Opinion on configuration of dual chemistry charging

[barold]

Looking for opinions (my questions below)-

Current Config:

• AGM start, AGM House
• Both combined through Isolator to Alternator; Individual wiring from Shore power charging (40A), set to AGM profile

Proposed:

• AGM Start, LFP (280AH) House
• Alternator to charge Start only
• Start wired to Orion TR DC to DC Charger to House
• House bank disconnected from Shore power; wired to MPPT Solar and Orion DC to DC Charger

Rationale:

• Alternator protection (in the event the BMS disconnects the house bank while motoring)
• Charge voltage customization for house bank management - Shore power has multiple chemistry profiles but can only select one at a time. AGM Float 13.6V max , Bulk (can disable) 14.4V max 2hr; LFP Float 13.8V and Bulk (can disable) 14.4V, up to 16 hours
• Orion can play double duty to pass charge from shorepower and alternator to house bank

My Questions

1. Am I over complicating things by adding the Orion - It's a 30A charger so it may not be up to the 40A potentially from the shorepower charger (which means I might have to use the sterling 50A B2B charger).
2. Are the charge profiles on my shorepower charger close enough that I can just use the AGM profile (13.6V Float or 14.4V Bulk and 13.6V float) to apply to both the LFP House and AGM start batteries (I suspect not)

[Adelie]

Why bother with start battery at all? Unless your auxiliary is stunningly large even an FLA house back at 30-40% State of charge will be able to start the motor.

If it’s something you really want for peace of mind, charge the starter battery with a 10-30w panel thru a small PWM controller and dedicate the alternator to house bank. Typical engine uses less than 1A-hr per start attempt. 30w panel will give you enough energy for 7-10 starts per day.

That doesn’t buffer the alternator from the BMS but it results in a simpler system. Also I’m curious whether a B-B charger will work where the 2nd battery will be charged when the first is at a lower voltage.

[barold]

Originally Posted by Adelie

Why bother with start battery at all?

That doesn’t buffer the alternator from the BMS but it results in a simpler system. Also I’m curious whether a B-B charger will work where the 2nd battery will be charged when the first is at a lower voltage.

It's true - I don't want to add the B2B but the main driver was the protection of the alternator (a balmar retrofit kit for yanmar is available but that would be in the 600 range - and still wouldn't help with ensuring the start battery is charge (if all charging is sent to the House Battery). As the House will be a 280AH LFP, it can accept quite a high charge current for some time - likely longer than the alternator is designed for. Another boat owner isolated the batteries and their start is only charged with a plug in AC Charger at dock.

[smac999]

There is no way you should get rid of the agm start. Not only you should have it , but the house switch should be a 1-2-all so when the lithium bank fails. You have emergency power from the agm. Every lithium system I have seen has failed. Including Mastervolt and victron systems.

I consider lithium to be experimental.

The charge from shore I would not be worried about. As generally you are plugged in for a while and 30 vrs 40 Likly still charge over night. It’s the alt you want full power from. If you run the alt to the start. 30 is too small. If you run the alt to the house. With a bms than at can shut it off. Then the 30 is probably enough.

[Adelie]

Ok, so I’m back to my first suggestion, charge the AGM off a small panel and do away with the B2B. Alternator straight to house.

[Justin Cook]

Couple of things to add to the discussion here:

LFP is not experimental; the chemistry has been in use for over 15 years and the only failures I've seen in 8 years of experience with it have been due to improper connection or flagrant abuse (the exceptions being failures of cheap knockoff brands). I still have a Dragonfly Energy (Battle Born) LFP 12v/100Ah drop-in that they sent me 7 years ago to test and after well over 1500 full 100-0-100 cycles, countless microcycles, being thrown around in the back of my truck, boondocked, covered in dirt, and used as a backup battery, 3 weeks ago I ran a capacity test and still pulled 117Ah out of it.

