Mountain cabin off-grid

Horsefly · October 2016

Hello everyone, it's me, the OP. I'm back with more questions. You guys have all been awesome so far, so I'm very optimistic!

So let's say I have a MPPT charge controller, and a inverter/charger (probably the Magnum Energy MS4024) both hooked up to my 24V battery bank. I also have a 9kW gas generator hooked up as AC in to the inverter/charger. My understanding is that if we run the generator the MS4024 will automagically route the generator AC to the cabin load, *AND* will charge the battery bank. What I'm not too clear on: Is the MPPT controller OK with that? Is it OK that it is trying to charge the batteries at the same time as the MS4024 is? Or do I need some third magic box to arbitrate between the two?
I think we are leaning towards AGP batteries rather than FLA, mainly to avoid the maintenance and venting. I realize the AGP batteries cost more, but I've found conflicting information on whether they last as long or not. What do you experts think? (I'm hoping on not stepping into a AGP vs. FLA religious war)
Since we've decided on a 24V system, it looks like I can get the same AH from four 6V batteries in series, or a couple of 12V batteries in series, for about the same $$. Aside from the weight of the 12V batteries (130 lbs!) is there any advantage or disadvantage of going with one config or the other? Extending that logic, I could also go with cheaper, lower AH 6V batteries, and satisfy our needs with two parallel strings of 4 batteries, for a little more. Is there any reason that would be better?

Thanks again! I feel like I leave this place smarter every time I visit.

Steve

mike95490 · October 2016

AGM batteries, generally, have shorter lifetimes than flooded

The MPPT controller will just throttle itself back as the batteries charge, it won't care, unless the other charging source overcharges the batteries and then you have no idea which charger to blame.

cheap 6V 200Ah golf cart batteries are always a good place to start, 4 in series will give a respectable 24V bank @ 200ah =4800wh.

Horsefly · October 2016

mike95490 said:

AGM batteries, generally, have shorter lifetimes than flooded

The MPPT controller will just throttle itself back as the batteries charge, it won't care, unless the other charging source overcharges the batteries and then you have no idea which charger to blame.

cheap 6V 200Ah golf cart batteries are always a good place to start, 4 in series will give a respectable 24V bank @ 200ah =4800wh.

Thanks Mike.

My brother-in-law doesn't like the idea of flooded lead acid. He thinks we won't (the three families of myself and my two siblings) won't do the required maintenance to keep them going, so their lifespan will actually be shorter than AGM. He also is afraid of the leaking acid, venting hydrogen, etc.

Good info about the MPPT. That is what I had hoped. Sounds like we don't need anything special to have both an Inverter/Charger that can charge the batteries and the MPPT charge/controller.

The config (4 x 6V) is one of the exact configs I am looking at, and specifically for a 24V by 200AH capacity.

Steve

Estragon · October 2016

I recently bought a new starting battery for my generator and decided on AGM for two reasons. First, although I have a dozen big FLA I maintain regularly, I figured I'd forget about the genset battery. Second, AGMs supposedly self discharge much more slowly which is important for the rarely used generator.

softdown · October 2016

Estragon said:

I recently bought a new starting battery for my generator and decided on AGM for two reasons. First, although I have a dozen big FLA I maintain regularly, I figured I'd forget about the genset battery. Second, AGMs supposedly self discharge much more slowly which is important for the rarely used generator.

I think the low self discharge is true. I had some top end gels with virtually non-existent self discharge.

mike95490 · October 2016

Beware of assuming AGM batteries are benign.

They are susceptible to thermal runaway and also venting explosive H & O2 gasses, and those have to be factored in, you need the same containment and vent system as flooded batteries do. Generally won't ever be utilized, but needed anyway, And Battery Temperature Sensors are NEEDED for all charging sources.

softdown · October 2016

I would encourage the Outback 3524 Inverter. The host sells it for a great price, it would save you $400 and quite likely offers a huge surge capability. Morningstar charge controllers are built to handle cold weather Hyper VOC and higher panel voltages...they do cost more. Otherwise, I would go with the Outback FM60 charge controller. Outback has a superior reputation and comes with a 5 year warranty when sold from this site (others may give the 2 year warranty).

Horsefly · October 2016

mike95490 said:

Beware of assuming AGM batteries are benign.

They are susceptible to thermal runaway and also venting explosive H & O2 gasses, and those have to be factored in, you need the same containment and vent system as flooded batteries do. Generally won't ever be utilized, but needed anyway, And Battery Temperature Sensors are NEEDED for all charging sources.

Thanks for that Mike. I hadn't considered that. I don't think I can overcome the momentum towards AGM at this point, but we can be prepared. The good thing is, batteries is probably the easiest decision to change late in the process, from what I can tell.

