diy solar

diy solar

Solar shed-proposed set up and questions

brucedelaney

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Joined
Sep 24, 2020
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Looking to do a Solar Panel for 10x20 detached Shed / Garage on my property.

Looking to Power:
12v Lighting in the shed (probably motion on switch)
Tender a back up battery for a garage door opener
Would like to tender two other batteries (Motorcycle & Riding Mower)

Proposed System:
100W Solar Panel
PWM Controller
35ah AGM Battery

Most garage door openers that have a 12v backup battery and 12v DC motor are generally 4-8ah batteries, so I'm thinking that 35ah should be more than enough and the 100W panel should be plenty to keep it topped off. Should I just take the backup battery that comes with the opener out of the equation and wire the bigger battery directly in or should I be running them both in parallel?

I'm looking at controllers that have lighting controls built in so I'd need to add a motion switch. If there isn't a lighting tie in on the controller would I just hook them up straight the battery as well?

Is there any way to use this system to tender my other batteries (motorcycle & riding mower) w/o adding an inverter or another panel and controller?

How many amp controller should I get?

Where should I be putting fuses in this system and how big?

I live in PA, winters generally get down to around 20s and Summers can get up to the 90s in F. Should I store the battery in any type of protective housing?

I also store about 5 Gallons of gasoline in this shed besides what's in the fuel tanks of the motorcylce and mower, is that safe with the batteries?

Regards,
Bruce
 
If you can power a tender with a 12V, then yes.

100W/12V = 8.3A, so any PWM controller larger than 8.3A can handle the panel.

Fuses between 1) SCC and battery, 2) battery and load, and 3) SCC load output and load (if used)

An AGM in an insulated box should help. Optimally, you should get a charge controller with temperature compensation (most cheap ones don't).

I store 11kW of batteries fed by 3kW of solar in the same container as my generator and a gas can, so I would say it's fine.
 
If you can power a tender with a 12V, then yes.

I thought using a charge controller would act as the tender?

100W/12V = 8.3A, so any PWM controller larger than 8.3A can handle the panel.

Fuses between 1) SCC and battery, 2) battery and load, and 3) SCC load output and load (if used)

An AGM in an insulated box should help. Optimally, you should get a charge controller with temperature compensation (most cheap ones don't).

I store 11kW of batteries fed by 3kW of solar in the same container as my generator and a gas can, so I would say it's fine.

Can you recommend a controller for the temp changes and how would you recommend wiring to tend all 3 batteries? Also should I remove the "tiny" battery in the garage door opener? Or should I be looking for a product like this? https://www.nationaltoolwarehouse.com/12-Volt-Intelligent-Battery-Maintenance-Station-P284825.aspx

Or something as simple as this... https://i5.walmartimages.com/asr/94...ae392_1.fd849f1f0ea26a2436c63dc74aacc94a.jpeg
 
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Will has a link to the Renogy Wanderer on this page:


It has the option for a temp sensor that you can buy separately.

The charging product you link is fed by 110VAC as far as I can tell. You'd need an inverter, but it looks pretty slick.

In all honestly, the more I think about this, the less I like the idea. if you want to maintain those batteries, bring them inside and put them on float chargers. That's really the right thing to do.
 
The charging product you link is fed by 110VAC as far as I can tell. You'd need an inverter, but it looks pretty slick.
You're right one page I saw mentioned solar and messed with my head.

In all honestly, the more I think about this, the less I like the idea. if you want to maintain those batteries, bring them inside and put them on float chargers. That's really the right thing to do.

That's fine for the mower battery but defeats the purpose on the back up for the garage door opener and the whole reason I'm exploring solar for the shed is so I won't have to remove and re-install the battery on the motorcycle in case we get one of those oddball days I can ride in the winter.

I have a small 10w Solar maintainer already that has it's own controller but was looking to avoid doing that x3 to keep all three batteries topped off. I can do that if I have to though and use some of the various solar lighting options to illuminate. I guess I could manually change what it's charging but again defeats the set it and forget it option.. LOL

What about getting a few 20-30w panels and using something like this?

Or is your concern about the number of batteries being charged in different temps... the mower and motorcycle wouldn't require charging during Spring through Mid Fall since they both charge when running.
 
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I almost suggested their solar products, but I don't have any direct experience with them. Others on here have their solar products have worked well for them. I've never seen that particular unit.

Honestly, I'd be temped to just try and charge everything with that little guy with 3 separate charge leads. 50W, 3A panel and 3A DC out. 1A is more than enough for float... float is usually tens of mA once charged. The only concern is you wouldn't want to connect them together at different voltages. If one is low, you can just disconnect the others until it's charged.

I'm sure this is not best practice or recommended, but damn if I don't like the idea of getting away with something for $100 between the panel and charger... :)

Ceiling mount with one of those splitter dongles you linked earlier. done.

Or get one for each battery...
 
Honestly, I'd be temped to just try and charge everything with that little guy with 3 separate charge leads. 50W, 3A panel and 3A DC out. 1A is more than enough for float... float is usually tens of mA once charged. The only concern is you wouldn't want to connect them together at different voltages.

