System Upgrade - Right path to go from marginal junk to stable system?

Mark_Kaohe

I am in need of some constructive criticism, I've been lurking here for a long time wanting to learn as much as I can before asking questions, but at the end there are a lot of complementary and competing design concepts to consider when making these decisions. I'm hoping those who have been living offgrid longer are willing to donate some of their time towards some critique and suggestions. If you want to post asking why I'm not running a chest fridge, please include what you would be doing instead (for example, which expensive DC chest fridge and expensive chest freezer?, or which cheap AC freezer, inverter and thermostat you would be buying instead? LG inverter fridge/freezer maybe!) Even though this huge wall of text is about what has happened so far and where it might be going, I might need some bad ideas in my head questioned to help keep the solution more affordable/efficient, and I will try to keep an open mind to wildly different approaches. For example, we could buy a couple nice coolers and buy ice blocks every week, that's an alternate solution I'm trying to avoid, but it's very workable is the truth.

In February 2016, my family moved to an offgrid farm near Pahoa, HI (we get a little bit less sun than Pahoa). The major issue we are having with the system is that the inverter shuts off when the fridge starts up, even though the classic believes the batteries should be 75-80% full. It's generally pulling 70-80AMP from the battery for around 10 seconds. I know that just improving the inverter wiring would probably help some--but I'm also trying to get breakers installed where they should be, grounding the system, etc. I've seen 12v at the battery and 11.5v at the inverter before so I believe rewiring the inverter is necessary. I also suspect that the 4 L16 batteries don't enjoy being hit with this much amp draw and it is causing some voltage drop at batteries.

When we started living at the farm, I bought a 20CU FT AC fridge/freezer energystar rated at 436KWH/yr, 4x 285w Suniva PV modules (in one string), 4 L16 deka batteries (8L16 model), and a Classic 200 (this was a mistake, should have been a 150). The batteries were wired at 12v because we had an old xantrex inverter on hand bought about 12yrs prior to run a swamp cooler at burningman (this had a 150amp DC breaker when installed but the breaker was broken/sheared bolt while moving the system months later and now lacks a breaker. Inverter surges to 3000w according to specs). When the solar electric system wasn't enough all the loads were moved to an eu2000 until the sun charged the batteries again. A shunt and whizbangjr were added shortly after.

This was meant to be a very temporary system, but as soon as it was functioning, all budgeting and priority shifted away from it and towards other major infrastructure projects. In fact, I was demonized for the less than $3000 I had spent on panels, batteries, charge controller, while I explained it was doing the work that neighbors were paying $10-20k to achieve (and explaining we need many of those same upgrades still). I quickly gave up on trying to budget the rest of the system components as it seemed like ruining the batteries and running on a terrible system was the only thing that was going to back up my opinion in the matter (I tried writing this post many times and gave up in shame many times). Further, I had done such a bad job of installing the system (plastic boxes sitting out in the weather with poor ventilation), it really couldn't be fixed up very well without giving it a better install location, and a better install location wasn't even being prioritized against other construction work.

Most of a year later, there had been no upgrades and I was spending most of my time off the property. My wife got some help to build a roof off the end of a storage container and put the components on the container wall under the roof. They did a good job of moving and reconnecting the components (other than destroying the inverter breaker), but none of the wiring was improved at that time, it's still a patchwork of wires that are too long and non-ideal (for example there is some aluminum wire in the inverter wiring, and they are too long for the wire gauge and 12v). I knew my wife was running the generator a lot during winter, and at least there was a place to install a 12v charger now, so I bought an iota 55amp charger from NAWS and installed it while visiting for a weekend, it was a huge improvement to be able to charge the batteries in a few hours.

Loads? It's all about the loads, I know. Is there a good way to get a summary of the loads we've been using for the last year from the classic since it is hooked up to a shunt? Is the classic local app the best way to pull that data? It seems like the historical data is not very detailed last time I had tried to look months ago.

