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Old 02-14-2022, 11:38 AM   #1
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LiFePO4, maybe but..

The recent LiFePO4 poll got me thinking: If I went this route and relocated my battery bank outside of the hot ER, how could I connect the alternator to the new bank location?

We're talking 300A max @12V, a 50' round-trip, and cabling within the ER. That means multiple 4/0 cables each way. I don't like using multiple cables because if every connection isn't perfect and identical.. Can't move the alternator from the engine, can't move the batteries to a closer, cool space..

Go to 24v battery bank. Replace the alternator. Replace the inverter. Get a big 24-12 converter for the 12v loads (or better, keep one large 12v AGM for those loads, charged with a 24v-12v charger). I guess that'd work but additional complexity and $.

..or 24v with a 12v AGM might not work. Could be the case that I'd run out of 12v well before the 24v bank (powering just the inverter) is run down. So put 2 AGMs in rather than 1. So now rather than my current 4 AGMs I have 2 AGMs and LiFePO4 . Getting silly-complex here.

Other ideas?
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Old 02-14-2022, 12:11 PM   #2
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Originally Posted by danderer View Post
The recent LiFePO4 poll got me thinking: If I went this route and relocated my battery bank outside of the hot ER, how could I connect the alternator to the new bank location?

We're talking 300A max @12V, a 50' round-trip, and cabling within the ER. That means multiple 4/0 cables each way. I don't like using multiple cables because if every connection isn't perfect and identical.. Can't move the alternator from the engine, can't move the batteries to a closer, cool space..

Go to 24v battery bank. Replace the alternator. Replace the inverter. Get a big 24-12 converter for the 12v loads (or better, keep one large 12v AGM for those loads, charged with a 24v-12v charger). I guess that'd work but additional complexity and $.

..or 24v with a 12v AGM might not work. Could be the case that I'd run out of 12v well before the 24v bank (powering just the inverter) is run down. So put 2 AGMs in rather than 1. So now rather than my current 4 AGMs I have 2 AGMs and LiFePO4 . Getting silly-complex here.

Other ideas?
Good questions and I don't think there is any simple answer without having someone who really knows their stuff inspecting your existing system and everything's location in person and designing a system for you. This is why getting it right is expensive and time consuming. It is easy to overlook details about your existing system that could cause problems when implementing this technology.

I would imagine that installing buss bars for the new battery system as close as possible to the new bank and then run a charging circuit between the alternator and this house bank. Controlling the alternator's output when charging LiFePO4 is one of most important considerations as they can absorb charge so much faster than other chemistry types that alternators can easily get overheated trying to satisfy the bank. Other battery types have internal resistance within them that slows charging and also protects the alternator, kind of by accident but we have grown accustomed limiting factor always being present and fail to account for it when doing a "drop in" upgrade to LiFePO4. Your alternator probably won't live long trying to continuously supply 300 amps to this new house bank, but whatever safe output you can safely meter it back to while feeding a LiFePO4 bank will still outperform that effective rate of charging your current AGMs.

I find the potential fascinating and hope to see the integration of it for Marine applications mature but I certainly don't claim any level of expertise.
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Old 02-14-2022, 12:30 PM   #3
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I'd actually measure the maximum charge current from the alternator after it heats up and derates. It may be a lot less than 300A. One 4/0 can handle the current, even in engine spaces, but at 300A there will be unacceptable voltage drop. At 150A it isn't great, but could be compensated for with remote sense. Or course 24V makes it a lot easier.

Another thing to consider is how much charge the LFP can actually take. It sounds like you would have a very large bank, but when I go through this exercise on my sailboat which has a 24V 440AH battery, it is problematic. Conventional wisdom is that you need only 1/2 the size in LFP, in my case 220AH, but that size would not be able to absorb the available current from my Electrodyne alternator. I either have to limit the output, or increase the battery size larger than needed. It would still be a plus though, because the recharge time even at the lowered rate would be quicker than AGMs.
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Old 02-14-2022, 01:58 PM   #4
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You should check out this group on FB. Many are familiar w/ Rod Collins, he's the admin. A lot of great LFP in there...

https://www.facebook.com/groups/293580215978963
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Old 02-28-2022, 07:40 PM   #5
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LiFePO4, maybe but..

