diy solar

diy solar

Help with charge controller

Swampfox

New Member
Joined
Jan 14, 2022
Messages
8
Hello. Thanks for having me. I'm pretty green at all of this.

I'm trying to power a den on solar and battery power. I figure 300 watt would work perfectly.
I've ordered some 250 watt Canadian solar panels 2 of them. I have more if needed. And a lifepo4 2.17 kwh battery. I've got a second one if necessary.
I'm stuck in the middle at the charge controller inverter. I'd like to have a hybrid set up. The battery is 12 volt. The solar panels are supposed to be compatible. So I'm looking for suggestions on a good reliable mppt pure sinewave charger 12 volt to 110_120 volt ac. With built in 3000 watt inverter or bigger.

Thanks ahead of time.
 
300W or 3000W inverter? If the latter, you're going to need more panels.

If you're running 24/7, even a good 3kW inverter is going to have a 28±5W idle consumption. Add 1-4W for your SCC, so say 34W total idle draw. 34W*24H=816Wh/day before you start running loads.

I leave it for others to chime in about Canadian real world production per nominal watt, though I expect a ceiling of one full power hour equivalent - AKA less than nameplate watts as watthours. ETA: This is for poor production cloudy days. Bright summer may easily get you 5+ hours nameplate output equivalent.
 
3000 watts would power anything I threw at it. Under normal circumstances it will run about 300 watts. I just wanted to have some growing room with 3000 watts.
 
OK, if you only run the inverter about four hours per day that makes a huge difference in system size. With the inverter going for active use only we can more or less ignore the idle consumption and just look at efficiency.

From what you're saying here:
Code:
  4hrs runtime
x 300W average consumption
÷.85   inverter efficiency
---------
~1412Wh evening usage
 
 +  3W  SCC idle
 * 18hr Solar idle
 --------
   54Wh daily SCC idle

Or, you need an average of 1.5kWh per day. For 2.17kWh in LFP, that is about 75% drain in the evening, assuming all draw is after the panels are no longer generating. Tolerable for LFP, but nothing much to spare. If you don't make it up the next day it'll be generator, grid, or do without. If you have a second battery, I'd definitely stick it on the system. That will be nicer to your batteries and give you enough charge to handle a zero input day.

Regarding SCC, I've been pretty happy with my Outback FM-80 and am near to pulling the trigger on Outback SCC & inverters for a new system, but am hesitating on finding they appear to use proprietary comms protocols only. Still a nice unit, and doesn't need any controller to adjust all settings for a small system. For the tiny additional price over the FM-60 I don't see why I'd ever by the FM60. Midnite is well-regarded, but I don't have experience with them.

Here in Hawaii, even on a rainy day I've been able to get 1.8kWh out of 1.28kW of higher end REC panels. As I've started to read the forum here I've seen winter reports of (panel watts/2) watt hours or less in a dreary winter day, even with MPPT charger. The 4.3kWh battery will help a lot with those grey days. Two days of half of usage charge would be no problem.

Off-grid is a matter of balancing generator/minimally used grid input vs. having more panels that don't provide any benefit during stretches of bright sunny days. That's a matter for your cost/benefit analysis to determine.
 
I'd like to have a hybrid set up. The battery is 12 volt. The solar panels are supposed to be compatible. So I'm looking for suggestions on a good reliable mppt pure sinewave charger 12 volt to 110_120 volt ac. With built in 3000 watt inverter or bigger.
Why do you need a 3000W inverter? For a den?

This unit here sorta matches your description- up until the 3000W part. You may know you need that many watts but that’s not clear. Your panel selection indicates you don’t need a 3000W inverter. Without knowing what you’re trying to power there’s no way to say.
 
I'll be running a tv, dvd player, maybe router and modern, a light and a box fan. Once a week or so I need to run a vacuum cleaner. Short time. I may at some point need a microwave for brief period of time. Like I said 300 will work for average usage I just want some growing room.

Additional panels can be added. I can double the panels and double the battery. I was hoping to avoid this as I wanted to build 2 small units instead on 1 medium sized
 
These are my thoughts as a newbie here. There's probably glaring errors so I hope some of the smart people will correct me!(y) Just food for thought... :)

2.17kWh battery....roughly a 180aH battery? Discharging down to 20% remaining power would mean you have maybe 145 battery amp hours to work with with a fully charged battery. System losses of maybe 10%....drops available amp hours down to around 130aH.

