Grid tie inverter (Chinese) + Batterie charging ??

[colerainescotty]

Hi Folks,

Thanks again for your advice, it's truly great what can be learnt here and thanks so much for your expertise and contributions.

After much searching I could not find exactly what I want to ask so sorry If it is indeed embedded somewhere else.

Righto... I had made a 36pcs panel 0.5V 3.6a sc. I have a battery bank of 4 X 75ah batteries 12V in parallell in my garage for my lights and other small appliances.

The panel always keeps the batteries at full capacity and it seems that I am wasting a lot of power as the panel is producing more than I am using so....

I bought a chinese 350W GTI from eBay and it works great.. (I love experimenting with this stuff)

So I seen a video on Youtube where a chap also from the UK had hooked up his panel to his battery bank via charge controller and then also linked up the GTI in parallel to this. So...He was keeping batteries topped up and exporting around his house also.

Please note: I have two 80W Mono panels on order as I do not want to use my DIY panel for the GTI (Just to clarify this) Heres the rough specs:

80W Panel Specifications:

Operatine Voltage: 18.0V
Max Operatine Current: 4.54A
Open-Circuit Voltage: 21.24V
Short-circuit Current : 4.95A
Max-Power: 80W
Max System Voltage: 1000V


But.. Can I link up my panels to the charge controller and GTI in parallel to charge the batteries and export excess around my home?

If so, is this safe? I would like to keep the battery system as a backup as the batteries are good Gel type deep cycle and it is a cool wee setup.

If however... And I think you may suggest this, you would rather recommend the GTI and that I just use from the grid as I need (To limit waste) then do you think I could sell my off grid setup when my new panels come? and if so.. How much do you rekon I could sell it for ?

My off grid setup consists:

- DIY solar panel with plenty of vent holes on it (Which has stamped out condensation)
- 4 X Deep cycle Gel type 12V batteries @ 75ah each (300ah)
- 1 X 12/24V Charge controller (eBay special
- The wiring, diodes etc
- 300W Belkin inverter 12VDC - 240VAC

Don't worry guys, I built the DIY panel for enjoyment (Although it's a good hardy panel and holds up to the rain pretty good) and I don't think obviously that it is worth what a new panel would be so no offence will be taken in advance

Finally.. Sorry for the long post

Lets say until I find a new home for my off grid setup (If that is whats advised) could I link this up also with my new 80W Mono panels from eBay 160W total + the DIY roughly 60W to export around my house?? (I thought no as obviously the DIY won't be as good but I welcome advice) The DIY puts out short circuit roughly 19V 3.2A

Guys.. cheers for your time and hope to hear back soon

Ryan

[Mike90250]

I don't really want to touch this, but you will soon kill your batteries.

Your 60w DIY panel, will barely keep the 4, 75 ah batteries charged (300ah) A 60 w panel can over a 5 hour good solar day, harvest 300 watt hours. That's 9KWh a month, or about a dollar worth of electricity. ( at 11 cents KWh )

Your GTI inverter, likely does not have an efficiency spec, so it's likely about 75%, as opposed to real ones with 95% eff.

There are 2 types of GTI inverters, one for strictly solar panel use, and one only for battery use. Plug the wrong one to the wrong source and you have smoke.

[Sunking]

I don't really want to touch this,.

I am not going to touch it either, let him learn the hard way so as he will not forget the lesson.

[Mike90250]

I would appreciate anyone who likes to explain and help out rather than someone who would rather make unnecessary comments that simply doesn't help!

The thing is, we are trying to tell you, but you don't want to hear our answers. the 2nd and 3rd time, we start making more comments to try to have you hear what we are saying. If you paint lipstick on a pig, it is still a pig.

[Mike90250]

Model # of the GTI inverter & it's specs

sticker info off the solar panels. Voc, Pmax, VpmaxSharp208_c.jpgBattery_Volt_Chart.jpgSolarPanelFire_1c.jpg

[Sunking]

OK here are the problems.

1. The inexpensive GTI you have is poorly designed and constructed, and terrible efficiency of 50% at best.

2. The price of th eGTI is extremely high compared to other units that are made for real applications.

3. Batteries are very inefficient and extremely expensive requiring constant replacement when used in the manner you plan to use them by over discharging them daily. You might get a month or two service out of them before they fail instead of lasting 3 to 5 years.

Add all that up and instead of paying your electric company say 20 cents/Kwh, you have now chosen to pay more than $2/Kwh or higher for what little power it can generate. In your location with the maximum 250 watt solar panel you can generate if you are lucky 1 Kwh/day, about 20 cents worth of power per day. Sooner or later you will realize (learn the hard way) it is costing you way more money than just buying from the local power company. You will be reminded about every month or so when you buy a new battery to replace the one you destroyed.

[Mike90250]

The GTI, if it's working properly, will hog all the power from the PV, and the battery won't charge.

GTI's generally have a MPPT input, and seek the max power out of the array, leaving nothing for the batteries.

Its generally a poor idea to put 2 different types of controllers and loads on the same PV array. They don't play well with others.

[rbtrrer]

So what is the GTI's supposed funtion?

[Mike90250]

So what is the GTI's supposed funtion?

GTI's generally have a MPPT input, and seek the max power out of the array, Ther function is to push as much power as the internals allow, out to the grid.

[rbtrrer]

Thanks Mike. From the diagram, I don't see how it does anything.

[Mike90250]

Thanks Mike. From the diagram, I don't see how it does anything.

Apparently, it has not had connection approval from the local electric company yet, so he's not showing it connected to the AC circuit