I used to have two banks of LA batteries. When they started dying, I bought LFPs. 4x170 AH, total 680 AH. Large enough to feed my fridge and freezers, plus the house a/c.
As long I am on shore power, the Mastervolt charger/inverter handles everything. Later I realized that to feed the LFPs while underway, I had to charge them from the main engineís alternator, or run my Perkins generator sometimes, to provide a/c to the house. The LFP bank is big, but it would be deflated after a while.
So, this is what I did. I still had the ProMariner charge controller connected to the alternator to charge the starter batteries. Two new LA 12v. I wired the empty bank connection to two Victron dc/dc chargers 30A each and parallel connected them to the bus bar for the LFP bank. I included a 60A breaker to each Victron. Theoretically I should have 60A total going to the batteries. The Victron chargers have settings for LFP batteries, which you need to manually enable through Bluetooth.
Of course, these chargers will only get current, when the ProMariner decides to provide it. It always charges the starter first. Once it is done, it will feed the other banks. This is when the Victrons come alive and charge. My alternator can do 160A when it is in a good mood, so it should top off the batt bank just fine. I used 3/0 cables. The positive from the ProMariner to the Victron location is long. The negative just plugs into the bus bar close to the Mastervolt and batt bank. Victron requires all wiring to be exact same when you parallel multiple dc/dc units. Those are smaller size, since the Victrons are only a foot away from the bus bar.
Again, this provides current only when the main engine is running and the starter batteries are full.

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Old 02-28-2022, 10:08 PM   #6
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A 300A engine alternator? What kind is that? If real then use a DC to DC charger to limit current to say 60 amps and then #2 wire should work fine.

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Old 03-14-2022, 05:06 PM   #7
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A 300A engine alternator? What kind is that? If real then use a DC to DC charger to limit current to say 60 amps and then #2 wire should work fine.

David
A big honkin' Leece-Neville. 320A I think though I've derated it to 280 based on the installed wiring sizes.
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Old 03-14-2022, 05:08 PM   #8
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So, this is what I did. I still had the ProMariner charge controller connected to the alternator to charge the starter batteries. Two new LA 12v. I wired the empty bank connection to two Victron dc/dc chargers 30A each and parallel connected them to the bus bar for the LFP bank. I included a 60A breaker to each Victron. Theoretically I should have 60A total going to the batteries. The Victron chargers have settings for LFP batteries, which you need to manually enable through Bluetooth.

Seems to me some type of FLA/Li hybrid like this might be the most reasonable solution. Someone (in this group?) mentioned Calder advocating such a system. Anyone have info on that?
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Old 03-14-2022, 05:30 PM   #9
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I mentioned it in another thread but instead of an alternator has anyone looked at an actual generator head?

Much less $$ and far simpler than big alts, charge controllers etc.

It was suggested to me by a marine electrician who lives aboard full time "unplugged" that 5kva heads new are around $600.
Have that wired directly into the inverter charger and you effectively have shore power when the engine is running at cruise speed and full charging capabilities.

Set belts and pulleys for cruising rpm and a light from power source on dash that is activated when in the correct rev range.
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Old 03-15-2022, 08:14 AM   #10
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Seems to me some type of FLA/Li hybrid like this might be the most reasonable solution. Someone (in this group?) mentioned Calder advocating such a system. Anyone have info on that?

I think it's fine for smaller systems/boats. With larger systems the issue is that you are limiting LFP charge by the capacity of the DC/DC chargers, where the alternator typically has much more charge capacity. So looking at the examples noted in the past couple of posts, 60A of LPF DC/DC charger capacity is a significant bottleneck when you have a 320A alternator.


With bigger systems, it's much better to reverse the alternator and DC/DC charger connections/roles. Connect the 320A alternator directly to the LFP bank, controlled by an external regulator. Then install a small DC/DC charger (20A, for example) from LFP to the start bank to top it up after starting. That way the lower capacity of the DC/DC charger is matched to the lower recharge demand of the start bank, and the higher capacity alternator is full utilized by the LFP bank. One of the big advantages of LFP is the ability to recharge it faster, so don't build a system that slow charges it, build one that fast charges it.