AC Loads:
 - Fridge (436KWH/yr). The fridge is under a roof outside, it probably uses extra power since it's exposed to warm breezes and gets opened a lot sometimes.
 - Laptop charging is highly variable from day to day--goes from 0 laptops to 3 laptops and one of them is a gaming laptop that definitely uses more power.
 - Around 12 10w LED light bulbs
 - Multiple phones, a tablet, speakers
 - Coffee grinder
 - 3amp Oven heating element (not used very often, runs when oven propane gas turns on instead of a pilot light--another misstep, we'd prefer the pilot light) Generator gets turned on sometimes for oven.
 - Fans are not used very often, own around 3 vornado small/medium room size, sometimes they do get used when the sun is out.  
 - Probably some stuff I forgot.
There are no DC loads, the batteries are not very close to the current living areas and the inverter always runs for the fridge.

Water heater is propane and uses no system electricity. The water pump is on its' own battery and 100w panel/pwm controller. The oven is propane other than the heating element and clock.

I am trying to plan what is going to be bought to replace the current mess. I'm curious about Magnum RD1824 or MM1524AE, or even a Samlex Inverter/Charger or Samlex Inverter+Iota24v (I don't know the Samlex models). Most things have been working so far on modified sine. I am leaning towards Outback GFX1424+mate2 since it's pure sine wave, has sealed chassis, and 5yr warranty, just may take a couple months before I can order it. I'm guessing the Samlex+Iota costs quite a bit less, but I think a transfer switch would be nice.

I'm also trying to figure out electric boxes for inverter DC disconnect, charge controller battery breaker, pv combiner, and other things I'm forgetting. Right now I'm leaning towards MNDC125PLUS, I think it will hold everything I need but I haven't really figured out where each item would be installed if I went with that approach. Should I be considering an ePanel instead? Are a couple breakers all that's needed for combining a couple PV strings or does the MNPV6 box do more (it has a metal plate circuit combiner too right?).

I've put a grounding rod/clamp/wire in my shopping list, and have done some research on installing it.

When the system has stablized and is running at 24v, I hope to add 2-4 panels, or move the existing 4 panels to a different site and buy 2KW of new panels. Getting a stronger charge on cloudy days would make a huge difference by keeping battery SoC higher, which would mean less inverter shutdowns. I understand it's possible to add more panel and stay at 12v, but we would need PV combiner setup, and sunny days would produce no more than they currently do (limited 80amp charge controller at 12v).  With 4 panels we typically see around 4.5KW produced on a sunny day I believe, unfortunately I don't have the numbers in front of me right now.

