LiFePO4(LFP) battery upgrade

[azuro]

Hi, all. I am going to upgrade to 2x314Ah lifepo4 battery pack w. OrionXs50A dc charger for my B42Cr, 2006 sailboat. Since I am not an electrician but diy sailor, I am looking for a typical diagram. Very basic usage for now, only the fridges, windlass, coutesy lighting, etc.  Just went thru the forum but not a complete answer.

I appreciate advice, experience but a full diagram from the community. Thanks.

O.

[symphony2]

Welcome

That is a huge amount of capacity for such modest usage - something like 5 times as much usable capacity as the original. How are you going to charge it? Do you have plans to live aboard for long periods away from shorepower with increased daily usage and a lot of solar to keep pace with consumption? Windlasses and bow thrusters are normally powered by the start battery in lithium installations with an interlock so they only get power when the engine is running.

[azuro]

Thanks Symphony2. Yep, I am onboard for long periods; 8 - 10 days w/o shorepower. Do not have solar and do not want modules on my boat; limits fun of sailing. Gonna charge them w. engine, 105A (as I recall) alternator and 45A Quick battery charger, original setup on my boat.

[UP]

Here is my boats power-electric system schematic (individual small loads connect to house bank main distribution bus bars). I drew it up in Miro, cant export a higher resolution with the free account. Is going to change a wee bit, but functions so far (I see the windlass is not wired up here, but I have it connected to the main LiFePO4 bank. I have three large lithiums in parallel and they can give out a stable ~400 A, which is way sufficient for windlass action which I have fused at around 250 A).

[SYJetzt]

As symphony mentioned, such an amount of energy does not make sense in my opinion. It will take 12h + to run the engine from empty to full. The size of your dc-dc charger seems ok. Your alternator will not deliver 50A at engine idle, but needs approx. 1500 rpm to generate the 50A without overheating. The usual way to design a lifepo system is:
1) Calculate your average daily consumption (sum of runtime of each item in hours x current draw in Amp). Start with your fridges, autopilot, nav instruments, ..). Fitting a battery monitor in advance to know your demands in helpful to avoid costly stranded investments.
2) This demand has to be produced somehow (shorepower, altnator, ...).  Divide the result of (1) by the max current of your charging device, and you roughly know how long you need to run it every day...
3) A sensible battery capacity is 1.5 to 2 times your daily energy needs. If you can't or don't want to produce your electricity daily, increase your battery capacity by the amount needed for each additional day without production.