This is my concern....

I've honestly considered just swapping what is getting charged each week but again kind of defeats the purpose... LOL
 
The only risks are:

1) if the batteries are more than about 0.2V apart, a large amount of current can move between them (thicker charge cables can address this.
2) If one of the batteries fails, it will drain the others.
 
The only risks are:

1) if the batteries are more than about 0.2V apart, a large amount of current can move between them (thicker charge cables can address this.
2) If one of the batteries fails, it will drain the others.

For the mower and the garage door opener that wouldn't be too costly... however the motorcycle could get pricey.

Would it make any sense and or would it even work if I hooked up one solar panel to 2 or 3 of those charge controllers and would that solve the issue of a dead battery draining the others or the current issue?
 
If you have a voltage rail to charge several batteries, you could put a diode in series with the positive connection to each battery.
That would let the battery charge (to a slightly lower voltage, because diodes drop 0.4 to 0.7V)
But battery would not discharge back into the rail.
So if any battery was dead, it might stop the others from charging but wouldn't discharge them.
 
Or would it just make more sense to put a small inverter with 2 outlets into the equation. I know it's redundant converting DC to AC to DC again, but I could have the 35ah on the SCC basically be the main direct power source for the Door opener through the battery backup for the 12v motor and the few 12v lights I'd wire in. Then the Inverter could have 2 battery tender JR's plugged in to keep the mower and motorcycle topped off through the winter. Normal consumption for this whole system will literally only be a max of few amps at any one moment and usually in the low mA range most of the time.

Or is that just too convoluted and asking for a big mess?
 
You lose quite a bit going from DC to AC back to DC however the setup you propose has the batteries isolated - good for batteries that range from fully charged (your 35ah main) to mostly discharged (one of the batteries you plug into the maintainers).

One caution though - with an inverter running 7x24 you have some risk of driving the main battery low, defeating the purpose of the system (lights). You could wire in another low voltage disconnect ( such as https://smile.amazon.com/Digital-Battery-Low-Voltage-Protection/dp/B07929Y5SZ ) to disconnect the inverter at a higher voltage to protect your main battery use.

The key to all of the above is having all the loads plugged into a something that will protect the battery - the load side of your pwm controller or other low voltage disconnect. I've had some of the cheap PWM controllers that ran the battery quite a bit lower than their specs stated.
 
You lose quite a bit going from DC to AC back to DC however the setup you propose has the batteries isolated - good for batteries that range from fully charged (your 35ah main) to mostly discharged (one of the batteries you plug into the maintainers).

One caution though - with an inverter running 7x24 you have some risk of driving the main battery low, defeating the purpose of the system (lights). You could wire in another low voltage disconnect ( such as https://smile.amazon.com/Digital-Battery-Low-Voltage-Protection/dp/B07929Y5SZ ) to disconnect the inverter at a higher voltage to protect your main battery use.

The key to all of the above is having all the loads plugged into a something that will protect the battery - the load side of your pwm controller or other low voltage disconnect. I've had some of the cheap PWM controllers that ran the battery quite a bit lower than their specs stated.

Hmmm... "new member" Chip512 (who joined a year ago) enters the fray with a solid first post!

Good points. DC-AC-DC conversion is only about 75% efficient.

Inverters have a parasitic draw as power is consumed in having a 120VAC plug ready for use. My 4kW Victron is 30W, but lower wattage units consume less. Will has mentioned some in his videos that consume only 4W.

If you go that route, you should factor in the inverter's use of power.
 
You lose quite a bit going from DC to AC back to DC however the setup you propose has the batteries isolated - good for batteries that range from fully charged (your 35ah main) to mostly discharged (one of the batteries you plug into the maintainers).
If they're plugged in to the maintainers all the time shouldn't they be on float for the most part?

One caution though - with an inverter running 7x24 you have some risk of driving the main battery low, defeating the purpose of the system (lights). You could wire in another low voltage disconnect ( such as https://smile.amazon.com/Digital-Battery-Low-Voltage-Protection/dp/B07929Y5SZ ) to disconnect the inverter at a higher voltage to protect your main battery use.
Actually the lights aren't my main concern it's the garage door opener... I want to maintain a battery to power the 12v battery back up portion. There are so many solar lighting options out there that I can run separate from this system...
 
Hmmm... "new member" Chip512 (who joined a year ago) enters the fray with a solid first post!

Good points. DC-AC-DC conversion is only about 75% efficient.

Inverters have a parasitic draw as power is consumed in having a 120VAC plug ready for use. My 4kW Victron is 30W, but lower wattage units consume less. Will has mentioned some in his videos that consume only 4W.

If you go that route, you should factor in the inverter's use of power.

Yes I pretty much figured this would be a less than optimal solution
 
You could try a few of these break away DC-DC chargers connected to the controller maybe?

One for each M/C and mower.

They're for charging the break away battery on a trailer. Break Away Charger
 
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