Mark_Kaohe

Current System
Have	Need	Part Number	Part Name	Details
4	2		Suniva 285w PV Module	Currently 1 string with 4 panels, no combiners or breakers, directly connected to Classic 200
1	0	CLASSIC 200	Classic 200 Charge Controller	Solar Charge Controller (should be a Classic 150, not using any long PV wire runs). Includes Ground Fault Protection.
1	0	Outback Shunt	Shunt	Charge controller battery monitoring
1	0	MNWBJR	WhizbangJr	Charge controller battery monitoring
1	-1		Xantrex Xpower 1750 Inverter	MSW Inverter, 12V DC to 120V AC. To be removed when rewiring to 24v.	-$150.00
4	0		Deka 8L16	Two 12v strings currently--one string doesn't use any distilled water. To be rewired to 24v.
1	-1		Iota 12V 55A Battery Charger	To be removed when rewiring to 24v	-$200.00
1	0		Junk Aluminum Inverter Cable	Way too long, around 8ft, maybe 2# wire? I have seen 12.0v at charge controller and 11.5v at inverter. Wiring is definitely a problem.
1	0	EU2000i	Honda eu2000i	This generator ran for many hours last winter, we didn't even have the iota charger yet so it was running 24/7 until the sun charged the batteries up.
Planned Additions
0	1	GFX1424	Outback GFX1424 Sealed	PSW Inverter-24V DC to 120V AC, Battery Charger, AC Transfer Relay.	$1,000.00
0	1		Outback Mate1/2	Inverter User Interface (not just a remote monitoring panel)	$240.00
0	1	Buy at Ace/HD	Earth Ground Rod	8' or 2x4' rods, 3/4 diameter if possible for stronger driving, ground wire, clamps	$50.00
0	1	MNDC125PLUS	DC Disconnect/Enclosure	Inverter to Battery breaker and space for additional needed breakers	$197.00
0	2	MNEPV20	PV Breakers	One breaker per future string of PV. Will change PV to 2 strings with breakers as soon as it is possible. Buying 20A fuses in case we do run 2 strings with 4 panels in each in the future, I think that would trip a 15A fuse.	$23.00
0	1		4' Cobra Cable X-Flex 2/0#, Battery + to 125A Breaker	Premade cables? If not, what connectors and crimp tool? My existing crimp tool is probably not big enough for 2/0# and it wouldn't crimp as well either.
0	1		4' Cobra Cable X-Flex 2/0#, Battery - to Shunt
	1		2' Cobra Cable X-Flex 2/0#, 125A Breaker to Inverter +
	1		2' Cobra Cable X-Flex 2/0#, Shunt to Inverter -

Aguarancher

when was the last time you checked your batteries with a hydrometer and what were the readings?

Photowhit

Like Aguarancher, I worry about your batteries, since 1 sting isn't using any electrolyte. You have them, so use them, but you might want to equalize the batteries via the charger before switching to 24 volt (one set at a time, if possible)

In reality, it appears you have a pretty good grasp of the situation. The fridge will run better/cooler on a pure sine wave inverter. I think the sealed unit has a pretty high surge (as I recall from my faulty mind). Read the instructions and use the correct wiring for the inverter. I would guess 2/0 up to 12 feet away from the battery bank. Your current system is likely suffering from voltage drop during the surge/inrush of current.

You can save the breakers and combiner box for the 2 strings of panels, It's up to code to install them with just a 'Y' connector. 3 or more and you will need a combiner box and fuses or breakers.

Run time on lights is important, and 3 laptops with a gaming laptop include sound like kids, known abusers of electric!

I suspect you will still be a bit undersized, but should be able to limit the generator run time a good bit with your suggested improvements.

Mark_Kaohe

Aguarancher said:

when was the last time you checked your batteries with a hydrometer and what were the readings?

Yes, the battery bank. My post creates more questions than it does answers, doesn't it?

It's been most of a year probably, and I don't have those readings. There were some small differences between cells but I didn't see a cell that was wildly out of place. Sorry for the lack of details, the hydrometer readings seemed difficult to read, the gauge didn't seem that great at indicating an exact number, and so I was doubting how good the numbers really were that I should have been writing down. It was a deka brand hydrometer and I wanted to get the midnite one or a digital refractometer for an easier reading at the time--then I didn't follow through with that.

One thing about this battery bank is that I add about a gallon to one string every couple months and the other string doesn't use almost any water. I'm not especially hopeful that everything will suddenly be good when rewired to 24v due to the time that the batteries have been running this way even if they were good when I bought them. The battery bank buy was something I did in haste and was not nearly careful enough about, the batteries were sitting outside at the installer's house, and didn't even have the same voltage readings let alone being checked by a hydrometer when I bought them. The guy I bought them from has a lot of happy customers from what I have heard, but I'm avoiding getting anything else through him at this point. When I asked if he could check them with a hydrometer he suggested just checking the voltages (because he doesn't own one or doesn't want to show the results? obviously the latter), voltages weren't even the same between batteries, I should have walked away and I didn't. Probably a $1300 mistake.

I manually equalize the bank every month or two at the same time I add the distilled water.

