With lithium do we actually need a dedicated starter battery?

[wholybee]

Originally Posted by 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

You need the Balmar to monitor the alternator temperature, so make sure you get that probe and connect it. That is the most important thing it does. Assuming you set it up correctly, you will be happy with it.

[catsketcher]

A couple pf points from someone who doesn't have a start battery (I have outboards that take very little starter current)

I think Nigel Calder and others sometimes recommend having lead acid as a starter because of the way Lithium BMS monitors will turn off the whole system if they get over voltage. So you can be going along charging your batteries and then, next thing you know everything powered by batteries is dead as the BMS turns off the Lithium battery to protect it from too high a voltage. This is supposed to fry the alternator because of the switch (same as when you switch to off with engine running IIRC). So you either need a smart alternator or a lead acid protecting the lithiums.

Cycling is also not a thing that is 300 cycles or so. The number of cycles from a lead acid is dependent on the number of cycles and the depth. Because starter batteries get so lightly discharged they have many more cycles than normal. Battery manufacturers can give you this data too.

Ask this question over at Nigel Calder's channel - he will be better able to answer it than me.

[rslifkin]

A well designed system shouldn't leave the start batteries without being topped off for weeks in normal use. But even if they are, an AGM (or a lithium battery meant for engine starting) will do fine starting an engine after sitting for a month without being topped off (assuming nothing is drawing from that battery).

Batteries also last a long time when their only job is to start an engine and then get topped off again. My AGM start batteries are now 6 years old and doing just fine. They never get meaningfully drained and live a generally very easy life.

[HankOnthewater]

My weigh-in in this discussing is quite light weight as I just started the LFP conversion on my boat and running LFP in a small campervan for over a year.

I am a little surprised with several opinions of others saying a LFP system is more reliable or less troublesome that lead acid.
I guess these are opinions with n=1 or 2?
But maybe that is true, LFP to be more reliable. I genuinely do not know. and because I do not know, I have chosen not going down the path the OP suggests: only to have one LFP bank, and no starter battery.
With one bank of LFP, and one external BMS, I just purchased a new AGM starter battery as well, same brand and model as I have in my big RV, that is still going strong after 13 years.

I don't think I am far wrong that most issues on the boat are of an electrical nature or electrons are involved, and just changing the chemistry of the batteries is -in my opinion- not going to reduce the electrical issues by much on a boat..... I think. And if it does, I will take that, as that would be an additional benefit of upgrading my system to LFP.
I will report back in 10-12 years' time

[Panope]

How does a BMS do in the event of a lightning strike?

Data Point: My 50 dollar LA Start battery is now 12 years and working fine.

[SailingHarmonie]

Originally Posted by Panope

How does a BMS do in the event of a lightning strike?

Data Point: My 50 dollar LA Start battery is now 12 years and working fine.

Panope nails it for me.

I keep hearing the lithium batteries never break, and can’t fail, blah, blah, blah. But the battery it self is useless without all the controlling circuitry. It has a LOT more controlling circuitry that needed for the lead acid starter battery.

Lightning is totally unpredictable and no battery system is immune from instant death. But having two totally independent systems gives you a much better opportunity to be able to limp home. The chances of a lead acid battery having a useful and accessible charge after a lightning strike are far higher than lithium (in my opinion). Not 100%, of course, but with lightning you always play the odds.

If your sailing grounds are in northwest North American you might not put this high on your priorities, but if you sail in Florida, the Chesapeake, or Panama and you are not thinking about lightning strikes you are ignoring the largest risk to your electrical system.

[skipperpete]

With the rapid introduction of electronically controlled common rail diesel engines into the cruising world I’m of the opinion that a dedicated engine battery is a necessity, not an option, the days of mechanical fuel injection are numbered and the electronically controlled ones need stable, reliable DC power as much as they need fuel. The OP can do whatever he likes with his own electrical system, we don’t have to agree.

[Pete7]

Originally Posted by rslifkin

Batteries also last a long time when their only job is to start an engine and then get topped off again. My AGM start batteries are now 6 years old and doing just fine. They never get meaningfully drained and live a generally very easy life.

Oh good, we are getting there I also think a lead acid starter battery is a good idea. Yes lead acid may only have 300 cycles if used in a house bank, but the amount of power taken to start a modern diesel is tiny, hence the long life members are reporting for starting batteries. Lead acid batteries are also tough and can take a huge amount of punishment or abuse. Not exactly an unknown phenomenon on the average yacht. LTO isn't really a good solution at 12v and it's a complexity I could do without if it goes wrong whilst at sea, in the dark.

