Multiple battery banks or one big one

[ErikFinn]

To clarify on my post #74 above, a boat fitted with just and only single house bank consisting of deep cycle Trojan T105 batteries taking care of EVERY thing, no starter battery, no windlass battery, would that be a badly flawed setup?

[noelex 77]

Originally Posted by ErikFinn

Can anybody shoot this down, please?

The problem is battery banks occasionally fail quite suddenly.

The starting battery provides a backup and redundant system. The cost of the starting battery is not high. It does not need to be a deep cycle battery and usually has a reasonably long life because of its shallow discharge.

[Terra Nova]

EF--bad idea to not have redundant battery power for starting engine. Maybe OK if you have a hand crank backup starter.

[Matt Johnson]

Lithium battery jump packs are cheap now. I bought a 600cca jump starter for $45 on Amazon Prime Days. You could keep one of these on board for emergencies instead of a dedicated battery and since self discharge is low, it only needs to be inspected every season.

Matt

[SailingFan]

Just to toss a little mudball into the fray, on the windlass issue (or any other remotely powered forward item you could install), why not just place your house batteries in the normal aft or midships position (where it already is), and add a dedicated windlass battery as close to the windlass as physically possible, with a solar charger wired to it alone?

It would seem that would eliminate the side issues of interactions between the windlass battery and the house/starter remainder, and the windlass battery can be used in a pinch to replace a bank battery or starting unit should such be required simply by disconnecting it and moving it aft temporarily to stand in for the damaged unit aft.

When that service is complete, move it back forward, reconnect, and you are done. No wires running fore and aft, no connection issues between them, no double fuses (one between the windlass and its battery, of course), and a simple small solar panel and its tiny controller are sufficient to keep the windlass up to snuff over transit time or even while on the hook or tied to a dock.

It sometimes seems things get "over-thought" here (even by me too). Am I missing something?

[mikedefieslife]

I'm enjoying this debate.

I have a bank of 6 Trojan batteries. A dedicated starter battery, and a forward windlass battery.

I too am wondering why not just have a massive house bank and eliminate the starter battery. From my over-landing days, I carry a lithium starter anyway. But it would be just as easy to carry a small LiFePo4 battery too for emergencies.

My windlass battery is adding 20kg of weight up front. It is connected to house bank (with tiny gauge wires) via a fused battery combiner relay. Am I to understand that is a super bad setup, and there is potential for massive current to try and find it's way forward? Might have to take a look at that.

[noelex 77]

I think some posts are trying to reinvent the wheel.

A seperate redundant battery supply has been standard on large boats for many years.

You can make this seperate supply a portable system, but then why not wire this in permanently to eliminate having to connect the booster cables in an emergancy? Then if the battery is going to be wired permanently and installed below decks why not go for a larger capacity battery so that multiple starting attempts are possible if there is a problem such as air in fuel. Once instalłed permanently, there is less need to make the battery pack easy to carry so why not go for a conventional lead acid battery instead of lithium? It will be cheaper and easy to replace anywhere. Lead acid starting batteries are not expensive.

Once you have a system installed like this why not use it as a routine to start the engine? This makes sure the battery is working and has some secondary benefits such as avoiding starting spikes for sensitive electronics and reducing thick cabling.

Now you have come full circle .

The issue of windlass/bowthruster battery is different. Here the main driving force is the high cost and difficulty installing the heavy cabling from the hose bank. Often it is cheaper (at least for the boatbuilder) to install a seperate battery in the bow. If you can avoid this, it usually produces a better system.

[Thorne]

Originally Posted by noelex 77

I think some posts are trying to reinvent the wheel.

A seperate redundant battery supply has been standard on large boats for many years.

You can make this seperate supply a portable system, but then why not wire this in permanently to eliminate having to connect the booster cables in an emergancy? Then if the battery is going to be wired permanently and installed below decks why not go for a larger capacity battery so that multiple starting attempts are possible if there is a problem such as air in fuel. Once instalłed permanently, there is less need to make the battery pack easy to carry so why not go for a conventional lead acid battery instead of lithium? It will be cheaper and easy to replace anywhere. Lead acid starting batteries are not expensive.

Once you have a system installed like this why not use it as a routine to start the engine? This makes sure the battery is working and has some secondary benefits such as avoiding starting spikes for sensitive electronics and reducing thick cabling.

Now you have come full circle .

The issue of windlass/bowthruster battery is different. Here the main driving force is the high cost and difficulty installing the heavy cabling from the hose bank. Often it is cheaper (at least for the boatbuilder) to install a seperate battery in the bow. If you can avoid this, it usually produces a better system.

This is the setup I have and knowing that I have 3 potential sources for
a. Starting the 65 hp Diesel
b. Running the windless for the 300 feet of chain
c. Running the electronics and bilge pumps

And solar panels to charge ... Slowly of course.... If they all go flat for various reasons at the same time.

Is a comfort for me.

It all depends on what kind of sailing you are doing and how far from a marina you are sailing.

Lot's of overnights with no shore power?
Long ocean crossing?
Short day trips?
Shallow waters w easy anchorage?
Point to point?
Cloudy conditions most of the time?
Small Diesel fuel tanks?
No TOW BOAT US around?

Everything is a factor.

Like to run the microwave?

Run SSB all the time to get weather? (How quaint)

Like to run that big high res Chart Plotter all the time ( just cus )? ( I confess, I do )
Have a laptop that eats power?
Big monitor?
Like to watch movies deep into the night?
Like to light up the deck for parties all the time while your at your favorite Island?

Electric water heater?
Water maker?

Like everything "It Depends"

[Panacea2183]

I run 8 Trojan t105re in the house bank and one dedicated 8d starting battery for both engines and genset.
780 watts solar
2800 watt inverter/120 amp charger
Separate charger for start battery
1-2-all switch to combine if necessary
House bank is connected between batteries and inverter with 4/0 cable Not a typo 4/0
2 gauge to DC pannel as well as windlass.
I do agree if you have a bow thruster (I don't) use a separate bank as running 4/0 that distance is a pain and expensive.
Bigger cable is expensive but it is your friend. Voltage drop is the single biggest problem in high aperage draw applications
I never discharge my bank lower than 70% SOC
I agree with splitting the house bank in 2 for isolation reasons if you have a bad cell somewhere, just leave the switch on "all" unless you have a problem.
PS: when wiring the house bank together, make sure your POS & NEG cables are on opposite sides of the bank for even discharge and charge.
Have your cables for the bank professionally made I.E.:crimped & soldered
I think Trojans website has infrared pics of both and the heat difference.

Lastly make sure your charging system is up to the task, flooded cell batteries take time to charge no way around this period! If you don't have solar panels, plan on running your genset for 4-5 hours to recharge. Match your charging system to be 10-15% of your amp/hour capacity.
The goal is to get as close to 100% charge every cycle as you can.
Recharging your batteries to only 80-85% is a sure recipie for short life.
Trojan 105re are supposed to be designed to be more tolerant of charging to only 85% SOC
Good luck