EDIT: And I can't go take the reading right now either, I am offsite, and won't have additional data for a couple weeks unfortunately. 

mike95490

Charging via generator, were you using the 12V terminals on the genset, or through the 55A Iota .

Moving to 24V is a GREAT idea. Moving the fridge (motor) to Pure Sine inverter is also Very Good.

Dave Angelini

New 24V 400AH  bank, monthly use of an hydrometer, and as much solar as you can afford for cloudy weather. One in ten chance that you can save that bank form what you have written.
Good Luck!

Estragon

Two things I would do ASAP. One is (ideally) replace the aluminum wire with properly sized copper. If that isn't immediately possible ( have to order wire or whatever), at least check any al/cu connections for corrosion, clean, and retighten. The 1/2v voltage drop suggests something funky with the inverter - battery connection. The other is to get a fuse or breaker on that circuit.

I found my old hydrometer hard to read as well and just got a midnite one. Neither have been calibrated. The old one consistently read low (1.23-1.25) from when the banks were new, but being consistent, and the banks behaving normally in terms of capacity and charging I didn't worry about it too much. The new one reads more normal SGs (1.26-1.28), but mainly I find it much easier to read. I do write them down, as I figure if I'm going to spend the time taking them, I might as well spend the little bit of time it takes to record them, so if I get a specific battery showing consistent problems, I can identify it and deal with it early.

I would be a bit concerned about one string using a lot more water than the other. Charging separately before combining would be a good idea.

Longer term, I agree 24v makes sense, as does a PSW inverter.

Mark_Kaohe

mike95490 said:

Charging via generator, were you using the 12V terminals on the genset, or through the 55A Iota .

Moving to 24V is a GREAT idea. Moving the fridge (motor) to Pure Sine inverter is also Very Good.

We never charged the battery bank with the generator until we got the Iota. Before the Iota, we just moved the loads to the generator and then left the generator running for as long as it took for the sun to charge the batteries.

Thanks for voting on pure sine wave! I think Samlex SA-1500+24v Iota or Outback GFX1424 are the front runners for me right now. I like that you get a few extra years of warranty with Outback if I can get the money together for it. I was just looking at the specs for Samlex SA-1500-124, and was surprised its' DC input range looks high enough to actually EQ my batteries with it on!!! That is exciting!



 

Mark_Kaohe

Dave Angelini said:

New 24V 400AH  bank, monthly use of an hydrometer, and as much solar as you can afford for cloudy weather. One in ten chance that you can save that bank form what you have written.
Good Luck!

Dave, we really appreciate your time and recommendations! It makes a lot of sense that more PV is going to help out with this since it's pretty stable on sunny days.

Mark_Kaohe

Estragon said:

Two things I would do ASAP. One is (ideally) replace the aluminum wire with properly sized copper. If that isn't immediately possible ( have to order wire or whatever), at least check any al/cu connections for corrosion, clean, and retighten. The 1/2v voltage drop suggests something funky with the inverter - battery connection. The other is to get a fuse or breaker on that circuit.

I found my old hydrometer hard to read as well and just got a midnite one. Neither have been calibrated. The old one consistently read low (1.23-1.25) from when the banks were new, but being consistent, and the banks behaving normally in terms of capacity and charging I didn't worry about it too much. The new one reads more normal SGs (1.26-1.28), but mainly I find it much easier to read. I do write them down, as I figure if I'm going to spend the time taking them, I might as well spend the little bit of time it takes to record them, so if I get a specific battery showing consistent problems, I can identify it and deal with it early.

I would be a bit concerned about one string using a lot more water than the other. Charging separately before combining would be a good idea.

Longer term, I agree 24v makes sense, as does a PSW inverter.

The inverter wires are very long, will be replacing with copper and moving closer to battery bank. I'd love to hear anybody's usual method for ordering wire--premade cables? If not, what crimper and ends do you rely on? A link to your favorite write-up on that subject would be great if you have one.