Steve

Horsefly · October 2016

softdown said:

I would encourage the Outback 3524 Inverter. The host sells it for a great price, it would save you $400 and quite likely offers a huge surge capability. Morningstar charge controllers are built to handle cold weather Hyper VOC and higher panel voltages...they do cost more. Otherwise, I would go with the Outback FM60 charge controller. Outback has a superior reputation and comes with a 5 year warranty when sold from this site (others may give the 2 year warranty).

Thank you softdown.

I did have the Outback 3524 inverter second on my list. Our initial inventory had a semi-worst case instantaneous demand of 3700W, with the surge of quite a bit higher due to the startup of the well pump. That's why I had fallen back to the Magnum 4024. However, I think either can handle nearly all of our needs.

As for the charge controller, I had gravitated towards the Outback FM60 as you mentioned, but hadn't looked at the Morningstar. I'm not sure how to factor in your comment on it doing well in cold weather. No one will be using any power during most of the coldest months. Looks like the Morningstar TS-MPPT-60 is pretty close in price to the Outback FM60, with similar top-order specs. I'll add the Morningstar for consideration. Aside from cold temp performance, are there other differentiators? I see both have Internet connectivity, but that doesn't contribute to us out in the woods (no Internet connectivity).

Steve

Vic · October 2016

softdown mentioned, ... "Morningstar charge controllers are built to handle cold weather Hyper VOC and higher panel voltages..."

This should be reference to MidNite Solar's Classic Charge Controller (CC) in particular, and, to a certain extent, the MidNite Solar KID (30 A MPPT CC).

IMO, the Outback FM CCs are dated. And have some limitations -- unlikely that any improvements will be made to them, as it is reported that there is NO more room for any additional code. And any Update, if there is new code will require a control board swap, or to send the CC back for new code update.

Morningstar CCs are limited, as any added function needs some expensive Optional accessory (generally), so they can become relatively expensive, IMO.

For new installations, there are probably better CCs, in the same price range.

AGM batteries do not require checking water levels, and adding Distilled Water, but, you cannot measure the State Of Charge (SOC), simply by using a Hydrometer. You must infer how well they are being charged, which can be difficult.

Parallel strings of AGMs are difficult to manage, although, you may not need more Capacity than would be provided by a single string of batteries.

FWIW, Vic

Horsefly · October 2016

Vic said:

softdown mentioned, ... "Morningstar charge controllers are built to handle cold weather Hyper VOC and higher panel voltages..."
This should be reference to MidNite Solar's Classic Charge Controller (CC) in particular, and, to a certain extent, the MidNite Solar KID (30 A MPPT CC).
IMO, the Outback FM CCs are dated. And have some limitations -- unlikely that any improvements will be made to them, as it is reported that there is NO more room for any additional code. And any Update, if there is new code will require a control board swap, or to send the CC back for new code update.
Morningstar CCs are limited, as any added function needs some expensive Optional accessory (generally), so they can become relatively expensive, IMO.
For new installations, there are probably better CCs, in the same price range.

Thank you Vic. It sounds like you would steer me away from both Outback and Morningstar CCs. Are you willing to name others you might recommend instead? I can't tell from your comments if you like the MidNite Solars. It sounds like the Magnum Energy PT-100 is newer, and more expensive. I think we will be needing something in the range of 40A or greater. We would benefit from a remote panel (like 50 ft away), but it seems like most CC's support that. Any further guidance would be appreciated.

Steve

Edit to Add: I think we need about 150V Voc, although that may be overkill. Still working the numbers.

westbranch · October 2016

Steve, read about Vics systemS in his sig line...

mike95490 · October 2016

Vic said:.......Morningstar CCs are limited, as any added function needs some expensive Optional accessory (generally), so they can become relatively expensive, IMO......

Limited ? The 60a MPPT has a ready to go web server for monitoring. I have it hooked to a wi-fi hub and watch it at my house 300' away. To update firmware, you need a 9pin serial adapter. You can even tweak the settings over the web interface,
If you want to add relay drivers and AGS gear, sure, that's extra.
I know, I have 2 of them now.

Midnight Classic has 2 aux outputs, but those are just to drive a relay, they can't handle any power. (have one of those too).
I use a win XP laptop to update it's firmware, many reports of bricked units being sent back for factory unbricking when windoze updater fails, http://kb1uas.com/mnsforum/index.php?topic=2663.0

softdown · October 2016

Horsefly said:

softdown said:

I would encourage the Outback 3524 Inverter. The host sells it for a great price, it would save you $400 and quite likely offers a huge surge capability. Morningstar charge controllers are built to handle cold weather Hyper VOC and higher panel voltages...they do cost more. Otherwise, I would go with the Outback FM60 charge controller. Outback has a superior reputation and comes with a 5 year warranty when sold from this site (others may give the 2 year warranty).

