With lithium do we actually need a dedicated starter battery?

[CaptainRivet]

Originally Posted by dave777

What DC2DC charger(s) do you recommend?


We can set our Solar and shore power chargers for LifePO4, just leave alternators on the Lead Acid starters?

Renogy 12V 20A (100Euro) till 40A (200Euro) depending on your alternator , no need to pay victron or Sterling premiums for the same. And compared to victron all renogy DC2DC have a switch where you can reduce ouput by 50%, great for eg motorsailing long distances.

Before getting a an expensive victron (the 30 A is 270Euro and the 50A even 460Euro or sterling DC2DC is equivalent bring your old alternator to the alternator shop and let them modify and right away overhaul it. Cost around 100Euro and an external ARS5 or balmar MC614 regulator is 300Euro. Like this you are safer (DC2DC just limits current but the alternator can still die an heat death, happens often in eg Greece in August...) because the external regulator actully measures temperature to protectband get more output then with DC2DC. Eg the 80A hitachi delivers arround 55 till 60A after external regulation for 100Eueo mod+300 regulator=400Euro while your victron 30A delivers only 27A for 270Euro, is a heater while the 40A sterling is 360Euro and you get 40A for your 360Euro. It never hurts to get more current from your alternator for the same money spent, even its your 3rd or 4th charge source and LifeP04 can take this charge.

And yes on some small old vessels a DC2DC charger solution makes economical sense of when we talk about <70A automotive alternators. But already the very common hitachi 80A found on many volvos profits strongly from external regulation versus DC2DC for the same costs.

[newhaul]

Originally Posted by CaptainRivet

Renogy 12V 50A , no need to pay victron premiums for the same. And compared to victron all renogy DC2DC have a switch where you can reduce ouput by 50%, great for eg motorsailing long distances.

No not the 50 amp unit it is a combined 50 amps from the DC2DC and the MPPT ie 25 from each source .
Either the 40 amp unit of the 60 amp unit they are " stand alone units .
Minor detail but makes a difference.
The best idea for long distance runs is having a switch built into the ignition sense wire to shut the DC2DC off . When your house is charged

[CaptainRivet]

Originally Posted by newhaul

No not the 50 amp unit it is a combined 50 amps from the DC2DC and the MPPT ie 25 from each source .
Either the 40 amp unit of the 60 amp unit they are " stand alone units .
Minor detail but makes a difference.
The best idea for long distance runs is having a switch built into the ignition sense wire to shut the DC2DC off . When your house is charged

Your right with the 50A, corrected later in another post as I couldn't modify the original.
A cutoff switch in the ignition is standard, best is to use a selector switch, off- half-full power. Off goes into ignition, half onto limiter switch of the unit.
If you for long distance shut it off or go half depends on the continuous loads onboard when on passage and if your other charge sources like solar and/or wind can cover that or not.
Often with sails up solar is heavly shaded and output greatly reduced.
Also compared to theory in real life some of the alternators charge is for free with no additional diesel consumption, on mine eg till 40A charge on 115A Mitsubishi alt on the D2-50 my diesel flow sensor shows no additional consumption if alternator off, 20A or 40A charge but above the 40A i do see an increase. Fuel sensor is correctly calibrated, what i filled in, consumed and refueled is inline with the sensor.
So motorsailing the alt stays on limited to 40A. I am overpowered instead 2x20 i have 2x50hp so it seems that enegry is either used by the alternator or lost in heat or the consumption is so minimal that its below precision of the sensor means i don't care either.

[s/v Jedi]

There is no need for a switch to reduce output to 50%.

A good charger allows a setting for maximum charge current to match battery specs. The configured charge algorithm should match battery specs.

[CaptainRivet]

Originally Posted by s/v Jedi

There is no need for a switch to reduce output to 50%.

A good charger allows a setting for maximum charge current to match battery specs. The configured charge algorithm should match battery specs.

Sorry thats wrong. First if you eg sail in diffferent temps in greece in April i can easly run 70A alternator at 40A but do this in august with a not so good ventilated engine room and you smoke it. Nothing of the parameters of the victron is avoiding that or i can adapt it so its charging with less.
Same if i know i do 10 or 20h motorsailing no need to stress and run the alternator on full blast plus waste diesel when with 50% power can avoid all this. Also if your engine is on the smaller side 50% charge leaves you more hp to motor or maneuvering and still covers you constant power needs so you start anchoring with full batteries.
Nothing of that has to do with any of the charge parameters which can be set to your liking at any of the mentioned DC2DC and the exoensive victron is not even offering that 50% power limitation.