CaptRivet suggested that a lead acid starter is good for coastal cruising because you can go ashore and buy another one. I would suggest that if you were doing an ocean passage, then they are also a pretty good idea in the event of the whole LFP / solar set up goes pear shaped. Just as I would carry an portable induction hob as a standby for the gas and to eek out the gas supply. Given a good lead acid, I suspect most of us could cobble something together mid ocean to get us to shore with a lead acid battery and some diesel.

Wholebee mentioned single point of failure, quite I don't even need to change the wiring to use the engine start battery and / or alternator, to run the domestics in the even of the hybrid LFP/FLA house bank going down for some reason.

Pete

[knot smart]

Originally Posted by wholybee

You need the Balmar to monitor the alternator temperature, so make sure you get that probe and connect it. That is the most important thing it does. Assuming you set it up correctly, you will be happy with it.

Yes, I did get the temp sensor for the alternator.. great point.. but additionally I thought that the regulator also ramps the voltage up and down by way of the field wire?

I am no expert

Also great point someone made about a BMS holding up to s lightning strike.. I would think all electronics would be cooked anyway but at least youd have nav lights if you have a lead acid..

[hlev00]

I have 480Ah FLA house bank plus a start. I always start my 50hp diesel from house keeping my start as a reserve. If my house get depleted too far I can use the Start. I start off it once a month as a test.

As far as LFP, until recently most, at least so-called drop-ins had limits due to the BMS or other components to safely deliver starting currents. Now many claim/offer their drop-in LFP are capable of delivering starting CCA necessary.

When my FLA need replacing I am looking for house bank of LFP only but keeping an adequate jump pack on board.

[ranger58sb]

Are there LFP batteries that can provide 1400 CCA? And 560A continuously for 4.5 minutes?

-Chris

[CaptainRivet]

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.

Actually my ElectrodacusBMS i have can exactly steer the solar panels like you done manuall, thats what it was originally designed for and then evolved but kept that possibility and i can connect lead or lithuim, just a matter of adapting the parameters...
No problem LFP either if solar controller and BMS go dead...first i have 2 spare BMS on board which extra cabling to cells so in case the balance leads should be compromised too. Exchange in under 1min with high seas, at anchor 10sec. Plug and play...wraped in alufoile and vaccumbaged. 2nd easy bypass and as my steering works with remotes i have manual switch too. So i can operate my lithium bank manually and a BMV712 takes care if i screw up. Then i have 1 mppt per panel with overhead, means 3 MPPT where i quickly can change at the breaker to parallel 2 panels on one Mppt and maybe loose 50W at peak hours and 1 spare. Nothing of this has to do with lead or lfp and starter or no dedicated starter.
I can always flip switch to connect a lead instead the LFP, all charge sources can do lead so if that happens on a remote island i can do it...but thats no reason to have now lead or dedicated starter anymore.
But well the chances my LFP go bust compare to lead is very very low.
Lead is not your lifesaver, its the root cause of trouble and unreliability. But if i need to i can alway use lead by flip of a switch and change some parameters in the victron gear

[JBP]

One of the first rules of seamanship is to always have a backup plan. Having two separate battery systems may have been a good idea since starting batteries and deep cycle batteries were different construction. A single LFP system can now do both, but now what is your backup plan? It might be to keep two battery systems, but for some people it might be fine to rely on a different backup plan. It might be call Tow Boat US, they are pretty pervasive in popular boating areas. It might be to carry an emergency starter pack if it can do the job. For some, the backup plan might be to anchor while the solar does it's Job.

[Kettlewell]

Whether or not you use LFP or LA batteries, I still prefer to have a dedicated starter battery that does nothing else and is trickle charged from the main battery bank so that it is always topped off. Since I have used this system I have never had a failure to start due to lack of electrical power, but I also have switching set up so that I can instantly choose to start from the main battery bank if for some reason the starter battery circuit isn't working. I just don't want to be dragging toward the rocks at 0200 only to find the normal starting circuit isn't working for some reason and not have an instant alternative. So, sure, start your engine from your main house bank whether LFP or LA if you wish, but please have an alternate starting source available with the flip of a switch, whether it is another big bank or a starter battery.

[rslifkin]

Originally Posted by CaptainRivet

Lead is not your lifesaver, its the root cause of trouble and unreliability

You may say that, but many of us have lead start batteries that last many years with no attention at all beyond using them. At this point lead rarely makes sense as a house bank, but for a start battery, it's simple, we all understand it, and it works. It's not necessarily the best possible solution, but it's a simple solution that's good enough in most use cases.