Alternator to LFP Bank or Start Batt?

[Poeme]

With the intention of installing an LFP house bank, I recently upgraded to a Balmar SG200 monitoring system as well as their MC-618 regulator...all controllable and programmable with Bluetooth. To charge the start battery I'd be connecting the lithium bank to the start through a DC-DC charger (Victron Orion, also BT programmable).
I bought the Balmar items to carefully program the regulator and monitor the lithiums, with the alternator B+ going to them first...while letting the DC-DC charger keep the start battery happy. My thinking was that the start battery really needs no in-depth monitoring, just an eye on voltage.
But do I have this backwards?
The Victron manual schematics have the alt going to the start battery first, as well as many YT installation videos, which btw seem all to be van installations. It would be the Victron then that controls the charging of the LFPs, not the Balmar regulator.
Seems this would obviate the need for having upgraded to the Balmars.
I have a Balmar APM-12 on the alternator to protect it from LFP disconnects and Balmar tech support tells me this is adequate. OTOH it does make sense as additional protection to have the alt go to the start first as a load dump...I get that...and I presume I'd be able to monitor the lithiums through the Victron Bluetooth app. But...is one way clearly better than the other?
(BTW...120amp Balmar alternator, 300ah of Battle Born LFPs)
I appeal to the forum for your advice!

[smac999]

Your setup will have the best charging.

only issue with your setup is if the bms opens under error. It can fry the alt. With an external bms it can shut the balmar reg off with control wire. Internal bms can not.

The chances of having a high voltage bms cutoff while charging is low with good equipment installed well.

If you go to the start battery first. You will need many dc to Dc chargers. Since they are only 30a each. Which gets expensive. You would need 4 of them for that alt. And they might fight each other a bit. (Some in bulk and some in float)

The alt to start. Then dc to dc to house. Is best if you do not have the balmar reg. And don’t have voltage control. But more important don’t have alt temp. Then You size the dc to Dc snaller then alt to stop it maxing out and keep it cooler .

Defiantly make sure you buy the balmar alt temp sensor.

[Poeme]

Thank you smac999 for your response.
That's a relief to hear, that my Plan A makes better sense. And certainly don't want to daisy chain a bunch of DCDC chargers as an alternative...hadn't even thought of that.
I did install Balmar's APM-12 (Alternator Protection Module) between the terminals of my alternator and am told it should do the job in case of LFP disconnect considering I'm not running some whopping 250amp alternator. Seems to be a higher-tech version of the old Zap-Stop from years ago. But I will run this by Balmar tech support once more, and see what they say about an external BMS to turn off the regulator. Hope it doesn't get more complicated than this. Thanks for your advice!

[CharlieJ]

@Poeme #3:

Turning off the alternator is a trivial issue. Install a NC relay in the B+ wire supply to the external regulator. On a Balmar this is the brown wire. Use the ATC signal from the BMS to control the relay. When the ATC permission is rescinded, the relay opens and the alternator stops producing power; just like turning off the engine. Easy on the regulator and won't damage the diode pack on the alternator.

Victron makes the SolidSwitch 104, a purpose built relay for this: https://www.victronenergy.com/accessories/solidswitch-104

[Poeme]

Thank you CharlieJ.
The link didn't open for me but will definitely look into the Victron unit you mention, accessing the brown wire etc.
May I ask, about the Balmar Alternator Protection Module (APM-12) I mentioned earlier (or the Sterling brand)...do you feel these do not provide adequate protection in case of LFP disconnect?

[CharlieJ]

@Poeme
By turning the regulator off there is no possibility of a spike. That said, the APM offers another level of protection but will never be challenged if the regulator is turned off.

[smac999]

Originally Posted by CharlieJ

@Poeme #3:

Turning off the alternator is a trivial issue. Install a NC relay in the B+ wire supply to the external regulator. On a Balmar this is the brown wire. Use the ATC signal from the BMS to control the relay. When the ATC permission is rescinded, the relay opens and the alternator stops producing power; just like turning off the engine. Easy on the regulator and won't damage the diode pack on the alternator.

