Simple 12v house bank

Kommy000

New Member
Joined
Jun 1, 2020
Messages
12
Well I'm finally now in the process of swapping my acid house bank 12v to LifePo4 bank I'm building out of 4 EVE 285ah cells.
Was going to finish my engine to electric swap first with 48v battery bank before changing the separate house bank but as of last night one of the Walmart "deep cycle" batteries died, started getting real hot and smelly and once I turned off the charger, its voltage dropped now to 6v. Right now I'm running 12v systems from the last Walmart battery secondary bank.
So instead of swapping it for another cheap battery, I thought why not use it as a practice build and just order the rest of parts and do the swap in a few weeks.
So as usual I'm starting to over think it.
I was hoping to use all existing electrical wires, except removing the extra wires for the first bank and changing battery switch to a simple on off since there will be only one house bank since it's LifePO4 with plenty of amps.
So, ordered overkill BMS 100ah with Bluetooth, and ordering one red and one black distribution bus bar with 3/8" 4 connections each rated for 250ah just in case.
Also ordering IP67 Victron charger with Bluetooth rated 13amp, since it will be running of 15amp ac circuit, like my existing charger. No other charging for now, no solar for now. Eventually once I have my main 48v bank done, I will probably run 48v-12v DC to DC charger as a back up if I'm not in the marina, since all of my solar will be charging 48v bank, but that is in the future so that is why I'm using positive and negative distribution bus bar so I can add those components later on without disturbing BMS and such and connect charger and load side through those bus bars.
My thought is to keep it simple: Get rid of old charger and redundant wires for secondary bank including secondary bank wiring running to the 3 position battery switch.
Connect battery to BMS, then BMS to those distribution bus bars and from there to the existing main wiring to the new batter on/off switch and from there to my 12v existing 12v panel with about 18-20 DC switches. Again, no inverters or solar charges- very simple.
My question, do I have to add in line fuses? If I do, where would you have it, right after bus bar or right in between? Also what size? This is a 32' sailboat with normal low loads, most stuff LED as lights, even if I wire fridge to 12v system it is very low consumption and only run it when I'm sailing when no access to shore power. Two most power hungry things I have is windlass and one power winch. I'm actually planning on removing both, bad location for windlass and no reason to have power winch on 32' boat. But even if I keep both, they worked just fine with current 100ah led acid batteries. And again, there will be no engine no alternator.
So basically, would I need some kind of fuse, which side negative, positive, both? And what size, or do I just not add anything? IP 67 charger is not a high power charger, plus BMS has it own protection plus I have no other charging power or crazy draw.
Am I over thinking it, and this is just simple swap and done?
Almost forgot, my current led acid bank I just kept charger on all the time, because I didn't care about killing these batteries. I still don't know on proper way to charge batteries. Do you just keep the charger on all the time and let it trickle charge the LifePo4 bank or do you keep on using LifePo4 bank and try to discharge as much as possible and then turn the charger on so it does full charging cycles because I know if I leave charger on all the time, I will never use more than 10 percent of my house batteries. So so I just keep an eye and turn charger once every few weeks since it will be 285ah bank? Thank you
 

12VoltInstalls

…myself everything do I…
Joined
Jan 18, 2021
Messages
4,242
Location
Vermont
Lifepo needs a lifepo-friendly charger.
More expensive when you kill a lifepo from improper charging/volts.

your lead acid battery sounds like it ran out of water? (aka electrolyte; it’s not really water of course)
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
3,494
For fuses for the main battery fuse, I don’t see anyway other than to bite the bullet and get a Class T inline fuse holder and Class T fuse. Size will depend on your loads.
 
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