With lithium do we actually need a dedicated starter battery?

[Riggerman]

Originally Posted by CaptainRivet

With LFP and the tight monitoring and massive current capabilities do we really need a dedicated starter…a LFP house at 2.8V can easily start the engine several times…a depleted AGM can‘t.

Where did a seperate starter actually come from:
Simple answer a lead battery is either
1) a deep cycle for storage, that cannot deliver high current otherwise you destroy it or
2) a starter that can deliver short terms high current but you destroy it if you take constantly current off.
Additional the leads needed to be always full to have full CCA or current capabilities, at a lower SOC they are much worse and if not charged full die very quick. Add to that Peukert effect means the more current you pull the more weak the lead gets and voltage sags deep cause devil cycle more current….
Additional monitoring a lead is still not a secure method to know it’s ok as eg a dry lead still shows the full voltage but as soon as you put a load it collapses.

With lithium this is all completely different.
Already most 100AH LFP can start an engine, 200AH LFP house can easily start your engines, if then BMS is the limiting factor.
A LFP is very tightly monitored and every second you know exactly the real!!! state of your battery.
Conclusion:
There is absolutely no reason not to start from your lithium house bank your engine…it’s actually beneficial as the house is normally that big in AH that it’s kindergarten for the cells to do, means you are at 0.1 till 0.3C and wear on the starter is much less as enough current capabilities and no significant sag in voltage. House is always in use so you know it will 1000% start your engine and you have no surprise of a dry dead starter that collapses when you put a load on

Redundancy:
A lead lives a short live (300cycles max) and is unreliable in monitoring, sure you need redundancy in having a starter that just does this job.

A lithium lives much longer 2000-8000cycles and has a reliable monitoring.
A lithium bank consist of several single batteries in parallel so you already have redundancy.
For a costal sailor which are mostly the small boats too and space is a premium that hybrid LFP house has enough redundancy and reliability compared to a lead setup and as you are close to shore and in the really unlikely event you get fast help if needed

For bluewater cruiser or boats often far way from coast still redundancy is good and senseful requirement but having sitting around a starter that 98% of time does nothing, you don’t know if it really works if you need it and is of no added value then just sitting around waiting to be ever used.

is it not time to modernize and change these concepts as the reason there was seperate starter and house bats is completely gone with lithium.
My clear answer is yes it makes sense and is long overdue.

A much better approach is a buffer battery as redundancy:
It’s much better to have a hybrid starter house bank and a buffer battery (LTO or LFP or AGM) which by default is always full (or near full depending on how you set BMS if LFP) and that isolates and serves as independent power source for our nav equipment at navstation and helm.
that buffer battery is always in use, so you know it’s working and always full or the SOC you target. besides being small AH if LTO or eg Winston cells or an LFP starter bat it is still able to start engine in emergency case, so you have your redundancy and know your redundancy works if needed.

To me much better setup, cheaper, simpler and solves a lot of issues you have with a dedicated starter.
No need for a lead starter ever again.

Depending on the battery you have. it might not be necessary. I have a dual purpose battery 280 amp reserve and 1000 CCA. But I have kept My starter battery anyway even if not needed. I use a DC to DC charger so that I did not have to buy an expensive Balmar charge controller for the alternator. So in short, no you might not need one. but better be safe then sorry.

[emilecantin]

Main reason to keep a starter battery IMO is that it lets you keep the huge current draw and associated voltage fluctuations to a separate circuit, leaving your fragile electronics unperturbed. Lithiums are better in this regard, still.


Of course, if your boat is set up with a 1-2-both switch and you switch everything to the starter battery when you start the engine, that kind of defeats the purpose... You need a separate circuit.

[sealandsky]

I'm still trying to figure out what a "devil cycle" is - Anyone? Bueller?

[newhaul]

Originally Posted by sealandsky

I'm still trying to figure out what a "devil cycle" is - Anyone? Bueller?

That time of the month for my redhead Irish wife .

[CaptainRivet]

Originally Posted by newhaul

Simplicity that's why. No need to buy expensive alternator or controller. The dc to dc does the job great and was cheaper than even a stock 75 amp replacement alternator.
I can raise all 125 meters of anchor chain off the bottom to do include my 25 pound CQR. no electric needed. Manual windlass.

The DC2DC also works via the 10AH buffer...and the buffer isolates your senstive electronic from any surges or distoration plus if the BMS sends you into dark non of your eletronics shut off as the buffer takes over and just buffer it.
Equally simple...
a buffer agm is cheap, has an easy and long life as automatically floated all the time. You just spec the buffer so it can start the engine on the edge...its emergency not permanent as started from LFP house.
A starter AGM is more expensive and has a hard life delivering current and needs artificially been floated to not die...the starter suffers too.
So whats better for less money?

[Wandering1]

Originally Posted by CaptainRivet

The DC2DC also works via the 10AH buffer...and the buffer isolates your senstive electronic from any surges or distoration plus if the BMS sends you into dark non of your eletronics shut off as the buffer takes over and just buffer it.
Equally simple...
a buffer agm is cheap, has an easy and long life as automatically floated all the time. You just spec the buffer so it can start the engine on the edge...its emergency not permanent as started from LFP house.
A starter AGM is more expensive and has a hard life delivering current and needs artificially been floated to not die...the starter suffers too.
So whats better for less money?

