Entry level system for a small cabin

[jpt]

Fireside, what are your experiences with the unit so far? I'm thinking about putting one into my overland truck, but I cannot find much info on them.

[Fireside]

Hey Xplode, for the life of me, I couldn't get a stable enough signal to reply from the bush lol. But I'm back in town for a couple of days and excited to take delivery of this.
P_20190328_160346.jpg
It's funny, mostly when I buy things online, they arrive and I think.. huh.. Looked bigger than that in the ad. But this was the opposite. It's a beefy unit and will require a quick rethink as to where I will mount it lol. As well as the controller/inverter I also picked up a PC connect cable and a bluetooth link so I can mess about with an android tablet and see about making a nice little indoor control panel, as the batteries and electronics will likely live in a service hut nearby.

I'm going to do work on my panel maths and cable routing plans. And will post back to see if I'm on the right track.

[Xplode]

Keep us posted, and if you can in sure we'd love to see done pictures of it coming together

[Fireside]

Hi Sunking, yep sadly there were 12.. But the guy selling them got them out on a windy day and just leaned them against the side of his shed for me to collect... With predictable results.. Honestly, I'm glad they all weren't shattered. Anyway, safe to say there was a renegotiation. Ideally, I've pictured trying to get up to 9-10 panels onto the cabin, leaving 1-2 to be installed on a pumphouse at a later date.

I hear you on the price of going off-grid. But I haven't really had a great deal of choices to choose between.. Just a guy trying to make things work with what he has. Australia has a massive housing bubble recently fuelled by Chinese property investors which have driven urban house prices through the roof. Even if I could find affordable rental accommodation with wheelchair access, I'd be spending every cent I could scrape together just to be there. So the short term discomfort of offgrid on a shoestring is something I hope to offset by building the workspace I need to start developing income streams which will give me a future..

If I'm honest, I think on balance I'm enjoying the challenge. Life isn't perfect and as an engineer, I've always dealt with degrees of perfection. In the real world, outside of a machine shop, things are rarely square or flat.. Solar systems are not as good as they could be.. You can't afford a million dollar tractor, so you make do with the 3k one you picked up from a salvage yard and welded back together lol. You use the power you've got, drink the water you collect and when it runs out, you go without or innovate. But I'm not afraid of hard work and I'm pretty good at saving, so the big perfect system will come.

I've made some decisions folks. I'm pushing the purchase button on the bigger of the two controller/inverters today. And I'm off to the bush so I will swing by the bloke who often trades in 2nd hand batteries place and see what he has. Thanks all for the input, I'll let you know how it pans out.

[Sunking]

I have 11 good panels to work with.

11 Panels is a PRIME NUMBER and not going to work. Only PRIME NUMBERS that work are 1 and 3

With a Prime Number only gives you two panel configurations of all in Parallel or all in Series. You need to Gain or Loose a panel so you can wire as many panels in Series like 2S5P, 5S2P, 3S4P or 4S3P. 11 in parallel is just plain foolish and waste of money.

Budget is no object going off grid. By going off-grid you choose to spend a fortune.

[littleharbor]

Here's a direct link to their Technical Info pages. There is a wealth of information throughout their site.

http://www.smartgauge.co.uk/technical1.html

[Fireside]

Awesome, thanks Mike. I've seen that page before and I think I'll study it till I know it back to front. I can see myself welding up a custom battery rack for this setup. Torquing down all the bus bars etc.

[Mike90250]

Wiring circuits in parallel is difficult to achieve perfect balance because of small differences in resistance, Bolt/Lug torque, Crimps, cable length and even Internal Battery Resistance.

AGM cells have very low resistance, so all the external factors will be the cause of current imbalance. then a couple of hot/cold cycles and stuff shifts and the resistance changes yet again !

Here's a long writeup about it http://www.smartgauge.co.uk/batt_con.html

[Fireside]

Lucky I didn't pay too much for it then huh... Oh well , all the more reason to get the new system up and move that little unit on to vehicle battery tending duties.

Sitting here trying to find what I read about not adding 12v AGM batteries in parallel, can anyone shed any light on that? If I could get my hands on say 4 of them, is there a reason to not have them wired 2x2 in series/parallel?

[littleharbor]

With so much blatantly mislabelled rubbish flowing out of China these days, I did some extensive research. One of the reviewers I found particularly useful is Adam Welch on youtube. He buys cheap charge controllers, puts them through their paces and opens them up for a look inside. I must admit, I bought this one based on this review and though I do have watt meters, I've not bothered to do further testing. https://www.youtube.com/watch?v=1z5r3Yo6fmQ

I have another small system running as a standby charge/backup system on a 4x4 which I have on the property, it's using one of the little EPever landstar 10A PWM contollers, the fully sealed waterproof ones. Which I've been very happy with..

