Newbie solar shed setup

[tvd1]

Hey all - Solar newbie here. I have had a 20w panel hooked up to a deltran battery tender for a few years but I now have a bigger shed and want to upgrade. Here's what I'm proposing to do, would love some input on what you think.

First off, i'm looking to power two Harbor Freight LED shop lights (https://www.harborfreight.com/light...ft-linkable-led-hanging-shop-light-56781.html), one motion sensor LED light for out front, and one Deltran battery tender for my motorcycle.

What im getting:
-100w HQST solar kit w/ 30A PWM controller (https://www.amazon.com/gp/product/B09WDM8CGP/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&th=1)
-Renogy 700W Pure Sine Wave Inverter ( https://www.amazon.com/gp/product/B07JMW8MMR/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1)
-For battery, im still not sure between the HF Thunderbolt Solar ( https://www.harborfreight.com/12v-35-amp-hour-sealed-lead-acid-battery-64102.html ) or the Wally world Everstart ( https://www.walmart.com/ip/EverStar...-Battery-Group-Size-29DC-12V-845-MCA/20531543 )
-And two fuses, one for between the panel and the PWM (https://www.amazon.com/gp/product/B08C26GJGQ/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&th=1) and one for between the battery postive and the PWM ( https://www.amazon.com/gp/product/B01LY2PRWW/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&th=1 )

Obviously i'll probably upgrade things as needed, like the charge controller or battery, but wondering if i'm starting off on the right track. Thanks

 

[Rednecktek]

I'm a huge fan of the WallyWorld 29DC's myself, MUCH better value than the HF 35a batteries, especially considering that lead acid batteries are only good for about 50% of their rated capacity (so the WallyWorld is 60Ah for $100, the HF is 17Ah for $70). Go with the WallyWorld battery.

That fuse to the inverter is waayy too small. It should be 700w/12v = 58.33, * 85% inverter efficiency = 67.08a * 20% overhead = 80.5a (but an 80a would be fine.

Where are you located? I'm in Western WA and I have 200w of panels on my shed feeding a 29DC and a 200w inverter. 4 months a year it can't generate the 120Wh of standby power that the inverter draws. A 100w panel is going to be good for about 300Wh a day with that controller nerfing your panel.

The lights are going to be about 160 watts after inefficiencies, no data on the motion light but it's going to have a constant draw of a few watts while it's off, let's call it 2w. The inverter according to the manual is going to use about 10w. So, adding all that up for a 24 hour day you're looking at:

Inverter = 24hr * 10w = 240Wh
Motion Light = 24Hr * 2w = 48wh
Battery Tender = 24Hr * 15w = 360Wh

Total sustained draw = ~650Wh per day. The DC29 is usable for 60Ah so 60Ah * 12v = 720Wh

Shop lights = 160W/hr * $N hours

That's only going to let you run the shop lights for about half an hour a day before your inverter is screaming about low voltage and your battery is complaining about being hungry.

Now, on to the panel. A 100w panel on a PWM controller is only good for about 75w of usable power due to the way PWM's work. Assuming the standard of 4 hours of good sun a day, you're going to need about 10 days of good sun to recharge your battery. Of course that can't happen with all the standing loads you've got so you're just going to have a damaged battery in about 2 days. The battery is going to want solid 12+ amps of charging current if it can have it, or about 3x what your panel can produce. Not Good.

What can you do about it? Well a few things are options to help:

1: More panels! Like 300w worth! If you live somewhere that has regular cloud cover like me, 500w isn't unreasonable.

2: MPPT Controller. For a single panel system PWM is "Good Enough" usually, but somewhere around the 250-300w mark the extra cost (they're about $100 for a decent one) they really start to shine and pay for themselves quickly. As a rule of thumb get 10a for every 100w of panel.

3: Smaller inverter, there are decently low standby power inverters in the 300w range that will save some power draw.

4: A DC-DC battery tender. Converting from 12v up to 120v then down to 12v is just death by a thousand cuts. Get something that is 12v powered, or just use the SCC's "Load" ports connected to the battery. I do that for my bike and just set the Low Voltage Disconnect on the PWM to 12.6v so if the battery gets too dead the SCC stops feeding the bike, and doesn't try to drain the bike like some cheaper PWM's will do (ask me how I know... grrrr). That battery tender is half your battery capacity not including the losses from converting the volts back and forth.

Sorry to be the bearer of bad news.

 

[tvd1]

Thanks for the thorough response! To respond..

1) I'm not sure what fuse you are talking about.. The one between the battery and controller? If so, the renogy one i was looking at only has a 60A and 100A, so i assume i'd go 100.

2) I'm in Massachusetts. I could go with two panels, I assume daisy chaining a second wouldnt be difficult if I had the need. I dont think I'll be running the lights for more than 15-20 minutes a day.. More like none on week days (if not for 5 mins here and there) and more on the weekends.

