With lithium do we actually need a dedicated starter battery?

[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.

[rslifkin]

Personally, I think starting power is safety critical and should ALWAYS be kept separate from house power. I'm fine with sharing a start source between an engine and a generator, but each propulsion engine gets its own start battery and should have a switch to select a secondary starting power source (can be the house bank or the start battery for a second engine). The dedicated start battery should be the primary source of starting power (not a backup) that way it gets tested at every engine start and you don't run into the issue of having a backup power source that never gets used.

Nothing should ever run from the start battery except the engine and its instruments, so it should be impossible to accidentally drain the start battery. This also keeps the load spike of the starter motor away from electronics, although with much less voltage sag with lithium batteries, that's a much smaller concern.

[CaptainRivet]

Originally Posted by rslifkin

Personally, I think starting power is safety critical and should ALWAYS be kept separate from house power. I'm fine with sharing a start source between an engine and a generator, but each propulsion engine gets its own start battery and should have a switch to select a secondary starting power source (can be the house bank or the start battery for a second engine). The dedicated start battery should be the primary source of starting power (not a backup) that way it gets tested at every engine start and you don't run into the issue of having a backup power source that never gets used.

Nothing should ever run from the start battery except the engine and its instruments, so it should be impossible to accidentally drain the start battery. This also keeps the load spike of the starter motor away from electronics, although with much less voltage sag with lithium batteries, that's a much smaller concern.

Typical mantra. You should but why should I? Please explain why?
Safety means engine must start.

You have house and dedicated starter,
I have hybrid house and a buffer bat that isolates electronics and with flip of a switch can start engine
We both are 4 weeks on anchor at the same place and unforcasted storm/squall comes in and we need to quickly move, classic liveaboard situation:
You: your house runs but your starter was not used for 4 weeks => you don‘t know if it works!!!
Me: hybrid house runs and used under load constantly=> I know 100% engine will start
The buffer isolates electronics from spikes => I see its really full, I see it runs under load constantly and it will be a reliable backup that 100% start my engine if it needs too.

Hybrid bank, cutoff is at 3.0V except starter so I cannot accidentally drain hybrid that much that engine cannot start. Goes directly onto bank with a breaker, no cut off. If starter fail breaker trips, if lights go out due to cut off I still have 80 starts left in the house till 2,5V and then another 30 till hybrid is totally drained and I can decide if it’s better to drain hybrid then boat on the reefs or if I have enough time to switch to backup…I have options, you don‘t.
And I still have a buffer that can start engine too. BMS of buffer cuts off at 40% SOC but again starter goes via breaker directly onto buffer. Again cannot drain accidentally.

Why and which benefits and advantage do I have from a battery that does nothing else then start the engine? I don‘t know if it works unless I try to start…and well 90% of boats from factory have windlass on starter that can really drain quickly the starter…

[ChrisJHC]

Or you go with the “belts and braces” approach:
Install a separate Lead Acid battery for the starter.
Lithium for your house.
If, for some reason, the starter battery fails to work you can always start off your house.
I should note that I often sail on boats with limited power and I am a bit paranoid about depleting the starter battery.

[jcapo]

Popcorn time.

[CaptainRivet]

Originally Posted by ChrisJHC

Or you go with the “belts and braces” approach:
Install a separate Lead Acid battery for the starter.
Lithium for your house.
If, for some reason, the starter battery fails to work you can always start off your house.
I should note that I often sail on boats with limited power and I am a bit paranoid about depleting the starter battery.

Read my post...not possible to deplete hybrid further the 3.0V and have 80 starts still in the bank+buffer battery as backup.

Why lead starter....gased out but monitoring shows full voltage and when i need it, it collapses and not starting engine.
Lithium is so cheap, not even cost reasons anymore.
So whats beneficial of that setup...i cannot see 1 reason why to do so.

[wholybee]

I don't think you need a separate start battery. I know a few sailors that have gotten rid of the start battery, and I will soon also. Really what is keeping me from it is that what I have works so well, why mess with it?

I think the whole point of a separate start battery is twofold. First is reliability, that you have a backup to either the house or the start if the other should fail. Second is safety from running down your start battery with house loads.

LFP are just so damn reliable, I don't think the need for that redundancy is there anymore. You could still divide up into 2 house banks if you want. But Lead Acid fail all the time from PSOC issues and poor overall maintenance that LFP don't need. Properly setup, LFP just work-seemingly forever.

And most LFP installations have very good SOC monitoring. SOC is darn near impossible to predict with Lead Acid, and because of PSOC issues you can easily get caught by surprise and run your battery lower than you thought. But that is unlikely to happen with LFP and reasonable care.

So, I feel that for an inland or coastal boat, a single LFP for house and starting is fine. For offshore, where you probably have a much larger LFP bank to begin with, you can divide it in 2 to create redundancy.

[Mal Reynolds]

I did this. Works fine. On a simple system (no windlass, thruster, etc.), no need for even a buffer battery. But...I built the battery so I knew it would handle the start circuit current.

I would only do this with an external BMS, and with confidence any and all induction spike currents can be handled by the internal battery connections.

Oh, and in a real emergency if there is a problem I carry this: https://myweego.com/product/weego-120/

[wholybee]

Originally Posted by ChrisJHC

Or you go with the “belts and braces” approach:
Install a separate Lead Acid battery for the starter.
Lithium for your house.
If, for some reason, the starter battery fails to work you can always start off your house.
I should note that I often sail on boats with limited power and I am a bit paranoid about depleting the starter battery.

