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Old 23-11-2021, 20:51   #1
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DC/DC or ArgoFet

Working on my LiFePO4 setup, I have to decide how to hook up the alternator.
I'm including a FLA starting battery to make sure I always have a load on the alternator should the BMS disconnect the LiFePO4 pack.


My current setup is a 100A Balmar with a MC614, and as I dont want to always run it hot, hooking it up to the FLA starter battery and stacking two DC/DC converters (30A each) to charge the Lithium makes sense.


However I'm re-powering and will include a 170A alternator as part of that effort.


My pack is CALB200AH in 3P4S for 600AH, protected via a REC-Active BMS.
Also, real estate for huge solar is not available on my boat (I will carry about 500W), so I do need that big-ass alernator.



This leads to some issues:
  • Having to stack four or even 5 of the Victron DC/DC chargers becomes very cost prohibitive, and the single 100AH FLA is in anyway not capable to supply that much to the LiFEPO4
  • If I go with 2 or even 3 DC/DC chargers, I don't really get the gain from that fandangled new high Amp alternator, and I quickly run into limits from the single FLA battery as well.
So, the alternative is to connect the Alternator through a Victron ArgoFET isolator, feeding the FLA on 1 output and the LiFePO4 pack through the BMS disconnect on channel 2 of the isolator.
Now, if the BMS disconnects, the FLA is still in circuit to protect the Alternator.

One other option I'm considering is to change the MC614 to a WS500.

The WS500 can be integrated with the REC Active BMS, allowing the WS500 to de-excite the alternator prior to a disconnect event.
As a safety precaution, going this way, I will still add one of the Sterling alternator protection doodads.

So, how did you guys solve this? Option 1,2 or 3. Or something entirely different?
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Old 24-11-2021, 05:47   #2
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Re: DC/DC or ArgoFet

Quote:
Originally Posted by Afrinus View Post
Working on my LiFePO4 setup, I have to decide how to hook up the alternator.
I'm including a FLA starting battery to make sure I always have a load on the alternator should the BMS disconnect the LiFePO4 pack.

My current setup is a 100A Balmar with a MC614, and as I dont want to always run it hot, hooking it up to the FLA starter battery and stacking two DC/DC converters (30A each) to charge the Lithium makes sense.


However I'm re-powering and will include a 170A alternator as part of that effort. [...]
This leads to some issues:
  • Having to stack four or even 5 of the Victron DC/DC chargers becomes very cost prohibitive, and the single 100AH FLA is in anyway not capable to supply that much to the LiFEPO4
That will indeed be rather cost prohibitive. What is your concern with the capacity of the FLA? I would think the current goes from the alternator to the DC/DCs and the battery is only there to stabilize the system somewhat?

Quote:

  • If I go with 2 or even 3 DC/DC chargers, I don't really get the gain from that fandangled new high Amp alternator, and I quickly run into limits from the single FLA battery as well.
So, the alternative is to connect the Alternator through a Victron ArgoFET isolator, feeding the FLA on 1 output and the LiFePO4 pack through the BMS disconnect on channel 2 of the isolator.
Now, if the BMS disconnects, the FLA is still in circuit to protect the Alternator.
The alternative option makes a lot of sense. It is quite popular as well. Why would you consider something different?

Quote:
One other option I'm considering is to change the MC614 to a WS500.

The WS500 can be integrated with the REC Active BMS, allowing the WS500 to de-excite the alternator prior to a disconnect event.
As a safety precaution, going this way, I will still add one of the Sterling alternator protection doodads.
As far as I'm aware, the REC Active BMS has an output that can be used to turn chargers on and off, such that a charger disconnect ought to never take place, and that chargers are at least turned off if it does happen. Could you use that output to control the MC614?

I assume you'll still need something to charge your starter battery if you choose to connect only the house to the alternator.

Quote:
So, how did you guys solve this? Option 1,2 or 3. Or something entirely different?
We'll go with the 'alternative' option. We already have the charge distributor so it is also by far the cheapest for us.
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Old 24-11-2021, 20:55   #3
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Re: DC/DC or ArgoFet

Thanks for the reply.

Maybe I'm overthinking the issue with the FLA. In my head I was thinking that all the current comes from the battery, but of course you're right - it only flows really when the alternator is charging.
Still does not solve the huge bill of 4 or 5 of these converters.

The reason I was down the rabbit hole of DC/DC is that pretty much everything I've recently read was singing the praises of going with this setup, hardly ever mentioning the ArgoFET approach.

That was, and still is my design preference at the moment.

Charging sources is a Multiplier when at the dock, Solar and the alternator. I might add wind as well, but not currently in the plan.

You're right that it's probably possible to set up the REC to cut off excitation from the 614. Haven't really looked into that yet.

Of course, There's an extra benefit of the WS500 - i believe it actually measures and uses current to the battery to control the alternator - a true closed loop controller.

