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@ghostwriter66 would also be curious to see your daily power budget. 300-400ah @ 24v (7,500-10,000 Wh) is not a small number, and the cheapest way to increase capacity is to consume less.
You also mentioned to make sure to build a balanced system. What exactly do yo mean by that?
I mean, scaling up your system proportionally. There should be balance between (1) your daily consumption (2) your charging systems (3) your battery bank).
Many people when they first start designing a system are overly focused on battery capacity for the wrong reasons. They assume a big battery bank will compensate for high power consumption, without considering the charging system. There are some situations where this is okay (like weekend trips), but for longterm sustainability its usually more important (and considerably cheaper) to focus on inputs (your charging systems) and outputs (your power consumers and power consumption habits), because if your inputs cant meet your outputs it doesn't matter how big your battery bank is. The primary utility of a large battery bank (like you correctly noted) is extending 'days of autonomy.' So in that regard, I think you are on the right track in terms of what you are expecting from your batteries.
But, the system needs to have some balance. Your charging systems need the capacity to not only meet your daily needs, but be able to recharge your battery bank in a timely manner if your batteries are depleted. This is something that many people overlook. There should be a term for this equivalent to days of autonomy that encapsulates this, maybe 'days of recovery' and you should have a target for this as well.
Taking (a simplified version of) your system as an example, lets consider the numbers:
With a 50,000 watt-hour system, daily consumption of 10,000 watt-hours, and a PV array capable of generating roughly 10,000 watt-hours on a very good day (2kw x 5hrs).
- On a good day, your system is sustainable (roughly7-10kW in 7-10kW out)
- Your system is sized to give you 4-5 days of autonomy in worst case conditions after which time your batteries would be fully depleted.
- But now you have a 40,000 watt-hour deficit to make up, it would take 4 days of full sun to make this up IF your power consumption was zero, but because your solar array is sized to just barely meet your needs you have no extra generation capacity to make up this deficit.
Ideally your system would design for days of autonomy which is the ratio of
usable battery capacity / daily consumption and also design for days of recovery which is the ratio of
usable battery capacity / (daily power generated - daily consumption)
So for example, assuming 4 days of no sun (40,000 Wh deficit) and taking your best case numbers of 7,500Wh daily consumption and 10,000 Wh daily PV generation (40000 / (10000 - 7500) = 16 days of good conditions. Put differently, assuming solar is the only input, it would take 16 days of good conditions based on best case numbers to make up for 4 days of autonomy, or 4 days of good conditions to make up for 1 day of no sun. Keep in mind these results are based on your best case numbers (300ah consumed, 2kw of solar @ max output for 5 hours), If we assume 400ah (10,000wh) the number of days of recovery increases from 16 to infinity.
Obviously reality will be a bit more complicated than this, good days will seldom be perfect, bad days will seldom be zero, 4 bad days in a row might be rare and 16 good days in a row will be even rarer. Moreover a generator or shore power would substantially change this equation, and shorten your days of recovery to hours. But then if you are reliant on a generator or shore power to charge your batteries one way or another, its at least considering whether the added cost of such a large battery bank is worth it, if the end result is that it will delay but not alleviate your reliance on a generator.
There are many good (and personal) reasons that it may still be worth it. And many specifics of your situation that make this decision personal to you. God knows I hate generators, and I would be willing to spend more on batteries and panels and efficient appliances if it meant I wasn't reliant on one. But I would first be looking at how to lower my power consumption, then at how to increase generation, and lastly at how to add more battery capacity which is the most costly component of your system.
And I would want to be clear eyed about what the extra cost would accomplish. Maybe you live in a part of the country where sunny days outnumber shitty days 4 to 1 or 10 to 1, in this case 4 days of recovery per 1 day of autonomy is reasonable and would cut down on your generator use substantially. Or maybe you live in the pacific northwest and will never be able to count on a sunny to shitty ratio of 4 to 1 outside of the summer months. But remember the 4 to 1 ratio was based on optimistic numbers and zero efficiency loss, so don't count on achieving that with your system as currently designed.
I don't mean to sound negative, and I truly am not trying to talk you out of your planned system (though I would strongly suggest looking into adding generation capacity, and cutting power consumption first), and to some extent i'm thinking out loud (well not technically out loud, but you get the point). I'm still thinking through this 'days of recovery' concept (and welcome critique, push-back, and/or additions), but I think its an oft overlooked component of system design. But reality is much more complicated than my little thought experiment, your system as planned might make the most sense for your situation, I can't really say one way or the other with the information I have.