At any time the meters he has connected to the controller are showing the SAME current, in and out. Also you can clearly see that the watts in is higher than watts out.. This controller is acting like a PWM controller would. MPPT controllers take the incoming power, (watts), and convert the voltage and current to suit the batteries needs. Basically, watts in = watts out, minus a small loss for efficiency. PWM controllers are basically switches and

whatever current coming in is the current going out, no boost. This is exactly what I see happening on this video.

As to the incoming voltage being higher than charging voltage, The panels are producing their expected voltage and the lower voltage out to the batteries is being clamped by the batteries. There is no magic there. When the higher voltage is stepped down by a real MPPT controller the current should be proportionately stepped up.

[Fireside]

Ok folks, I've been doing my homework. I researched the configurability of those EPever Upower all in one units and they are as configurable as the Tracer mppt controllers. Which means I can limit max charging amperage if required.

I haven't heard back from the guy who might have some 2nd hand batteries to sell. But I will follow up with him tomorrow. He's one of those, will get to it when he does kinda guys, and if pushed too hard, he'll just bail on the whole thing. It's kinda why I hadn't pursued that option as a preference. But in any case, I will still try to find out what he's got laying around. But I've taken onboard the advice about avoiding telco batts... FWIW, these ones come from remote, solar powered cell tower sites, which have been getting upgraded to include 5G infrastructure. But still I will approach with extreme caution. The ones from mines are usually big thin 150AH AGM's that have had a very short service life, if any..

I feel like I have a time crunch, as I need to head back to the bush tomorrow, and I still haven't ordered anything. The wheels turn slowly out here, so even if I do get something ordered soon, it will be weeks before things arrive.

So, if I may bring this back to the two controller/inveters I mentioned in the OP, I'm convinced that I can't buy separate controllers, inverters and AC backup chargers for the price of one of those Upower all in one units.. And given it's a brand I keep reading good reports about. I'm pretty much ready to push the button on purchasing one of those. Do I just grab the one with the smaller MPPT charger in it? or pony up the extra $200 for the bigger one with a view to hooking up more panels? The fact that I can safely attach more PV to the big one and limit it's charge Amperage as required is definitely making me lean towards that one.

[Fireside]

Hey Xplode, thanks for your thoughts. Straight up, I just want to say I agree with everything you're saying.. But I guess I've been trying to save you guys from having to hear my whole lengthy and probably boring story lol. The key notes are.. Catastrophic life changing motor vehicle accident with spinal injury which caused a total financial implosion. Which leaves me largely broke, broken, unemployable and fighting anxiety. I've used up any favors I ever earned. Stretched every friendship I ever had and sold off every asset that is surplus to requirement. But I am nothing if not stubborn, and so I'm trying to put some sort of life back together piece by piece. I've learned how to walk again, which is handy.. And I have some tools and talents which I'm trying to position myself to take advantage of.

Right... So the assets are, A piece of rural land in a remote location that I own outright. A car which I own outright, that I'm just barely holding together. And a bunch of tools that I can use to dig myself out of this financial hole I'm in..... If I can just develop my setup enough to do so.. Which is where I'm at currently.

So, I've achieved Step 1. I built a camper, and assembled some basic tools for clearing brush and carving out a small livable patch. I have a serviceable 12v setup, which is barely.. but just enough to exist.

Being honest... And realistic about what I can and can't achieve.. I simply don't think taking a leap to the 48v system is do-able. Initially, I focused my efforts on developing a modular solar solution that I could build upon. But there are so many points of compromise.. like.. Battery banks. you can't just add more new batteries to your old ones over time. Well you can, but as we know, It's an expensive way to wind up with a half new bank that performs like an old one. The cost of 48v controllers is a big step up... The cost of 48v inverters is a bigger step up.. A whole lot of factors have combined to convince me that my best option is to install an interim 24v system for the cabin I'm building, which will be a big step up from my current camper on 12v.. The goal of Step 2 is some rudimentary level of comfort.

My reality is, I simply cannot afford the system I need, and I know it. Heck, friend.. I'm not even close... But I am getting very good at living within my means.. I am literally picking berries and hunting to eat here lol. And I guess the other thing is, in my part of the world Winter is coming.. And it snows here. So I guess I'm scrambling to get a better roof overhead and some panels on it. Because I know I can't afford to run the Genny that much.

On the plus side, If I build a nice little 24v system for now, and it makes life more comfortable for the next 12 months, allowing me to get my workshop built and to develop additional income streams, I can always sell the 24v system as a 1 year old going concern and invest whatever I can sell it for back into the bigger system.

Anyway, sorry for going on a bit.. I'm not angling for attention or sympathy lol.. I just can't think of any better way to explain the situation than the truth as such. I really will use whatever available power I can create.. And not a watt/hour more.

[Xplode]

Hi Xplode, yes the ARKPAK 730P battery box is pretty good in feature terms. According to it's own display, the inverter draws around 8-12w just in standby.. And I definitely switch it off whenever I don't absolutely need some AC power out of it.