Maybe I'll have a new, never used MC614 for sale soon

Happy Thanksgiving everyone!
Cheers
Pieter
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Old 21-01-2022, 00:39   #4
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Re: DC/DC or ArgoFet

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Originally Posted by Afrinus View Post
Thanks for the reply.

Maybe I'm overthinking the issue with the FLA. In my head I was thinking that all the current comes from the battery, but of course you're right - it only flows really when the alternator is charging.
Still does not solve the huge bill of 4 or 5 of these converters.

The reason I was down the rabbit hole of DC/DC is that pretty much everything I've recently read was singing the praises of going with this setup, hardly ever mentioning the ArgoFET approach.

That was, and still is my design preference at the moment.

Charging sources is a Multiplier when at the dock, Solar and the alternator. I might add wind as well, but not currently in the plan.

You're right that it's probably possible to set up the REC to cut off excitation from the 614. Haven't really looked into that yet.

Of course, There's an extra benefit of the WS500 - i believe it actually measures and uses current to the battery to control the alternator - a true closed loop controller.

Maybe I'll have a new, never used MC614 for sale soon

Happy Thanksgiving everyone!
Cheers
Pieter
I have a balmar alternator charging my LFP bank via a Victron Argofet (AGM start battery on the other Argo output).

The brown wire to Balmar 614 is connected via the BMS to cut charging in case a cell goes out of balance. In my system, I set the Balmar to 13.9v bulk/absorb.

This system works OK, but the AGM start battery is bit undercharged and this may impact it's life span.

The other option to my mind is to charge the LFP direct from the regulated alternator and put a DC-DC charger on the start battery. You would need to add something like a Sterling Alt Protect or other load dump. Not sure if that would work for alternators as big as 170amps. Mine is just 100amps.

I am just an amateur - but i think both options work if carefully implemented.
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Old 21-01-2022, 08:18   #5
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Re: DC/DC or ArgoFet

This is actually what I ended up doing. No ArgoFET.
Instead I connect the FLA via a Cyrix Li-ct directly to the house bank (downstream of the Loadside Battery Protect).
My charging setup is set at 13.8 which will leave the FLA slightly undercharged, but I'm confident that would be ok.
The BMS will disconnect the Cyrix at a higher load than the min LiFePO4 load.
The alternator is a smart device that gets its settings from the BMS via CAN bus, so won't be an issue for uncontrolled disconnect.

If I can get a start capable Li battery. I will probably get rid of the FLA completely
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Old 21-01-2022, 09:23   #6
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Re: DC/DC or ArgoFet

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Originally Posted by Britishsea View Post
I have a balmar alternator charging my LFP bank via a Victron Argofet (AGM start battery on the other Argo output).

[...]

This system works OK, but the AGM start battery is bit undercharged and this may impact it's life span.

The other option to my mind is to charge the LFP direct from the regulated alternator and put a DC-DC charger on the start battery. [...]
Also possible: both an ArgoFET and a small DC-DC to the starter battery.
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Old 21-01-2022, 10:43   #7
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Re: DC/DC or ArgoFet

.

If I can get a start capable Li battery. I will probably get rid of the FLA completely[/QUOTE]

I have always thought that it would be interesting to mix in lithium titanate as a start battery (plus windlass) . It seems to me the 2 chemistries should be fine together ( this is of course conjecture)
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Old 21-01-2022, 11:12   #8
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Re: DC/DC or ArgoFet

LTO is great, but nothing special specifically for Starter usage. Mixing chemistries on the same circuit is always more complex thus fraught. Just having another LFP pack for Starting, or having both Starter and House as LTO would be simpler, thus better.
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Old 23-01-2022, 01:08   #9
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Re: DC/DC or ArgoFet

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Originally Posted by lmxr View Post
Also possible: both an ArgoFET and a small DC-DC to the starter battery.
Yes you could do that, but if your goal to is separate your house and start bank, wouldn't the DC-DC charger accomplish this? Or is there a benefit I am missing?

I have considered ditching my Argofet and adding a small DC-DC charger to charge the start battery and a Sterling Alternator Protect to act as a load-dump in case the LFP bank hits HVC. But I did not think to keep the battery isolator in the circuit.

