StirCrazy wrote:
no thats not it, it averages about 2amps higher output through out the day also. so if we have a nice sunny day I get the extra say 3AH for the extra time morning and night, then I get an extra 8 to 18AH for the rest of the day depending on the time of year.
Steve
I'm certainly no expert, but that statement doesn't sound right to me. Consider these two examples: (Assume it is not early morning or late afternoon, but rather close to full sun which is most of the day. And we are only talking about sunny days in this discussion and not worrying about shade.)
Example 1: Two 12v panels in parallel producing at 20v and 4 amps each. The MPPT charge controller would see 20v and 8 amps. Assuming the charge controller wants to charge at that moment at 14v, it would supply (20v / 14v) x 8 amps = 11.4286 amps at 14v going to the batteries.
Example 2: Two 12v panels in series producing at 20v each (40v in series) and 4 amps each (which would be 4 amps total). The MPPT charge controller would see 40v and 4 amps. Assuming the charge controller wants to charge at that moment at 14v, it would supply (40v / 14v) x 4 amps = 11.4286 amps at 14v going to the batteries. The SAME amount of charge to the batteries.
I suppose voltage drop on the wire (worse with parallel panels) could have some affect. I plugged in an example into a voltage drop calculator (assuming a 30' run and 10AWG wire) and the series example above was about 2% better. 2% of 11.4286 amps would be about 0.229 amp more for the series example. After a 10 hour day of charging that would be 2.29amps extra total into your batteries if routed in series due to voltage drop savings. So if we add that to the 2-4amps extra due to earlier morning charge and later evening charge and it seems like series would provide about 4-6AH extra to your batteries compared to panels in parallel. This is using the above 200w example. I guess a 400w system would produce double the bonus or close to it. I guess it's something, but to me at this point not worth the hour or two up on the roof to reroute the panels. Maybe if I get bored sometime just for kicks I'll do it and see if I can tell a difference.
StirCrazy wrote:
now I don't know if I switched my curent 12V panels on my 5th wheel to series if it would get that same efficiency , I think part of it has to do with the split cell panel on the camper and it also has a higher effecniency rating, and the ones on the 5th wheel are you basic 12V go power panels, so probably over priced garbage.. Ill see up to 23amp going to my battery in the peak hours of the day with the 24V panel, but the 5th wheel with 30somthing percent more panel wattage at best does 21amps...... but mostly 20.
Steve
I'm not sure you can draw any series vs parallel conclusions from your two systems that are using different panels and perhaps different wiring (or distances) and perhaps different solar charge controllers. Too many variables?
On a separate (related?) note....I solve most of these "inefficient panels", "Series vs Parallel", "MPPT vs PWM", "wire sizing", "tilt vs no-tilt", etc issues with ONE SIMPLE FIX: Just put up 50% or 100% more panels than you actually need and you will be fine! (...and since I like to use very inexpensive used panels (tested) the panels are next to nothing when factoring the expense of everything else and my time to do the install). On my 500w installs, I really only wanted/needed 200-250w but I found 250w used panels for $35 each so I put up two (500w) for each of those solar installs. I think this is a easy solution for most weekend warriors who boondock less than 15 days per year. For those serious (or full-time) boondockers witih serious power needs, yes they want to be more accurate.
Happy Camping!
Chris