Now, to the numbers.. Way back when I started researching all this, I sat down and ran the numbers.. And those note's are long lost. But here's the thing I learned whilst doing that. A: I will use all and any power I can get my hands on. So need is a hard number to determine. And B: Budget is my main limiting factor.

So I abandoned the very sensible approach of working out what I "need" and building the system to supply it.. Leaning instead towards working out what my budget is and just squeezing as much power out of it as I possibly can.... I will then simply adapt my lifestyle to live within my means. My big picture, without going into too much detail is step1 basic 12v system to get me started {done}.. Step 2 Achieve relative comfort with minimal fuel use with a bigger 24v system. Step 3 Develop income streams and build a nice big 48v system to run everything I want. {Hopefully not much more than 18 months away.}

FWIW, with my current setup, if I use the laptop for 3 hours of an evening, then run the CPAP with no humidifier, + a dc fan overnight, I will use approximately 15% of my current 135AH battery which has never been deeply discharged and should be in fair-good condition. If the next day is sunny, After recharging my lights, phone etc. I can usually claw back around 12-13% of those losses, and then every 3 days I will need to fire up the genny to give it a good top up.

I think you should re-evaluate your system of "living with your means" and "using whatever you can get your hands on" You would be wise to engineer the system a little so it will last you better. This is kind of the equivalent of buying cheap tools that break so you buy them over and over again. Would have been cheaper to buy the quality tool to start with. and you'd still have it. Now, I am not saying you need to go buy high end controllers and such. Budget is always a factor, and I am reasonably happy with my Tracer3210AN/4210AN units which were quite affordable.

If you don't have an idea of what you're going to use, then you'll abuse your batteries and they will die in a year or two. Then you'll be out the money for your batteries and you'll have to start again. If you're planning to end up with a 48Vsystem, then you should probably buy 48V equipment from the start, or at least keep that in mind. There are charge controllers that will run at 24v now, and switch to 48v when you replace your battery bank later. You'll spend more now, but you'll have a far superior product in the long run.

Since you haven't really mentioned any larger loads (I'm talking high current draw for extended periods), I would think you're probably ok on 24V. Get yourself a Tracer4210AN or 4215BN and you'll have a cheapish 40A charger than can be used with your 12V system now (they'll run 12 or 24V), then save up and buy a nice battery bank when you can, and switch to 24V. That'll mean a new inverter as well, but if you're surviving on 300W now, a 500W 24v unit won't really be that expensive. 48V is really if you're intending to run larger loads, or have a constant draw that is pulling killowatt hours off the batteries every day, then you want the higher voltage so you can sink the extra power back in to the batteries faster while charging (ex 100ah battery at 24V should be charged at around 15Amps is 360Wh per hour going into the battery (ignoring losses for now). A 100ah battery at 48v still charging at 15Amps is up to 720Wh going into the battery. This is all assuming your panels are producing that much, but with a batch of 190W panels, you'll be able to do that.

100Ah is just an example, but if you manage to get yourself the 225Ah bank at 24V, you'll have 5.4kWh of battery bank, and you only really want to drain it a little every day, then recharge. So you limit yourself to about 1kWh of usage per day from the batteries. You should see if your loads will work within that, especially overnight. During the day when the sun is up, your batteries can recharge, and if you're generating more than the batteries are taking - you can use it up with your inverter. So charge your laptop and phones and do things during the day if you can, so long as your batteries make it back to 100% charged by sundown, you can use up all the excess you can handle, and that doesn't count towards your 1kWh limit we've imposed.

Now if you have a few days of bad weather, you've still got enough battery to run you and hopefully stay above 50% charge. and if you've oversized your array (like in the chart posted above) your batteries should hopefully be able to charge back up again when the sun comes back out. if not, you have to run the genny.

Hoping that makes sense - And if I'm off-base on anything one of the gurus can jump in. I've learned a ton from these guys, but they will eat you alive with the "meh don't care about knowing my loads" kind of attitude. it WILL cost you more money, and you're going on about budget so you'd be wise to listen up.

Also - I'm not factoring any efficiencies or losses in with my examples - you will have to. Consider the inverter to run at 80%, and the charge controllers to run around the same. They'll claim higher, but the batteries don't charge 1amp in = 1amp charge. so 80% is probably a good rough number. So you're only getting 800Wh of real energy out of the 1kWh daily limit and you need 1.2kWh of solar energy to replace it. so 800Wh out needs 1200Wh in.

[Greta Gremlin]

If you can use the 300 watt pure sine wave inverter you already have,
that may open up more options for you, since you could purchase a stand-alone charge controller instead of the controller/inverter type.
With this you may also be able to find a charge controller that has higher voltage ratings for around the same price of the original options of controller/inverter.
Doing that would allow you to utilize more of your panels.

[Mike90250]

Don't buy or accept for free - any used telco batteries, they are not deep cycle, and are made to keep telcom plants alive in case of Grid failure. After a couple years, or a couple activations of the bank, they cycle new batteries in and look for a place to dump the old ones.

Are there no golf courses around you that use electric carts ?