What i would have expected from a 50A DC2DC that costs a whooping 460Euro would have been a temp sensor i can put on the alternator an the DC2DC automatically scales back the current limit at least in increments of 5 or 10A per step to really protect the alternator and on the other side maximize the output of DC2DC. That would be worth 460Euro and what i expect fromma top notch company like victron.... but what they delivered now i can convert any alternator to external regulation+ external regulator with real protection and get for the same money much more then 50A charge and that safer.

[newhaul]

Originally Posted by CaptainRivet

Sorry thats wrong. First if you eg sail in diffferent temps in greece in April i can easly run 70A alternator at 40A but do this in august with a not so good ventilated engine room and you smoke it. Nothing of the parameters of the victron is avoiding that or i can adapt it so its charging with less.
Same if i know i do 10 or 20h motorsailing no need to stress and run the alternator on full blast plus waste diesel when with 50% power can avoid all this. Also if your engine is on the smaller side 50% charge leaves you more hp to motor or maneuvering and still covers you constant power needs so you start anchoring with full batteries.
Nothing of that has to do with any of the charge parameters which can be set to your liking at any of the mentioned DC2DC and the exoensive victron is not even offering that 50% power limitation.

What i would have expected from a 50A DC2DC that costs a whooping 460Euro would have been a temp sensor i can put on the alternator an the DC2DC automatically scales back the current limit at least in increments of 5 or 10A per step to really protect the alternator and on the other side maximize the output of DC2DC. That would be worth 460Euro and what i expect fromma top notch company like victron.... but what they delivered now i can by 2x40A Renogy for.

On my boat in my scheme the 40 amp DC2DC with my 75 amp internally regulated alternator ( paid $30 USD for the alternator ) limits the output and thereby the heat buildup. An aside my average daily usage in summer is 35 to 40 ah 12v. winter I use a bit more . ( Forced air diesel heat)yes my cutoff switch for the alternator stops from over charging as well as gives me the additional hp when needed fighting strong currents
Takes about 1.5 hp per 25 amps of alternator output.

With your setup why d ok the dual 40 and not just go for the 60 amp unit and call it good .

[s/v Jedi]

Originally Posted by CaptainRivet

Sorry thats wrong. First if you eg sail in diffferent temps in greece in April i can easly run 70A alternator at 40A but do this in august with a not so good ventilated engine room and you smoke it. Nothing of the parameters of the victron is avoiding that or i can adapt it so its charging with less.
Same if i know i do 10 or 20h motorsailing no need to stress and run the alternator on full blast plus waste diesel when with 50% power can avoid all this. Also if your engine is on the smaller side 50% charge leaves you more hp to motor or maneuvering and still covers you constant power needs so you start anchoring with full batteries.
Nothing of that has to do with any of the charge parameters which can be set to your liking at any of the mentioned DC2DC and the exoensive victron is not even offering that 50% power limitation.

What i would have expected from a 50A DC2DC that costs a whooping 460Euro would have been a temp sensor i can put on the alternator an the DC2DC automatically scales back the current limit at least in increments of 5 or 10A per step to really protect the alternator and on the other side maximize the output of DC2DC. That would be worth 460Euro and what i expect fromma top notch company like victron.... but what they delivered now i can convert any alternator to external regulation+ external regulator with real protection and get for the same money much more then 50A charge and that safer.

No, you are doing it the mickey mouse way. A proper install has a regulator controlling the alternator that is smart and has a temperature sensor on the alternator to limit it’s output when it gets too hot.

You really need to do this right or stay home, don’t use dinky-toy grade gear

[newhaul]

Originally Posted by s/v Jedi

No, you are doing it the mickey mouse way. A proper install has a regulator controlling the alternator that is smart and has a temperature sensor on the alternator to limit it’s output when it gets too hot.

You really need to do this right or stay home, don’t use dinky-toy grade gear

So what's my install then ? I have internally regulated alternator and a 40 amp DC2DC to charge my bank .
So is my setup a Mickey mouse way to do it?

[s/v Jedi]

Originally Posted by newhaul

So what's my install then ? I have internally regulated alternator and a 40 amp DC2DC to charge my bank .
So is my setup a Mickey mouse way to do it?