Britsea
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Old 23-01-2022, 04:11   #10
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Re: DC/DC or ArgoFet

Quote:
Originally Posted by Britishsea View Post
Quote:
Originally Posted by lmxr
Also possible: both an ArgoFET and a small DC-DC to the starter battery.
Yes you could do that, but if your goal to is separate your house and start bank, wouldn't the DC-DC charger accomplish this? Or is there a benefit I am missing? [...]
The DC-DC charger is indeed sufficient to separate the banks. I was thinking of the following two benefits:
- The start battery acts as a load-dump protection, eliminating the need for a separate protection device.
- The Argofet allows the start battery to support large loads for extended duration without requiring a large DC-DC as long as the engine is running. In case an issue arises with the LFP house bank, all loads can be switched over to the start battery without having to worry about depleting it, even in case autopilot, electric winches, bilge pumps etc. are used. Some boats also have the windlass on the start battery.
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Old 23-01-2022, 06:21   #11
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Re: DC/DC or ArgoFet

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Originally Posted by PaulCrawhorn View Post
LTO is great, but nothing special specifically for Starter usage
Sorry that’s completely wrong, LTO are the best and reliable starter battery you can get.
They do 10C continuous and 20C peak load and discharge and do 30000cyles. Drop in and forget. And you don‘t need a BMS for that in 6 cell 15V setup, with 24V (or LTO 25,8V/27.8max) setup you need.
Which means a 40AH 6 cell LTO battery can deliver 400A continuous and 800A Peak and that 20000cycles Minimum. enough to start any boat diesel up to 140hp minimum and handle the windlass too even if they are discharged to 3% with 10V left (It started easily a 7lV8 Z06 corvette engine, we tested that and recharge normally after that). The abuse this LTO can take is from another world.
They are undercharged when charged with a li-Profil but won‘t get damaged. I would charge them with a DC to DC charger and in emergency you can join a LifePo4 house and LTO. Alternatively you can charge via Alternator with a LifePo4 Profil and add a small 50-90W flexible solar Panel with a regulator and LTO Profil to top up till full. The AH taken out of the starter when starting or even using windlass (in normal situations, not trying to get a stuck Anker out for an hour) is minimal so the LI charge Profile of alternator gets it full to 70%, solar slowly during the day full.

How do I know….had LTO in my cars and boat, installed a 6 cell 40AH LTO in my buddies 7lV8 Corvette Z06 with a real 3000W stereo system and that’s the only battery that survived longer then 6 month till now, actually going strong for 3 years now.
LTO as house only makes sense if you only have small space for batteries but high current needs and not much space for batteries and solar. Had that on my old longkeeler 40ft ketch…800A oversized bow thruster, full electric galley, so I fitted a 280AH LTO house+starter+bowtruster with a 300A alternator and 600W solar that get 50% shaded in best case when sailing. The 20min-30min motoring to maneuver when ankering put my full daily consumption in from the alternator, solar supply the basic load constantly. Worked like a charm.
Now I have 840AH LIfePo4 on the cat with LFA starter but will get LTO starter soon as prepping the cat for a world circum and want 100% reliable starters.
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Old 23-01-2022, 12:55   #12
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Re: DC/DC or ArgoFet

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Originally Posted by CaptainRivet View Post
Sorry that’s completely wrong, LTO are the best and reliable starter battery you can get.
They do 10C continuous and 20C peak load and discharge and do 30000cyles. Drop in and forget. And you don‘t need a BMS for that in 6 cell 15V setup, with 24V (or LTO 25,8V/27.8max) setup you need.
Which means a 40AH 6 cell LTO battery can deliver 400A continuous and 800A Peak and that 20000cycles Minimum. enough to start any boat diesel up to 140hp minimum and handle the windlass too even if they are discharged to 3% with 10V left (It started easily a 7lV8 Z06 corvette engine, we tested that and recharge normally after that). The abuse this LTO can take is from another world.
They are undercharged when charged with a li-Profil but won‘t get damaged. I would charge them with a DC to DC charger and in emergency you can join a LifePo4 house and LTO. Alternatively you can charge via Alternator with a LifePo4 Profil and add a small 50-90W flexible solar Panel with a regulator and LTO Profil to top up till full. The AH taken out of the starter when starting or even using windlass (in normal situations, not trying to get a stuck Anker out for an hour) is minimal so the LI charge Profile of alternator gets it full to 70%, solar slowly during the day full.

How do I know….had LTO in my cars and boat, installed a 6 cell 40AH LTO in my buddies 7lV8 Corvette Z06 with a real 3000W stereo system and that’s the only battery that survived longer then 6 month till now, actually going strong for 3 years now.
LTO as house only makes sense if you only have small space for batteries but high current needs and not much space for batteries and solar. Had that on my old longkeeler 40ft ketch…800A oversized bow thruster, full electric galley, so I fitted a 280AH LTO house+starter+bowtruster with a 300A alternator and 600W solar that get 50% shaded in best case when sailing. The 20min-30min motoring to maneuver when ankering put my full daily consumption in from the alternator, solar supply the basic load constantly. Worked like a charm.
Now I have 840AH LIfePo4 on the cat with LFA starter but will get LTO starter soon as prepping the cat for a world circum and want 100% reliable starters.
This is exactly what I was thinking.

