Advice and input greatly appreciated...

[swhiting8]

I have the following items:

-GroWatt SPF 3000 LVM 24v .
- (2) Renogy 12v AGM 100Ah batteries .
- 250 Amp 32v bolt fuse .
- shutoff switch .
- (2) 100 Watt panels @ 22.4 Voc .
- 2 awg cables connecting everything.

If I hook the panels up in series, on a good day I should have a Voc of 44.8 , am I correct in this thinking???

If I connect the batteries in series, I should benefit from a 24v system @ 100Ah, an I correct in this thinking??

Will this be enough to utilize the GroWatt 3000, 24v, MPPT AIO system?

If not... what can I add or change? I will however, decide later what I'll be running off this setup, but for now, my main concern is whether or not the GroWatt will function properly as inverter and mppt charge controller.??

Also.. in a side note... do I need to invest in a BMS for AGM batteries or are those only for Lithium Phosphate batteries? And if I need one, what might you suggest?

Thanks for any suggestions and advice.

 

[ghostwriter66]

Yes you are correct on series being 44.8

As for amp - the 100W panels - on a good day will give you about 80% rated power ....

Thats a pretty good size inverter ... not sure what you are running .... or where you are located at .... also remember - you have a 24V 100A battery which is going to be begging for much more in panels then you are providing ... so depending on what you are running - you may not keep up ...

Also -- that inverter draws X% from the battery 24/7 idling - so with your system being small -- if you are not using it - turn off the inverter ...

YES - you should be able to use the MPPT system perfectly fine ..

again -- i would need allot more info -- but looking at what you provided -- your OK ... just really need more panels ...

NO to the BMS -- LiFePO4 is NOT FORGIVING -- AGM's are ... well at least until you start running real power into them -- but you are fine ... if you want a BMS you can find a cheap one for a few dollars ... I like BMS's because I can see the system on my iPhone and don't have to measure it physically each time

 

[Darren67-72]

It should work, looks like you understand the basics!
With 2 solar panels bringing in about 80%ish of their rated capacity and only able to trip the startup voltage, at near midday, of the mppt. I just wa t to remind you... you can only get out, what you put in. (Or a little less).
Good start!!!

 

[ghostwriter66]

It should work, looks like you understand the basics!
With 2 solar panels bringing in about 80%ish of their rated capacity and only able to trip the startup voltage, at near midday, of the mppt. I just wa t to remind you... you can only get out, what you put in. (Or a little less).
Good start!!!

And by the time you subtract the true 20% from the panel rating, the battery inefficiency, the MPPT being 97% ... the inverter being 85-90% --- yeah they all add up .... thus why i said -- MO' PANELS ...

 

[Mattb4]

With only 200w of panels you really do not have enough to cover your inverter's daily self consumption. I would suggest at a minimum 600w.

 

[Hedges]

Probably voltage is OK. You're correct in using Voc to check maximum voltage. (If many more in series, need to do adjustment for record coldest temperature, make sure it remains under 145V)

Minimum MPPT is 30V. Panel Vmp under STC conditions is 18.6V, two in series 37.4V. That drops a bit with temperature and reduced illumination, likely remains above 30V.

More panels!
You can get bigger, higher voltage panels. They may be a better deal, especially used. But large commercial panels require truck shipping, so look for local sources.
You can mix PV strings of different brand, but connect various numbers in series so Vmp is similar.
More than 2 strings in parallel (into a single MPPT input), each should have fuse of value shown on label.

 

[swhiting8]

And by the time you subtract the true 20% from the panel rating, the battery inefficiency, the MPPT being 97% ... the inverter being 85-90% --- yeah they all add up .... thus why i said -- MO' PANELS ...

I will definitely consider this.. and as of now. I'll only be powering up my cable modem, and wifi router. So I have continuous internet access.. my router communicates to my wireless door lock and my wireless ring doorbell. I'm building all this up on a handtruck, for portability.

But thank you much in your second opinions and advice.. and I will also add 2 more Agm batteries within this coming year.

 

[swhiting8]

Probably voltage is OK. You're correct in using Voc to check maximum voltage. (If many more in series, need to do adjustment for record coldest temperature, make sure it remains under 145V)

Minimum MPPT is 30V. Panel Vmp under STC conditions is 18.6V, two in series 37.4V. That drops a bit with temperature and reduced illumination, likely remains above 30V.

