Q: Is there any advantage in adding solar panels to an existing system? ie insitu: 3x120ah batteries 2x80kw solar panels and a 2000kw inverter (3.6kw Onan genny with charger for back up). Have room on the roof for a 200kw solar panel. The current system is handling my demand ok, any advantage in installing the extra 200kw panel?
Excuse my ignorance, I too am a semi retired pilot with not too much knowledge on this subject.
Yes I guess it all depends on how much "power" or energy you can put back into your batteries in a day. My initial thought that perhaps extra solar panels may be a waste as there is only so many volts or amps that the batteries can hold. However as I learn, each panel doesn't "automatically" just top off your batteries during the day but each panel only replaces some of the power which has been drawn. ie each panel only trickles a certain power input to the batteries and it could take quite some time for the batteries to reach full charge and in fact not reach full charge at all over the period, either from usage, insufficient input or wx etc. Therefore the more panels the "quicker" the batteries reach full charge. I really hope I am not confusing everyone....I think I am starting to believe my own BS :)
Q: Is there any advantage in adding solar panels to an existing system? ie insitu: 3x120ah batteries 2x80kw solar panels and a 2000kw inverter (3.6kw Onan genny with charger for back up). Have room on the roof for a 200kw solar panel. The current system is handling my demand ok, any advantage in installing the extra 200kw panel?
Excuse my ignorance, I too am a semi retired pilot with not too much knowledge on this subject.
Thanks for all and any help B+E
Hi B+E
To my thinking you do need some more panels. Two x 80w panels is the minimum to exist with.
However if you drive every day, and your vehicle charges the batteries, then no problem. But if you do not start the engine for a while then two 80 Watt panels will be a bit frugal and would not keep your batterys charged if you used much power. You might use the genny instead but perhaps you do not need to if you had more solar input. Also depends on whether you free camp or stay in powered sites usually.
My suggestion is to get a copy of a book by Colyn River on Solar. He has written a couple, and assess what you want from your camper. Then you will be able to decide. But the solar power is free after you have set it up. And verrry quiet. Also you must monitor the batteries state of charge to ensure you are not bringing the voltage down too far, or they will die young. There is a bit to learn but it's not rocket science
Good luck jaahn
-- Edited by Jaahn on Monday 23rd of June 2014 02:34:51 PM
Lead Acid batteries Have a recommended min Draw on the Batteries of 50% SOC [ State of Charge ] - When charging the batteries the general rule of thumb is 50% - 80% SOC the batteries will take everything you can throw at the batteries.. ie Amp's.. - Once the regulator Registers that the batteries have reached 80%SOC [Which is a set minimum voltage] the charging drop's down in Amps and is pulsed..
So basically 80% SOC the batteries will only take a trickle charge till they are Full.. or close to Full..
The above chart is what you would see in the individual cells of the 12v Battery.. you need 6 of these to make up a 12v battery..
We have 300-400ah of batteries and 400 watt of panels.
Solar has heaps of varibles ....summer winter can have 30-40% impact on the amount you get out of them.
We did kick off with one 200 watt panel and ran out of power after a couple cloudy days at day 6.
Yes put the extra panel in....run a 8mm cable for it to your controller.....is that 20 -30amps rated?
I have been thru this exercise, having 2 x 80 watt solar panels and 2 x 6 volt 225 amp/hour deep cycle batteries. Without going into reasons why, I installed another 80 watt panel and another battery, 12 volt 100 amp/hour. I find now that I can dispense with the 12 volt battery and I have no low voltage problems even with several days of overcast conditions...On 12 volt, I run a refrigerator; TV/DVD; a few LED lights; water pump and a 300 watt Inverter used for my laptop and cellphone charger. In your case, I would install another panel of 80 watts. You should also check out the current rating of your PV Controller. A 20 ampere unit is ok for 3 x 80 watt panels, but if you go for 200 watt, which I think is over kill, you'll be up for a larger and costly PV controller.
__________________
Retired Airline Pilot and Electrician..
I'm not old, I've just been young a long time....Ken
Since light travels faster than sound, some people appear bright until you hear them speak.
Also you must monitor the batteries state of charge to ensure you are not bringing the voltage down too far, or they will die young. There is a bit to learn but it's not rocket science 