That works. Just understand that the Lead *WILL* fail and you *WILL* use the LFP house as a start battery when that happens. The LFP properly setup just won't fail.

Other people are paranoid about depleting the house battery and losing navigation equipment, the freezer, etc. Its just what you choose to be paranoid about.
The answer to that is to size the bank properly and use reasonable care in managing and charging it. LFP installs typically have much better SOC monitoring, so less to worry about if you know the meter works properly. If you do deplete the LFP, it won't be damaged, and will charge via solar to a point it will start the engine much faster than lead acid will. A lead acid might be damaged and need replaced if fully depleted.

[Kettlewell]

Well, playing Devil's advocate here, I like stuff on boats that is dead simple and idiot proof. What can go wrong, will go wrong, and always at the worst possible moment. So, let's say your SOC monitoring and solar controllers go at the same time, while you're offshore on a passage, and you have no easy way to troubleshoot or replace parts as needed. With a good old LA battery and a functioning alternator on an engine you can keep the ability to start and also run a few navigation instruments. I've also run solar power for years (12 approx.) with no controller at all--just me keeping an eye on voltage and cutting the panels off with a switch while charging LA batteries and living aboard. And, then if the starter battery dies in some remote island kingdom I can still purchase some old car battery at a local store and keep going. Even if the alternator or its controller have failed. These scenarios have all happened to me and others.

[wholybee]

Originally Posted by Kettlewell

Well, playing Devil's advocate here, I like stuff on boats that is dead simple and idiot proof. What can go wrong, will go wrong, and always at the worst possible moment. So, let's say your SOC monitoring and solar controllers go at the same time, while you're offshore on a passage, and you have no easy way to troubleshoot or replace parts as needed. With a good old LA battery and a functioning alternator on an engine you can keep the ability to start and also run a few navigation instruments. I've also run solar power for years (12 approx.) with no controller at all--just me keeping an eye on voltage and cutting the panels off with a switch while charging LA batteries and living aboard. And, then if the starter battery dies in some remote island kingdom I can still purchase some old car battery at a local store and keep going. Even if the alternator or its controller have failed. These scenarios have all happened to me and others.

You can go in circles forever with arguments like that. They just don't follow logic. Following your argument, if the SOC meter fails, and the solar controller fails, the alternator would still charge the LFP and keep the boat running.
Lead Acid batteries are far far more likely to have a problem than an LFP. By an order of magnitude, at least. They are more likely to fail than the SOC meter, or the solar controllers. So, the more reliable system is to remove the less reliable component. To really make the system reliable, you would also look at all single points of failure, and add redundancy there. A separate solar controller for each panel for example. A second alternator, or carry a spare, or have a generator on board as a backup. But no matter how you do it, throwing a Lead Acid starting battery in the mix will bring overall reliability down, not up. And a Lead Acid battery certainly isn't going to help in any way if a solar controller fails.

[Kettlewell]

And a Lead Acid battery certainly isn't going to help in any way if a solar controller fails.

I ran a solar and wind-powered boat for 12 years of living aboard with no controllers and gell cell LA batteries. Used the same set of batteries for all 12 years. Just watched a voltmeter and turned off or on charging sources as needed. This was before most people had any solar or wind onboard. LA batteries are very forgiving.

[knot smart]

my interpretation is that the primary issue is that whatever the standard BMS installed in a lithium battery cant take the heavy load of the starter, which is why most lithium batteries specifically say "not a starter battery".. However, the route we chose to go was the Dakota lthium which has a beefed up BMS and is designed to be a lithium starter battery.. a Victron Argofet isolator, and 2 400ah chins lithium for the house, standard 125amp alternator with a Balmar618 regulator..my interpretation is that you need the Balmar regulator to monitor the current state of the battery to regulate the voltage output of the alternator.. we'll see if it works in about 6 weeks or so

[Fore and Aft]

Captain Rivet for a start battery are you talking lead acid or AGM. If you're talking AGM start battery, then they last way beyond 300 cycles. Century batteries provide a 40-month warranty. My own cars powered with Century batteries prove how good they are. Just last week our paddock basher which hadn't been started in who knows how long easily fired up and was moved by my son.
Just about every boat I survey has a separate start battery. I imagine it is because in the early days of lithium batteries (10+ years ago) a few troubles were encountered. One client of mine had an issue with his lithium only battery bank and had to sail to the marina then get towed in because he could not start the engine. I was doing a night sail with a friend and suddenly the whole boat went dark. My friend couldn't sort out the issue but luckily, he had a separate start battery so we could still make it to the anchorage where the issue was sorted out. I have no idea how the problems were fixed but stories like this being passed around have probably encouraged the use of a separate start battery.
The other issue I encounter is that most Chandleries don't stock lithium batteries but stock AGM batteries. So, if there is an issue it is easy to swap a battery.
Cheers
https://carbatteryaustralia.com.au/u...nth%20Warranty.

[wholybee]

Originally Posted by Kettlewell

I ran a solar and wind-powered boat for 12 years of living aboard with no controllers and gell cell LA batteries. Used the same set of batteries for all 12 years. Just watched a voltmeter and turned off or on charging sources as needed. This was before most people had any solar or wind onboard. LA batteries are very forgiving.

The same will work with LFP. LFP are also very forgiving. In some ways, more so than LA.