More panels!
You can get bigger, higher voltage panels. They may be a better deal, especially used. But large commercial panels require truck shipping, so look for local sources.
You can mix PV strings of different brand, but connect various numbers in series so Vmp is similar.
More than 2 strings in parallel (into a single MPPT input), each should have fuse of value shown on label.

Got it... more panels... thank you much for your expertise and advice.. this forum is what I needed before flipping the switch..

 

[Hedges]

The point Mattb4 was making:

60W no-load power consumption of inverter? x 24 hours = 1440 Wh/day.
200W of panels, 170W if you're lucky, 1020Wh in a good 6 hours effective sun day.
Lead-acid battery maybe 80% round-trip efficiency, 800 Wh/day to feed inverter.

You would have to power inverter off 12 hours each day just to have no-load AC the other 12 hours.

You need more PV panels just to keep your head above water.

Router, etc? Can you feed them from 12V directly, ditch the inverter?

 

[Hedges]

... And by the way, I think Ghost Writer has installed more systems than a dozen of us put together.

 

[Doggydogworld]

Router, etc? Can you feed them from 12V directly, ditch the inverter?

I second this motion. Look at the AC power supplies for your router and modem. Do they both put out 12V? If so I'd convert them and just run a 12V system. You could probably even use a $10 PWM controller off Amazon (not a recommendation, just saying....). Save the power-sucking Growatt for another project when you have a lot more panels.

 

[swhiting8]

I second this motion. Look at the AC power supplies for your router and modem. Do they both put out 12V? If so I'd convert them and just run a 12V system. You could probably even use a $10 PWM controller off Amazon (not a recommendation, just saying....). Save the power-sucking Growatt for another project when you have a lot more panels.

Hi. So when you say convert them, and run a 12v system, what equipment are you suggesting I'll need besides the pwm. I already own a Renogy Wanderer Li30. That's what I'm using currently, but I don't have any inverters. That's why I decided to go with the AIO Growatt . But I'll hold off on the GroWatt if you could give me an idea or diagram of what is included as a 12v system instead. Thanks for all your advice and suggestions in advance.

 

[Hedges]

First see if your equipment would operate off 12V (if it requires a different voltage, then consider DC/DC converter). Just get a cord/plug for that (and maybe add a fuse.)

You could use PWM, maybe want an MPPT charge controller. Here's one retailer with several models:

Charge Controllers | SanTan Solar

www.santansolar.com

PV --> MPPT --> battery --> loads

RV Solar Power Blue Prints

Building a vehicle mounted solar power system? Let me help.

www.mobile-solarpower.com

 

[swhiting8]

First see if your equipment would operate off 12V (if it requires a different voltage, then consider DC/DC converter). Just get a cord/plug for that (and maybe add a fuse.)

You could use PWM, maybe want an MPPT charge controller. Here's one retailer with several models:

Charge Controllers | SanTan Solar

www.santansolar.com

PV --> MPPT --> battery --> loads

RV Solar Power Blue Prints

Building a vehicle mounted solar power system? Let me help.

www.mobile-solarpower.com

You all are awesome.. thank you much.. I'll let you know what I decided to go with.. thanks a bunch.

 

[chrisski]

If I hook the panels up in series, on a good day I should have a Voc of 44.8 , am I correct in this thinking???

Yes, but VMP is around 36 volts. As long as you are over 5 volts more than the battery charge you will be fine. The two cases this could drop is the panels are in partial shade or cloudy days. It could be better to hook them up 3S. Honestly though in those instances, I do not produce enough power on my 2S panels to add another in series.

Also.. in a side note... do I need to invest in a BMS for AGM batteries or are those only for Lithium Phosphate batteries? And if I need one, what might you suggest?

I would say no, but some sort of shunt to monitor the battery itself is great. I have the Victron 712 BMS, but any shunt will do.

My highest constant consumption is about 2000 watts and I have about 2.6 kw of panels, and I use the shunt to be sure I am actually getting enough solar during this time to not drain from the battery.

Actually, for you, what to watch out for is nor to put too many amps into the AGM. Batteries. Your spec sheet will say, but a FLA battery this limit is 10% so 10 amps. Could be any where from 10% - 30% Four X 100 watt panels can exceed that limit.
=====
The idle draw of your inverter could chew up to one panel or more production a day, so if you want to use the Growatt, may need more batteries and panels.