My engine batteries have a long life as they are on a DC/DC converter on float permanently.
A pair of 12v engine batteries was €210. Its simple, reliable and cheap. I see no reason to change.

[Fuss]

7000 views 150 posts and I guarantee not one forum member buys 18$ scib Toshiba LTOs and makes a battery based on these posts.

There is a lot more to it that just ordering 6 cells at $18 each.

And also If you need Rivet to install them for you then you are equally not informed enough to have them.

[mikereed100]

Originally Posted by ikebartlett

A 6.354 Perkins has 500 amp instantaneous starting draw followed by 80-100 amps once cranking. If you don’t have at least 600 amps lithium , the BMS is going to open.

And yet, I have started the Perkins 6.354 on my trawler with one of those dinky $90 lithium battery jumpers from Amazon that's not much bigger than my multi-tester. How do they do that? No BMS? Sorcery?

[newhaul]

Originally Posted by CaptainRivet

The DC2DC also works via the 10AH buffer...and the buffer isolates your senstive electronic from any surges or distoration plus if the BMS sends you into dark non of your eletronics shut off as the buffer takes over and just buffer it.
Equally simple...
a buffer agm is cheap, has an easy and long life as automatically floated all the time. You just spec the buffer so it can start the engine on the edge...its emergency not permanent as started from LFP house.
A starter AGM is more expensive and has a hard life delivering current and needs artificially been floated to not die...the starter suffers too.
So whats better for less money?

My system is cheaper and actually works much better.
My boat my setup my choice .
Same with you your boat your choice . I'm usually available if you need help with a problem you can't figure out .

Remember I used to design and install complete off grid systems for mainly sailboats but a few land systems as well.

[Coltrek]

On my C&C 39, I had three large deep cycle batteries, 2 for house, one for Engine. I found that I just set it to combine, and never deviated from that. I also always kept a Genius 70 Lithium jumper battery in a drawer, so I was never concerned. Keep in mind, most of these engines are not much more than large lawn mower engines.

[SOLAR SUPPORT]

Originally Posted by Fuss

7000 views 150 posts and I guarantee not one forum member buys 18$ scib Toshiba LTOs and makes a battery based on these posts.

There is a lot more to it that just ordering 6 cells at $18 each.

And also If you need Rivet to install them for you then you are equally not informed enough to have them.

It is a good idea to have one 6 cell LTO battery pack to start your engine, bow thruster, e-winch(es) and windlass from one LTO bank. Those equipments above do not work togeather smiltuanously but all of them require high starting currents which a 6 cell LTO battery can deliver to any of them when needed. You do not have to deal with extra two or three battery groups and their infrastructure. Their CCA is very high 10C and short term max peak current discharge rate is 20C. I think using them as service batteries is not significant in moderate climates but it is possible for boats to use them as service batteries also where they sail in very cold climates.

[roland stockham]

Haven't read all the posts but just want to point to some real, and probably dangerous, thinking. "Lithium is just so reliable it won't fail!" You are happy to bet your life on that! The is no such thing as a system that cant fail and the more complex a system is the more fail points it has. Every switch, fuse, connection or component in a circuit is a potential fail point and one fail will usually knock out the entire system. If it is a critical system, which starting the engine is, the question should be "what is my strategy when this fails?" The chemistry is not that relevant as long as it is a reliable backup. I agree that a backup system that is used on a regular basis is an excellent idea because you will know that it is working but it should be entirely independent. I used to carry a set of jump leads so I could connect the house bank directly to the starter. Now I have a lithium portable pack instead, keep it in the truck and take it onboard for each trip.

[newhaul]

Originally Posted by roland stockham

Haven't read all the posts but just want to point to some real, and probably dangerous, thinking. "Lithium is just so reliable it won't fail!" You are happy to bet your life on that! The is no such thing as a system that cant fail and the more complex a system is the more fail points it has. Every switch, fuse, connection or component in a circuit is a potential fail point and one fail will usually knock out the entire system. If it is a critical system, which starting the engine is, the question should be "what is my strategy when this fails?" The chemistry is not that relevant as long as it is a reliable backup. I agree that a backup system that is used on a regular basis is an excellent idea because you will know that it is working but it should be entirely independent. I used to carry a set of jump leads so I could connect the house bank directly to the starter. Now I have a lithium portable pack instead, keep it in the truck and take it onboard for each trip.

Wish my current one was capable of hand starting like my last 2 boats.

[Kettlewell]

The problem with the portable lithium pack is that I know with 100% certainty there will come a time when I can't find the pack, it is discharged, or I left it onshore. The same has happened to me with the one I "always" keep in the car, except for the one time I needed it and it was on the charger at home...Portable lithium packs are wonderful, but I vastly prefer to have the 0200 emergency backup via a switch that I flip and go as the rocks get closer.

[aqfishing]

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