Electrical Systems - Starting or House?

[john61ct]

Originally Posted by Pizzazz

The more interesting question is where you connect the alternator output
...
you can connect it to the house bank but then you need to monitor the starting battery and charge it every now and then (less work but could leave you stranded).
...
In my case, I have a solar panel that typically charges the starting battery.

Alt should go directly to the bank that needs the charging the most, House. With proper charging configuration, ideally via MC-614 VR.

Temp and voltage sensor wires critically so, but Output best that way too.

Same with any solar IMO.

If starter bank is for starter **only**, it is used so little, an ignition wired solenoid to combine is plenty, assuming same charging voltage as House is OK. Otherwise, a small-amp DCDC converter/charger.

I would definitely not rely on remembering a manual switch, personally.

[john61ct]

Originally Posted by Andy on Destiny

We can emergency start the engine off the house bank by a master switch ( Remember that you must also be able to disconnect the engine bank at the same time or you will suck the juice out of your good battery)

A momentary switch works well for that, if not already included in the ACR/VSR setup.

[Lepke]

Only items needed to start or run (electric fuel pump, gauges, etc.) the engines should be connected to the starting batteries. At anchor other items could drain the batteries and keep you from starting.
If you can afford the boat you can afford a dedicated starting battery.

[sbender]

I only have the starter and bilge pump on the starter bank. I can live without everything else. Would never leave the battery switch on both. I use a Blue Seas switch witch has On/Off/Both and an ACR so I charge both banks when the engine is running. Crazy to risk running both banks down.

[Stu Jackson]

Originally Posted by Scot McPherson

Stu,
So I read your reasoning on the other site, but to be quite honest...your reasoning is why I keep the banks joined during normal use. Both batteries are discharged much less.

>>>>>>>>>>>>>>>>>>>>>>

Nigel's quote:
2. All other things being equal, any increase in the overall capacity of a battery bank will produce a disproportionate increase in its life expectancy (through reducing the depth of discharge at each cycle).


So you see, I draw less from each battery by sipping off both.

Then, Scot, I take it all back.

You're essentially running one big bank.

[Nightsky]

I have starter and windlass on start bank. Everything else on house bank.

[john61ct]

Originally Posted by Stu Jackson

Then, Scot, I take it all back. [emoji2]

You're essentially running one big bank.

So take a similar idea, two "half-banks" joined when charging, in fact always joined, until the "Propulsion/reserve" side gets down to within 20% SoC of where cranking starts to be a strain. All essential loads needed for safety, navigation, radios, GPS, windlass, bilge etc are on that circuit.

House side has non-essential loads only, fridges, entertainment, computers, and is allowed to run down much further, without affecting the Propulsion essentials.

But the "top end" of the Propulsion bank does help share in feeding the House loads. A lower SoC on that bank (below the LVD isolation setpoint,) from say the windlass, bilge etc, could set an audible alarm, a bit lower autostart a fossil fuel power source.

For "belt & suspenders" beyond "both" self-jumping, something like this https://www.amazon.com/OEMTOOLS-2445.../dp/B00RI446SI

or a bigger one, is kept charged for cranking just in case.

To me there is a safety benefit to isolating Essentials from Auxiliary, and keeping both combined while SoC is high keeps the "one bank" advantage.

Which, as a side note, I believe goes away completely if we're talking LiFePO4?

[daletournier]

The lodgic of keeping one battery seperate so that you never get stranded is obviously sound. Scot has a valid point as well, battery health due to combining resulting in lower discharge.
Boats are abit different today relative to times past, better equipped. Starter battery is 220ahr deep cycle that sits there doing nothing! I have 480w solar and a honda generator combined with 60 amp charger, multiple charging sources. In the case of a cell shorting and taking down the whole bank it should be relatively easy to isolate the bad battery and get things rolling again. This was briefly discussed in another thread with A64 last week, as he mentioned he combines his batteries. It seems a shame to have a third of your battery power doing nothing? So is the long standing practice still as relevant?
The other thought i had was keeping my batteries combined and carrying one of those jump start battery setups that are very common today, used to carry one in the car, it was awesome, this us your spare start battery.

[Dockhead]

Originally Posted by Stu Jackson

1. Start on start or reserve bank

2. Everything else is house
. . .

I think that's best practice -- keep them as totally separated as possible.

Best of all with separate chargers and separate alternators and no interconnection of any kind.

