More Battery, Or More Solar?

[MakersTeleMark]

In adding capacity to an RV system, what is the calculus used to determine whether it is best to add another panel to a current system (1 battery) or adding another battery (1 panel)?

[Honu]

To many variables ?
Do you camp in the trees a lot or in places where you can get sun ?
Power needs etc....
I might say how long do you want to go and how much solar would you need to recharge properly in a timely manner
Can you permanent mount etc...


I setup my trailer so I could go 5 days without a charge up
My current setup for my truck is about 3-4 days before charge up is needed
Switched to goal zero for my lights and fan etc... And my fridge is now off its own battery

Here in AZ I know I can rely on sun
When we did two weeks in Oregon we brought a Honda generator cause of weather and tree cover etc...

I might say list out as much as ya can so some of the solar brainy people can help ya out more
Current setup your needs wants budget etc...

[Countryboy69]

Alot of good information at this site http://handybobsolar.wordpress.com/t...ging-puzzle-2/

[dwh]

With a stationary system:
You generally first figure out what your daily loads are.
Then figure the battery size to supply those loads while keeping the battery from going below a certain state of charge (generally 50%).
Then figure out how much solar you need to recharge that much power into the battery with X hours of good sun (how much good sun you get is dependent on the location on the planet) in one day.

With a mobile system, you go the other way:
You figure out how many watts of solar you can fit.

That tells you what your daily power budget (harvest) will be.
That tells you how much battery you need to store that power budget.


To figure your expansion:
You need to know how much the solar will harvest on average per day.
Is that enough to completely recharge the existing battery from a 50% drain in a single day?

If so, then the system is perfectly sized. If you add solar, then you should also add battery and vice versa.

If it's not enough to fully recharge the battery from 50% drained in one day, then add solar.
If it's too much (can fully recharge in less than one day's good sun) then add battery to soak up the extra wattage from the solar.

[pods8]

All depends on use. Weekend/extended weekend warrior is going to have different needs than a long term traveler. The latter needs to recharge in one manner or another (solar/altenator/generator/shore power) on a regular basis, the former just needs to ride out their trip while not hammering their batteries and then can fully recharge them once home. I've got two batteries for 210ah of bank, I picked this so I could sit somewhere w/o moving for 3-4days regardless of weather conditions and stay above 50%, I figured that would cover 90% of my needs since I'm not a full time traveler. When the cheap solar panels were available last fall I picked up a 100watt panel because it was too good to pass up. With this if I have good sun I could likely sit indefinitely, which I don't have the luxury of in terms of vacation time unfortunately, however for the majority of time it'll just keep the discharge cycle quite low on my bank which will in turn support longer the battery life.

Long story short I make sure I'm not solar dependent for a few days since weather is unpredictable, thus for me that's a two battery bank. After that it makes sense to add solar as opposed to another battery and its associated cost/size/weight.