Do I really need a separate starter battery

[AKA-None]

Originally Posted by Grattaway

and no one has mentioned having a crank handle on board

A bit scary for me

[mvweebles]

Compression on a diesel is about 3x compared to gas engine. Makes a difference- I had an old generator with a 1-cylinder Yanmar with belt-drive to an AC power head. Starter motor was also belt drive and not very reliable. Also had a hand crank. Process was to hold open a compression release valve, crank like hell until you built enough flywheel inertia, then stand back and release the compression release and hope for the best. Occasionally the handle would kick-back mid wind-up and whack you solid.

Peter.

[CarinaPDX]

On rare occasion I used to hand start my old 18hp Sabb. That was only when necessary and was quite an effort but it always worked. One time I had to hand start for a couple of weeks while I waited for a new starter motor; the Caterpillar start switch stuck on "start" and the engine drove the starter into oblivion... But hand starting takes an engine designed for that purpose, with hand crank and cylinder decompression control, and the new engine doesn't have that. Progress.

Greg

[HankOnthewater]

Originally Posted by Frankly

Those that carry a spare starter motor/ solenoid please raise your hand.

Yes I have spare starters both engines and genset, as I have alternators, fuel lift pumps etc. See more in last paragraph.

But even with a spare startermotor, it takes at least a few hours to replace, not quite right when dragging anchor on a lee shore.

I have seen engines that had 2 startermotors fitted, one each side. I have been looking to buy such bellhousing plate, maybe not seriously, but if I saw one for sale, I would buy it.
But to keep in the spirit of this thread, it is often electrical issues that cause the startermotor not to do its job: turning the engine.

Maybe another (expensive) solution is to carry a windup startermotor, either bolted on the other side of the engine, or as a spare. How many of us did try to unbolt the startermotor to see how easy it is or not, to remove it, and if the spare startermotor fits? I did that recently after 5 years or boat ownership, and...... the spare startermotor did not fit, although the bolt holes were correct its shape was slightly longer and did not fit the space, without removing the dipstick assembly.

[Philtao]

Originally Posted by smac999

Lithuim is still highly Experimental at this point. It’s on maybe 0.1% of boats. Bms’s and cells fail leaving you with no power.

Yes if you use drop-ins or a poorly designed BMS. Some BMS can connect the LA battery to your installation before disconnecting the lithium battery or in case of a BMS failure.

[goboatingnow]

Firstly Lithium’s make excellent starter batteries. Much better in fact then any FLA.

Whether you have a house and start bank or one bank I’d still suggest it’s advisable to have a backup. A separate lithium diesel stater pack that you can charge would be ideal in this case.

[Zzmeyer]

I’ll have to learn more about failure of bms due to engine starting. If acceptable I might just get a cheap flooded battery and store in a locker along with the engine spares.

[Bill Seal]

Just rig a Coffman starter and carry lots of shotgun shell blanks

[goboatingnow]

Surely you’ve all practiced starting the engine using a line to the boom and a decent gybe

[mcon12000]

I’m in the separate start battery group. “If” your BMS fails you’ll be able to start and if your LA start battery fails you’ll be able to jump using the house bank.

There are quite a few Lithium starter batteries on the market. Aviation and racing have created a market. Might be a better choice than using a battery optimized for house loads.

If your alternator isn’t externally regulated the LA start option will allow you to safely connect it to this battery. Then add a DC to DC charger to direct that energy to the lifepo4 house bank.

[dbraymer]

This actually happened on a Transpac. A mechanic dropped a wrench just perfect, and it landed accross a batteries posts. The wrench welded itself in place and within several seconds, the boat was without 12 VDC This was a race boat, no extra anything.
The happy part of the story is that they sailed on without radio and weatherfax and won the race! (after paying the time penalty for not reporting in!)
Stuff can happen out there. I have 6 batteries, two of them just for the engine. I know that this is overkill, but it allows me to use deep cycle capable batteries every where. I can swap things around if something goes wrong. (All batteries same size, weight, posts and polarity orientation...)
Count me as a somewhat pessimistic fellow, but I have sat on the water when the wind was barely moving, and the sky was really cloudy. If you plan that stuff is sure to go wrong, separating the batteries is at the top of the preparedness list.
Second on the list is a separate alternator for the house bank. Otherwise the most important engine on the boat is the single alternator, as its failure can take out your ability to start the diesel.
There is of course a house/engine bank combiner switch. There is a label affixed there that says "Only the captain may touch this switch!"

[Bill_Giles]

The engine start battery is going to be relatively cheap compared to your domestic battery bank. Our engine battery is ten years old and it replaced on of similar age. I am a belt and braces man and wonder why you would want not to have a backup especially if you are offshore.

[Zzmeyer]

Not a matter of not having a backup, but how many. The flooded battery is cheap, but I worry about the complexity of combining with lithium and the equipment required to integrate the two. DC to DC converter, relay. I'm still learning, but it seems a lot simpler, and therefore potentially less likely to fail, to minimize the number of systems on board. My concerns with not having a separate starter battery only relate to the effect on the lithium house batteries of starting an engine using them. The probability of having a discharged 900 amp bank with the battery monitoring system and 1200 watts of solar is so low for me as I'd rather have other backup systems elsewhere. If the house bank fails entirely I have lots of problems including no navigation instruments or lights

[Zzmeyer]

There is of course a house/engine bank combiner switch. There is a label affixed there that says "Only the captain may touch this switch!"
Question - can you use such a switch with a combination of lithium and flooded battery?

[CaptainRivet]

Just use 6 Yinglong 40AH LTO cells in series,no BMS needed. Install and forget it, it will outlast your boat... 30000cycles, 10C permanent, 20C peak=800A and can be discharged to 0 and recharged again. Perfect starter battery that will always work. Very low resistance so you need a external regulator for it but if you have lithium house you have that already.