being a posterchild for ODD, how do I do this?

[skysix]

Working within physical constraints of available weight and volume for batteries and roof space for panels, how do I reverse engineer a system?

Plan to use 4 Trojan L16H-AC AGM 6v/370 AH (20 hr rate) batteries wired as two 12v banks in parallel for a potential of 740AH or realistically lets say 300AH at 40% discharge (1300 cycle life, 200AH at 27% gives 2000 cycles and 350AH at 48% gives 1000 cycles)

Have a max of approx 14' by 7' of roof space (less vents etc) and 2/0 or better welding cable.

Minimum baseline projected power requirement (15 min or more, does not consider brief surge loads which may be twice as much) is 150W (120VAC) as running an electric fridge/freezer and LED lighting (both 120VAC) plus laptop etc and occasional "800W" microwave, max in future of 1800W (120VAC) - will switch batteries to a 24v string then and use a different inverter.

Would prefer using some form of flexible panel that can be walked upon. If additional panels are is needed they would have to be mounted on over-window awning structures during travel and angled sunward when parked

Useage will be Cascadia generally and northwards (NorCal, OR, WA, MT, ID, AB, BC, YT, NT, AK) and be more fall/winter/spring than summer.

SO:

What capacity of MPPT do I need?
How many W of panels?
How many A of trickle charge?
How many A of MPPT shoreline battery charger (have 13A/"24"vdc or 26A/"12"VDC available currently) will I need - assuming can charge a single 12V bank at a time

And then finally, how many AH of useage will I have between recharges (from a safe deep cycle AGM level) and how long (hrs of sun/generator/shore power) will a rechrge take.

 

[DiploStrat]

General Roolz

Grossly: You want all the solar you can get; you can never get enough, because:

-- Sunlight is variable due to clouds, trees, and hours of daylight.
-- The better solar controllers have very good charger controllers - multistage, etc.
-- Solar is most useful in providing the long, long absorb stage that lead acid batteries require. (You truck alternator is better for the boost stage because you don't run it as long.)
-- More solar installations underperform due to poor installation (typically undersized wiring) than due to poor quality materials.

These are common rules of thumb.

-- You want 100w of panel for every 100Ah of battery.
-- You can get 5A of charge per 100w panel. (Bit more in strong sun.)
-- You can get 20-30Ah per panel, per day, with good sun. N.B. Winter can sometimes be better as the trees lose their leaves.)
-- Lead acid batteries want to be discharged a little as possible and recharged as quickly as possible.
-- The worst thing you can do is leave a lead acid battery discharged for any period of time.
-- The 50% discharge rule is good; you can go more than 50% IF, and only IF, you will recharge the batteries IMMEDIATELY and completely.

My typical overnight usage is about a 20% discharge and, at two years, the batteries still perform as if new. The solar gear on my truck came from AM Solar; talk to them: http://www.amsolar.com

 

[skysix]

so for a 740AH battery bank I should use about 800W of panels, but what amp rating of charger?

Do the AGM lead acid batteries have the same deep discharge characteristics?

 

[DiploStrat]

so for a 740AH battery bank I should use about 800W of panels, but what amp rating of charger?

As noted, a 100w panel produces 5-6A of charge so do the math or look on the AM Solar site. With 800w (I'm jealous; I only have 500w for 600Ah of battery) you are looking for a 40-60A Solar controller. Some brands will allow you to slave or cascade controllers, but it is easier to wire, and manage, a single unit large enough to handle all of your panels.

N.B. Rigid panels are more efficient than self adhesive panels.

Do the AGM lead acid batteries have the same deep discharge characteristics?

Yes, if you are planning to use Trojan, go to their site and download their technical manual. If you can't find that, use the one from the Lifeline site. (I have Lifeline AGMs and their tech manual is very detailed and useful.

 

[Jr_Explorer]

Here's some good e-readin' on all thing battery and solar.

https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
https://handybobsolar.wordpress.com/