You have 500w of pv panel. With the MPPT scc maybe a 90% efficiency, so 450w of power.

I'm not sure of your location, so solar sun hours are unknown...even in Canada there is a fair amount of variability. Thinking optimistically, let's say 3.5 sun hours averaged annually per day (more in the summer~5), less in the winter~2). The 450w pv system will *roughly* provide 130 amp hours per day. The max amp hours available from the battery appear to be fairly well matched to the pv panel production for the *average* sun hours....provided every day is a good, sunny day.

So, for clear blue skies you can burn 130aH a day. The 900-pound gorilla in the room, though, is a rainy day...or two rainy days. You need to consider conserving some of those amp hours for "no sun" days. One rainy day...cut the usage in half. Two rainy days, better cut back to a third of the usage...around 43aH. More pv panels and more battery capacity extends the run-time during "no sun" spells.

In all of this, don't forget that the inverter will require a portion of that power....probably 15-20%....?????:unsure:

But, anyhow, I would do an energy audit to see what my needs are. Check the amps used on the appliances that your interested in using. Then figure the amp-hour use of them. Your modem uses maybe 0.25amp...so in an hour it would use 0.25 amp hour....four hours would add up to one amp hour. Something that uses 10-amps will use 10 amps over an hour period. Something running 1.5-amps will use 1.5 amps over an hour period....1.5aH. Two of the 1.5amp devices powered for two hours would use 3 amp hours. Etc., etc.,... Time x current. Take the anticipated usage amounts of your devices and subtract the total of them from the 130aH production of your pv system...for a "sunny day" calculation. Don't forget to look at the "rainy day" scenarios, too. And, don't forget to include inverter losses.

Your battery has the capacity to store all the daily production of your 500w pv system. But, your pv system cannot restore your completely discharged battery...only around 130 amp hours and on a sunny day. So, live within your means regarding your amp-hour usage and all is well. (Again, don't forget about those rainy days.

These are some jumbled, disconnected thoughts but maybe they will give you figures/ideas to look at.

Best wishes!(y)
Ed
 
In all of this, don't forget that the inverter will require a portion of that power....probably 15-20%....?????:unsure:
 
I live in the USA in the state of Virginia. I get around 5 hours of good sunshine per day. I use 285 watts per hour. This converts to 2.85 amp per hour so 11.4 amps per normal day. I did not factor in system losses. Did I calculate that right?

Let's say I'm now building a 1000 watt solar array with 4.3 kwh battery. I need a charge controller /inverter combo for that 12v to 110 pure sinewave mppt. Anything else I need to look into and any recommendations?

Thanks to everyone who has chimed in so far. You're help is much appreciated
 
Did I calculate that right?
Amps per day is not correct. Do you mean Ahrs? It would be easier to follow if you stuck with a single unit of measure instead of alternating between Ahrs & Watthrs.
Also a 1000 Watt of solar will not produce 1000 Watts except under perfect conditions. Summer and winter could also vary by 50%.
 
Last edited:
Let's say I'm now building a 1000 watt solar array with 4.3 kwh battery. I need a charge controller /inverter combo for that 12v to 110 pure sinewave mppt. Anything else I need to look into and any recommendations?
The MPP Solar 12V AIO sounds like it could work for you. Look it up, read the specs, get confused with the lingo :) and come back here and use your thread to learn what you need to know

Have compiled the specific device watts and time periods you are planning to run?
 
With those measurements, the numbers I wrote above will come out about right, maybe giving you a little breathing room, which is good. Take them to this calculator https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP and start plugging in some numbers. It should give you a decent guess at what you need for panels and batteries. Change the discharge cutoff to 50% if you're thinking some kind of lead acid, 75% for LFP.

Note: I don't know whether it adds anything for system efficiency to your consumption input. I suspect not, but if it does you running your inverter only 4hrs per day would help. OTOH, having all consumption in the evening is harder on the system. Anyone more familiar with planning and/or this calculator have input here?
 
I plan on using approximately 300 watts from 110 volt for a 4 hour time span pretty much every day. I want an aio pure sinewave inverter that can handle anything I though at it. I will have twin 12 volt, 2.17 kwh batteries and 1000 watts of solar panels. I live in SW VA. I get decent sunshine. I think my setup as described should be sufficient enough to watch tv?

