Advice on workshop system

[Atlin]

New to this forum, but not new to solar (have been on and off-grid since 1980s). I'm building a small workshop that will be off-grid and looking for advice/confirmation that I'm on the right track with a solar system. Usage will be perhaps once a week a small heater in winter (350W x 2 hours) plus occasional LED lighting (very low usage) and occasional power tools. Tool usage will be restricted to benchtop drill press, small bandsaw, and shop vac. None of these would be operated more than maybe 15-20 minutes/day, and not every day.

My proposed system would be a single ~300W 12V panel with charge controller serving 3, ~100Ah 12V batteries. On the output end, I'm thinking a 1500W/3000W surge square wave inverter, since there will be no sensitive electronics in the system. I would expect the biggest draw and surge demand will be the shop vac. Location in western CO, average daily sun hours ~5.5 and no obstructions/trees etc. The goal is to never let the system get below ~20-25% DoD. I will have a gasoline generator to use if/when necessary but hope to only require it maybe once or twice a year.

So I'm looking for input on whether this system sounds reasonable to do what I want. Specifically, I would be interested in any input on panels, batteries (I'm planning AGM for ease of maintenance), charge controller, and inverter from those of you who have dealt with these things recently and/or regularly. Is there any reason to go to a pure sine wave inverter? Smaller or larger capacity? More batteries? Like most, I'm trying to keep costs in line.

Thanks,
Atlin

[Sunking]

Something does not work, a common mistake we see here every day.

A 300 watt panel into a 12 volt battery can only handle a battery up to roughly 200 amp hour plus or minus 50 AH and require a 30 amp MPPT controller. Basically a pair of golf cart 6-volt 225 AH batteries A pair of Trojan T-105 on it best day can only handle a 1000 watt watt Inverter at most and that is pushing your luck. That will not run a shop vac or drill press and nothing with a motor will work right using a Modified Sine Wave Inverter.

A 1500 watt Inverter really needs to be 24 volts, and to run a 24 volt 1500 watt inverter is going to require a 24 volt 225 AH battery or 4 of those same trojan batteries wire in series. Just to keep those batteries charged properly will require 600 wat panel and the same 30 amp MPPT controller. If you require to run motor loads like a shop vac or power tools demands a good True Sine Wave Inverter.

If you insist on doing this your way, is going to require a very expensive 12 volt 200 AH AGM battery made to handle very large loads. Something on the order of a pair of Concorde Sun Extender PVS-2240T, 6-volt 225 AH AGM battery. Those can handle a 150 amp load for 15 minutes before the die.

What you are over looking any battery has minimum and maximum charge/discharge limits. Your design is way outside limits. Lastly using 12 volt batteries in parallel is just plain ignorant. Doing that and you just cut th ebattery life in half abusing them. If you need 12 volts @ 300 AH, you use 300 AH batteries. That would be a pair of 6-volt batteries. If your Inverter is 1000 watts or more means you should be using 24 volts. You are stuck inside a 12 volt toy box since the 80's. Only RV, Campers, Toys and DIY use 12 volts. Shops, homes, pros or any serious use will be 24 or 48 volt. Much less expensive and a whole lot safer.

[AzRoute66]

Another way of saying that might be 'when you fully research your inverter needs and select that, you will find that the obvious inverter support will probably look something like [see above]'. Took me months, but 12 volt systems really are hard to justify unless you are looking at the typical small-ish camper/RV.

[Atlin]

Well, I guess I'm sorry I asked. Not particularly cordial to be told I'm an idiot in the first reply when I'm just asking for advice. This is a small system, mostly used for lighting and only rarely for tools or the little heater, thus the initial thought of going 12V. If it can be done with 24V reasonably inexpensively, that would be fine and probably preferable but I've not seen many relatively inexpensive inverters for 24V.

I'm looking for constructive advice, not just castigation.

[Sunking]

No one called you an idiot. You were told your idea will not work and how to make it work. Using solar for electric heat and power tools do not play well together and anything but cheap.

Go over to Arizona Wind and Sun Forum. There they will will hold your hand and tell you what you want to hear like how great and smart you are, then sell it to you laughing all the way to the bank.

Here you will get the truth and facts which you do not want to know or hear. So go stick your head in the sand over at Arizona Wind and Sun Forum. Ask for Karrak or Dan,

[J.P.M.]

Well, I guess I'm sorry I asked. Not particularly cordial to be told I'm an idiot in the first reply when I'm just asking for advice. This is a small system, mostly used for lighting and only rarely for tools or the little heater, thus the initial thought of going 12V. If it can be done with 24V reasonably inexpensively, that would be fine and probably preferable but I've not seen many relatively inexpensive inverters for 24V.

I'm looking for constructive advice, not just castigation.

I thought the first response to your inquiries was full of useful information presented in a straight forward and professional manner.

I didn't read the word idiot or idiocy in that first response. I did see the word ignorant. But ignorance is not a mental deficiency. Just means you don't know something (yet). Happens all the time and one big reason why people ask questions and look for input - just like you did in the first post to this thread.

Besides, around here it's all free for the taking, so take what you want. Just be careful what you ask for.

[Lars1361]

Greetings - I am new to the forum, but thick skinned so fire away

This post really caught my attention.

My personal needs might be unorthodox, but I am hoping the experts have a solution.

Live in Pennsylvania, near Pittsburgh.
Building a storage garage, an off grid system is what I need.

The garage will have:

#1 - quantity six - 16ft 75 watt 12VDC LED (UL IP68) light tapes (max four hours use per day)
#2 - quantity one - garage door opener - Genie 750 chain drive with 12VDC battery back up - (max usage will be 10 times per day) Motor is rated at 3/4 hp, and will be operating approximately one minute on each event - it will always be operated as 12VDC - the factory battery that supports this function is 12VDC 8Ah - there must be some small current also necessary for the equipment to receive the signal from the car remote, but I do not know what that is.

So in my simple mind, I am looking for a 12VDC system that utilizes an cost effective battery system. Initially I thought several deep cycle marine type batteries but I am guessing the experts might have better ideas.

Again, my needs will all be 12VDC.

Thanks !