Buy high-quality components, connect them properly, treat them well, and you won't have any issues.
And sure, a good 100Ah LFP battery is 4x the cost of a decent 100Ah Pb battery, but you get 2x the usable capacity from LFP and 6-8x the cycles, so it's a good investment so long as -as noted above- you get high-quality units.

As for the Orion, please note that you want the Orion-Tr Smart when you're talking about a DC-DC charger... this is very very important, because the Orion-Tr is a completely different product. This is just a heads-up for whenever you order your components: make sure you're ordering the right thing.

You don't need to worry about the Orion being overwhelmed by a 45A charge from your shore power charger to the start battery; first, the Orion's rating is in current delivery, not pull: it's delivering up to 30A of charge to your house bank, but it'll pull somewhere between 38 and 45A from your start battery to accomplish that (depending on wiring and length of run and several other factors). Second, it will only pull what it needs - you could be throwing 100A into your start battery and the Orion will still only draw what it needs to appropriately charge your house bank; it can't be overwhelmed by the charge into the start bank.

So, direct answers:
1. No - the Orion-Tr Smart really doesn't add any complication. Your proposed solution will work perfectly if implemented properly.
2. Yes, you'll probably be fine at the AGM profile, but it depends on which batteries you buy. Battle Borns would be perfectly happy with your shore power charger's AGM profile. Other LFP batteries (Victron, for instance) are more finicky - it all depends on the BMS in the battery. The thing to really watch is to make sure that if your shore power charger has an automatic equalization setting, make sure to disable it, because exposure to equalization voltage will certainly cause an LFP battery's BMS to shut down the battery.

[barold]

Thanks Justin. The Orion that I've looked at (and read the manual) is the Orion TR Smart DC to DC Charger. That it can pull more amps makes sense as Victron's van wiring diagram (which I've been scrolling through at 400% zoom) shows a 60A breaker on the supply side (from the AGM). I'm going to be spending nearly as much on breakers as will be on the Orion, but I think it's money well spent for peace of mind.

Your comment about the orion pulling let's say 40A from the shore charger by only charging the house at 30A worries me - Would passing that much current through another device create heat and potentially wear out the orion faster?

I will have to compare the charge profiles of my shore charger to the LFP. I imagine there may be a bit of voltage drop as well - so I will have to test it after launch.

[Justin Cook]

Well the breakers shouldn't be too expensive... For this purpose I'd recommend use of a 60A Bussman Series 187 (surface or panel mount, depending on your application) on the input side and a 40A 187 on the output side, both of which are around $30 (apologies, I'm on mobile right now and can't look up our prices on those).

The Orion will take 6AWG wire at its input/output, but if you have a long wire run, you could easily use a heavier gauge for the majority of the run and step it down to 6 at the unit - this will combat voltage drop over a long run and will further help keep it cool since it will be running at maximum efficiency.

I wouldn't worry too much about the mentioned heat/wear on the unit... It's designed very well and in my own bench-testing of it I've run it full-bore for 12 hours straight and only measured a 5C rise in temperature at the unit. Obviously I'm testing under relatively ideal conditions, but if it's connected properly with appropriate wire gauge, I'm confident in its real-world performance. Furthermore, the unit will manage itself as it needs - if it's getting too hot, it will derate accordingly until it cools off.

By the same token, it shouldn't put undue wear on your shore charger either because -depending on the brand of shore charger- the AC-DC charger should also be designed to be run full-bore as necessary... It is after all why we have these chargers. Now, if your shore charger is a Xantrex or other questionable brand I might think twice about it, but if it's a Victron, Sterling, ProMariner, or other high-rep brand, I'd have pretty high confidence in it.

And, of course, if your house bank is also being maintained by solar charging, it generally won't be so far depleted that either your shore charger or the Orion should need to be running full-bore for very long anyway... These units will be performing more top-off operations than anything else.

[two-rocks]

The system you are thinking of has been thought of, by me
I answered the same question on the Victron forums not Long ago.

Isolated engine start battery (agm), alternator, shore power...
Connected to:
Orion dc to dc isolated.
Connected to:
House LiFePO4 and solar...