No, you don’t charge your lithium bank with the alternator. You charge the lithium bank with the dc-dc converter.

That said, if your alternator can overheat with the added 40A load from the dc-dc charger then yes, it becomes a mickey mouse system. There should never be a manual action required to prevent overheating because it is a recipe for disaster.

[lateral]

I need to replace my 12yro sla start battery and will install a 800w windlass at same time and run both starter motor and windlass off it.
I’m thinking yin long LTO 45Ahr x5 plus balancer and drop target voltage of mc618 to 14v, currently 14.2v.
One year into 4s2p, 2x 200A bms, 2x bmv 712 with hvlv audibles, one for each LiFePO4 , argofet to alternator. Goes great. Have a spare Victron iso 12/18
DCDC that I haven’t installed yet. Was going to protect electronics with it or hook up to lead start battery. Never happened. Gravity seems to be stronger these days.
Any suggestions greatfully received.

[CaptainRivet]

Originally Posted by s/v Jedi

No, you don’t charge your lithium bank with the alternator. You charge the lithium bank with the dc-dc converter.

That said, if your alternator can overheat with the added 40A load from the dc-dc charger then yes, it becomes a mickey mouse system. There should never be a manual action required to prevent overheating because it is a recipe for disaster.

And thats exactly the problem with DC2DC chargers that they don't protect the alternator as nobody on the hottest day of the year actually limits the current on his installation in different RPMs. and then figure out which limitation on current in his installation is save means the alternator stays below the temp his/her alternator can withstand. i would assume that 99% don't even know what that temp acctually is on their alternator.

99% incl. professional installers just take 50% of the rating of the alternator as limiting current and they think all is ok but is that really ok??
99% have no glue as they don't mount a temp probe on their alternator and monitor the temps and thats why i said i would have expected from a victron DC2DC that when newly developed and a whooping price of 460Euro like the 50A it has a temp probe that goes on alternator so the DC2DC finally knows when eg automatically switch to 50% output to really protect the alternator. But victron failed as they meanwhile turn into another lemon squeezing company and their aim was just to produce the same thing cheaper and less of an heater but not safer.

And the DC2DC is advertised and recommend from highly regarded installers and even installed by french mass manufacturer now on totally dumb old alternator means they only have a regulator but no temp sensor.
Means a huge part of installations out there is a micky mouse installation due to Jedi. And i agree, thats why i said below 70A alternator a DC2DC makes also no sense financially as modifing the alternator and regulate it externally with temp protection cost the same then a DC2DC but is not protecting it.
Below that 70A threshold using a DC2DC with 50% rule is fine as thats mainly small boats with small energy needs plus the alternator is so cheap then in the rare case when it goes up in smoke you just buy a new or used like newhaul for 30 bucks and if you have a renogy DC2DC you just charge it from now on with 50%.

There are some case with big dumb alternators like Simi with his power boat that after you observe the alternators temp over a longer periode with temp probes and then get DC2DC like the 60A renogy or sterling to limit the current when you install lithium as this is much simpler and economical to install then installing eg new cables etc. For external regulation.
Where a DC2DC really make sense is what Jedi is doing in his own installation when your alternators are 12V but your lifepo4 house is 24V or 48V and your alternator is just a backup charge source and should simply be safe operating and not go up in smoke.

But the majority of the cases on newer vessels if the alternator has a proper working internal temp regulation it protects itself and a DC2DC is just a waste of money as not needed at all to protect the alternator as the alternator does that himself. Additionally it limits the output unnecessarily as what the alternator can deliver depends only on the internal temp of it which the DC2DC don't know and limits the current when its absolutely not necessary.
Then you have 2 possible installations:
A) write Nordkyn design if your alternator can be steered by Nordkyn VSR200 modul which without modification turns it into a fully regulated one, chance is very high it does. Its around 300 to 350Euro depending on VAT and shipping location. You get a surge protector and say goodbye for good to the dread lead chemistry also as starter.
B) you use an splitting diode with your lead or LTO starter. Charging a lifepo4 works with every lead regulator and in 95% of the case the alternator with internal temp protection has an agm charge profile and goes not above 14.5V. The you take Victron ArgoFET and the AGM or LTO is always there when BMS or a BMV shuts of the charge with a contactor because Lifepo4 is full ( best at SOC 95-98% and let solar do the rest).
If you have the rare case that the temp protected alternator has a FLA regulator that goes up to 15V then take an Argodiode that with its voltage drop brings the voltage down to 14.6V instead 15V, rest like above.
Then you use a small 5 or 10A DC2DC from Lifepo4 to lead start to keep it in float or who is smart actually uses a small MPPT or even a cheap PWR does it with a 50W panel which you can mount on any vessel and float the starter like this. Or even more smart and use an LTO as starter which needs no floating at all and no charger at all to keep it charged and in the very rare case you need to recharge it without running the motor simply parallel it to lifepo4 with the selector switch
And that a BMS can switch off a source to optimize charging or discharging a lot can meanwhile do and there is nothing wrong about that, if you are a purist like Jedi use a battery monitor, which should be on the Lifepo4 anyhow, to shut it off the charge from alternator when lifepo4 house is full.

[CaptainRivet]

Originally Posted by lateral

I need to replace my 12yro sla start battery and will install a 800w windlass at same time and run both starter motor and windlass off it.
I’m thinking yin long LTO 45Ahr x5 plus balancer and drop target voltage of mc618 to 14v, currently 14.2v.
One year into 4s2p, 2x 200A bms, 2x bmv 712 with hvlv audibles, one for each LiFePO4 , argofet to alternator. Goes great. Have a spare Victron iso 12/18
DCDC that I haven’t installed yet. Was going to protect electronics with it or hook up to lead start battery. Never happened. Gravity seems to be stronger these days.
Any suggestions greatfully received.

You need 6 LTO cells, not 5 cells for a 12V system. The majority of capacity ia between 2.0 and 2.4V ao 6x2.4=14.4V and LTO doesn’t care if you never charge it full, the active balancer can balance at any SOC and you maybe loose 1 till 2AH not charging to 100% but 95%. With only 5 cells you loose much more...around 10AH.

I highly recommend to use the 40AH yinglong cells, they are the most stable and best cells they produce for over 10 years unchanged ( just perfect as they are) while the 45AH are the old 50AH version derated because they still have production issues and are far less stable then the 40AH one.
Another good alternative and also easier to install would be the 20AH Toshiba SCIB LTO cells, just get 12 cells and make 2 batteries each 1p6S and parallel them. Gives you redudancy as 1 can handle both. Batteriehockup.com sells them for a huge bargain of 18$ per cell. Cannot go wrong with that, i have them too.

Keep your voltage at 14.2V with the 618. If you have the DC2DC 18A lying around its not hurting when you top up the LTO to 15V from lifepo4 with it. your starter and windlass ( normally a big voltage drop due to long cable so 14.0V at the windlass) will love it. And 15V is also safe for your whole 12V installation in case you need the LTO as emergency house backup because eg the lifepo4 house BMS shuts it off due to any reason. The ignition or remote switch of DC2DC need to be connect to BMS of lifepo4 as load means shut off in case of LCV
Do you have a battery monitor on the starter, if not i highly recommend to use the victron BMV 700 or 712 with BT that also have a relay output and with that output you also in series connect it to the remote of the DC2DC so in HCV the BMV shuts off the DC2DC too.

To protect senstive electronics i would get a Victron DC2DC converter, the 30A isolated orion TR 12/12/30 (non smart version!) Which is around 130Euro. That delivers a stabilized adjustable output voltage so you can supply your senstive electronics with perfect clean 14,8V doesn't matter at which SOC your Lifepo4 house is. Check ebay or Craigslist or alike, you often get that converter much cheaper as peoole think they are smart and buy the much chepaer none smart Orion-TR and think they get a DC2DC charger without bt function and when installing weeks later realize its only a converter and cannot return it anymore...paid 65 for mine new.

[lateral]

Cheers. Looks to me 14.2V will only get to 75-80% Soc, 30Ahr?
https://www.researchgate.net/publica...-at-T-25-C.png

[newhaul]

Originally Posted by lateral

Cheers. Looks to me 14.2V will only get to 75-80% Soc, 30Ahr?
https://www.researchgate.net/publica...-at-T-25-C.png

Actually a bit higher close to 99%
What are you referring to wrt the 30ah part. My bank is 250ah with 265 actual so I'm happy with 99% when the sun goes down
We all mainly charge with solar and some wind as well.

[lateral]

Originally Posted by newhaul

Actually a bit higher close to 99%
What are you referring to wrt the 30ah part. My bank is 250ah with 265 actual so I'm happy with 99% when the sun goes down
We all mainly charge with solar and some wind as well.

The LTO battery