solar system for shed

[Freeesun]

Ya I've read with a mppt you can change the voltage. But those are expensive cc

[littleharbor]

I just found out that I could use a 24v panel to charge a 12v battery..... this kinda changes everything. I'm surprised nobody said this earlier.

Would that be using a MPPT controller? If using a PWM controller you will get poor performance. There's lots of things you CAN do but that doesn't make them right, practical or safe.

[Freeesun]

I just found out that I could use a 24v panel to charge a 12v battery..... this kinda changes everything. I'm surprised nobody said this earlier.

[sdold]

Go read this when you get a chance, it's a good explanation of why 72-cell grid-tie panels are preferred over 60-cell panels for small 24V systems (less than 300 watts or so) using inexpensive PWM charge controllers. It also explains why a "12V" panel is not really 12V, and a "24V" panel is not really 24V.

https://www.altestore.com/blog/2016/...s-60-72-cells/

[Freeesun]

Ohh lol I didn't click it. Ya that another option as well. The reviews on their equipment seem good.

Whats funny is I thought solar was so basic and I keep learning more and more about it and once I finally thing I know it all you hit me with a 24v panel can't charge a 24v battery bank.

you have to be an electrical engineer or study the laws of the Thermal dynamics to be able to connect a panel to a battery.

[sdold]

32 volts is about the Vmp (max power) of a 60-cell panel, so I'm guessing that's what it is.

EDIT: Don't go the Harbor Freight route, you will not find them recommended here. That link I gave you was for an extension cord.

[Freeesun]

Ya I found a company that is willing to sell me a Canadian solar all black panel. 295watt that does 32v
i will look into harbour freight I've seen. A lot of videos of people using them

[sdold]

Also I would like to do it as cheap as possible but everything is really expensive.

Harbor Freight makes a good product that would work well in this application. I'd recommend it over any of the other options discussed.

Seriously though, when you say a 24V panel, are you talking about a 60-cell grid tie panel? I don't think those have enough voltage to charge a 24V battery. I think you'd want a 72 cell panel. Others will confirm. At any rate grid tie panels should be the cheapest/watt if you can get them locally. Are there any solar installers up there that would sell you one panel?

[Freeesun]

It's very hard for me to put a number on it because it's a shed and I won't be using it everyday but when I do I would like to be in there for a while and have electricity. Also I would like to do it as cheap as possible but everything is really expensive.

i found 2 Trojan gel battery's that have 77ah but they're $200 American each

costco has car deep cycle for I believe $150 each. But they are 95ah which I still believe is too high because I don't have a mppt I have a pwm

i think as of right now I'll get the 24v panel. 12v high watt panels are rediculosly priced. And two Costco deep cycle car batteries and hope they last for a long time

[sdold]

i probably ahouldnt buy a 24v panel and just get a 12v panel and buy 2 batteries and not 4. I've read that the only reason to go to 24v is if your over 1000watt sysatem

It doesn't sound like you've defined your loads and how much energy you need. Everything is based on that and you can't select anything until you know how many watt hours per day you need. You need to pick a number and design from there. Forget about running things like heaters or air conditioners, just the bare minimum that will get you by.

[Freeesun]

Every time I think I'm getting somewhere something stops me

[Freeesun]

The ones at Costco have 208ah which is way to high for a 300 watt panel. The panel I want says it outputs 9.14a so I would need a battery which is 90ah

i probably ahouldnt buy a 24v panel and just get a 12v panel and buy 2 batteries and not 4. I've read that the only reason to go to 24v is if your over 1000watt sysatem

[SunEagle]

Ok so even though the amps are lower the volts are higher keeping it the same.

The store closed by the time I went to go get the panel so I'll get it money.

anybody know any good battery stores to buy golf cart battery's at?

You can find golf cart batteries at Costco, SAMS, Rural King or even Batteries Plus.

[Freeesun]

Ok so even though the amps are lower the volts are higher keeping it the same.

The store closed by the time I went to go get the panel so I'll get it money.

anybody know any good battery stores to buy golf cart battery's at?

[J.P.M.]

Ya but what I mean by it is that once you do the math for lights bulbs for instance and power consumption goes way down because your dividing everything by 24v and not 12v so basically it's double the power but not really

9w led x 1 hour = 9 % 12v = .75
9w led x 1 hour = 9 % 24v = .375

so basically not literally a 24v setup at 50ah is 12v at 100ah.

my run times with a 24v setup with all my appliances the same will double?

No. Unless, that is, you've found a way to violate the 2d law of Thermodynamics - but that's a bit off topic.

Your ignorance of the basics is causing problems with your logic.

The power consumption is the variable. It's the load that needs to be met. If a task, no matter what it is, requires 9 W of power (power == the rate at which work is done, or the rate at which a task consumes energy), it requires 9 W of power. That power can either be supplied by a 12 volt system or a 24 volt system, or "any" volt system. The power draw will be 9 W regardless of the battery or system voltage. What you may be missing is that power == (system voltage) * (current draw).

A 9 W load met using a 12 V system will produce a current in the circuit of 9 W/12 V = 0.75 A.
A 9 W load met using a 24 V system will produce a current in the circuit of 9 W/24 V = 0.375 A.

You need to understand that the energy stored in a battery system is what counts. 12 V and 100 Ah = 12*100 = 1,200 W-hr. of stored energy. If a load consumes power at the rate of 9 W, it will use 9 W-hr. of energy for every hour it runs. So, 1,200 W-hr. of stored energy will be enough to meet a 9 W load for ~ 1,200 W-hr./9 W = ~ 133 hrs.

A 9 W load running in a 12 V circuit will draw twice the current of the same 9 W load running in a 24 V circuit. For the same run times, the energy consumed by the 9 W load will be the same for either circuit.

Go back and review the basics of how electricity works.