Sandy5 wrote:
There is currently one battery box 11.5x8x8
And may I ask why marine or RV batteries are not as good?
A few replies stated:
"compromises like the RV/Marine batteries"
and "marine deep cycle are compromised batteries"
Are they not truly deep cycle?
The design for starting batteries is lots of thin plates. Surface area defines how many amps a battery can throw off. For starting, thin plates provide more surface area and thus more amps. Your average dual purpose battery is just a starting battery with different lugs compared to a dedicated starting battery.
The design for deep cycle batteries are fewer but thicker plates. With less surface area, they can throw off fewer amps. Thicker plates are better at storing more energy (ie: they can throw off their amps for a longer period of time). Outside of very expensive specialized batteries, you will find difficulty sourcing a 12v deep cycle battery. 6v golf cart batteries on the other hand are easy to source and true deep cycle designs.
Note: Assuming they can put out the amps, there is no harm in using deep cycle batteries for starting. (example: on a sailboat with a 30hp diesel and a large house battery bank, you can use the house bank to start the engine with no problem).
Now back to your question:
Before running out and buying batteries, make a stab at estimating what your power consumption will be. Otherwise, you may wind up spending money on items that don't work and then may not fit in with your final solution.
Start with an energy audit (it won't be perfect but better than people randomly telling you to get X system).
- Decide how long you expect to be off grid.
- Guestimate how long each item will run (lights, TV, waterpump, furnace, laptop/phone chargers, etc...) Find the wattage for each and multiply times the duration they will operate. This will give you a total watt-hour you need to replace each day. Add 20-30% as the systems aren't 100% efficient and you might miss some items.
- Don't plan on air/con unless the generator is running (this is a whole different subject)
- Divide your watt-hr by 12 to get amps-hr @ 12v. Then double it to see how big of a battery bank you need. Lead-acid batteries generally don't like to go below 50% charge, so you can't use the full rated amp-hr.
- 6v golf cart batteries are likely the cheapest option and if only 2 or 4, likely a good choice. If you need much more than that weight starts becoming an issue in a small RV. Then you move into lithium which is a new subject with different considerations.
- Now you need to charge the battery bank. If you are just weekending for a couple of days, you can just double the watt-hrs and install a larger battery bank. Or you can run the generator to charge them (caviot: it takes a very long time to go from 90% to 100% with lead-acid batteries, so it may be more effective to go a bit larger on the battery bank as 50-90% can charge fairly quick). Alternatively, you can add solar. Figure 4-5times the nominal watt rating in watt-hr (ie: a 100w panel will generate 400-500watt-hr per day)
This should give you a good idea of the scale of what you need.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV