Solar Power Question

free bump because your avatar is the best carved pumpkin I've ever seen in my life.

Thank you AC!

A common formula in electronics is Volts x Amps = Watts
or Watts / Volts = amps. So 20watt panel / 12v = 1.7 amps.


Now with about 8 hours a day of solar, you will charge your battery 1.7 amps x 8 hrs = 13.6 amps per day you can put into your battery. This is called Amp hours or AH and deep cycle batteries are rated in AH.

This works out to you using 1 amp for 13 hours or 13 amps for 1 hour or .5 amps for 26 hours etc.

The 30 amp charge controller is too much for what you are doing because that would be good for 360 watts of solar panels and now you are spending some $$. For your system go on ebay and buy a cheap solar charge controller of 10amps for about $15 -20. The more panels , the more batteries you'll need, the bigger cables, the bigger inverter...see what I mean? 10 amp charger would allow you to expand up to 120 watts of panels.

Have you seen the Harbor Freight 45 watt solar panel kit that comes with the panels and charger? They retail for 299 , but if you check sales and online you can get it for 149.


BTW
Do not use a car battery as that is rated in Cold Cranking Amps or CCA. you need to look for AH. You'll ruin a car battery in a few weeks.

Good Luck

Good advice, AC. I'm guessing 30 amps would damage the system?

Edit: And yeah that 12v battery I have now is a 230 cca starter battery. I picked it up cheap for some electronics projects I was working on. I plan to get some deep cycle batteries in the future.

You can buy a small solar household batteries charger for C,D, AA, AAA rechargeable batteries for about $19 at HF. It a small kit about the 1/3 size of shoe box. This will keep
small radios and flashlights going in SHTF. The best solar bang for the buck.

I don't think the 30 amp will damage you system , just overkill and more expensive for no gain , unless you got a 30 amp for free or really cheap.

Tell me your budget and what you have on hand already and I'll give better advice. Me.. I've got 1000w solar and 8 golf cart batteries with 5000 watt inverter. I had a steep learning curve.

Well the reason I thought about getting a 30 amp charger was because I plan on expanding. No sense in getting say, a 10 amp charger if later I just have to switch it out, right? Right now I'm budgeted for about 1600.00. I'd like to keep it under that of course :)

On hand I've got the 20 watt 12v panel, the 350 watt inverter, one 12v starter battery, one 12v marine battery which is about 5 years old, and a couple of 6v batteries. Like I said, I'm starting with next to nothing here lol
Yeah I'm learning too since I have practically no experience with solar systems.

A MPPT (Maximum power point tracking) controller will give you 20-30% extra power that otherwise will turn to heat, but they cost a little more.

If I were you I would get 15A or maybe 20A from the start so that you can expand.
If you are handy, you can solder your own Li-ion batteries cheaper than absolutely most lead based batteries.
But then you need a different type of solar charger.

I'm just about to make the transition to li-ion myself. Otherwise you need deep cycle batteries and they are not cheap.
I guess the li-ion gets 2-3 times cheaper and should handle 1000-2000 cycles.
They produce less heat when charged also.

I know a little about pwm and mppt but not much. What type of controller would I use for li-ion batteries? I know once I start buying deep cycle batteries I'm going to pay some major $$$

Another question. Should I get a higher rated inverter? The 'inverter' that I have now, is actually a 350 watt ups that I rigged a 12v battery up to. So far it has worked pretty well for small appliances and such.

Ideally, you will make a transition to devices that are 12V native.
First of all, lights. There are quite some amounts of LED's that are designed for 12V.
Second, you will need an amplifier, lol. Buy one for cars that also runs on 12V.
Unless you are not planning on using heavy machinery, I think the inverter you have will do for the rest.

I have found li-ion batteries that costs less than $1 / 10Wh

Just google "li-ion pack solar charger" to find the charger, but I will make one myself.
The thing with li-ion is, that the cells have about 3.7V, so you can only design batteries that are multiples of that. 11.1V (3 cells) is closest to 12V.
I'm thinking of going for a 24V native system (i.e 22.2V).

I will do that. Thank you Sweden!

Here is a whole kit

[link to www.ebay.com]

Inverter

[link to www.ebay.com]


Leaves you with about $800 for batteries

One more thing you need to consider is how much sunlight do you get in one day. If you are only going to have one or two 12v deep cycle batteries a 7amp charge controller should be enough. The larger the power inverter used, the more power it drains from the battery. Just an approximation a 1KW power inverter with no load draws 1.5-2 amps just sitting there so you only want to have it on when you need it. If you want to run an entire house, minimum you would need around 3KW of solar panels and a bank of batteries for it to be of any practical use. Sharp sells 80 watt panels with a 25 year warranty. Look at website called wholesale solar-- You can get a better price than retail stores.-- Hope this helps.

It's sometimes cheaper to make your own battery cables, especially if using multiple batteries. You want flexible , multi strand wire for DC. The cheapest source for this kind of wire is at a welding supply house. The longer the run, the thicker the diameter. The diameter of a Sharpie marker would be good and allow for some expansion and higher amps. Learn how to hammer crimp

Thank you guys, really great advice. From what I read, I should get about a 15 amp mppt charger. I'm fine with my inverter for now but I will have to upgrade eventually. I will also need bigger wire...

Ok so now, I have a 12v 20 watt panel and a 12v 100 watt panel. If I wire these together in parallel, will that give me 120 watts at 12 volts?

OMG I finally saw The Road



what a great movie! how sad!