Victron makes the SolidSwitch 104, a purpose built relay for this: https://www.victronenergy.com/accessories/solidswitch-104

His battleborn batteries have no way to shut off the alt

[donradcliffe]

How many Battleborns will you have in parallel? If there are 3, the chances of all 3 BMS opening at the same time get pretty negligible. I would put a high voltage alarm on the B+

[Poeme]

Yes this stumped me a bit...a Battle Born battery's BMS is internal with no coms out. BB tech support was absolutely terrific as I considered these batteries...so will pass this dilemma by them asap. Hope I didn't jump the gun. Thanks for keeping an eye on me smac999...optimistic to get this safely up and running soon.
BTW, and for anyone looking in...Class T fuses are recommended for lithium installations...but Blue Seas is OUT of fuse blocks for fuses 200amp and under. West Marine here has had them on back order since February. Supply chain issues I was told, can't get them manufactured...
Suppose I can continue with my ANL type in the meantime?

[Poeme]

Originally Posted by donradcliffe

How many Battleborns will you have in parallel? If there are 3, the chances of all 3 BMS opening at the same time get pretty negligible. I would put a high voltage alarm on the B+

There will be 3 in parallel for starters, with a possible 4th at some point. I hope to be very careful dialing in max voltages and current using Balmar's "belt management" (something like that) system. Have Alt temp sensor attached as well to keep things tamped down. Will consider high voltage alarm idea...thanks
donradcliffe!

[CharlieJ]

@smac 999 and OP:
I missed the BB in the original post...my bad. I had just answered a similar question on another forum.

BTW, the lack of comms outside of the box is precisely why I made a business decision not to install BB on a boat. I will, and have, install them in RVs-they are great batteries, just not for boats.

[two-rocks]

I have almost exactly the same setup.
The alternator in my setup goes to an agm start battery with an isolated Orion pulling - 30 amps from there to the BB lifepo4. (I have 3).
I have the sc200 for the house setup, and my balmar and controller to the start only.
Why? Because, should the alternator get disconnected for whatever reason, it can fry everything connected (my balmar alternator is very inexpensive considering ‘everything else’).

The reality is that would be very very rare occurrence (individual bms is part of that reason) but still in the realm of possibility.

We primarily charge with solar (95+ %) my 100 amp balmar gets too hot to touch at idle, only pulling the 30 Orion amps (plus agm needs and losses). Haven’t measured the temp yet (it’s been sunny no need for alternator charging).

In summary: alternator as the primary source of electrons has risks. Use solar if you can. The significant advantage of lifepo4 is the added charging efficiency increases your solar capability with a limited footprint on a boat.

[Poeme]

Looks like I may have jumped the gun. Not sure there's a solution w/o external comms. It's the "everything else" getting fried (tnx two-rocks) that really has my attention.
I do have 400w solar. But, running the engine...uh-oh...

[CarlF]

As suggested, running the alternator to the start battery will mean the alternator is pretty much useless charging the house bank due to the 30amp limitation of DC-DC chargers.

You have no worries about a BMS shutdown. The alternator protection device will work. But a Victron DC-DC charger to the start batteries will also absorb the surge of a BMS shutdown. (I assume other DC-DC charger brands would work too). So you have belts-and-suspenders for this eventuality.

I was also looking at Battleborns but chose to go with Kilovaults. Highly reviewed by Mainesail and Will. I know six other cruising boats that have installed them. They have bluetooth communication that will hopefully meet the upcoming ABYC TE-13 standard for communication while Battleborn doesn't. The worry is that surveyors and insurance companies will eventually require TE-13 compliance although there are now so many boats with non-communicating batteries that it may be impractical to enforce. But I decided I didn't need this worry.

Insurance companies seem to be increasingly worried about owner installed lithium banks. I would pay a "professional" to help with the installation. I recently filled out an insurance application that asked if the lithium batteries were "professionally installed" and the name of the installer.

[two-rocks]

Oh no - not the insurance and surveyor fear mongering!

Let me put things another way - probably a much greater chance of a lighting strike than a alternator frying pan situation.

BUT - I can’t control lightening like we can design a more robust system.

Also, see mainsails (and others) about alternator temp and continuous ratings. It’s just not the best way - we have them and use them, but solar is cheap, silent, maintenance free.