We have a good 12v charger, should be able to top off the individual strings before making an attempt at 24v. Also reading the cell SGs before combining them into 24v and writing them down so I can get an idea of how much difference there is between cells and start planning the battery bank replacement. 

I'm glad to hear I am not the only one who had trouble reading a good old normal hydrometer, when I looked online at the dial on the one that midnite made (edit: sells, not makes), it seemed like they understood my frustration also.

Mark_Kaohe

Photowhit said:

Like Aguarancher, I worry about your batteries, since 1 sting isn't using any electrolyte. You have them, so use them, but you might want to equalize the batteries via the charger before switching to 24 volt (one set at a time, if possible)

In reality, it appears you have a pretty good grasp of the situation. The fridge will run better/cooler on a pure sine wave inverter. I think the sealed unit has a pretty high surge (as I recall from my faulty mind). Read the instructions and use the correct wiring for the inverter. I would guess 2/0 up to 12 feet away from the battery bank. Your current system is likely suffering from voltage drop during the surge/inrush of current.

You can save the breakers and combiner box for the 2 strings of panels, It's up to code to install them with just a 'Y' connector. 3 or more and you will need a combiner box and fuses or breakers.

Run time on lights is important, and 3 laptops with a gaming laptop include sound like kids, known abusers of electric!

I suspect you will still be a bit undersized, but should be able to limit the generator run time a good bit with your suggested improvements.

Photowhit, I nearly missed your response until now.

I had no idea that two PV strings could be just combined together (and meet code)--this will help a lot with prioritizing which work needs to be done first. I understand it's pretty common to put the PV on a breaker for maintenance and troubleshooting but I won't be considering that as one of the "big problems" that we are facing now.

mcgivor

Earlier you mentioned inverter choices, Magnum or Samlex, although the Samlex is fine, for full time off grid the Magnum would be a far better choice, finances allowing of course, having a built-in charger offsets the price difference  somewhat, they are however  in different leagues from one another.

Estragon

I use premade cables as much as possible. To crimp big wire, I use a hammer type crimper, which I got from our host. For small stuff, I use a west marine one with interchangable bits.

myocardia

Mark_Kaohe said:

Aguarancher said:

when was the last time you checked your batteries with a hydrometer and what were the readings?

Yes, the battery bank. My post creates more questions than it does answers, doesn't it?

One thing about this battery bank is that I add about a gallon to one string every couple months and the other string doesn't use almost any water. I'm not especially hopeful that everything will suddenly be good when rewired to 24v due to the time that the batteries have been running this way even if they were good when I bought them.

 

Hi Mark, t sounds to me that you have your batteries wired improperly. The reason why one of your strings is using so much water, and the other is using hardly any could really only be because you are only using two of your batteries. Whichever set of your batteries that you have the positive and the negative load wires hooked to will be the only two batteries doing nearly all of the work. You have to use one set of batteries' negative terminal, and the other set's positive terminal, if you want to use all four batteries.

See this link for the reasons, along with pictorial examples. I was referring to what smartgauge calls "method #2", which is by far the easiest of all of the almost perfect ways to wire in parallel: http://www.smartgauge.co.uk/batt_con.html  Note that their example is how to wire four 12v batteries into a 12v bank. You'll still want to keep the two sets of batteries that you have wired in series, just switch where you draw the other half of your current...to the opposite corner. Oh, and it makes no difference whether you move the negative or the positive. Just move whichever one happens to be easier. Good luck.

Mark_Kaohe

myocardia said:

Mark_Kaohe said:

Aguarancher said:

when was the last time you checked your batteries with a hydrometer and what were the readings?

Yes, the battery bank. My post creates more questions than it does answers, doesn't it?

One thing about this battery bank is that I add about a gallon to one string every couple months and the other string doesn't use almost any water. I'm not especially hopeful that everything will suddenly be good when rewired to 24v due to the time that the batteries have been running this way even if they were good when I bought them.