[Dockhead]

Originally Posted by daletournier

The lodgic of keeping one battery seperate so that you never get stranded is obviously sound. Scot has a valid point as well, battery health due to combining resulting in lower discharge.
Boats are abit different today relative to times past, better equipped. Starter battery is 220ahr deep cycle that sits there doing nothing! I have 480w solar and a honda generator combined with 60 amp charger, multiple charging sources. In the case of a cell shorting and taking down the whole bank it should be relatively easy to isolate the bad battery and get things rolling again. This was briefly discussed in another thread with A64 last week, as he mentioned he combines his batteries. It seems a shame to have a third of your battery power doing nothing? So is the long standing practice still as relevant?
The other thought i had was keeping my batteries combined and carrying one of those jump start battery setups that are very common today, used to carry one in the car, it was awesome, this us your spare start battery.

There's some sound logic in this, and I guess it's tempting to want to use the start battery's capacity if the house bank is small.

But what a start battery DOES is actually quite different from what a deep cycle battery does. It's just not the same thing. I think it is far better to add another battery to the house bank, then molest the start battery with an alien duty which compromises its primary -- and life safety critical -- function.

A diesel engine, especially in cold weather, needs quite a jolt of CCA to start. Will your deep cycle batteries, pulled down to 50%, manage it? Even a whole bank of them?

[Dockhead]

Originally Posted by Stu Jackson

Then, Scot, I take it all back.

You're essentially running one big bank.

Then add one dedicated start battery to this, and he's golden

[daletournier]

Originally Posted by Dockhead

There's some sound logic in this, and I guess it's tempting to want to use the start battery's capacity if the house bank is small.

But what a start battery DOES is actually quite different from what a deep cycle battery does. It's just not the same thing. I think it is far better to add another battery to the house bank, then molest the start battery with an alien duty which compromises its primary -- and life safety critical -- function.

A diesel engine, especially in cold weather, needs quite a jolt of CCA to start. Will your deep cycle batteries, pulled down to 50%, manage it? Even a whole bank of them?

Hi Dh, yes agree its the best way. Im thinking more specifically of my setup. The starter is a 220a/hr deep cycle which is the same battery as the two combined house batteries. No expert but i think a large deep cycle at 50% would start the yanmar. Part of the reason for combining is that the extra capacity results in batteries never getting down to 50%, they dont get down to 50% when just on house.
It always comes down to money, space and using what ive currently got. I liked Johns 2v setup on his catalina on another thread (same boat as mine) I'll go that way most likely down the track.
Anyway abit if a thread drift.

[john61ct]

Originally Posted by Dockhead

But what a start battery DOES is actually quite different from what a deep cycle battery does. It's just not the same thing. I think it is far better to add another battery to the house bank, then molest the start battery with an alien duty which compromises its primary -- and life safety critical -- function.

A diesel engine, especially in cold weather, needs quite a jolt of CCA to start. Will your deep cycle batteries, pulled down to 50%, manage it? Even a whole bank of them?

Yes, even a smaller bank, same way an elephant has no trouble crushing your Coke can.

[Dockhead]

Originally Posted by daletournier

Hi Dh, yes agree its the best way. Im thinking more specifically of my setup. The starter is a 220a/hr deep cycle which is the same battery as the two combined house batteries. No expert but i think a large deep cycle at 50% would start the yanmar. Part of the reason for combining is that the extra capacity results in batteries never getting down to 50%, they dont get down to 50% when just on house.
It always comes down to money, space and using what ive currently got. I liked Johns 2v setup on his catalina on another thread (same boat as mine) I'll go that way most likely down the track.
Anyway abit if a thread drift.

That's the theory, but the problem is if you forget to switch it over, or if the combined banks get discharged by accident. I had the 1 - 2 - Combine switch on my previous boat, back in the last century, and it happened from time to time, and it was a PITA if not an actual danger to the crew. I do agree with someone who posted above, that a portable Li Ion jump starter -- IF it is sized to turn over your diesel engine -- and IF you could be sure to keep it charged all the time -- could be a neat solution to this risk. Such things didn't exist in the '90's, and the high discharge rate of Lithium is a real game changer, what concerns devices like these.

[john61ct]

Combining/isolating should be fully automated, ideally with customizable setpoints.

Manual switch, ideally momentary, is just for very rare to never emergency self-jumping from House. Built into most ACR/combiners, or a plain switch or solenoid will do.