What's the purpose of a Victron Orion-Tr DC/DC isolator?

[Krumelur]

I'm in contact with Liontron as I'm planning to replace my aux batteries with the LX LiFePo4.
My current setup is:

* The original charger installed by Bavaria
* A Victron Cyrix-ct battery isolator (thanks Yngmar for recommending! :-))

According to Liontron (and my research confirms this), the LX battery can be used as a 1:1 substitute for the aux battery; to the external world, it acts like a lead-acid battery and is compatible with the charger.

Now what I don't get: the Liontron support wrote: "to deal with the charging current, a Victron Orion-Tr 12/12 would be required".
I don't understand why. If the engine is running and the alternator is delivering energy to the batteries, the Cyrix-ct would connect both starter and aux batteries and charge them. The voltage would not go above 14 volts (or whatever the alternator's limi exactly is). If energy is consumed, the Cyrix-ct would separate the batteries. I fail to see a scenario where the Liontron LX would have to deal with voltage levels outside of its specs?

[Yngmar]

Not everything is an isolator!

The Cyrix-Ct is a VSR - a voltage sensing relay. Victron calls it a battery combiner, as that is what it does (when certain voltage conditions are reached).

The Orion is a B2B - battery to battery charger, taking DC from one battery bank and stepping it up into a suitable charging voltage for another. A DC to DC charger.

I don't know the LX system, but it sounds like a drop-in-replacement for a lead acid battery, in which case it internally regulates its charging and should work with either. Perhaps the supplier isn't aware of what the VSR does and just always recommends the one solution they know to be working (the B2B charger). Since it sounds like you're already in conversation with them, just ask why they insist on this.

It might be because the lithium battery has a very different discharge curve that may not trigger the VSR to separate until it is discharged. So it will work for charging but not separate batteries and keep the banks combined for too long when discharging. That depends on the exact voltages in play.

[Krumelur]

I’m so isolated 

Like you suggested, I asked them, and the reply is really unsatisfying because they sent me an explanation copied from some technical article. Now I know what the device is, but not why it’s recommended. They are unable to give me the information I need like if the battery automatically limits the charging current.

Reading some blog posts and watching videos, I’m getting the impression that my experience with the technical support is representative; Liontron and the businesses they are connected to (Greenakku and Bosswerk) don’t seem to have the best reputation and now I’m looking into alternatives.

[elias]

Hi , the amount of current that the Lifepo4 can draw from the alternator is enormous and can even lit it ! Check this
https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/

In order to limit the amount of current that your lifepo4 bank will draw from your alternator I believe the dc dc is suggested .

[Krumelur]

Yep, when charging a plain vanilla lithium pack that is always the case.
Here, however, we're talking about a battery advertised as a drop-in replacement for a lead acid 12V pack.
The question is if it should then not limit itself to not fry the world it's being "dropped into" :-)

[elias]

Depends , if you just make a small capacity bank with the drop in lifepo4 then it might be ok with your alternator I believe. The “drop in” I believe stands for voltage , case geometry , pole attachment etc . Think also that your alternator could fry also with lead acid bank if for example the bank is huge and in the meanwhile of charging with alternator you draw also current through appliances of your boat . I don’t know if there is such thing as a sophisticated internal BMS in your new battery that limits the charging current . I haven’t seen one

[tiger79]

In order to limit the amount of current that your lifepo4 bank will draw from your alternator I believe the dc dc is suggested .

The Orion-Tr 12/12 outputs 12.2v.  The LX battery is said to accept charge at 14.6v.  If it's being charged at 12.2v presumably it'll take longer to charge?

The LX is promoted as a drop-in replacement for lead-acid batteries, and has an internal BMS.

[tiger79]

Reading some blog posts and watching videos, I’m getting the impression that my experience with the technical support is representative; Liontron and the businesses they are connected to (Greenakku and Bosswerk) don’t seem to have the best reputation and now I’m looking into alternatives.

I reckon that's a good plan.  If you can't get sensible info before you buy, what's the chance of support if you have a problem subsequently?

Victron lithium batteries look good, but prices are eye-watering.

[elias]

In order to limit the amount of current that your lifepo4 bank will draw from your alternator I believe the dc dc is suggested .

The Orion-Tr 12/12 outputs 12.2v.  The LX battery is said to accept charge at 14.6v.  If it's being charged at 12.2v presumably it'll take longer to charge?

The LX is promoted as a drop-in replacement for lead-acid batteries, and has an internal BMS.

With an output of 12.2v no battery can be charged . It need a higher voltage from the side of the charger to enable current flow . 12.2v on a lifepo4 is empty level .The Orion I think acts like a charger converting input voltage to proper output voltage to meet the charging pattern of the battery installed , this case Lifepo4. The BMS as I understand it has some features like stopping excessive amp draw , temperature etc , but it doesn’t work like an internal charger . I don’t know though in the case of the battery model we are discussing . Victron has a comprehensive explanation of setup of lithium that applies everywhere .

[SYJetzt]

As you have already noticed:
a lithium drop-in battery is not drop in!
These drop-in batteries are really killing your alternator! Don't ask me, why i know this!
This orion TR DC/DC isolator is a battery to battery charger. The main advantage is to be able to set ALL of the necessary parameters (and there are a lot of them!) for charging your lifepo's AND reduce the drawn energy from your alternator to survive in real life.
Although VP claims their stock alternator is capable of 115A, their continuous output in the hot engine bay is far less. I run my alternator at 70-75 amps and that is the highest limit thermally possible.
I use a Votronic 12/12/70, which was difficult to set up because the high charging current caused the battery voltage of the starter battery to drop slowly below the voltage threshold set by Volvo penta and triggered the battery monitoring of the engine electronics.
You are on the safe side with the Orion, even if it only delivers 30A charging current for your lithium batteries and therefore takes longer to fully charge them. You don't need an isolated converter either, a normal common ground converter will do the job as well.

[tiger79]

As you have already noticed:
a lithium drop-in battery is not drop in!

Depends on the battery; Victron SuperPack lithium batteries have fully integrated BMS and are literally drop-in.