With this method you have complete control of the house bank. If the house bank bms shuts down the LiFePO4, you can run the Orion as a power supply mode. No switch required. If the start battery dies, the 1,2,both would be good. I am not going to use one, but that’s me.

You will limit alternator charging to the Orion capacity, and not maximize the ability to quick charge the lithium bank, so plan accordingly. I want to charge with a fractional/c, so I’m ok with that. Solar and alternator, or solar and shore power will be additive.

This method also allows me to keep my legacy shore power charger, with an upgrade path to add another charger with more bells and whistles someday...

[MJH]

Originally Posted by barold

Looking for opinions (my questions below)-

Current Config:

• AGM start, AGM House
• Both combined through Isolator to Alternator; Individual wiring from Shore power charging (40A), set to AGM profile

Proposed:

• AGM Start, LFP (280AH) House
• Alternator to charge Start only
• Start wired to Orion TR DC to DC Charger to House
• House bank disconnected from Shore power; wired to MPPT Solar and Orion DC to DC Charger

Rationale:

• Alternator protection (in the event the BMS disconnects the house bank while motoring)
• Charge voltage customization for house bank management - Shore power has multiple chemistry profiles but can only select one at a time. AGM Float 13.6V max , Bulk (can disable) 14.4V max 2hr; LFP Float 13.8V and Bulk (can disable) 14.4V, up to 16 hours
• Orion can play double duty to pass charge from shorepower and alternator to house bank

My Questions

1. Am I over complicating things by adding the Orion - It's a 30A charger so it may not be up to the 40A potentially from the shorepower charger (which means I might have to use the sterling 50A B2B charger).
2. Are the charge profiles on my shorepower charger close enough that I can just use the AGM profile (13.6V Float or 14.4V Bulk and 13.6V float) to apply to both the LFP House and AGM start batteries (I suspect not)

Yes, you are complicating things unnecessarily. Keep It Simple. Use one chemistry for all batteries and both banks, House and Start. There was a recent post of someone that only used one bank and it failed.

~ ~ _/) ~ ~ MJH

[barold]

Originally Posted by two-rocks

The system you are thinking of has been thought of, by me
I answered the same question on the Victron forums not Long ago.

Isolated engine start battery (agm), alternator, shore power...
Connected to:
Orion dc to dc isolated.
Connected to:
House LiFePO4 and solar...

With this method you have complete control of the house bank. If the house bank bms shuts down the LiFePO4, you can run the Orion as a power supply mode. No switch required. If the start battery dies, the 1,2,both would be good. I am not going to use one, but that’s me.

You will limit alternator charging to the Orion capacity, and not maximize the ability to quick charge the lithium bank, so plan accordingly. I want to charge with a fractional/c, so I’m ok with that. Solar and alternator, or solar and shore power will be additive.

This method also allows me to keep my legacy shore power charger, with an upgrade path to add another charger with more bells and whistles someday...

When connecting the two charge outputs to the House bank (MPPT and Orion) do you use the Cyrix Li combiner -- I see that as redundant as I can set the charge voltages on the MPPT and Orion - and the current would be additive. Thanks for all the help (everywhere!)

[two-rocks]

Originally Posted by barold

When connecting the two charge outputs to the House bank (MPPT and Orion) do you use the Cyrix Li combiner -- I see that as redundant as I can set the charge voltages on the MPPT and Orion - and the current would be additive. Thanks for all the help (everywhere!)

The Cyrix needs a bms signal, I'm using battle born batteries and don't know much about it.

[smac999]

Originally Posted by barold

When connecting the two charge outputs to the House bank (MPPT and Orion) do you use the Cyrix Li combiner -- I see that as redundant as I can set the charge voltages on the MPPT and Orion - and the current would be additive. Thanks for all the help (everywhere!)

the BMS controlled switch is for the when the **** goes wrong. a charger could fail and start putting out 20v. who knows. I used the battery protect as a charge relay. it works great for the load or the charge side. used one for each side. they draw very little current which is an issue for the victron BMS