New 2 panel solar array questions...

[daonlyillwiz]

Ok so i got my MPPT Tristar CC (mppt45), i hooked it up to my 2 batteries (2x145aH AGM in parallel) and to my 2x lg panels (520W output power). I have installed a 50A breaker right before the positive terminal on the battery, am i also supposed to install one on the positive out of the solar array right before the CC, if so what size do i need to install?

[russ]

Hi abbas - Welcome to Solar Panel Talk!

Russ

[abbas17haider]

my introduction

Hi,
I am abbas and new on the forum and have little or no information on solar panels, but i want to learn more. Hope you can help me

[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?

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

Darn. I got all wrapped up it explaining the battery charge ratio I didn't respond to your second statement.

As inetdog states; those cheap grid tie inverters that plug in are illegal in the US and unsafe. Please do not even consider using them.

A grid tie system needs to meet your Utilities requirements and the local electric code. You can't do that by just putting in a couple of panels and an inverter.

[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.

[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]

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

[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]

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 poking fun at you.

Me too. Back at ya.

[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.

[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

[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.

[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.

[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