Acei wrote:
westend wrote:
Have you done the calculations for daily use? 1800AH of storage is huge, also 500 lbs. of added weight.
The Sanyo panels are nice but I doubt the price will bear out any increased efficacy over the life of comparable modules, sold at much lower prices. Of course, value may not be your criteria. There is worth in buying the higher priced item, sometimes.
Edit: Saw where you used the spreadsheet to calculate daily use. Something is probably amiss (like refrigerator duty cycle?), you are about double what most power gobblers report for daily use.
I've simply done it based on a residential fridge power consumption. I took annual power consumption number from bestbuy.com then figured out the daily consumption from that. It worked out to be about 100Ah. Does this sound about right? Alternatively, I can go with that compressor based one which appears to use about half that, but obviously the capacity is far smaller.
And the Sanyo panels - I have three reasons for this panel. First is, as you mentioned, for additional few % efficiency, which I agree isn't enough to justify the price difference. The second, is that the pannel _should_ (I didn't confirm this yet) work better under less optimal lighting conditions due to its hybrid use of amorphous and mono cells. Third, is more of an insurance. This combo overall may only return an additional 20% power over a panel that costs half as much (inc. cloudy conditions), but if I do end up using that extra 20% once a month, I would pay for it. Besides, I do plan to keep this trailer for 8+ years, so I don't think the price difference is going to make that much difference at the end.
Having said that, if I made wrong assumptions, please point them out!
I believe your AH estimate for a fridge is on the high end. If you go with the Danfoss 12v compressor unit, you should see about 20-40 AH/day, depending on use and ambient. I use a small dorm fridge and it uses 80w at a 1/5 duty cycle. The newer Samsung 10 cu. ft. models use just a bit more.
To each, his own, on the module choice. I don't see that the Sanyo HIT modules are that much more efficient to harvest 20% more power. I chose to buy a discontinued 235 watt USA made panel for about a third the price of the Sanyo. I'm about 99% sure any warranty is out the window but the Mfg. is still building modules. If warranty is important, then a Sanyo or Sharp module makes sense.
Good luck with your solar installation!
Edit: Yup, 900AH for those Trojans, I should have caught that. Still, a heck of a lot of capacity.