Thank you softdown.

I did have the Outback 3524 inverter second on my list. Our initial inventory had a semi-worst case instantaneous demand of 3700W, with the surge of quite a bit higher due to the startup of the well pump. That's why I had fallen back to the Magnum 4024. However, I think either can handle nearly all of our needs.

As for the charge controller, I had gravitated towards the Outback FM60 as you mentioned, but hadn't looked at the Morningstar. I'm not sure how to factor in your comment on it doing well in cold weather. No one will be using any power during most of the coldest months. Looks like the Morningstar TS-MPPT-60 is pretty close in price to the Outback FM60, with similar top-order specs. I'll add the Morningstar for consideration. Aside from cold temp performance, are there other differentiators? I see both have Internet connectivity, but that doesn't contribute to us out in the woods (no Internet connectivity).

Steve

If the system is hooked up during the winter, usage will have no impact on the possibility of a Hyper VOC incident. Hyper VOC tends to strike very early in the morning before there is sufficient sunlight to turn the charge controller on which helps to drive the incoming voltage down.

It is a legitimate issue with 48 volt systems in very cold environs. I have not studied the practicalities with a 24 volt system. Hyper VOC forced me to limit my system to two panels in series instead of three. Charge controller warranties do not cover Hyper VOC incidents.

If you go with Outback, there will never be an issue with a troubleshooter being unfamiliar with the equipment. As far as flashing and updates etc...."The worst enemy of good is better?"

Horsefly · October 2016

softdown said:
If the system is hooked up during the winter, usage will have no impact on the possibility of a Hyper VOC incident. Hyper VOC tends to strike very early in the morning before there is sufficient sunlight to turn the charge controller on which helps to drive the incoming voltage down.

It is a legitimate issue with 48 volt systems in very cold environs. I have not studied the practicalities with a 24 volt system. Hyper VOC forced me to limit my system to two panels in series instead of three. Charge controller warranties do not cover Hyper VOC incidents.

If you go with Outback, there will never be an issue with a troubleshooter being unfamiliar with the equipment. As far as flashing and updates etc...."The worst enemy of good is better?"

I think I get what you are suggesting. Sounds like there are differences in opinion on the different lines of charge controllers.

Regarding Hyper VOC: You definitely got my attention. I was planning to go with three panels in series until I saw your post. Now I'm a little worried. I had seen the term in some of the MidNite Solar docs, but not anywhere else. I assume that is just the term they use it? I've tried to find the NEC multiplier info, but can't seem to. I'll search some more. I don't even know what the coldest temperature might be up there in the winter, but I'm sure it is below zero. I suppose I could go with charge controller rated for 200V Voc and be safe.

westbranch · October 2016

A Classics Hyper VoC is determined by the CC's max voltage rating (150) plus the banks voltage (24) to give you HyperVoC (174) at which point the CC is built to be in max defense mode, ie shut down.... IIRC.

mike95490 · October 2016

Each charge controller mfg has a String Sizing calculator on their web page, and you input your panel and weather data there, to plan for array size & configuration.
http://www.midnitesolar.com/pages/classic/classic_sizingTool.php
http://string-calculator.morningstarcorp.com/

Dave Angelini · October 2016

There is nothing wrong with the outback charge controllers for what you want to do.
It can be a pain for you to deal with different brands of equipment.
Stick with the same brand and everything can be networked and you (and your SO) will only have to learn one language.
I would also price out a split phase Schneider SW and their controller at our host before you decide.

softdown · October 2016

This is all you need to fill out to determine the proper charge controller and panels in series: http://www.midnitesolar.com/pages/classic/classic_sizingTool.php

Here is the $1000 question from that sizing tool: Environmental Data


*Coldest Ambient Temp F° _*___Your number____

Your number will probably be below -20 F I may think. This adds a significant amount to voltage calculations.

It is important that you use the coldest number found in the past 30 years or so. Some would even say the coldest number ever recorded. You certainly do not want your precious charge controller to go interstellar .

I wish I knew how often Hyper VOC takes out charge controllers. It is definitely a very cold weather phenomenon.

I have been saying Morningstar when I should have been saying Midnite. I am surprised this did not get corrected. Perhaps the companies are related?

westbranch · October 2016

Soft down, you should go back and use STRIKE THROUGH so we can see what you really meant...

softdown · October 2016

westbranch said:

Soft down, you should go back and use STRIKE THROUGH so we can see what you really meant...

Ha....I spent more time trying to format than it might appears.

Horsefly · October 2016

Dave Angelini said:

There is nothing wrong with the outback charge controllers for what you want to do.
It can be a pain for you to deal with different brands of equipment.
Stick with the same brand and everything can be networked and you (and your SO) will only have to learn one language.
I would also price out a split phase Schneider SW and their controller at our host before you decide.