Also keep in mind that one of the big reasons people keep the alternator connected to the start bank rather than direct connect to LFP is so they can use drop-in batteries, punt on the issue of alternator damage in the event of all BMSes disconnecting, and to avoid adding an external alternator regulator. In my opinion, this approach compromises every other aspect of the system, all to avoid addressing these simple issues.


If you add an external alternator regulator, it can properly regulate the alternator for LFP, and can be shut down in a BMS failure event. If you have a system with an external BMS, in a failure situation it can shut off the alternator before disconnecting the batteries. And the alternative with internal BMSes is to use a clapping diode to protect the alternator. These are available from Sterling and Balmar.
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Old 03-15-2022, 09:11 AM   #11
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I think it's fine for smaller systems/boats. With larger systems the issue is that you are limiting LFP charge by the capacity of the DC/DC chargers, where the alternator typically has much more charge capacity. So looking at the examples noted in the past couple of posts, 60A of LPF DC/DC charger capacity is a significant bottleneck when you have a 320A alternator.
I agree with this and everything else you wrote. In going through this mental exercise I've concluded that for LFP to work the way I'd want it to would require much, much more than just battery replacement. I knew this but am now realizing just how much more it would require.

Every solution will have compromises. 60A of LFP charge is certainly a compromise. However, assuming I mount the LFP batteries in the laz to keep them cooler, there is no practical way to get a large charge to them from the alternator at 12v.

Getting the ER cooler would be a solution but I've already got decent airflow and the reality is that things get heat-soaked and forced ventilation doesn't make that much difference in my ER. Just the nature of the design I suppose.

A 48v LFP bank mounted in the laz could work. Replace the alternator and inverter/charger.

Except this is a 12v boat. Converters aren't a practical answer for things like the windlass. So put a 48v bank in the laz fed by the alternator (and inverter/charger). Keep a 12v AGM bank, fed/charged by the LFP at 60a or so. All draws come from the AGM which are kept topped by the LFP which is charged by the alternator and inverter/charger.

So what have I gained here? Additional capacity and maybe some faster charging. I don't have a capacity problem now (more is always nicer but..) and can charge at 200+a even with the alternator hot.

My conclusion from the exercise is that LFP doesn't make sense in my case. If I want more capacity then a couple solar panels or a couple more AGMs is a more cost-effective approach.
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Old 03-15-2022, 09:39 AM   #12
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I agree with this and everything else you wrote. In going through this mental exercise I've concluded that for LFP to work the way I'd want it to would require much, much more than just battery replacement. I knew this but am now realizing just how much more it would require.

Every solution will have compromises. 60A of LFP charge is certainly a compromise. However, assuming I mount the LFP batteries in the laz to keep them cooler, there is no practical way to get a large charge to them from the alternator at 12v.

Getting the ER cooler would be a solution but I've already got decent airflow and the reality is that things get heat-soaked and forced ventilation doesn't make that much difference in my ER. Just the nature of the design I suppose.

A 48v LFP bank mounted in the laz could work. Replace the alternator and inverter/charger.

Except this is a 12v boat. Converters aren't a practical answer for things like the windlass. So put a 48v bank in the laz fed by the alternator (and inverter/charger). Keep a 12v AGM bank, fed/charged by the LFP at 60a or so. All draws come from the AGM which are kept topped by the LFP which is charged by the alternator and inverter/charger.

So what have I gained here? Additional capacity and maybe some faster charging. I don't have a capacity problem now (more is always nicer but..) and can charge at 200+a even with the alternator hot.

My conclusion from the exercise is that LFP doesn't make sense in my case. If I want more capacity then a couple solar panels or a couple more AGMs is a more cost-effective approach.

Well, it's proof that every boat is different.


Re getting high amps to the laz, voltage drop can be accommodated by sensing voltage at the battery rather than the alternator. This can be done in one way or another with all the external regulators that I know about. Sizing cables for ampacity will yield much smaller cables that sizing for voltage drop over a longer distance. I am pushing 400A from ER to laz for charging, for example. Not that this solves all problems, but it might help.
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Old 03-15-2022, 12:34 PM   #13
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How many years do LiPo last compared to AGM?

Our AGM lasted about two years before we started seeing noticeable reduction in power. At four years they were barely alive. They were properly taken care of and on solar charge from day one.
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Old 03-15-2022, 12:40 PM   #14
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How many years do LiPo last compared to AGM?

Our AGM lasted about two years before we started seeing noticeable reduction in power. At four years they were barely alive. They were properly taken care of and on solar charge from day one.

That's an unusually short lifespan for any battery unless they were either in a very high temperature environment or being cycled fairly deeply every day.
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Old 03-15-2022, 01:08 PM   #15
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Sizing cables for ampacity will yield much smaller cables that sizing for voltage drop over a longer distance. I am pushing 400A from ER to laz for charging, for example. Not that this solves all problems, but it might help.
Never thought of that. Seems like a neat approach. Hmm..
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Old 03-15-2022, 01:27 PM   #16
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THere are larger cables than 4/0 that could be used to avoid the multi conductor setup.

I have been out of the electrical trade to long to remember the details but many of those cables use the same insulation as the Ancor and similar competition. The only thing missing may be the tinned individual strands.
But I will emphasize "MAY" as I have seen cables like that that were not Ancor and were tinned

If the ends of each wire is dealt with properly that should not be a problem.

It will take sealing well between the lug and the wire insulation, an anticorrosion spray, a darn good crimper and good workmanship.
Those gaps between the insulation and the lug will need to be sealed well.

Ask around at actual electrical distributor and/or electrical wiring specialty houses. You may have to dig around. Any one supplying robotics cable may be able to help as they need high flexibility, heat resistance, and lots of these machines use lots of power.

And as T.T. mentions some of the Vdrop can be taken into account by the use of the controller/regulator remote sensing function.


It is just a suggestion.
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Old 03-15-2022, 04:25 PM   #17
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How many years do LiPo last compared to AGM?

Our AGM lasted about two years before we started seeing noticeable reduction in power. At four years they were barely alive. They were properly taken care of and on solar charge from day one.
Something is wrong in your setup or operations. Properly cared for good quality AGM batteries will last 8-10 years. I'm on 15 years now on one boat and yes they need to be replaced but are still functioning. If you discharge them deeply every day for 3 years, then yeah, they might be done, and you are an excellent candidate for LFP.
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Old 03-16-2022, 02:32 AM   #18
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Something is wrong in your setup or operations. Properly cared for good quality AGM batteries will last 8-10 years. I'm on 15 years now on one boat and yes they need to be replaced but are still functioning. If you discharge them deeply every day for 3 years, then yeah, they might be done, and you are an excellent candidate for LFP.
Well, we discharged ours 25% of total or 50% of usable - 180ah out of 840ah @ 24v bank
2500 watts of solar had them fully charged by lunchtime
On rainy days, always got a big headstart with genset
Maggoted after 5 years of full time use.

Everything on the interwebs points to AGM having between 500 to 1000 cycles

Lifepo4 between 3000 and 6000 cycles
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Old 03-16-2022, 06:49 AM   #19
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Well, we discharged ours 25% of total or 50% of usable - 180ah out of 840ah @ 24v bank
2500 watts of solar had them fully charged by lunchtime
On rainy days, always got a big headstart with genset
Maggoted after 5 years of full time use.

Everything on the interwebs points to AGM having between 500 to 1000 cycles

Lifepo4 between 3000 and 6000 cycles
Victron rates their LFPs at 2,500 cycles using an 80% range of use. My guess this is a tested metric, not the untested marketing hype of other suppliers.
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Old 03-16-2022, 04:04 PM   #20
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I mentioned it in another thread but instead of an alternator has anyone looked at an actual generator head?

Much less $$ and far simpler than big alts, charge controllers etc.

It was suggested to me by a marine electrician who lives aboard full time "unplugged" that 5kva heads new are around $600.
Have that wired directly into the inverter charger and you effectively have shore power when the engine is running at cruise speed and full charging capabilities.

Set belts and pulleys for cruising rpm and a light from power source on dash that is activated when in the correct rev range.
Did you get any feedback on this? Initial thoughts are that it's an easy way to gain considerable recharge capacity with minimal marginal cost, effort, spares, maintenance etc.

In what other threads has this been discussed?
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