Join Date: Oct 2016
Location: California, East Bay-Area
Mentioned: 3 Post(s)
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It all depends.
Make your use and charging estimates.
Your 880 Ah at 6V is 440Ah at the typical 12V and double of mine.
With at most 50% discharging I can get 110Ah * 12 V = ~1320 Watt hours (1.3 kWh) out of mine.
As you see below I use maybe 0.3- 0.9 kWh.
In your situation I would maybe leave some room in the battery box area for expansion but fit your estimated use cals until you see that is not enough.
Batteries are heavy and take up valuable room in the van and if you can store the extra for a little while you see if you need to add them!
My calculation three years ago was pretty spot on and as far as I can tell the battery is still great shape and seldom touches 12V when discharging.
For me a single AGM 220 Ah 12V with 200 W solar panels did the trick.
I can charge my battery if needed from the engine but have only needed this twice (since early 2017, 120 days /year use), even when traveling in Oregon and Washington.
We are nice weather campers and only have a heating blanket to take the chill off the mattress.
My biggest user is the fridge: Watt * Hours or Amp * Hours (Ah) at 12Volts (mine runs 10 min per hour when constantly on) 24 Ah/day
Then occasional the use of the water pump and air fan together are at most 10 Ah/day.
Minor users are phone chargers, LED lights, propane sensor 5 Ah/day
The heating blanket (75W) would add another 5-10Ah for 30 to 60 min preheating the bed.
I also heat my water tank in the morning with the 300W water heating element (2.5 g water storage) =300Wh or (12V * 25A * 1 hr = 25 Ah at 12V) after an hour the water is used for dishes and washing up.
That water heating is about 25% of the 110Ah I can use from my battery storage.
So on the largest use days 60-70% of the 110Ah is used, more typical 30-40%, and the 200W solar panels replenish that before the sun goes down.
I can easily switch the water heating to the engine CCP during driving, which is what typically happens and allows the solar to recharge the battery even faster.
If we would add an electric coffee grinder, microwave, hair dryer etc I will need more storage. Before that, I will probably add another 100W to my solar as I value my indoor space highly.
2016 T250 3.7L 148WB HR Cargo, TrueTrac LSD, Oxford white, Ionic Running boards, MaxAir, 2x100W LenSun solar, 200Ah batt, Novakool R3100-DC, 15g fresh H2O 18g grey, ShurrFlo 4008-101-E65, DD HU AVH-4200NEX, 2x Scopema swivels, Curt Hitch