Electrical Systems - Starting or House?

[Stu Jackson]

Originally Posted by Dockhead

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

Yes.

What gets me is that after all these years folks still are only beginning to understand. Many of us developed these ideas before the internet. Now, with all this information available... It's not like we're hiding it!

Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

[Stu Jackson]

Originally Posted by daletournier

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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.

The point, Dale, is to simply build it in.

Some do what Dockhead does: keep the start and house separate.

Others use it as a reserve. Most who do have good sized house banks of around 400ah with daily loads of 100ah so they can stay at anchor two nights without recharging. In this case, small start type batteries are needed for small diesel engines. Grp 24 or 27 work just fine. Maine Sail has documented starting currents.

Those of us who go this route start on our house banks all the time, and watch the start bank and use it sometimes to confirm its health. Not so hard.

Seems silly to lug something around that may be rarely used and needs to be connected to work, instead of just turning a switch.

Your boat, your choice.

[waterman46]

Originally Posted by john61ct

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.

John, absolutely correct on all points. Nothing but starter motor and its associated circuits (usually termed "ignition" even in a diesel installation) should be connected to the starting battery. It is your last precious lifeline to create more power when needed.

Use a battery isolator. All batteries same chemistry, then relative size of starting and house banks does not matter. Connect alternator current directly to house battery, not through the isolator, to avoid voltage drop since its charging current can be very high. Lower charge current required by starting battery can come through the battery isolator relay. A second relay can connect charge current to a windlass battery forward. I've had relay contacts gradually go resistive on me, but feel they are still more reliable than a solid state device.

Your AC "dock" charger output also connects directly to the house battery which is electrically the same point in the circuit as your alternator output, so either charging source has the same effect.

I dislike any switch that could connect starting circuit to house circuit. Too easy to forget and there goes your starting battery when you leave the reefer on too long, etc. Properly isolated, your starting battery will way outlast your house battery and you would almost never need a jump. But carry a set of jumper cables just in case. After using them, you'll trip on them which will be a reminder to remove that forbidden connection between starting and house battery banks.

Bottom line, it must be simple to use, completely foolproof in not discharging your starting battery and not depend on having to remember to operate switches often.

[daletournier]

Originally Posted by Stu Jackson

The point, Dale, is to simply build it in.

Some do what Dockhead does: keep the start and house separate.

Others use it as a reserve. Most who do have good sized house banks of around 400ah with daily loads of 100ah so they can stay at anchor two nights without recharging. In this case, small start type batteries are needed for small diesel engines. Grp 24 or 27 work just fine. Maine Sail has documented starting currents.

Those of us who go this route start on our house banks all the time, and watch the start bank and use it sometimes to confirm its health. Not so hard.

Seems silly to lug something around that may be rarely used and needs to be connected to work, instead of just turning a switch.

Your boat, your choice. [emoji2]

Hi Stu, I understand how it all works, im actually a motor mechanic by trade. Just questioning the way we've always done things as our boats are changing with modern tech. But also don't want to start redoing that part of my boat yet, not waiting to get everything perfect before I go, in fact I've already gone :-)

[Rick]

Let us cut through the philosophical crap and realize that the start battery should serve only the engine Electrics and nothing else however you choose to charge the start battery beyond the engine alternator is another question

[Rick]

Never use a deep discharge start battery if it is flooded if it is AGM or gel that is ok flooded battery should only be start only for start engines because flooded batteries that are deep discharge have to have an internal resistance for starting use start only Start batteries if they are flooded

[Rick]

Sorry meant to say that deep discharge batteries have high internal resistance not to be used for starting if they are flooded AGM and gel have low resistance regardless

[Tasso]

Originally Posted by friz

Rewiring the project. I am deciding what systems to hook up to the starting battery and which to the house bank. I recall seeing a thread about that last year but haven't found it. Obviously the starter/ignition run off the starting battery. Beyond that, which of your systems are powered from where? Does the ABYC give any guidance on this?
Nav lights
Cabin lighting
VHF Radio
Sonar
Bilge pumps
Engine blower
Water pumps
Gages on the helm
Outdrive Tilt/Trim
Trim tabs
12v reefer
Anything else?

I would say it depends on whether you have a Automatic Charge Relay (ACR) installed and what kind of redundancy you're looking for. I'm curious whether you have a motor or sailing vessel... Dedicated started batteries are more common on motor vessels as they have no redundant propulsion.

On my sailboat - my back-up starter battery is a booster pack. Works for me. I have dual isolated banks because for me my Nav system is critical equipment and my engine less so...

Interesting discussion - but personal choice. I wouldn't let someone impose their solution on me because my definition of critical systems may be different.

The argument from Nigel Calder is good stuff though... Food for thought for sure.

[Tasso]

Originally Posted by Rick

Let us cut through the philosophical crap and realize that the start battery should serve only the engine Electrics and nothing else however you choose to charge the start battery beyond the engine alternator is another question

I am astounded that one can offer such definitive advice without understanding the redundancy objectives, whether and what kind of ACR is installed etc....

I'm not sure your solution is best for all cruiser or all boat types.

Just saying....