diy solar

diy solar

1st time solar setup for garden

eljazera

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Joined
Jul 21, 2021
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I'm trying to incorporate solar power into a home automation project mainly just to be able to say I can do it rather then massive savings on energy use. Hopefully though it will lead to bigger and better things.

A bit of background, we rent our current property and as much as I'd love the owner to install panels on the roof for household power, it'll be a cold day in hades before he concedes and does it. Our house is an over 100 year old workers cottage in the inner western suburbs of Melbourne Australia. Thankfully I have insulated it well to deal with the Australian version of winter (I'm originally from Winnipeg, so it ain't that cold) and the blistering summers. But I digress.

My project that I'd like to add solar to is just a range of 12v items in my back garden. A small pond pump, a water tank pump for the garden beds, some solenoids and a range of spot/fairy lights throughout the garden.

I would like to build the system for potential growth, so don't want to be under powered too quickly, but I guess the main issue I want some of your advice on is what happens if I'm build too big for my usage in the short term?

If I installed a 50W panel and hooked it up to a 18amp hour lithium battery, would it be overkill if my most extreme usage in a day was 198 watt hours of power? That's with the two biggest wattage users being run only basically during daylight hours (the two pumps). I'm not planning on putting an inverter into the mix right away but could see it being added not too long afterwards to supply outdoor 240v power to run a projector for summertime movie nights (once or twice a week for maybe 3-4 months of the year, when I have 8-9 hours of daylight). Although that would be at night so maybe a bigger battery is better.

So besides the question of whether or not the initial setup is overkill or not, do I also think about a bigger battery from the get go and worry about increasing the panel output later?

I also plan to run all the 12v devices through a couple of Sonoff 4 Channel devices so I have smart control over the on and off capabilities of them. So basically it's 4 cables from the fuse box, one to each of the two 4 Channel devices for powering them, which is constant power for them to stay connected to wifi and then another cable to each to supply the 12v spread across 4 separate devices each.

Charge controller and battery will be within a metre of the panel, which will face north for best sunlight collection. 12v wiring might then run 10 or so meters to 4 channel device an on to actual location.

There is no doubt I can run this all inexpensively enough direct from mains power with a 240v to 12v power supply, but if I can keep the project under say $800 AUD to begin with at least, I'll consider it a success, with room to grow and perhaps find a way to reduce actual substantial mains power usage.

Any suggestions or advice warmly welcomed.
 
I prefer to go a little overkill usually (if I can afford the extra cost), since it will be more future proof. You can parallel more batteries in later, and more solar panels, so it will scale to some extent... Are you going to get an MPPT charge controller?
 
If I installed a 50W panel and hooked it up to a 18amp hour lithium battery, would it be overkill if my most extreme usage in a day was 198 watt hours of power?
18Ah x 12.8V = 230Wh

If the battery were completely full this should work.

230Wh / 50W = 4.6 h to recharge (with no load)

If you got a little more panel and used most of your power during the day your system would easily work for your stated goals nicely. Possibly with your listed equipment or if you were able to move the 50W panel to follow the sun a couple times a day.
 
I prefer to go a little overkill usually (if I can afford the extra cost), since it will be more future proof. You can parallel more batteries in later, and more solar panels, so it will scale to some extent... Are you going to get an MPPT charge controller?
Thanks, I was planning on getting a MPPT charge controller just so I didn't have to upgrade that later
I prefer to go a little overkill usually (if I can afford the extra cost), since it will be more future proof. You can parallel more batteries in later, and more solar panels, so it will scale to some extent... Are you going to get an MPPT charge controller?
 
18Ah x 12.8V = 230Wh

If the battery were completely full this should work.

230Wh / 50W = 4.6 h to recharge (with no load)

If you got a little more panel and used most of your power during the day your system would easily work for your stated goals nicely. Possibly with your listed equipment or if you were able to move the 50W panel to follow the sun a couple times a day.
Yes I doubt I'd ever use the full 198 wh in a day even on the busiest day, thanks
 
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