Entry level system for a small cabin

**littleharbor** · 03-22-2019, 10:06 AM

The EP line has this chart on how much you can over panel their controllers. Not exactly your controllers but as the chart shows, rated charge power vs. Max PV input. MPPT controllers process the incoming power differently than PWM controllers and their amp rating is referring to their output charging amperage. Basically they can be over paneled.

EP max panel power chart.jpg

**Mike90250** · 03-22-2019, 11:36 AM

You have a nice batch of panels that can do a lot !
I'd strongly suggest considering starting with a batch (four) of 6v 200ah Golf Cart batteries. That would give you 24V @ 200ah of storage, which will run lights and laptops for a long time

The learning curve for a "new to solar" can be steep and those pricey AGM batteries are easy to kill while you are learning the ropes.

**Xplode** · 03-22-2019, 02:11 PM

I agree with Mike about the golf cart batteries. That is, unless you already have the AGM batteries. If you've already got them, then I'd say use them for now and replace them with larger capacity units when you can save up.

I'm not familiar with the epever units you posted about, but I've become quite familiar with the TracerAN series. They let you configure the max charging currents to match your batteries, so you could over panel and over size your charge controller in an attempt to line up with the better batteries you can hopefully afford soon.

Those panels seem like a good batch to you, and you've got more than you need. Post up what the watt hour requirements of your loads are and maybe we can try to help you out with an overall configuration.

**Greta Gremlin** · 03-22-2019, 04:06 PM

What equipment are you using for your current 12v system?

**Fireside** · 03-22-2019, 07:52 PM

Originally posted by littleharbor

The EP line has this chart on how much you can over panel their controllers. Not exactly your controllers but as the chart shows, rated charge power vs. Max PV input. MPPT controllers process the incoming power differently than PWM controllers and their amp rating is referring to their output charging amperage. Basically they can be over paneled.

EP max panel power chart.jpg

Arrgh... I'm having a mind blown moment.. So, just to be sure I'm understanding correctly. I need to obey the voltage limit, but there appears to be significant flexibility on the wattage/amperage of my array, over and above the rated power???? I can't believe in everything I've already read, I never saw that before. Thanks.

FWIW, I'm sure the Upower all in 1 series will have one of the Tracer mppt unit integrated. I'm going to try to confirm that today.

**littleharbor** · 03-22-2019, 08:02 PM

The critical voltage level is the Open circuit voltage, namely the elevated voltage panels will produce on cold cleat mornings. If you live in a cold part of the world and your string open circuit voltage is already close to the limit you need to find the coldest expected temperatures and factor them with the temp coefficient of the panels.

**Fireside** · 03-22-2019, 08:13 PM

To Mike and Xplode, I read you loud and clear on the battery thoughts... FWIW, I just can't find anything that resembles affordable FLA 6V deep cycle batteries down under. It's like the whole market has just gone to AGM already and things like Trojan 105's are $350AUD each. I've been hunting for a long time now for any 6V based deep cycle solutions that I can afford and I'm just not finding. Basically it seems like 90% of the Aussie home PV market is grid connect, and most of the offgrid sellers are busily catering to the RV market, selling pairs of 12V AGM batteries.. So that seems to be where the best volume sales price point is here. There are of course off grid 2V banks available, at take out a mortgage prices..

I've got one last lead to follow up, I just called a guy who I've known to buy pallets worth of 2nd hand telco batteries and even some near new banks straight out of the mines. (mines just throw money around, they will build an entire camp, then the dollar value will change and they just cancel that operation and do something else for a while.) I hope to hear back from him today with good news about making a 2nd hand battery purchase which could get me into the 4 or even 8 x 6V 225AH ballpark.

My to do list has finding out if the Upower unit is as configurable as the Tracer series.. I'll be surprised if it isn't. but that will be very handy to know.

To Greta, Hi. My current dinky little setup, powering my slide on camper is an 80W 12v panel, running through a CPT-LA10 controller http://vodasi.com/en/product/CPTLA10.html
One of the very few cheap Chinese controllers that actuall has MPPT beyond the screen printing on it's case lol. And that is feeding a single 12v 135AH AGM in an all in one box (charger, inverter, etc..) Giving me some basic light, a tiny bit of laptop and 300w of pure sine to run my CPAP machine overnight basically.

