batteries being nearly dead.
From what I understand, the reading just means that the batteries are discharged a bit. (75-80%SOC?) They were not topped off when I disconnected them. The 2 offline are at 12.4 OV and 1.23 SG now.

As far as Absorb voltage, the specs on the controller are ...
"boost" 14.4 for 120 minutes.
float 13.8
equalize 14.6 for 120 minutes

Thanks for the wizzzdom.

westbranch · September 2014

Re: Critique my System. Help wanted!

Dweller. please add your equipment make, model, etc as a signature line so a search of the entire thread is possible so as to answer your questions.
thanks...

Cariboocoot · September 2014

Re: Critique my System. Help wanted!

We're looking at resting Voltages here: for a 12 Volt system that should be up around 12.75, not down around 12.4. For batteries in use brought up to over 14 Volts for long enough it certainly should be able to maintain higher than that providing the loads aren't too severe.

An SG reading of 1.220-1.230 is far below the 1.265 of a fully charged battery. This indicates they've not been getting fully charged, and if this has been going on for some time sulphation has likely already set in.

14.4 "boost" (Absorb) Voltage is actually minimal for FLA's. Trojan specs 14.8 Volts. Likewise the Absorb time of 120 Minutes is pretty minimal even for a single set @ 225 Amp hours. EQ Voltage would be 15 or even a bit more.

I don't know how adjustable that charge controller is, but it needs some adjusting.

ayurtdweller · September 2014

Re: Critique my System. Help wanted!

Thanks all for your input. I guess I need a real controller.
Before my next purchases I will confer with yall.
My usage is +-800 watt hours a day, most likely more in the future.
I am thinking that I need to start over with my system, minus the pv's. And I guess I can run with the batteries as long as they will hold out.
My new plan, with your guidance, is to add another 500 watts pv (for a total of 1k) with similar characteristic panels. Outback Flexmax 60 or similar MPPT, and run a 24v 225ah battery bank. Of course I will need a 24v inverter also.
Please advise.
Thanks from New Hampshire!

Cariboocoot · September 2014

Re: Critique my System. Help wanted!

800 Watt hours a day is fairly easy to achieve:

800 / 0.85 (conversion losses) = 941 Watt hours. Inverter consumption needs to be added in, and that will depend on the inverter involved and how it is used. Otherwise to continue:

941 Watt hours DC / 24 Volt system = 39 Amp hours used. At 25% DOD that's (39 * 4) 156 Amp hours. This is easily supplied by four common golf cart batteries @ 220 Amp hours. In fact you can get over 1 kW hour from them without difficulty. If you need more than that you size accordingly. Note there is some flexibility in capacity according to when the power is used as some can be had 'directly' from panels when the batteries aren't demanding full output. This is where we make use of opportunity loads, and how I get away with murder on my system.

Once you have the battery bank sized for the expected Watt hours you construct the array to recharge them. Example: 220 Amp hours @ 24 Volts wants 22 Amps peak charge current * 24 / 0.77 (typical panel derating) = 686 Watts minimum. Again it's a good idea to round up to the nearest available panel size.

There is some room for 'fudging' such as being able to vary loads as needed or count on PV output or go for higher PV output. Numbers don't have to be exact to work, but it works better if you err on the side of caution:
1). Expect loads to be more than anticipated and round up.
2). Don't really on even 50% battery capacity: round up to the nearest available size that will cover usage at 25% DOD. Battery capacity goes down over time.
3). Likewise try for PV that will provide minimally 10% peak charge current at system nominal. Again round up. If there are circumstances in your location that warrant it, round way up. Go for higher than 10% current if need be. Anything that interferes with PV output such as high temps or atmospheric blocking from fog, clouds, et cetera needs to be taken into account.

westbranch · September 2014

Re: Critique my System. Help wanted!

concur with 'Coots comments... just today did a quick , back of the brain assessment of our 'temp maintenance setup' as we are in the construction phase, and electrician is about done with the wiring and circuit breakers. Just the basement to do... ps I hate extension cords so I am over Code for # of outlets, less than 6 feet between plugs...

We currently have 280W and on a good day should be able to cover all the evening lights with 4 hrs of good sun, so ~ 800 realistic Watts of input... so I will be able to do some evening work and ? and a bit of internet without the gen running. Also we can take advantage of opportunity loading once Absorb is reached...
Adding another 500W will give you lots of head room...

ayurtdweller · September 2014

Re: Critique my System. Help wanted!

Will a Midnite-Solar-The-KID controller handle this? 1kw pv, 4 panels in series. (30.x volt & 8.5 amp). Put on a 24 volt 225 ah battery bank?
Thanks.

westbranch · September 2014

Re: Critique my System. Help wanted!

you will need to use the Kid array sizer found here: http://www.midnitesolar.com/sizingTool_kid/index.php

there are a few more numbers you will need to fill in the chart, I guessed and it shows me you need >1.2 kids and pushing the limits of the Kid... Also said that 3 of those panels is max. You can go over but are limited to 30A max output, 150V input, and you will not be able to use a lot of the PV output...

enjoy.

Photowhit · September 2014

Re: Critique my System. Help wanted!

ayurtdweller wrote: »

Will a Midnite-Solar-The-KID controller handle this? 1kw pv, 4 panels in series. (30.x volt & 8.5 amp). Put on a 24 volt 225 ah battery bank?

