New 2 panel solar array questions...

[SunEagle]

I see, thanks for clarifying. My 4 batteries are 12v 35Ah.

If i go with the batteries hooked up in parallel for 12v i will go with the following inverter:

http://www.amazon.com/gp/product/B007SLDDHQ/ref=ox_sc_sfl_title_4?ie=UTF8&psc=1&smid=AWZ3LXPHZK09

As for the lights, I will have a total of 3 fixtures with 2 bulbs each and the bulbs will be those cree 9.5w lightbulbs. so total consumption will be 57W and the tickle charger is rated for 20W.

With only a 12volt 140Ah battery system I would look for a smaller inverter in the 400watt range max. You loads are small so using that 1000 watt inverter will just use battery capacity even if no load is on.

With those 57watts of lights and that battery system you can probably get away with running them about 7 hours a night. If you add the trickle charger and depending on what wattage it really consumes you can run those light only about 6 hours a night.

The problem is the low Ah rating of your batteries even with 4 wired in parallel. That system gives you about 1680 watt hours total and you should not discharge your batteries more than 25% each day. So 25% of 1680 watt hours comes to about 420 wh. That gets you about 6 hours with a load of 70 watts.

I just realized your batteries can not handle a 45 amp charge. They are too small for that and will get hurt. Use only one of those 260 watt panels not both.

[daonlyillwiz]

If that is the case then i can return the batteries because i just bought them.

There is someone locally selling two 12v 125ah batteries. You think i should return the ones i have now and buy the ones he's selling ? If i do this will i be able to hookup both panels ?

PS: i can also buy 1 245Ah battery instead of the two 125Ah batteries for a little less. Would one battery do the job ?

[daonlyillwiz]

Just got back from the store, i returned the 4 batteries. Im awaiting your advice

[SunEagle]

Just got back from the store, i returned the 4 batteries. Im awaiting your advice

A single 12volt battery rated 245Ah would be better then the 2 x 12v at 125Ah. Unless the cost is a lot more for the one compared to the 2.

Now with those 520 watts you are still pushing the possibility of over charging that 245Ah battery if it is a FLA type. If it is AGM then you may be ok.

The charge rate would be about a C/6 which is high but only if the panels are performing at their maximum output.

[daonlyillwiz]

Yep the 245ah is an AGM battery. I may just get two of them and connect them in parallel if i can get some sort of discount on them if i get two, if not ill just get one. Thank you so much for all the input, i learned a lot today

[Sunking]

A single 12volt battery rated 245Ah would be better then the 2 x 12v at 125Ah.

Well heck Yeah if your knuckle's drag the ground when you walk upright. A 12 volt 245 AH batteries weigh in around 150 pounds. Be better off getting 2-6 volts 245 ah battery.

[SunEagle]

Well heck Yeah if your knuckle's drag the ground when you walk upright. A 12 volt 245 AH batteries weigh in around 150 pounds. Be better off getting 2-6 volts 245 ah battery.

I agree. I was thinking of you when I thought of that battery.

He didn't mention if any 6volt batteries were available so the single 12volt 245Ah (while very heavy) is sure better than two 12volt 125Ah in parallel. Even then that 520 watts of panels may be too much for that 245Ah on a really sunny day. But the OP got the panels first and now is trying to make them work.

[daonlyillwiz]

I agree. I was thinking of you when I thought of that battery.

He didn't mention if any 6volt batteries were available so the single 12volt 245Ah (while very heavy) is sure better than two 12volt 125Ah in parallel. Even then that 520 watts of panels may be too much for that 245Ah on a really sunny day. But the OP got the panels first and now is trying to make them work.

Exactly i bought the panels and now i have to just make them work. I got a really good deal on them too, they are brand new and paid 480 for both panels + mounting hardware (including brackets and rails). I will look around to see if i can find 6v batteries but if i cant ill get 2 of those 245Ah batteries.


PS: My wife and i go to gym so carrying that heavy battery shouldnt be so bad

[Sunking]

I agree. I was thinking of you when I thought of that battery.

He didn't mention if any 6volt batteries were available so the single 12volt 245Ah (while very heavy) is sure better than two 12volt 125Ah in parallel. Even then that 520 watts of panels may be too much for that 245Ah on a really sunny day. But the OP got the panels first and now is trying to make them work.

Just poking fun at you.

[SunEagle]

Just poking fun at you.

Me too. Back at ya.

[daonlyillwiz]

Just curious, when you guys said "The batteries can not handle a 45 amp charge. They are too small for that and will get hurt. Use only one of those 260 watt panels not both." How do you calculate this?

Also i wont be doing this but am curious. If i wanted to tie these two panels into the electrical for my house is it as simple as just getting a grid ties inverter and plugging it into an outlet that can handle the amperage or is that incorrect?

Source for the above question:https://www.youtube.com/watch?v=YZKaZfEZHro

[SunEagle]

Just curious, when you guys said "The batteries can not handle a 45 amp charge. They are too small for that and will get hurt. Use only one of those 260 watt panels not both." How do you calculate this?

Batteries have a designed charge and discharge parameters. An FLA battery is between C/8 (highest) and C/12 (lowest) where the C = Ah rating and 8 & 12 are hours. So based on that range your 140Ah battery could be charged at C/8 = 140Ah/8h = 17.5amp or C/12 = 140Ah/12h = 11.7 amps. Too fast a charge rate requires the charger to raise the voltage above the battery limits and can cook the battery.

Now with your 520 watts you can get up to 43 amps of charge capacity. So that 140Ah battery system would see a ratio of 140Ah/43amp = 3.25hr which is way too fast for FLA.

If you only use one 260 watt panel you can get 21.5 amps of charge. So now that 140Ah battery would see a 140Ah/21.5amp = 6.5h which is fast for a FLA battery but ok for an AGM type.

Battery Ah size needs to be "matched" to the solar panel wattage and charge controller. Too big or little on one side will either run your batteries down quickly or over charge them.

With a 245Ah battery and 520 watts of panel & MPPT charger you can get charge rate of 245Ah/43amp = 5.7h which while again fast for FLA should be ok for AGM.

Someone check my math because I am doing this without any coffee.

[daonlyillwiz]

Makes sense, thanks for clarifying. How about getting a grid tie inverter and connecting that directly to an outlet in my house? and if i were to get a grid tie inverter i would need to get something w/ at least 65v and 600w right? Just trying to wrap my head around that. Im still going to do the battery setup but i would like to learn

[inetdog]

Also i wont be doing this but am curious. If i wanted to tie these two panels into the electrical for my house is it as simple as just getting a grid ties inverter and plugging it into an outlet that can handle the amperage or is that incorrect?

I am very glad that you will not be doing that.
The "plug and pray" grid tie inverters, in low wattages and intended to be plugged into a normal household receptacle, usually on an existing circuit, are totally illegal for use in the US and most other industrialized countries. They are a fire hazard and their efficiency is far lower than claimed.
The National Electrical Code does not allow for any method of connection for a PV GTI system other than hard wiring by an electrician.

[daonlyillwiz]

I am very glad that you will not be doing that.
The "plug and pray" grid tie inverters, in low wattages and intended to be plugged into a normal household receptacle, usually on an existing circuit, are totally illegal for use in the US and most other industrialized countries. They are a fire hazard and their efficiency is far lower than claimed.
The National Electrical Code does not allow for any method of connection for a PV GTI system other than hard wiring by an electrician.

Yea thats what i thought haha. It seemed a little questionable, thanks for clearing that up.