Getting rid of the start battery

[valhalla360]

Assuming we are talking about a cruising sailboat with a relatively small engine and a big house battery bank...you are golden.

We can talk what-if scenarios and make any system fail...does your motor have two independent starter motors in case one fails and you are about to be run down by an oil tanker? I don't know of any single engine cruisers who do and yes, starter motors can and do fail.

A big house bank that drops the voltage enough to kill the electronics suggests it's worn out. If you take it to the extreme and your house bank is a single 12v starting battery, yeah, that's pretty marginal but assuming a good size house bank, it's not a big issue.

The jump pack should handle the what-if of the house bank being dead.

What I might suggest:
- If using the jump pack involves crawling into an engine room, set up some leads (protected from shorting), so you can connect the pack quickly without any gymnastics.
- Put on the schedule to test/charge the jump pack on a periodic basis.

PS: We did this minus the jump pack for several years. Of course, our primary propulsion was a 25hp outboard and we could pull start if the battery died providing a backup way to start.

[ranger58sb]

Originally Posted by seandepagnier

He has that lithium battery starter battery which is probably better and more reliable anyway, so it has a starter already, and you can still hand-crank, or raise the anchor up the mast and drop it to start the engine anyway.

But then again, in an emergency starting an engine is not needed or helpful as I have found my self in bad situations but never once wanted an engine.

Would one have to leave the helm to use a jump-starter? If so, would that be a comfortable thing to do in a navigation emergency of some sort?

I'd guess you've been lucky.

-Chris

[gonesail]

depending on how big your engine is .. I think a healthy house bank is fine for starting purposes .. along with the lithium emergency battery stowed and charged.

[Statistical]

Originally Posted by PaulCrawhorn

Yes, jf your system works fine off two single 12V lead batts, then it cannot be simplified further without increasing risks.

I am not suggesting would be an improvement for everyone, just responding to the OP with food for thought.

My scenario is more along the lines of a 600Ah and 300Ah, ideally both LFP

and the Reserve being larger than a Starter, is adding Redundancy for more than just cranking functions.

Also, when there are already multiple batteries for Starter, or the other functions mentioned, these get consolidated, reduced to two in total, which is IMO the minimum safe count

Why a reserve LFP house bank? Why not a 900 Ah house bank. It will mean the battery spends more time at a modest SoC which is better than longevity rather than a highly used 600 Ah bank and an almost never used 300 Ah bank.

I agree that if you are going to have two LFP banks and never combine them except in emergencies you could get away with not having starters but that seems a solution in search of a problem.

Starting motors requires very little energy just a lot of power and a 12V boring simple lead acid battery is amazingly good and cheap for that job.

[Statistical]

Originally Posted by valhalla360

What I might suggest:
- If using the jump pack involves crawling into an engine room, set up some leads (protected from shorting), so you can connect the pack quickly without any gymnastics.
- Put on the schedule to test/charge the jump pack on a periodic basis.

PS: We did this minus the jump pack for several years. Of course, our primary propulsion was a 25hp outboard and we could pull start if the battery died providing a backup way to start.

In that case though you really aren't getting rid of a starter battery just making it an infrequently used less convenient portable one.

I mean to make it more convenient you could permanently mount that portable emergency battery pack, put it behind a switch, and to ensure it is always charger wire in the charger as well. We just reinvented the starter battery.

On a more serious note those jump starters are not designed for starting a motor. They are designed to give a lead acid battery just enough of a boost to be able to turn over the starter. While you could maybe use it to recharger a "dead" large LFP pack understand that CCA is not linear with energy capacity. So with a large house LFP pack that jump pack may not be able to get it to a place that can deliver sufficient CCA to turn over the starter motor.

While I agree that a starter battery isn't absolutely required if you have a large house LFP bank and are willing to be competent with it (maybe install a low voltage cutoff with manual override). The flip side is lead acid starter batteries are dirt cheap and largely just work. Removing it seems like a solution in search of a problem.

[PaulCrawhorn]

Originally Posted by Statistical

Why a reserve LFP house bank? Why not a 900 Ah house bank

Only having a single monolithic bank means no redundancy if it fails, or if it gets accidentally drawn too low.

My final suggestion gets the advantages you mention but a LVC isolator preserves the Reserve.

[more]

Originally Posted by alctel

I am completely rewiring my boat, and I was thinking last night - why not get rid of the start battery entirely?

I would keep something like https://no.co/gb40 on the boat instead, .

do you know this is small 4ah lithium battery with big cable.

[PaulCrawhorn]

Originally Posted by Statistical

In that case though you really aren't getting rid of a starter battery

The goal of the Reserve concept is to add redundancy, eliminating dedicated Starter is just an ancillary result. The point is avoiding dedicating a bunch of batteries to single functions, only complex systems with multiple Starter batts and other multiple banks are actually getting simplified.

There are high powered jump starter packs designed to start large diesel engines with a completely failed Starter batt.

But I agree these are only for belt & suspenders extra, not primary redundancy.

[Statistical]

Originally Posted by PaulCrawhorn

The goal of the Reserve concept is to add redundancy, eliminating dedicated Starter is just an ancillary result. The point is avoiding dedicating a bunch of batteries to single functions, only complex systems with multiple Starter batts and other multiple banks are actually getting simplified.

There are high powered jump starter packs designed to start large diesel engines with a completely failed Starter batt.

But I agree these are only for belt & suspenders extra, not primary redundancy.

But you aren't adding redundancy you are replacing one redundancy with another less convenient more likely to not be tested regularly and so less likely to be available when actually needed.

House bank, starter battery & jumpstarter would be adding redundancy although I would argue it is overkill as Housebank plus starter battery is already highly redundant.

Now if starter batteries were short lived, expensive, and maintenance prone I could see it but they largely just work for a long time at minimal cost.

[donradcliffe]

I bought a boat with 2 house banks and a starter bank. I put 500 ahr of gel batteries them and switched all banks on in parallel. In 15 years of full time cruising I never had a problem starting the engine, even when one of the house batteries shorted a cell. and that was before the days of the small cheap lithium starter battery.

Seamanship is knowing the level of your battery bank, and having a low battery alarm.

[Cadence]

One thing I hadn't seen mentioned, what is the size of the engine/current requirement for starting. One solution does not fit all.
I for one like a dedicated engine start battery, but I'm old school.

[Minggat]

20 years on same boat. No starter battery. California to Mexico, Mexico to Hawaii.

It depends on your setup and how you use your boat.

Now with Lithium, a separate AMG started battery required.

[Statistical]

Originally Posted by Minggat

20 years on same boat. No starter battery.

Now with Lithium, a separate AMG started battery required.

Well maybe not. If someone has a large LFP bank that can deliver the required amps and is fine with having no redundancy it isn't required.

Smaller marine diesel auxillery engines (30 to 80 HP) don't usually pull more than 100 to 200A for a couple seconds. If your lithium housebank can deliver that it will start.

So the choice of a starter battery for added security in most cases is just that a choice.

[Minggat]

I do agree with Statistical above. I could have been more clear. And of course I didn’t require an AGM, just a starter battery. A bigger LFP $etup would have been another option.

[poiu]

I got rid of a starter battery. I paralleled the engine and genset bats to get rid of one pair. I still have house as back up. It has worked fine for years.