While this would be over paneled, I think it would be fine and give you a bit higher current on cloudy over cast days. The array could produce about 40 amps on perfect days, but if you can find the NOCT (Normal Operating Cell Temperature) ratings for your panels, you will find that panels typically produce 75-80% of their name plat wattage.

ayurtdweller · September 2014

Re: Critique my System. Help wanted!

Thanks gurus.
Installed Classic 150.....what a difference!
Still running 12v while I search for a decent 24v inverter / charger in my price range. (used?)
Batteries aren't holding up too well, but they get me through the night. I have to unplug the fridge and then fire up the genny in the AM for the first cooling of the day.
Got an offer for trading firewood for pv, we'll see if the guy comes through. My fingers are crossed...

Photowhit · September 2014

Re: Critique my System. Help wanted!

ayurtdweller wrote: »

decent 24v inverter / charger in my price range. (used?)

If your looking used, might check eBay for the ExelTechs in a 24 volt version, At least one person here has been using an XP1100 to run some pretty heavy loads, I have one but use it for my garden odds and ends, but have used with a heavy string trimmer. I say that since reportedly they will rebuild their inverters for $100, From NAWS web site;

"...We also still support and repair units from 20 years ago, and do so for a flat fee. Case in point: If you accidentally reverse connections on an XP1100 inverter you bought in 1994, or an MX module from 1993 .. or even an old SI1000 from 1991, and blow it up .. if it's repairable, we'll fix it for $100 and (if possible) upgrade it at the same time. Turn-around time generally averages less than a week."

So this would limit the risk.

I've had good luck with the Prosine 1800 watt version in 24 volt. Though they tend to run $6-800 in used units sometimes you can pick them up cheaper. They have a military version called an Iris Quiet Power inverter that can often be found cheaper, retired military... You might be rolling the dice with a sandy unit on it's last legs here though, and much less repairable...

ayurtdweller · September 2014

Re: Critique my System. Help wanted!

I had an offer from an installer.....he has a few Xantrex 2424's that he has pulled off for upgrades. He says that if they light up, he'll sell for $500. I am unsure if it would be fool hearty of me to pick one up if there is so much unknown.
Are these units robust? What is the expected life span? Are they repairable or serviceable if something goes awry?

Photowhit · September 2014

Re: Critique my System. Help wanted!

He's either talking about the DR2424 (made until about 2005)or the TR2424 recently discontinued according to NAWS. It doesn't look like Schnieder is going to be very supportive of the older lines of inverter.

These are Modified Sine Wave inverters, very good ones, but modified sine wave... I personally would either stay away from them or see if he wants to sell one very cheap ($250 - or so max) Don't know the life span, but I recall the DR having a pretty good rep... Retail was around $1000, I think Backwoods had new Tr2424's in their bargain bin for around $600 and it took a while for them to sell out... though it might have been DR's can't recall.

They had built in chargers so if you needed to charge your batteries through the inverter via grid or generator, that would be handy.

I ran for a good while on MSW inverters, but once I went to a larger inverter I went with a pure sine wave. Unlike others I didn't have huge problems with MSW. Some people get buzing from CFL lights some claim flicker, but I never had those problems. I ran a fan, but through a wall wart. The one thing I did find was my LED lights on my power strips seemed to burn out/be killed by them. I am talking very cheap inverters. Motors will prefer a pure sine wave.

ayurtdweller · January 2015

Re: Critique my System. Help wanted!

So I picked up a Midnite Classic 150 and dropped down to 4 t105 at 24 volts. They are running rough but still chugging along. Still running the 2 x 250 solar world monos. http://www.altestore.com/store/Solar-Panels/SolarWorld-250W-Solar-Panel-Sunmodule-SW250-Mono-V20-Frame/p9879/

I am looking to add some wattage to charge batteries at c10. I have my eye on these http://www.altestore.com/store/Solar-Panels/SolarWorld-315-Watt-Solar-Panel-Sunmodule-SW315-Mono/p11463/ even though there are some size differences, even physically.

What are your thoughts on that?

Thanks....and let's welcome back the sun to the Northern Climes......more and more every day!

Photowhit · January 2015

Re: Critique my System. Help wanted!

ayurtdweller wrote: »

What are your thoughts on that?

To work well with your existing panels and charge controller, you should look for panels that match your current panels VMP of @31 volts, and connecting the 2 in series like your current panels(assumed?) Otherwise you will waste the difference.

ayurtdweller · January 2015

Re: Critique my System. Help wanted!

Photowhit wrote: »

To work well with your existing panels and charge controller, you should look for panels that match your current panels VMP of @31 volts, and connecting the 2 in series like your current panels(assumed?) Otherwise you will waste the difference.

What about putting one of each on two separate strings? Series /parallel.

BB. · January 2015

Re: Critique my System. Help wanted!

For Solar World 315 watt panels (if I have the right ones--you should double check):

Rated power
P_r
SW315

Peak power
P_mpp
315W

Peak power voltage
V_mpp
36.8V

Peak power current
I_mpp
8.63A

0pen circuit voltage
V_oc
45.9V

Short circuit current
I_sc
9.16A

Max Series Fuse*

15A

And for the 250 Watt Solar World panels:

Vmp=31.1 Volts
Imp=8.28 Amps

So, yes, putting one 315 watt panel in series with one 250 Watt panel should work OK. The Imp is within 10% of the ratings.

-Bill

Critique my System. Help wanted!

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