Hi all.
All my tests have shown that 100w is enough for the average couple summer camping with a compressor fridge. This is particularly so with the Ocean as you have two batteries which gives a good buffer in case the weather is poor for a few days.
100w gives 5.4 amps max charging.
I use 100W panels because they are narrow, and this means they don't flex much at all, which means they will not suffer fatigue faults. I used 120W panels for a while as that is all i could get, and they are not much wider. (8cm). I abosrbed the extra cost.
I now have 100w panels and will have for the forseable future. I've got another 200 in production.
I can't mount 160w panels the way I do (unless they are traditional framed panels, which are much much heavier), and then, they will be too wide fot the Cali roof. Panels tend to go wide past 120w . There isn't much motivation for matufacturers to make them long and narrow.
You can add panels to my 100w kits very easily, the 1st panel slides forward, the new one takes it splace, and then plug into each other. As long as you go for a Victron 75/15 or 100/20, or the Epever Duo, then you can simply add a panel and keep the same charger.
The MPPT charger "wattage rating" is simply the amount they can "take" and then pass on as battyery charging. Even then, they can take more, but they discard anything over their limit. They are rated in watts as to what they can charge, not what they can receive.
I've chosen 100w as:
- My tests, with logs, show an 80W panel will keep a compressor fridge running ad infinitum in the summer in the UK. So 100w gives some headroom, and allows for the fact the thin panels lose a bit of efficiency when they get hot.
- They are structurally more rigid than larger thin panels.
- 100w is a size that enables the use of roof bars and roof boxes, if some care is put into positioning.
- 100w is an easy amount to multiply up. 2 panels, or, as recently 3 panels. You can still put your roof bar feet in between the panels and retain your roof carrying capability.
- Anything over 100 to 120w in thin panels is priced at a premium as to make 2 x 100w more cost effective
- 100w panels will go width ways on ALL vans with no issues.
This is why 100w is a "magic number".
p.s. you can't have a 160w panel that is the same size as a 100w panel. The cells are a very specific size and panel dimensions increase with wattage. There are of course "tweaks". Back contact panels are a bit smaller, but, overall, the sizes reflect the wattage. If I had a motorhome I'd have the biggest panels I could fit on it, but motorhomes and VW vans are two different beasts.