Seperate Engine and House battery systems

[salish_wanderer]

I have 3, 2 year old, 125ah FLAs that I esentially got for free, but im reconsidered putting unsealed batteries on board. I still need to build a battery box that I want to seal and vent out to the cockpit, but Im wondering if it is worth the hastle.

Im rebuilding my electrical system from scratch so I have room to re-engineer. My start battery is AGM with 45amp altenator, and installing 220 watts solar on the bimini. I dont want to spend the money on external alternator regulation. If I isolate the systems I will get an mppt charge controller. Cost and labour are a huge consideration, as well as longevity.
Another consideration is that I live in the Pacific Northwest.

My rough plan:

220watts solar
Mppt charge control
200ah Gel house
Vhf, ssb, fan, led lights, charge tablet/phone


Yours thoughts are aprreciated

[svMira]

I installed my two house batteries and one small starter battery through one of Blue Sea's Add-a-battery systems
https://www.bluesea.com/products/7650/A ... Kit_-_120A
This way the systems are continuously connected for charge, but dedicated for draw. This way your solar will be keeping your start battery topped up. I've been happy with for four years, but I'm just a 'weekender' with low battery use. No fridge or radar, etc.

[atomvoyager]

A 200 to 250AH house bank may be on the small side for live-aboard use even with 200 watts of solar since you're in the rainy PNW, It may be fine if your electrical use is small enough. As a backup you will probably want the ability for the engine to charge the house bank occasionally, even if you have to throw a switch to do it. Either way, I don't bother special venting for even double that size flooded bank. You probably have some venting for the engine anyway.