Thanks Dave. I do get the idea of staying with the same brand.

I hadn't even looked at the Schneider SW stuff before. They have a 3500W inverter/charger that looks pretty good for only $1495. That's cheaper than either the Outback VFXR3524A ($1770) or the Magnum MS4024 ($2079). I need to go look at their charge controllers too. Is there a catch with Schneider? How come I don't see stuff about them as much as Outback, MidNite, Magnum, etc.?

Steve

softdown · October 2016

Remember that when the charge controller handles more voltage, you pay the price of the controller handling less amperage. When studying the Midnite string tool, you will notice a significant correlation.

Estragon · October 2016

Getting the same brand and networking stuff together is interesting to those of us who are into that sort of thing, but personally I wouldn't do it. Sort of like getting an Iphone because you use a Macbook. Use the right tool for the job. If you are a bit of a geek like me, you can probably find a way to do the integration stuff.

That said, Midnite may have an inverter out soon that I might have seriously considered if it was available when I bought a couple of Outback inverters. I should add that I recently had a problem with one of the Outback inverters close to the end of warranty and Outback were very good with getting it solved.

Dave Angelini · October 2016

Horsefly said:

Dave Angelini said:

There is nothing wrong with the outback charge controllers for what you want to do.
It can be a pain for you to deal with different brands of equipment.
Stick with the same brand and everything can be networked and you (and your SO) will only have to learn one language.
I would also price out a split phase Schneider SW and their controller at our host before you decide.

Thanks Dave. I do get the idea of staying with the same brand.

I hadn't even looked at the Schneider SW stuff before. They have a 3500W inverter/charger that looks pretty good for only $1495. That's cheaper than either the Outback VFXR3524A ($1770) or the Magnum MS4024 ($2079). I need to go look at their charge controllers too. Is there a catch with Schneider? How come I don't see stuff about them as much as Outback, MidNite, Magnum, etc.?

Steve

There are alot of hobiest solar people here who do not mind a mixed system. I mainly work with large homes offgrid and people who do not have time to play arround with this for one reason or another. I think if you looked into the forum over the years and not just the short time you have been here you would find that Schneider/xantrex/trace have been the leader along with Outback. They are the only two I use because they build a balanced system that is networked and can be viewed anywhere in the world as a system.

Mountain Don · October 2016

IMO, if you want the system to be the most user friendly to all family members go with a single brand that can be networked. Before being struck by lightning and having to replace all the electrnics we had all Outback. After the strike I decided on the MN Kid because I did not need the capacity of the FM60 and I saved some $$ with the Kid. But I sort of miss the networked features I had with all Outback parts.

icarus · October 2016

Coming to the party late, but I second the idea of leaving a couple of panels vertical for the winter. I have three panels wall mounted on hinges so that when I leave for a while in the winter the small array is plenty to keep the batteries in float. Mine have held up fine for as long as several months.

Tony

Mangas · October 2016

Same manufacturer and best equipment you can afford.

My opinion scale 30% more capacity into the build than it calcs out to accommodate future expansion.

Agree with Dave's advice.

Horsefly · October 2016

Thanks to all you guys for such great information. I asked some stupid questions, and you were kind in answering. Between this thread and a ton of other data on the Internet, I think I've come a long way. I've got an initial design penciled out from PV through charge controller, battery bank, and inverter/controller. Per comments here, I'm trying to stay with the same manufacturer for the CC and Inverter, and I think I've settled on Schneider Electric. I'm hoping to have my PV panels such that one or two can be moved to vertical during the winter.

Our cabin will be shutting down for the winter by mid-Nov, so I have the bulk of the winter to iterate and refine the design and parts list with my brother, sister, and brother-in-law. I feel much more confident in what I'm looking at now, due in no small to this advice in this thread and elsewhere on this forum. It's especially nice to feel some of the cobwebs shaking off my MSEE brain cells after so many years!

Thanks again!

Steve

BB. · October 2016

A suggestion or two... Get a sheet of plywood sub floor (or something like 3/4 inch ply--depending on how heavy the stuff you will hanging), and build/wire your system at home--And test. Disconnect the battery+panel wiring, and take the whole assembled unit up to the place in the spring.

Another suggestion--possibly, if you use exposed wiring (instead of metal conduit)--You might want to sheath the face of the plywood with sheet rock or cement board--And put some cement board (or ceramic tile, etc.) at the base of the e-panel installation. I am always a bit concerned about fire--And keeping the equipment/wiring mounted in such away to avoid spreading flames is not a bad idea.

Lastly--E-panels... Pre-wired panels that are available for some models/brands of equipment. Can save a bunch of work getting all of the parts together.

https://www.solar-electric.com/catalogsearch/result/?q=schneider+epanels

Have fun!
-Bill

Mountain cabin off-grid

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