Getting rid of the start battery

[Dieseldude]

Originally Posted by N Coast Murray

Sorry...more evidence of my spectacular low level of understanding of all things electrical.

There are, I believe, 3 connecting wire harnesses between the start switch and the starter, which can be problematic.

You can only answer this by looking at the engine electrical drawings. If there is no rely, it would be prudent to add one to preserve your start switch contacts from arc burn.

[mcon12000]

Couple of observations.

ABYC allows you to omit the fuse in the starter circuit so a blown fuse doesn’t land you on the jetty.

ABYC does not allow for the omission of a fuse from the house bank.

With those rules in mind a BMS is much like the fuse if used in the start circuit so a Lifepo4 house bank that also starts the engine is not ideal.

My system has all charging sources alternator, solar and shore charger connected to the house bank. There is no Battery 1-2-All switch. I have a Braille Racing Super compact LA start battery that is charged by a DC to DC charger via the house bank.

If you sail offshore for more than 24 hrs at a stretch you will eventually encounter a situation where the house bank is in a low state of charge and you need to get the engine started with let’s say contaminated fuel. A portable jumper box won’t solve this scenario. If you’ve ever had to bleed your engine at sea you’ll appreciate the amount of time it can take to start popping dinosaurs again.

You could have a portable generator on board (many do) but it’s all but useless in a messy sea state.

So my $.02 is keep a designated start battery for safety.

[Dieseldude]

Originally Posted by stormalong

Both edits are right. Does Yanmar have a relay between the start position on the key switch and the solenoid? Why?

A relay will extend the life of the start switch by protecting the contacts from arc burn. Only the small relay coil of a fraction of an amp is switched by the starter switch instead of several amps of solenoid current. It also allows the safety feature of a lock out switch. A lock out switch mechanically coupled to the gear box will prevent the engine from being started in gear, just as in a land vehicle.

[David Mathis]

A separate starting battery is a waste of money and space, unless you need it. Like having a parachute.

[Goodxcharly]

I would agree that you don’t really need a start battery since my new purchase of a 36’ sailboat without one. I thought it was odd that it did not have one and was planning on installing one. Though it came from the factory that way.

I’ve changed my mind since. It has 2 banks of 6 volt golf cart batteries which were recently converted from single 12 volt. It takes 3/4 of a second to pop the universal to life..

If I did decide to go with another starting battery I would probably install another bank of 6 volt golf cart batteries if you have room. Then you have starting and increased storage capacity. Dual purpose. Coastal cruiser like myself 2banks is fine.

[OS2Dude]

Depends where/how you sail. We're on a freshwater lake and I combined the two separate batteries into one larger bank. The two AGMs are more than capable of starting the M25 diesel. If all else fails, I wait for full sun so the panels can start it, sail back, or in worst case call sea-tow. If I was sailing the world and had to worry about unknown harbors/anchorages, it may be a different story.

[Martinini]

Keep the dedicated Start battery wired into the system. You will be happier and safer!

[team karst]

As I float here is this current anchorage; a few days ago, a 35kt gale came thru. We were thinking of our process for an anchor drag. We are sandwiched between two shoals 1/4mile apart with a ripping channel current in the middle holding our anchor.
So, its 3am, and anchor alarm sounds. I need to IMMEDIATELY start 2 engines and get the wife on the bow to manage 100' of chain for an anchor that may not be still connected to it... looking for a jump pack doesn't fit our process. While trying to get to the last known anchor position.

[Dieseldude]

Originally Posted by team karst

As I float here is this current anchorage; a few days ago, a 35kt gale came thru. We were thinking of our process for an anchor drag. We are sandwiched between two shoals 1/4mile apart with a ripping channel current in the middle holding our anchor.
So, its 3am, and anchor alarm sounds. I need to IMMEDIATELY start 2 engines and get the wife on the bow to manage 100' of chain for an anchor that may not be still connected to it... looking for a jump pack doesn't fit our process. While trying to get to the last known anchor position.

In such a situation, it sure is essential to have instant starting available from a dedicated battery that is there for the sole purpose of starting the engine and running only engine accessories. Will save your vessel and save your life. Had your house bank been depleted, or a portable boost battery dead, you would be on a shoal with holes in the hull.

[Statistical]

Originally Posted by Dieseldude

In such a situation, it sure is essential to have instant starting available from a dedicated battery that is there for the sole purpose of starting the engine and running only engine accessories. Will save your vessel and save your life. Had your house bank been depleted, or a portable boost battery dead, you would be on a shoal with holes in the hull.

Yeah and if starter batteries were high maintenance or had a high cost it might be different. But they are pretty much buy and forget for 5 years until you replace them. Removing the starter battery isn't going to save you any significant cost or maintenance.

[Cadence]

Originally Posted by Dieseldude

In such a situation, it sure is essential to have instant starting available from a dedicated battery that is there for the sole purpose of starting the engine and running only engine accessories. Will save your vessel and save your life. Had your house bank been depleted, or a portable boost battery dead, you would be on a shoal with holes in the hull.

[smacksman]

I was amazed how good my little lithium emergency starter battery was. Size of a mobile phone yet cranked my 2.5L diesel no problem. Charged by 5v USB

[R Hutcheson]

You could certainly do it. Assuming the boat sails well, and you have the proper skill set, you should be able to sail out of a situation where you might otherwise want to motor. You'll probably be more conservative in your decision making as a result. Keeping your backup supply charged would become a regular maintenance task, and one which would be easy to overlook, thus rendering your backup ineffective. With that said there is no shortage of sailors/boats with unreliable engines out there, and most of them manage. It's not a solution I would want, but I certainly think you could do it.

[Dieseldude]

Originally Posted by smacksman

I was amazed how good my little lithium emergency starter battery was. Size of a mobile phone yet cranked my 2.5L diesel no problem. Charged by 5v USB

These mini emergency starter batteries are ok for a back up. They can get you out of a jam if there is time to find and connect them, and if kept charged. But they are no replacement for the capability of a dedicated starter battery. The real starter battery is always in its place and always getting charged when engine is running. It is always connected and ready in an instant. No time wasted to find it and connect it. When drifting toward a shoal or in danger of collision, a portable mini lithium is no substitute for a real dedicated battery.

[Shaneesprit]

Just because it say’s Battery on it - that doesn’t mean it’s the same thing.
House banks are designed to discharge slowly, while a crank battery is designed to release its power instantly.
How far away is the house bank from the starter motor? This length and then the associated cable size is critical. The further the battery the heavier the cable needs to be and maybe it’s ok when everything is perfect and warm, what about in 5 years when it’s cold and damp and the Engine doesn’t start first time
Battery CCA - Cold Cranking Amps unlikely the house bank even has a rating for this.