newbie trying to build solar system on a budget

learningsolar wrote:
hello everyone.....I was pointed here from popupportal as I am trying to create a decent pv system.....I used to work at a manufacturing plant and so I have 72 cell 240 ish watt panel i am trying to use... voc today in terrible conditions was 45.2 volts with 2.3 amps....but have found controllers to do this job are very expensive....I have removed junction box cover and was able to get 3 circuits at 15 volts which would allow me to use a cheaper controller as I would assume even in the best of conditions I would be under 20 volts amps I would assume would be under 20 and allow me to purchase a cheaper controller....I have a 1500 watt inverter and am going to be using either 2 12 grp 29dc battieries from wallmart or maybe 3 if needed but doubt it... I am on a budget and so trying to do this as cheap as possible while having a good system.....here are some pics of components I am using....also a drawing of how cells are wired within panel....any help would be appreciated...oh ya and this is for my newly purchased coleman Utah tent trailer.....allot of power for a tent trailer but might also be temp camp on lot until built so I wanna make it good....
thanks



mix and match panel with mono and poly cells in it


opened j box with 4 leads and diodes to isolate circuits so if one cell gets damaged whole circuit isn't compromised....I am not worried about that though

and this is how ever circuit is wired.... each string of cells is 12 cells long in series on 72 cell and 10 on 60 cell panels


am I on the right path?? these panels can be purchased very cheap from the manufacturer because of defects but still produce good power and can be used off the grid, everyone avoids this thought because mppt controllers are so expensive to reduce voltage they would rather buy ct solar kit @ 30 watts cuz its plug and play

what are the pros and cons to re-wiring down to 12-20 volts instead of higher voltage???

thanks

learningsolar wrote:

I understand that but don't know what kind of drop to expect to see with load on it and cuz i don't have a controller or any sort of load to hook up its the only measureable number i can get and sc amps from panels....I have individual cells as well and so i could measure individual output if numbers are wanted....i planned on making my own tailored to a 12 volt system but way better with already assembled panels just got to get that voltage down by either wiring or a fancy controller...

westend wrote:
Guys, will the Ecoworthy controller work for his module without all the rewiring fuss?

red31 wrote:
Voc is zero power (no amps), that's why 12v panel is Voc of ~21.

pianotuna wrote:
Hi CR,

My nose (and hat) are off to BFL13. He loves to play. He has helped many folks and his research is always worth looking at.

He and I look at solar from a different perspective. He wants a small system that is aimed and portable. I want a larger fixed "set it and forget it" system. Both approaches work well, but I get to camp while he gets to tweak his panels.

Canadian Rainbirds wrote:
Voc should be in the 18-21volt range as far as I recall.

Pianotuna and BLF13 both have extensive solar experience. At the risk of putting Don's nose out of joint :B , BLF13 has I think more experience in playing with actual numbers and doing innumerable experiments.

Don has lots and lots of experience using solar in the Great White North. (Read COLD and SNOW)

There is lots of good Solar help here.

In fact I am going to be posting a question for a recommended new solar controller very soon.