A few Contentious Question re electrical

[Stephen Oliver]

HI All

I have a few questions and wanting general opinion just to gauge which way I will go 🙂

Background. After having all 6 dual purpose AGM’s die within 2 weeks of each other (7 years old so can be forgiven) I am going LIFEpo4 – 326ah pack – all systems are being replaced regarding charging and wiring etc and i’m throwing in a large inverter also (victron multiplus) my questions revolve around what should be attached where.

1, 24 hours circuits – Bilge pumps mainly – connected to house bank or 1 of the starters?? (1100cca group 31) – House bank is bigger will last longer – but also gets pulled down all day – Solar is planned so will top up the bank too i guess.

2, Windlass – Currently connected to one of the crank batteries – rarely used as we are generally on a mooring buoy – keep connected or add to house – I have 100a engine charge capacity to the house bank from the engines (via 2x DC2DC chargers) and pretty much the same to the crank batterys (connected to alternator)

3, Flybridge Power – I was planning on running this from lithium house bank, Engines are kept separate as they have their own wiring harness to the bridge, all electronics etc could be run from house and kept completely isolated from the engines. This includes Radios, GPS etc.

Thoughts and opinions welcome 🙂 – Spectators please get your popcorn 🙂

Steve

Topic

[Stephen Oliver]

Well i’m trying to reply but it wont let me.. try again – Looks like it wont let me quote people.. oh well another bug..

OK Rob

I had a big reply typed out and the system ‘Block’ wiped it out. So i’ll try again..

I probably didnt explain my self well enough – My 6 AGM house bank died, so I am replacing the house bank with Lithium (1x 326ah battery – equivalent to more than the 6agms capacity wise) Crank batteries are already in place (bosch S4) and were feeding the house bank via one way VSRs from each crank to the house battery bank. In replacing the AGMs with lithium I am removing the VSRs and replacing with DC2DC chargers. My enquiry was over what should be connected where. So I have gone..

1, 24 hours circuits – Bilge pumps etc – Lithium – More capacity
2, Windlass – Crank Battery – only use it when engines are running and cranks are good at delivering large current intermittently.
3, Bridge – Running from Lithium – the engine instruments are all powered by the harness – the rest on the bridge will be from house – House system is completely isolated from the Engine systems.

Hopefully that makes sense?

Phil

Yes you are correct different charge process etc. I have attached my wiring diagram so hopefully it makes sense. The lithium take as much charge as they can get so if left unchecked they will burn the alternators out. My new battery can take 326a of charge continuously, but the Battery management system (BMS) limits it to 250a. Even both of my alternators couldnt keep up with it if they tried, so I have replaced the VSR’s with DC2DC chargers. Makes the system very simple. The only small complexity is the addition of ignition activated relays on the DC2DC input as I have a small crank battery charger to float charge the cranks when at dock for periods of time. Without the relays the DC2DC chargers would be pulling the cranks down to 12.8v all the time the chargers were on.

Word of warning on the lithiums – make sure the BMS is capable of dishing the current out that you need. or if multiples are used their combined output is suitable. Lots to like though.. 150kg weight saving and 6 batteries worth of storage as I have shoved my battery behind a sofa in the cabin. – the one battery weights 28kg and cost about 30% more than replacing the AGM. It was bought from a place in VIC and i’m pretty impressed. If you need to know more feel free to DM me..

Steve

[Phil Lack]

But doesnt the problem arise where you have 2 different battery types and when charging off the alternators, I am assuming both house and cranking batteries get charged and Lithium batteries require a different charging regime ??

I too am currently facing this dilemma and would like the house to be all Lithium batteries but dont want the cans of worms to be opened up (have been thru this on a previous boat).

regds,
Phil (in Melbourne)

[Rob Schepis]

IMO, it’s all house stuff and the house needs to see a charge whenever the dedicated engine is running. Leave the engine batteries as crank only and you can save money here – nothing but two FLA Grp 31’s, one Port and one Starboard. Leaves you more $$ for a potent house bank.

[Author]

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