Will this work for garden shed.

[Rich585]

Hello all.

Reading through the posts gave me an idea to recycle some stuff I already have to get me some power to a garden shed 150 ft away from house.

My primary intent is to have a light in shed to see when dark and to have a small 3A battery charger on the riding lawn mower battery.

Last year we had a drought and I did not start the lawn tractor for 6 weeks and it killed the battery after only a couple of years. (Past 12 month warranty) .

So I am thinking of going a new LiFePO4 for my trolling motor, so the basic idea is:

Take the old 5 year old size 24M AGM trolling battery (65 aH when new still works, but lost some capacity).

Purchase a 10A solar charge controller and 50W 12 V solar panel connected to the AGM battery.
Buy a 10 ft long solar cables 12 AWG from solar panel to charge controller inside shed. (Canadian $100-200)?

Then for garden shed, buy a $20 - 12 V light meant for RV in the shed (has built in switch).

Use 12 or 14 AWG automotive copper gauge wire (overkill for 3-5 A load, but I have 50 ft spool) to wire from solar charge controller to batteries and light.

Use automotive 10 A fuses in splice in fuse holders at each battery end and one in the line from solar panel. I guess this is safer to leave unattended than just clamping on a set of jumper cables between the two batteries.

For the lawn tractor, I have a Canadian Tire Motomaster 200w modified sine wave inverted I could hook up to AGM battery to power a Noco Genius 3500 (3.5A charger) or just connect the lawn tractor battery to the AGM battery. I have concerns of the mismatch of the two batteries (marine AGM (big) and lawn tractor battery (small starting).

I live 30 minutes south of Ottawa, On Canada, so Vitron panel calculator estates average 0.3 KW production per day April to Oct.

My questions are:

1) Is will the first option work of using the cheap 200w inverter to power the charger. The charger will almost be on float 90 % of the time keeping the lawn tractor battery from discharging. This is only from spring to fall. In winter I bring the battery into the garage and trickle charge it.

2) Should I use the inverter and charger (already have, sitting around not being used) or connect the batteries in parallel ?

3) Would 50 Watt solar panel be enough? Assume the AGM battery is charged and solar is only maintaining a float on it. The led light 3 or 6 W might get used for 1-2 hours 3-4 times a week. There is no other electrical need in shed (used for garden equipment storage, not a work shop (garage).)

Any suggestions ? Anything I am doing wrong?

Thanks

Richard

 

[45North]

Hi Richard and welcome to the forum.
You could also run a line 150ft from the house to the shed in a trench or something, although I can certainly see the merits of hooking up a lot of neat stuff, especially if you already have them.

 

[svetz]

Welcome to the forums!

... intent is to have a light in shed to see when dark and to have a small 3A battery charger

idea is:

• 5 year old size 24M AGM trolling battery (65 aH when new still works, but lost some capacity).
• 10A solar charge controller
• 50W 12 V solar panel connected to the AGM battery.
• 10 ft long solar cables 12 AWG
• Canadian Tire Motomaster 200w modified sine wave inverted
• Noco Genius 3500 (3.5A charger)
• Vitron panel calculator estates average 0.3 KW production per day April to Oct.

Don't forget to check the ampacity of all wires.

... I have concerns of the mismatch of the two batteries (marine AGM (big) and lawn tractor battery (small starting).

I'd just use the best of the two, an LED light wont take much. I'd hook them up like this:

...Panels->SCC->battery -> lightSwitch
....................... ->Timer -> Noco -> tractor

Or use a cheap pwm SCC to trickle charge the tractor when the sun's up since it's just to keep that battery topped off:

...Panels->SCC1->battery->light switch
........ ->SCC2->tractor

My questions are:

1) Is will the first option work of using the cheap 200w inverter to power the charger. The charger will almost be on float 90 % of the time keeping the lawn tractor battery from discharging. This is only from spring to fall. In winter I bring the battery into the garage and trickle charge it.

Depends on the wattage requirements of the charger, but 3.5 amps x 12 = 42 watts so should be okay. Verify it doesn't need a pure sine wave inverter.

2) Should I use the inverter and charger (already have, sitting around not being used) or connect the batteries in parallel ?

see above

3) Would 50 Watt solar panel be enough? Assume the AGM battery is charged and solar is only maintaining a float on it. The led light 3 or 6 W might get used for 1-2 hours 3-4 times a week. There is no other electrical need in shed (used for garden equipment storage, not a work shop (garage).)

Your post said you could expect 300 watt hours per day, so 6W at 2 hr/day = 12 watts. To know for sure you'd need to know the consumption of the SCC and the charger, but at a glance it looks like plenty.

 

[Rich585]

Thanks for the replies.

I first thought of a running a wire to the shed, but a few years ago I ran a 50 ft long cable to a hot tub and it took a full day with a rental trencher to dig out the 50 ft. (Lots of softball sized rocks in the fill the builder used).
The 150 ft length would take 3-4 days plus the cost of wire, and electrical inspection, so between the cost and the effort to dig, it has not been worth it for a lawn tractor.

I am still a little confused on wire ampcity. For wire amp handling, the tables I have looked at indicate that 14 gauge wire (copper) should be good for 15 - 20 Amps, so the 5 amp expected load (use 10 amp fuses) I think should be plenty if I read them right. 120 VAC wiring is simple, electrical code book states 14 gauge=15A breaker, 12AWG = 20A, 10 AWG = 30 A. The DC charts have a big range depending on voltage drop. 12 Gauge wire has max amp handling from 5A (30-100ft) to 25 A (6-20 ft). Not as clear and kind of confusing. So I am assuming bigger is better (up to a point cost wise).

I was thinking of poor man's version of Will's milk crate solar generator. Have the old marine battery in a marine plastic case and bolt the SCC and inverter to the lid and just run the wires to the battery case so its a mobile/temporary installation.

Thanks for doing the math for the sizing. I was not sure if 50 W panel would be big enough or too big. The main load will be maintaining the U1 size 200-300 CCA starting battery if I don't cut the grass for a few weeks. I think since size wise it is only a 2 x 2 ft panel, good way to start and I can leave it outside all the time instead of a portable panel that I have to worry about wind blowing away, rain etc.

From what I read it is only MPPT chargers that are damaged unplugging battery, PWM I can leave the panels hooked up and just disconnect the lawn tractor battery ?

Still cold here, but so have lots of time to sort this out.

Thanks for suggestions and clarifications. It is appreciated.

 

[svetz]

...
From what I read it is only MPPT chargers that are damaged unplugging battery...

You might enjoy https://diysolarforum.com/threads/trying-to-destory-my-sccs-i-cant-do-it.3896/

 

[deeuubee]

I would get a 100 W panel just to make sure there was enough to charge the battery on cloudy days.
On a good day, the 50W is at most 3amps. The cost is probably the same.
For the batteries, I'd get a basic diode 2 battery isolator. You could hook both up and not have them interfere with each other.
There are hundreds of light choices. From 5V usb's that plug right into the controller to 12V table lamps.

 

[Rich585]

Svetz - interesting link. Good controllers not a problem, cheap controllers gamble. I am seeing Victron gets a lot of love here.

Deeuubee- That is an interesting bare bones option. Going to look into that. Thanks.

 

[deeuubee]

Frugal is my middle name
I'm in the process of doing the same for my shed.
I put a simple switch circuit in and just ordered these for light: 12V DC Bulbs

I'll be charging a trolling motor battery and riding mower that way.