Personally I am a fan of using inverters over going the Dc route and believe in designing the system to overcome the conversion losses and idle draw losses. For what I’ve done on my RV would never pay to convert anything From AC to DC. Also, having an inverter is so handy for other things you might want to do.

 

[Hedges]

Some way to shut off loads, preventing lead-acid battery from being discharged too low, as Chrisski says.

Max/ideal charge current. FLA I think wants about 0.12C. The brand AGM I have actually wants 0.2C minimum and says it can take higher currents for a while. Lithium typically accepts 0.5C
100 Ah x 12V x 2 batteries = 2400 Wh total.
0.2C x 2400 Wh = 480W charging or 40A into 12V battery.

An SCC sized (or programmed) for 40A would avoid charging faster than that.

I think you can put in about 50% more PV, 700W or so, without clipping (wasting available power) if you orient 350W South East and 350W South West. Just connect those sub-arrays in parallel and the MPPT will harvest power from them for more hours of the day.

You could still built a 24V system, and turn on an inverter when you want AC. But using a 24V to 12V DC/DC converter for the always-on loads would let you get by with less PV, less battery.
Those of us with bigger systems just use AC/DC adapters for small additional loads. I have considered using AC/DC + PV to maintain a 12V battery so some equipment has a backup system running off a backup system, since I do sometimes run down the batteries on my 48V whole-house backup.

 

[Doggydogworld]

Hi. So when you say convert them, and run a 12v system, what equipment are you suggesting I'll need besides the pwm. I already own a Renogy Wanderer Li30.

Here a video of a guy quick-and-dirty splicing a modem cord to use a 12V cigarette plug. The circuit diagram @Hedges linked is good. Just cut out the inverter part.

Some cheap controllers have "load" terminals. They're only designed for light loads, like a few light bulbs. Or..... a cable modem. You can usually program them to shut off under certain conditions, e.g. three hours after sunset or if voltage drops below a certain threshold so you won't drain your battery too far. I don't see load terminals on your Renogy Wanderer, though. So you'd need another way to monitor things. Which could be as simple as regularly checking it manually. Or if you have the Wanderer's optional Bluetooth module you could have it send alerts to your phone or something.

If you plan to power lots of other devices from these (and additional) panels an all-in-one makes sense. But for a modem and router I'd rather keep things simple and use what I already have. You can always spec out a bigger system later.

 

[swhiting8]

Here a video of a guy quick-and-dirty splicing a modem cord to use a 12V cigarette plug. The circuit diagram @Hedges linked is good. Just cut out the inverter part.

Some cheap controllers have "load" terminals. They're only designed for light loads, like a few light bulbs. Or..... a cable modem. You can usually program them to shut off under certain conditions, e.g. three hours after sunset or if voltage drops below a certain threshold so you won't drain your battery too far. I don't see load terminals on your Renogy Wanderer, though. So you'd need another way to monitor things. Which could be as simple as regularly checking it manually. Or if you have the Wanderer's optional Bluetooth module you could have it send alerts to your phone or something.

If you plan to power lots of other devices from these (and additional) panels an all-in-one makes sense. But for a modem and router I'd rather keep things simple and use what I already have. You can always spec out a bigger system later.

Got it. Thank you..I believe I will do this.. but I will take it a step further.. I will attach the 12v plug and have it all spiced together having the option of ac or dc ? As long as both aren't plugged in at the same time, I see no harm in that, do you?

 

[swhiting8]

I second this motion. Look at the AC power supplies for your router and modem. Do they both put out 12V? If so I'd convert them and just run a 12V system. You could probably even use a $10 PWM controller off Amazon (not a recommendation, just saying....). Save the power-sucking Growatt for another project when you have a lot more panels.

Yes. Both has the 12v , 2A on one and 12v, 1.5A on the other. So I can do as you suggested. I also have an Alexa echo that uses 12V, 1.25A. All of my lights are Bluetooth controlled and use 8.5 watts. So a I start progressing later on down the road..I can start wiring my essential devices into 12v system.. and ordering an inverter if needed , but will get the suggested 40A mppt charge controller, so if I should get the inverter I can add it down the road..

 

[Hedges]

Something like this can be operated in parallel with the solar charge controller. So long as AC is present, battery will be kept a float (longer life).

4 Amp Fully Automatic Microprocessor Controlled Battery Charger/Maintainer

Amazing deals on this 4 Amp 12V High Freq Battery Charger/Maintainer at Harbor Freight. Quality tools & low prices.

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