What am I forgetting? Amps, someone asked about amps. I used an online calculator to convert 285 watts and that's what it gave me.

I apologize for being so green. It seems like a simple question in my head but few aio units seem to exist that advertise pure sinewave.

Am I asking too much from my setup?

Do I need to change inverter size? 2000 watt surge should do it 99% of the time.

Should I forget about the aio and use a charger and an inverter?
 
having all consumption in the evening is harder on the system.
I don’t think there will be an effective difference. Unless a fridge needs to run turn inverter off.
Anyone more familiar with planning and/or this calculator have input here?
Not me

I didn’t do the math either, but wildhat guessing I’m pretty sure I could do what he listed with my 800W system if I wasn’t running the furnace for winter. Def in summer. The battery spec is a little light on Amp Hours to be happy.
But that’s very much a seat of the pants wild guess. The battery bank specs seem fluid.
but few aio units seem to exist that advertise pure sinewave.
I think that’s the other way around
Am I asking too much from my setup?
I don’t think so. But your numbers vary here and there so…not sure.
Do I need to change inverter size? 2000 watt surge should do it 99% of the time.
What is going to surge?
One of your lists and your 300W mentioned seems like the 1000W would be fine
Should I forget about the aio and use a charger and an inverter?
An Epever and a Giandel may be less money than an AIO but then you’ll need a few other things with separates.

Honestly the AIOs look more attractive all the time. I wish for a 1200W or 1500W pure sine output that will take 150V on the SCC and have string disconnects built in with a switchable 10A/50A 120VAC smart charger built in. A PnP zero-export UL grid-down disconnect would be a bonus It’s a unicorn though. :)

Lower-priced AIOs just don’t look sketchy anymore like they did a few years ago. Maybe it’s just me or hanging out here has made me more comfortable but I used to be askeered of non-component stuff.
 
Last edited:
I don’t think there will be an effective difference. Unless a fridge needs to run turn it off.

Not me

I didn’t do the math either, but wildhat guessing I’m pretty sure I could do what he listed with my 800W system if I wasn’t running the furnace for winter. Def in summer. The battery spec is a little light on Amp Hours to be happy.
But that’s very much a seat of the pants wild guess.

cant get the calculator to work.



With those measurements, the numbers I wrote above will come out about right, maybe giving you a little breathing room, which is good. Take them to this calculator https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP and start plugging in some numbers. It should give you a decent guess at what you need for panels and batteries. Change the discharge cutoff to 50% if you're thinking some kind of lead acid, 75% for LFP.

Note: I don't know whether it adds anything for system efficiency to your consumption input. I suspect not, but if it does you running your inverter only 4hrs per day would help. OTOH, having all consumption in the evening is harder on the system. Anyone more familiar with planning and/or this calculator have input here?
 
Regarding units, there are three, and two of them sometimes have an added time component:

Volts: how much force is pushing the energy through the system.
Amps: how wide the stream of energy is.
Watts: Volts x amps. A measure of how much power is flowing through the system.
Watthours: Watts x hours. Energy equivalent to a specified number of Watts consumed for an hour. This is the key unit.
Amp-hours: A somewhat dangerous unit used for battery capacity. Specifies how many amps x hours can be drawn from a battery. This is somewhat variable as a slower draw will allow more apparent capacity. The only reason this works is a battery has a specified nominal voltage, which means if you know the battery voltage you can calculate Watthours from it. Unless you're directly comparing batteries just convert to Wh and be done with.
 
For the calculator, put in your location and fill in the right box like this. Adjust panel angle and orientation as appropriate to your plans. The performance tab will tell you the most at a glance about your proposed system.
 

Attachments

  • solarexampleswampfox.png
    solarexampleswampfox.png
    34.1 KB · Views: 2
That's a good start. For off-grid systems the key is balancing how much you need auxiliary power from a generator with sizing the system for the worst winter weather. The latter will leave capacity on the table during summer. With a pretty direct sun and about a year and a half of not always paying attention, the worst days I see reasonably often are barely 1.5 sun hours equivalent, and 2-2.5 sun hour days are fairly common. The sun here is relatively hard to block, peaking 44° from S horizon in winter, and 92° in summer.
 
Back
Top