 

Hi Mark, t sounds to me that you have your batteries wired improperly. The reason why one of your strings is using so much water, and the other is using hardly any could really only be because you are only using two of your batteries. Whichever set of your batteries that you have the positive and the negative load wires hooked to will be the only two batteries doing nearly all of the work. You have to use one set of batteries' negative terminal, and the other set's positive terminal, if you want to use all four batteries.

See this link for the reasons, along with pictorial examples. I was referring to what smartgauge calls "method #2", which is by far the easiest of all of the almost perfect ways to wire in parallel: http://www.smartgauge.co.uk/batt_con.html  Note that their example is how to wire four 12v batteries into a 12v bank. You'll still want to keep the two sets of batteries that you have wired in series, just switch where you draw the other half of your current...to the opposite corner. Oh, and it makes no difference whether you move the negative or the positive. Just move whichever one happens to be easier. Good luck.

Thanks to everybody who has replied on this thread, I did read all advice and have taken action accordingly.

It does definitely sound like the batteries were wired incorrectly, I agree! They were using a positive from one string and negative from the other string, connected at opposite corners of the bank.

I ended up finding a battery connection bolt that was a little bit loose, it was on the positive terminal. I was able to tighten it a full turn or two. However, by this time, I had already ordered a 24v inverter, so I was never able to watch and see if the bolt tightening made a difference. Now there is only one string of batteries and I've spent quite a bit of time tightening every bolt I can find.

Before I upgraded the inverter I did some investigating with a new clamp meter (True RMS). The old inverter was putting out 14.6A@120v at startup, the fridge alone was over 13.5amps. The DC wires were hitting 150amps. I think the old modified sine inverter and the fridge compressor motor really didn't like each other.

I tried to order an inverter that isn't very common, and that caused me some issues. After going through the reasonable options with NAWS, and how long they were going to take to get to me, I went with a Magnum MS2024. I had made the mistake of pricing this inverter without being logged into the website, and it made a big difference, I wasn't considering it before that point but it quickly became my preferred choice based on specs and availability.

 - 5' 4/0 battery cables (2/0 would be sufficient now that this is 24v--local supplier took pity on me and gave them to me at a good price for 2/0). Did you know Magnum specifies that the positive and negative DC wires should be bundled every 6 inches to help increase surge capacity?

 - Tightened battery bolt on 12v bank. Didn't keep as 12v long enough to see if it was helping.

 - Removed ancient xantrex xpower 1750 12v inverter and Iota 12v charger

 - Rewired batteries to 24v using diagram from Magnum manual

 - Installed Magnum MS2024 24v inverter and ARC50 remote

 - Enabled automatic equalize on classic charge controller now that the inverter can handle the voltage, will be topping off water monthly


So far things are going great, but it has also been fairly sunny since I made the inverter change last Friday. Hopefully it works well because I'm offsite for a couple weeks now (traveling for work). After the new inverter was put in, I checked the fridge startup with a clamp meter and it was showing 4amps AC!!! I don't know if the really old inverter was broken/degraded (think burningman alkali dust storms, it's been camping with me for 12 years) or if the difference was modified sine wave.

I actually want to know now how well it would run if I had bought a samlex+iota system, but I'm extremely happy with this magnum inverter so far, and it has a lot of great bonuses (like an automatic transfer switch, etc). I think my next steps are 2-4 additional PV panels, and possibly a wired generator in case we decide to use more power for a short period.

I have started taking specific gravity readings on the batteries, but never did get a reading at 100% with 30 mins rest. I'm happy that I got better at using my basic hydrometer (deka pro), and will finally get a better baseline soon. I did write down the last readings I took, so I may be able to compare differences between cells growing or narrowing even without a great baseline. Batteries ran through an equalize cycle before inverter change as well as after.