Wow, figuring out how to put a lithium battery-based system together that will be functional for an offshore boat (not a camper van) and not break the bank, is even more complicated than I thought when I started this.
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The good news is that we are getting a handle on it. So far we have covered:
We need real understanding, not:
With all that out of the way, let's dig into how much peak current (amps) we need our system to be able to supply. Oh, no one ever mentions that on YouTube?'Exactly'
First, let's cover the minimum current capability that any BMS should have for us to consider it.
We all know that lithium batteries can supply huge amounts of current, and accept prodigious charging rates'think a Tesla with amazing acceleration that can be recharged in less than an hour'but that does not mean that the BMSs and batteries we will be considering can do that.
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In fact, many (perhaps most) boat lithium battery-based systems can actually supply less peak current (amps) than a good lead-acid battery.
What gives?
It's all about the Battery Management System we choose and how robust the internal wiring of the battery is. Let's deal with the BMS first.
Vigness,
The best advice is always to go with a 48VDC system, if at all possible. Twelve and 24 volts are fine for smaller systems -- remote cabins, RV, marine applications -- but the higher current demands of a full size residence means that a 48 volt system is the most efficient solution. The GVFX is a very sweet inverter, and I can highly recommend them. There are 48 to 12 volt DC-to-DC converters. There's a regular poster here with the name "jnh" who can help you with that sort of set-up.
Being in Kansas doesn't mean anything in particular, other than that you do have a high quality wind resource at your disposal, in addition to good summer solar power. The utility buy-back rates appear, from what I've read, to not be completely favorable -- the laws I've read indicate that payment is at 150% of "avoided cost", which may be less than wholesale if they are using "fuel surcharge" as the "avoided cost". A properly designed system CAN be configured to minimize selling. My 2.8KW system sold 746 watt-hours today compared to 7.247 kilowatt-hours inverted so far today (and it hasn't finished -- I should stay off-grid until after midnight, so that 7.247KWh should be closer to 8KWh before the end of day).
Once you decide to follow my recommendation to go with a 48VDC system (others here will agree with me), you just need to start planning what your daily loads will be like. Since you are planning to build yourself, my advice would be to start with the construction of your "power shed" so you have construction power available. It'll also give you a place to store your tools.
Several of the regular posters here, myself included, will help you with your overall system designs. If you want wiring diagrams and prints, that will cost extra. If you want to ask questions as you go (bad idea, in my opinion), you just keep asking them here.
That's about all there is to know. Good luck, and keep us informed.
Julie in Texas
I ride bicycles. A lot.
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