On a good day, I claw back about as much energy as I used the night before.. And on a cloudy day I fire up the genny and pour money into it. My plan, once the bigger system is in play, is to install the 12v system onto a little truck I have for farm duties. Just as a maintainance system/backup.

**Xplode** · 03-22-2019, 08:31 PM

Since I'm not familiar with this (sounds like combo charge controller + Inverter?) I'll suggest you find out what the Idle losses are on the inverter portion (total lost energy whenever it's on) and see if the inverter portion can be turned off when you don't need it.

A rough guess (if you can get the 225Ah x4 batteries) means you've got about a 5kwh battery bank. Shooting for a daily cycle of 20%DOD you've only got about 1kwh per day of usable power. That should be fairly easy to recover with a handful of 190W panels in a sunny location I think.

Have you worked out what your watt hour needs are? How much does that CPAP machine use? If you haven't done it yet, you need to tally up your devices. Let us know

**littleharbor** · 03-22-2019, 09:14 PM

Originally posted by Fireside

To Mike and Xplode, I read you loud and clear on the battery thoughts... FWIW, I just can't find anything that resembles affordable FLA 6V deep cycle batteries down under. It's like the whole market has just gone to AGM already and things like Trojan 105's are $350AUD each. I've been hunting for a long time now for any 6V based deep cycle solutions that I can afford and I'm just not finding. Basically it seems like 90% of the Aussie home PV market is grid connect, and most of the offgrid sellers are busily catering to the RV market, selling pairs of 12V AGM batteries.. So that seems to be where the best volume sales price point is here. There are of course off grid 2V banks available, at take out a mortgage prices..

I've got one last lead to follow up, I just called a guy who I've known to buy pallets worth of 2nd hand telco batteries and even some near new banks straight out of the mines. (mines just throw money around, they will build an entire camp, then the dollar value will change and they just cancel that operation and do something else for a while.) I hope to hear back from him today with good news about making a 2nd hand battery purchase which could get me into the 4 or even 8 x 6V 225AH ballpark.

My to do list has finding out if the Upower unit is as configurable as the Tracer series.. I'll be surprised if it isn't. but that will be very handy to know.

To Greta, Hi. My current dinky little setup, powering my slide on camper is an 80W 12v panel, running through a CPT-LA10 controller http://vodasi.com/en/product/CPTLA10.html
One of the very few cheap Chinese controllers that actuall has MPPT beyond the screen printing on it's case lol. And that is feeding a single 12v 135AH AGM in an all in one box (charger, inverter, etc..) Giving me some basic light, a tiny bit of laptop and 300w of pure sine to run my CPAP machine overnight basically.

On a good day, I claw back about as much energy as I used the night before.. And on a cloudy day I fire up the genny and pour money into it. My plan, once the bigger system is in play, is to install the 12v system onto a little truck I have for farm duties. Just as a maintainance system/backup.

Funny, With all the info that is within the ad for that charge controller I don't see the Max Voc. limit anywhere. This makes me more than a little suspicious about this being a real MPPT controller. What gives you the feeling this is not a fake? What is the voltage you have coming off your array into the controller? What is the current coming from your array and the current coming from the controller, into your batteries?

**Fireside** · 03-22-2019, 09:20 PM

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.

**Fireside** · 03-22-2019, 09:46 PM

Originally posted by littleharbor

Funny, With all the info that is within the ad for that charge controller I don't see the Max Voc. limit anywhere. This makes me more than a little suspicious about this being a real MPPT controller. What gives you the feeling this is not a fake? What is the voltage you have coming off your array into the controller? What is the current coming from your array and the current coming from the controller, into your batteries?

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..

**Mike90250** · 03-22-2019, 11:25 PM

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 ?

**Greta Gremlin** · 03-22-2019, 11:35 PM

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.

**Xplode** · 03-23-2019, 12:36 AM

Originally posted by Fireside

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.

Entry level system for a small cabin

Entry level system for a small cabin

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