LiFePO Batteries ???

[tpenfield]

Quick Update . . .

Prices on LiFePO batteries have come down nicely over the past year, so my budget for the battery/electrical project is about $1,500 vs. my original budget of $2,500+.

I have also simplified the design a bit which saved a few $$$.

Here is my latest design. I'll probably be buying the stuff in a couple of months. Since there is wiring-a-plenty in the boat, I think I'll be able to re-purpose much of the heavy cabling.

 

[Scott Danforth]

and this is simpler/lighter/cheaper than a 5kw genny?

 

[tpenfield]

and this is simpler/lighter/cheaper than a 5kw genny?

Definitely . . .

 

[909]

I recently bought a total of 380AH of lifepo4 for under $800 for my offgrid cabin.

It was originally more than double.

 

[tpenfield]

I recently bought a total of 380AH of lifepo4 for under $800 for my offgrid cabin.

It was originally more than double.

I'm going with 2 100Ah batteries. I could get a single 230 Ah battery, but my thinking is with 2 separate batteries, if one goes bad, there is a second.

 

[alldodge]

I'm going with 2 100Ah batteries. I could get a single 230 Ah battery, but my thinking is with 2 separate batteries, if one goes bad, there is a second.

You know better then I but, if one goes bad most likely you won't see it coming and it doesn't take long for one to take the other out

 

[tpenfield]

You know better then I but, if one goes bad most likely you won't see it coming and it doesn't take long for one to take the other out

Yes, I'm not sure about the difference of LFP vs lead acid, but my thinking is that if the battery 'goes bad' the BMS will (should) shut it off. Hopefully, this theory will remain untested

 

[Scott Danforth]

How much magic smoke comes out when the battery goes bad?

 

[alldodge]

Yes, I'm not sure about the difference of LFP vs lead acid, but my thinking is that if the battery 'goes bad' the BMS will (should) shut it off. Hopefully, this theory will remain untested

Your drawing does not show any fuses/breakers between Bats. So unless they are currently left out, you would need to be there with a wrench to stop it

 

[tpenfield]

How much magic smoke comes out when the battery goes bad?

All of it. . .

 

[tpenfield]

Your drawing does not show any fuses/breakers between Bats. So unless they are currently left out, you would need to be there with a wrench to stop it

The BMS would be 'in charge' of disconnecting the battery. . . sort of depends on how much functionality is within the BMS. I'm not really concerned about it . . . until such a thing happens

 

[alldodge]

Bats in parallel BMS has no effect if one shorts out

 

[tpenfield]

Bats in parallel BMS has no effect if one shorts out

That would be more of a lead-acid situation. With the LiFePO4 batteries, the BMS is in charge of short protection, over-charge protection, over-discharge protection, and cell balancing. So, one battery would protect itself from the other in a parallel connection.

There are precautions with connecting LiFePO4 (and lithium in general) in parallel so that you achieve load and charging balance among the batteries. One of the key precautions for parallel connections is to have the batteries of the same spec. (preferably same brand/model)

 

[tpenfield]

I cleaned up a few of the notes, etc. in the diagram. Although the diagram look busy most of it (physically) is located along the engine room bulkhead and the 2 engine room electrical panels.

EDIT: 2/2/2024 . . . a few more edits to the picture.

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[tpenfield]

Much of the electrical alterations will have to do with the inverter battery bank (currently 4 AGM31's) and the accessory battery ( 31 AGM).

I don't have the factory drawing of the inverter installation, by CY put a plaque of the wiring on the engine bay.


The port engine is currently wired to charge the inverter batteries via an isolator. In switching (and combining) the 'Inv' & 'Acc' battery banks over to LFP batteries, I'll be using the '2 alternator/3 bank' isolator along with a DC/DC converter w/ MPPT to provide charging from either/both engines as well as the solar panel
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Here are the 300 amp fuse, Port engine isolator, inverter switch all along the main bulkhead.
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I'll have to chase down the alternator lead from the port engine . . . hopefully it is connected at the '2 alt/3 battery' isolator.

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Re-purposing the wiring should save some $$$, since it is really heavy gauge. My budget is looking like $1,300 ish for this upgrade.

Not sure what I'll do with 7 Group 31 AGM batteries though . . . I think 1 or 2 of them are dead, since when I connect shore power and charge them, the inverter goes right up to its maximum charging (80 amps) and the ProNautic goes up to its maximum (30 amps) and stays there for quite a while.

 

[alldodge]

7 group 31's is about 200 lbs. Hope they were not all on one side

 

[tpenfield]

7 group 31's is about 200 lbs. Hope they were not all on one side

Yes, the 7 AGM group 31 batteries weigh in at 72 lbs each. . . 504 lbs. total

I'll be replacing all 7 with just 2 Group 24 AGM (45 lbs each) and 2 LiFePO4 100 Ah (24 lbs each) for a total weight of 138 lbs. So, 4 batteries total vs. the 7 that were there, and should be a fair amount of space freed up in the engine bay.

The weight reduction is going to be 366 lbs., but probably more like 350-360 lbs. figuring the addition of the DC/DC converter.

The Amp-hour capacity of the combined accessory/inverter bank will be a little bit less than what is there now (250 Ah vs. 180 Ah +/- ).

 

[bruceb58]

I love lithium batteries...have them in my travel trailer. In fact I made 2 280AH batteries myself for my trailer.

Personally, if were to buy a couple batteries today, they would be the Epoch batteries....especially the 460AH ones.

And for the naysayers, LiFePO4 are probably safer than lead acid batteries....mine are under our bed.

Here are mine that I made.

 

[bruceb58]

Also...I highly suggest the 50A DC to DC that Victron just came out with. I just bought one for my trailer.

I would NEVER EVER use Renogy equipment.

I don't see it in your diagram you should add a battery monitor like a Victron Smart Shunt or BMV-712.

The main reason you go with two separate batteries is that each 100AH Lithium will have a 100A BMS so with two in parallel, you will have 200A.

I would have no problem talking on the phone about lithium setups. Been using LiFePO4 for nearly 6 years.

 

[redneck joe]

well if under your bed yall be quick to know if sh.. went bad