3) I know the MPPT's are better.. Do you have any recommendations for a good starter one for my setup?

4) So you think the 700w inverter is overkill? If so, what 300w unit would you reccomend? I saw this on amazon ( https://www.amazon.com/AC120V-inver...66&sprefix=300w+inverter,aps,159&sr=8-11&th=1 ) ... maybe this will do the trick?

5) DC-DC tender: I have actually thought about that. Currently im using this wired directly to a 20w panel ( https://www.batterytender.com/Battery-Tender-Solar-Controller ). This works great, but of course turns off when the sun goes down. But its enough to keep my moto batteries topped off. Honestly its only charging a few minutes a day, the rest of the time its in maintenance mode. But i was thinking of wiring that battery tender controller into the load ports of the PWM/MPPT.. but that might be redundant, or maybe the MPPT could do that natively as you mention.

Anyway, thanks again for your help!

 

[tvd1]

Anyone got any good small inverter recommendations for this set up?

 

[GLC]

I wonder how good these batteries are from Wallmart, Ampere Time 200AH batteries for 700? Sounds good just wonder if they are any good

 

[GLC]

Anyone got any good small inverter recommendations for this set up?

The thing about inverters is buy what you can afford, buy what has a low watt draw with no load and buy what you may want to expand to in the future. Not a problem at all to buy like a 1000 to 2000 watt inverter with a low amp draw where in the future when you expand the system, it will be there for you. Also factor in if you try to use a small watt inverter in the future with something that has a motor it may be too small to pull it because of the start up draw.

 

[tvd1]

The thing about inverters is buy what you can afford, buy what has a low watt draw with no load and buy what you may want to expand to in the future. Not a problem at all to buy like a 1000 to 2000 watt inverter with a low amp draw where in the future when you expand the system, it will be there for you. Also factor in if you try to use a small watt inverter in the future with something that has a motor it may be too small to pull it because of the start up draw.

thats the thing.. looking for something with a low watt draw off my battery. My system isnt exactly beefy so wherever i can save, I want to do that. So thats why im looking for a recommendation. This is what i have coming (https://www.amazon.com/gp/product/B07JMW8MMR/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1 ) but i'll return it for another if I can find something that pulls lower

 

[GLC]

First what ever you choose, get a pure sine wave converter. Modified sine wavs converters will create havoc with electronic devices, charging stations and motors. As far as smaller inverters, Giendel makes good units with low amp draws at idle. My 4000/8000 watt inverter only draws 7 watts at idle. That is almost unheard of as far as low energy draw. I am attaching a 600, 1500 and a 2200 watt version below .
https://www.amazon.com/Inverter-600Watt-Control-Outlets-Emergency/dp/B07J4ZXVTS/ref=sr_1_24?crid=DTW8IJXJ94UW&keywords=Giendel+inverter&qid=1653584682&rnid=5911589011&s=automotive&sprefix=giandel+inverter,aps,96&sr=1-24&th=1

https://www.amazon.com/Inverter-600Watt-Control-Outlets-Emergency/dp/B0918Y4HYX/ref=sr_1_24?crid=DTW8IJXJ94UW&keywords=Giendel%2Binverter&qid=1653584682&rnid=5911589011&s=automotive&sprefix=giandel%2Binverter%2Caps%2C96&sr=1-24&th=1

https://www.amazon.com/GIANDEL-Inverter-Control-Display-Outlets/dp/B07CKBJ9KP/ref=sr_1_22?crid=DTW8IJXJ94UW&keywords=Giendel+inverter&qid=1653584682&rnid=5911589011&s=automotive&sprefix=giandel+inverter%2Caps%2C96&sr=1-22

 

[tvd1]

So here it is complete (still gotta clean up the wires a bit). 100w HQST panel on the shed (which is partially shaded). Harbor Freight 35ah battery (mem weekend sale, $50!), upgraded to the Renolgoy Rover MPPT 30a. 300w pure sine inverter, and a 30amp fuse between the battery and MPPT. Also a 15 amp fuse between the panel and MPPT (not visable). Definitely some tradeoffs but its a start.

So far i'm powering an LED strip light on the load side, and off the inverter is my moto battery tender running there. So far in the past few days the battery does struggle to fully charge and usually by the end of a sunny day the battery is at 60%. I'm going to add a motion sensor LED light to the front of the shed.. not sure if i can put it on the LOAD of the MPPT or i need to wire it into a plug on the inverter (Thoughts?).

Anyway, already looking like a second panel is likely going up in the near future, but that location would be even more shaded than the first one. So we'll see. Let me know what y'all think.

 

[tvd1]

Rain tomorrow.. should be interesting to see how it holds up.

 

[tomsoftail]

This was a great thread for me. Thanks a lot for it!