Electronic Accessory Q's - Heading Sensors / Lithiums

[Flex]

Thought behind this was that I can spread the batteries out and fit them in where I can under the deck. There's a lot going on under there with safety gear, tackle storage, fridge and batteries.
The other train of thought for 3 12v batteries was that if one died, I could then sacrifice say Live and the front Sounder and connect the remaining 2 for the electric.

Yeah, I won't be doing that, all intentions is to charge separately. I've been warned that it's not a good idea.

Would this mean a 12v DC-DC charger going from the start battery to the 12v Lithium, then a 12-24v DC-DC charger going from the 12v Lithium to the 24v Lithium? I'm keen to learn the best way of charging everything if I'm going to set up onboard charging.

The complete configuration is still adaptable, so if there is a better way to do it, I can change it all. I just need to make sure it fits in under the cast deck and has the ability to spread the weight around, and it is reliable for remote travel, or be able to be reconfigured while remote to keep some things going still.

physically how far appart are the batteries your plan on putting in series? if its a long run to another compartment that adds all sorts of weird complexities. cell imbalanace, no fuse/breaker in your cables. i think its a huge no-no.
also running anything 12v off half of a 24v series bank is a bad idea for lifepo4.. you mentioned running a 12v fridge of one of the series batteries you are also using for your electric? this is a terrible idea for battery longevity. not sure how the battery individual BMS systems would handle that. especially since the kraken can pull nearly 90amps at full noise.then your fridge compressor kicks in drawing 5-6amps from just one battery. definitely not ideal in my opinion.

I've done multiple installs on mine and colleagues boats. I honestly think the best setup for a offshore boat is 2 x standard 12v batteries, One for starting and One house. AGM's start batteries or marine lead acid etc, deep cycle start battery like optima bluetop is ideal. . (lithium start battery tech isnt quite there yet i believe for offshore reliability, totally fine for a tinny though).
Then run a single 24v or 36v lifepo4 battery for your electric with dedicated onboard charger thats fed off your house battery.

I personally use a redarc 12v to 24v onboard charger. has its own built in VSR so it never drains your house battery , can take solar input and is waterproof. its very slim and can be mounted anywhere really.

So to charge at home. you slap on a stock 240v-12v charger straight onto your start battery, then house battery charges via VSR then once they are done your 24v/36v lithium will charge.. super easy and set and forget.

plus if you go long range your lithium gets charged via outboard or solar .great for long range trips.

This is by far the best way to do it in my opinion

This way you can run a fridge from your house at 12v or from your lifepo4 at 24v.

[Corry]

I'm liking your advice Flex, I'm gunna read it a few more times and wrap my head around it all, but to answer some questions,

The layout of the batteries that would be going in series would see the battery post ends almost butted up together, it's more that they're only around 120mm wide and would fit sideways under the deck. The little area I'm looking at putting them is about 150mm wide by the width of the boat, hence a bigger wider battery would mean finding somewhere else to put it.
As for the fridge, from feedback and research, now I would look at running the fridge on either 24v, off the two batteries in series, or 12v off the third battery that is powering the Live and front Sounder. As you say, not a good idea to run 12v from one battery in series.
I'll look into the Redarc chargers, I'd like something that can charge the 36v Lithium in the big boat from the house batteries, this would suit that set up great, obviously in a 12-36v charger.

I'll also look further into a similar charger for this set up. Do you have any advice on when there is more than 1 extra battery? So if I end up going a 24v and a 12v, or a 300aH 12v and a 100aH 12v, for charging would it mean funning two chargers from the house to each battery, or run a charger between the house and one battery, then another charger between that battery and the 3rd... if that makes sense.

[Flex]

for any extra batteries you need just install a VSR between them and the house. run everything off the one charger and the batteries will sequentially charge.

google "blueea systems wiring diagrams and they have some excellent drawings on how to do it.