With lithium do we actually need a dedicated starter battery?

[Fortytwo]

40hp Yanmar

4 100 amp hour Battleborn house bank, starts motor fine

https://battlebornbatteries.com/prod...cycle-battery/

1 125 amp hour Ionic Blue starter battery, starts motor fine

https://lithiumhub.com/product/12v-1...cycle-battery/

Backup…
NOCO Boost X GBX45 1250A 12V UltraSafe Portable Lithium Jump Starter, Car Battery Booster Pack, USB-C Powerbank Charger, and Jumper Cables for up to 6.5-Liter Gas and 4.0-Liter Diesel Engines
https://a.co/d/45tuvZW

Always good to have at least one back up.

Always have proper fusing and alternator protection.

[SOLAR SUPPORT]

The first thought that comes to the mind of anyone who changes their service battery from LA-AGM to LFP is to convert the engine LA battery on the boat to an LFP battery or to think about whether an LA battery is really needed. This is due to understanding the difference in life, performance and net capacity between LFP technology and LA technology after experiencing the performance of LFP batteries.


I was busy with the same thoughts and realized that I had to continue using my LA Motor battery. I kept the manual switch I added to temporarily parallel connect my LA engine and old AGM service batteries, which are isolated from each other with the Battery Isolator, in case of emergency. After replacing my service batteries with LFP batteries, I continue to use them with the same installation.


Before using the switch that connects the LA motor and LFP service batteries in parallel, I checked the total bms continuous and peak current values ​​of the LFP service batteries and the short-term peak current resistances of the fuses in the installation. Before this attempt, you must make sure that the current values ​​mentioned above are above the CCA capacity of the LA engine battery. After these checks, your LFP service battery will start your engine even if the LA battery is completely dead. Disabling the over-discharged LA engine battery will allow the LFP service batteries to start the engine more easily.


Completely removing your LA engine battery is pointless as it will leave you unprotected in case of surprise LFP bms outages. If you go this route, you should definitely use an APD device.

[CaptainRivet]

Originally Posted by Mal Reynolds

For clarity, I assume you are thinking about cell balancing here. Yes, LFP should be balanced periodically, the period being driven by number of cells in series and C rate in and out. HVC, LVC, HTC, LTC can all be managed easily manually as long as the boat is attended. I did this for 20,000 miles.

It should be noted that not all BMS's actively cell balance.

The broader point is, even if a BMS fails, you can easily bypass it and get to port. Or just carry a spare.

that's right in emergency always without BMS possible BUT you need to have that manual override designed in eg i have start and windlass with a breaker directly wired after the 500A NH3 fuse to Lifepo4 bank, BMS shunts account for its energy but BMS cannot cut them off.


i mean here constantly running without BMS on Lifepo4.
a 1p4S winston bank, without any hesitation always no BMS just a BMV700-712 which does LCV and HCV with its relay output steering a disconnect relay and/or eg cut off MPPT/inverter&charger via its remote port.
When run >100AH then a neey 4A active balancer who also does cell monitoring, just because of what this cells cost as extra security (not really needed), otherwise a cheap cell monitor.

with 8S (maybe low C-rate winston bank like 4S without) or 16S always BMS.

[Fortytwo]

https://www.sterling-power-usa.com/S...iondevice.aspx

Alternator only charges my starter battery.

Solar charges the house.

[newhaul]

Originally Posted by CaptainRivet

https://batteryhookup.com/products/2...prismatic-cell


18$ per cell and never cycled.

Plus taxes and shipping
Those 4 cells are $100 to me not counting the connecting cables and custom BMS ( if I use one for them)
Vs a $20 FLA start battery .
Life of my FLA is about 10+ years . ( Based on the life of the same battery that starts my tractor at the house . )
Price today at tractor supply $49.95

[CaptainRivet]

Originally Posted by seaexplorer

You've piqued my interest with these LTO SCiB cells.
I've wanted to get rid of my lead acid starter batteries for a long time.

I have a 4.5L John Deere Diesel with 24v starter on my port side (starboard side removed and replaced with 48v 50kW Molabo inboard electric powered by 105kWh LFP 48v bank).

I already have 2 independent battery banks (24v & 48v) and will also have a 12v 100ah LFP for 12v backup so I really don't need the starter batteries for anything other than starting the diesel.

Currently I have the 2x 24v 100Ah LA banks still in place charged by a Victron Isolated DC-DC Converter / Charger in engine room from my 24v Victron LFP bank at front of boat (via another Victron DC-DC converter). It is a big boat so the cable run from the house LFPs to the engine is over 25m.

I think that if I replaced all 4 LAs with 12 LTO 2.3v SCiBs then I could keep the same config and lose over 100kg of lead at the rear (which is significant on a performance cat).

You mentioned them not needing a BMS only a balancer. What do you suggest?

Alternatively I could charge them parallel with my Victron 24v LFP bank but would need to run another thick cable to the rear

What do you think?

how many watts does your starter on your 4,5l deer has? 100Ah 24V with 1400CCA assume thats 4-6kw starter....

for 24V you need 11 cells.
I would go for 22 cells each a 1p11 battery with a balancer and then parallel. I like to use the 4A neey active balancer, which is with 130Euro a bit more expensive but a) it really balances with 4A per cell and 2) you have a bluetooth cell monitor too where you get the cell voltages to the nav/helmstation. with that load on them i would want to see each cell...for a 78ft alu cat 130Euro more is peanuts...one should on limit start the engine if 5kw, so 2 batteries for redudancy and reduce load.