Use 40-80 ah 6S of LTO as a starting bank and windlass battery. Run it through my battery splitter (Argofet) with no BMS (but with a balancer). It will get charged at around 14.1v, so will stay around 75% full all the time. DC-DC charger also an option.

I like the ideal of no longer having to constantly plug in to maintain a AGM battery ( i have no permeant solar on my boat - only a temporary set up).

Very hard to find a source of grade A LTO in north america however. I have been looking...

This is off topic for this thread, so for fear of highjack, perhaps I'll start a new one...

Thank you very much CaptianRivet for sharing your real-world experience.
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Old 23-01-2022, 16:04   #13
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Re: DC/DC or ArgoFet

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Originally Posted by Britishsea View Post
This is exactly what I was thinking.

Use 40-80 ah 6S of LTO as a starting bank and windlass battery. Run it through my battery splitter (Argofet) with no BMS (but with a balancer). It will get charged at around 14.1v, so will stay around 75% full all the time. DC-DC charger also an option.

I like the ideal of no longer having to constantly plug in to maintain a AGM battery ( i have no permeant solar on my boat - only a temporary set up).

Very hard to find a source of grade A LTO in north america however. I have been looking...

This is off topic for this thread, so for fear of highjack, perhaps I'll start a new one...

Thank you very much CaptianRivet for sharing your real-world experience.
No active balancer or BMS needed if 6S setup, just perform a proper top balance befor assembly. Maybe all 3 years after fully charged parallel all cells for 24-48h but that is just for the perfectionist

You don‘t need grade A LTO, even if 10000cycles left it will survive longer then your boat does. Good grade b do well too.
Only get 40AH LTO linglong cells 202mm long as this is the Max. Size AH in this Format and also the ones which the best production quality.
The 30AH cells are same size but often degraded 40AH, if 35AH offered 100% for sure degraded 40AH as they only produce 30 and 40AH. That’s not what you want.
Stay away from the bigger 55AH cells, the production quality is very unstable and again any other AH then 55AH is a degraded 55AH one.

If you plan to run the windlass I suggest use 2x40AH so 12 cells as you have to account for a stuck anchor and you are battling 1h+ using the windlass often.
Yes it will recharge very quickly sucking every amp from the alt in…

Would highly recommend Solar or Dc to Dc charger to top up to full. It’s a huge advantage if the LTO delivers 16-18V to starter and windlass, less wear and more pulling power.
Advantage of charging with Lithium from your alt you can direct the full amps into the LTO so they charge up faster in case you drained them with the windless or an engine that has bad glowplugs and stops charging if reached the 14,3V…
a little solar panel with a small (which you can fit on every boat somewhere) and cheap MPPT will charge it then to full 18V
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Old 23-01-2022, 18:57   #14
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Re: DC/DC or ArgoFet

Thxs again very much for this info.

I was tempted by some cells from Battery Hookup (https://batteryhookup.com) which were advertised as 35amp hours cells that they claim are testing in house btw 36-38ah. So as you say, these are likley relabeled 40 ah cells.

So is it your opinion that by the time a LTO cell has lost 10 - 15% of its original rated capacity, its basically at or near end of life

Good point re. the windlass needing more capacity. There are times i have hooked something on the bottom (rock, cable, etc) that takes a while to finagle off of.

To avoid the expense of 80ah of LTO, I could put my windlass on my 280 ah LFP bank. It's rated for 1 C continuous loads (EVE 280). Unless that is a bad idea. I only use the windlass it when the engine is running, so that might be OK and the wire funs are shorter from my LFP bank, which is located under my nav seat. I also have an electric winch, which is used more intermittently, and might be better suited for 40ah LTO bank.

Britsea
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Old 23-01-2022, 19:24   #15
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Re: DC/DC or ArgoFet

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Originally Posted by lmxr View Post
The DC-DC charger is indeed sufficient to separate the banks. I was thinking of the following two benefits:
- The start battery acts as a load-dump protection, eliminating the need for a separate protection device.
- The Argofet allows the start battery to support large loads for extended duration without requiring a large DC-DC as long as the engine is running. In case an issue arises with the LFP house bank, all loads can be switched over to the start battery without having to worry about depleting it, even in case autopilot, electric winches, bilge pumps etc. are used. Some boats also have the windlass on the start battery.
I had to think about this for a bit, but you are right. These are very good points.

If i have this right, the Argofet goes directly to the LFP bank and the start battery. Also attached to the LFP bank is the DC-DC charger (as power source) to the start battery (DC_DC's charge output) so that the voltage is boosted up for the start battery to get the correct charge.

Only downside i can see is that when the DC-DC has charged the start battery and turn off, the Argofet will still be providing 13.9 - 14v to the start battery so charging will not fully stop.

Not a big deal as 13.9 is pretty low voltage and not much current will flow. Would be perfect for a lead acid start batter which like to float at 13.8v. Might be a bit high for a AGM...?
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