you have your 25m cable and that was enough to charge lead, so with better efficency LTO is defintly enough. Assume the front DC2DC converter is used to compensate voltage drop on a 25m cable and the DC2DC in engine room to adapt charging profil to lead.
keep it like this, switch engine DC2DC charger to lithium and as they are pure starter best is you use all voltage they have and charge to 11x2,8V=30.8V or as high as the DC2DC charger can be raised. your starter likes 1,6V more then LFP and will turn over easier and you charge to 100% SOC or close and have full 2x20AH capacity.
What exact model is the front DC2DC and the rear?

a start is not more then 1-2AH so the you don't need 320A recharging the cells from 0%SOC to full in 6min...
but build nice boxes with balancer inside for them, battery terminals so you can carry them around as they good emergency or jumper batteries too. if you have 12V equipment i would put a 3rd positive terminal into box with takeoff at the 6th cell, so you can use it on 12v too, balancer will fix that later back to 24V battery. 11x550g=5,5kg+box

2x11p can be put in series =48V and you can even recharge them by paralleling them to your 48V system or your 24Vsystem anytime you need or want, also in case the DC2DC break.

[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.

[CaptainRivet]

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.

one 20AH LTO scrib will manage that on the egde, 40AH will definetly do.
100AH Winston cells will also easily manage that, 3C continous=300A and 6C peak for 1min=600A and 1000A for 5sek. take the 150 or 200AH cells with a BV712 battery monitor+4 A neey active balancer and ready is your hybid starter/house bank...no BMS that can break and the battery monitor does LCV/HCV plus neey does BT cell monitor and fixes any imbalnce that a winston ever can suffer from. simply, easy, super robust and 1000times more reliable then every lead setup.

[CaptainRivet]

Originally Posted by newhaul

Plus taxes and shipping
Those 4 cells are $100 to me not counting the connecting cables and custom BMS ( if I use one for them)
Vs a $20 FLA start battery .
Life of my FLA is about 10+ years . ( Based on the life of the same battery that starts my tractor at the house . )
Price today at tractor supply $49.95

for your tiny boat yes but a 100AH AGM is 100Euro...quite equal in price, no BMS just a 30Euro active balancer.

[Icarus]

Originally Posted by CaptainRivet

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…

I think starting an engine when you need it is a benefit... Surly you don't run your anchor winch from the starter battery..?
If so why?

[Icarus]

Originally Posted by 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.

Seems to work for you.. Great..

[Nicholson58]

We repowered with Blue Heron lithium. 24 volt boat so lithium is ~26 volts. We have house 630 AH and start bank 110 AH HIGH OUTPUT. Banks are switched on in parallel. 115 HP 6 cyl monster old Westerbeke with high draw starter. This works vert well. House bank would probably do the starter alone but the extra amp capacity makes starts instant with no serious impact to the house.

12.5 kw generator with plain old lead acid starter 12volts.

985 watts solar. We are fully charged daily.

[CaptainRivet]

Originally Posted by newhaul

Plus taxes and shipping
Those 4 cells are $100 to me not counting the connecting cables and custom BMS ( if I use one for them)
Vs a $20 FLA start battery .
Life of my FLA is about 10+ years . ( Based on the life of the same battery that starts my tractor at the house . )
Price today at tractor supply $49.95

Originally Posted by Icarus

I think starting an engine when you need it is a benefit... Surly you don't run your anchor winch from the starter battery..?
If so why?

because its setup like this from manufacturer running of starter, on my lavezzi too. that why you need to run the engine so you cannot deplete the starter completly and beacuse the lead starter won't support getting 80m chain from the 20m deep anchorage....sure i changed that

because the surge would kill your mosfet BMS used as house bank, especially cheap dropins aka chinese surprise boxes without communications...and won't let you emergency start from housebank either (cells can do but not BMS).
on the other side lithium house banks are on most boats 35ft and up min 300AH means they can all start your engine and support get 80m chain in easily without huge voltage drop and strain on the motor, best DIY or dropins that can be opened (eg SOX marine or sunfunkits) so you have access to cells and can choose a good BMS, if mosfet with enough constant and peak current capabilities to do both of the house.
if you need lead as surge protection for alternator or for DC2DC use either a
a) small 10AH motorbike AGM as buffer too that protects the senstive electrics form surge, spike and distortions.
b) FLA big enough to start your engine as backup...will be just sitting around. why start not from lead...simple more strain on the starter, its just a backup you need as surge protector and i will garantuee it will die unused if your lithium bank install is correctly done and stress tested...it still work as surge protector if nearly dead.

[newhaul]

Originally Posted by CaptainRivet

because its setup like this from manufacturer running of starter, on my lavezzi too. that why you need to run the engine so you cannot deplete the starter completly and beacuse the lead starter won't support getting 80m chain from the 20m deep anchorage....sure i changed that

because the surge would kill your mosfet BMS used as house bank, especially cheap dropins aka chinese surprise boxes without communications...and won't let you emergency start from housebank either (cells can do but not BMS).
on the other side lithium house banks are on most boats 35ft and up min 300AH means they can all start your engine and support get 80m chain in easily without huge voltage drop and strain on the motor, best DIY or dropins that can be opened (eg SOX marine or sunfunkits) so you have access to cells and can choose a good BMS, if mosfet with enough constant and peak current capabilities to do both of the house.
if you need lead as surge protection for alternator or for DC2DC use either a
a) small 10AH motorbike AGM as buffer too that protects the senstive electrics form surge, spike and distortions.
b) FLA big enough to start your engine as backup...will be just sitting around. why start not from lead...simple more strain on the starter, its just a backup you need as surge protector and i will garantuee it will die unused if your lithium bank install is correctly done and stress tested...it still work as surge protector if nearly dead.

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.

[Pete7]

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.

Quite