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Old 11-12-2024, 11:06   #16
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Re: Critique my lithium wiring plan, please

With intervention I was thinking of, worst case, isolating the unbalanced battery and top balance properly for a while until all OK again as indicated by the app. You may find that the battery not hooked up via the smart shunt will not be fully charged very often. But with the app you know what's going on in the box so I would not be too concerned in first instance with the set up as proposed.
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Old 16-12-2024, 08:20   #17
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Re: Critique my lithium wiring plan, please

I would recommend you spend some time with a decent paint type app and draw a decent diagram. I did mine using an app named paint.net and just cut and pasted using images from the web. (I tried to resized the images to be fairly actuate as to relative sizes.)

Currently, the ABYC only requires a Class-T at the bank, but a pending revision will require one at each battery. Remember fuses protect the cable, not any devices. Use the appropriate gauge cable for the ampacity of your bank. A fuse should also be present if you drop down in cable size.

To my knowledge, adding a 100Ah LFP to a 460Ah battery will lead to the premature death of the 100Ah. I'd try to sell it or find a use other than a part of your house bank. (Maybe an inexpensive inverter for use at your home.)

As others have said, the house bank needs to go to a set of bus bars. You should NOT stack a lot of connections on the battery posts directly.

This is the diagram I made for my desired setup:
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Old 16-12-2024, 10:04   #18
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Re: Critique my lithium wiring plan, please

Seems like 99% is covered now here's an idea I didn't see why not use the 100ah lifepo4 to drive the windlass in place of the AGM.? Charging with a small dc2dc off the agm start bank when engine is running?
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Old 16-12-2024, 10:43   #19
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Re: Critique my lithium wiring plan, please

I'm a little counter culture on that 100Ah battery (and many other things as well).


Batteries know ONE THING -- their voltage (and current, I guess). They know nothing about anything else in the system. The 100Ah knows nothing about the 460Ah. It doesn't cause premature death, it doesn't cause over charging.


Mixing battery sizes doesn't matter one iota. As long as the chemistry and charge profile are the same, they don't care.


Differing length wires (and associated resistances) can cause a minor variation in discharging profiles, especially at high currents. But, on boats where 99% of the day is running currents under 10% of the design currents, the voltage drop on the cable is extremely minimal. Remember, we design them for 3% drop (.36V) at full load, so at 10% of load, the drop is .036V. That means the batteries are going to be well within .1V of each other. LFP has a very flat charge curve, and so .1 is a lot -- in the mid range. But when one of the batteries starts to get full (or empty), its voltage will start to climb (or drop) and the other battery will pick up the extra. Bottom line, in the mid-range, one or the other batteries may be ahead or behind on charge, but at under 1% or over 99%, they will automatically re-align. And you will NEVER get a situation where one is at 10% and the other is at LVC, or where one is at 90% and the other is at HVC. And, at the end of the day, when the batteries are full or empty, you will have essentially both batteries capacity (546Ah) available.


Since you absolutely MUST get to 100% charge periodically (SOC meters get out of whack over time, and if they never get to 100% and "reset" they can get WAY out of whack), every time you get to 100% they will be re-balanced and ready to provide service again.


One thing to keep in mind in paralleling. ABYC assumes that in a parallel situation, loose connections can make all but one wire off line -- and so that 100Ah battery needs a wire matched to the main fuse, even if it normally provides a very low current. Typical boats use 4/0 for the main battery line, and so that means that 100Ah needs 4/0.
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Old 16-12-2024, 11:40   #20
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Re: Critique my lithium wiring plan, please

Quote:
Originally Posted by Peregrine1983 View Post
Assuming a maximum load on this house bank of 200 amps, am I right to assume that a 200 amp load on a 460ah and a 100ah battery wired in parallel would only be pulling 43 amps from the 100ah?

Any thoughts appreciated.
This assumption is absolutely NOT correct. There is no mechanism that would distribute the load according to the batteries’ capacity.

The exact answer is complex, and depends on large numbers of factors that are virtually impossible to quantify in the real world. You would be closer to the correct answer if you assumed that parallel batteries split the current equally, although your wiring setup with remote batteries in parallel makes any guesses inaccurate because of significant differences in connection resistance.
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Old 16-12-2024, 11:47   #21
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Re: Critique my lithium wiring plan, please

Consider having an abc automatic fire extinguisher bottle in the battery compartment. It could give you just enough time to save your life. Lithium fires cannot really be put out so your design should consider that. A thick gauge steel asbestous insulated battery box would be my choice.
However, I would never consider lithium because of the fire hazard.
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Old 16-12-2024, 14:19   #22
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Re: Critique my lithium wiring plan, please

Quote:
Originally Posted by Lewis Harry View Post
Consider having an abc automatic fire extinguisher bottle in the battery compartment. It could give you just enough time to save your life. Lithium fires cannot really be put out so your design should consider that. A thick gauge steel asbestous insulated battery box would be my choice.
However, I would never consider lithium because of the fire hazard.
We are talking lifepo4 chemistry.
Less likely to thermal runaway than your hydrogen producing lead battery.

Lifepo4 is safe for all installations.
Do some research
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Old 16-12-2024, 20:24   #23
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Re: Critique my lithium wiring plan, please

Quote:
Originally Posted by Lewis Harry View Post
Consider having an abc automatic fire extinguisher bottle in the battery compartment. It could give you just enough time to save your life. Lithium fires cannot really be put out so your design should consider that. A thick gauge steel asbestous insulated battery box would be my choice.
However, I would never consider lithium because of the fire hazard.
Sorry, but you are clearly uninformed. LFP batteries as used on boats are entirely different than the chemistries used in consumer devices and cars, and have none of the fire hazards. In addition to a large installed base with approximately zero fires initiated by or sustained by LFP batteries, various informal tests have been done including impaling with metal spikes, heating with blow torches, etc.


Come back after you have done some research.
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Old 17-12-2024, 11:07   #24
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Re: Critique my lithium wiring plan, please

Quote:
Originally Posted by Peregrine1983 View Post
Hi all,

Looking for critiques of my plan to convert our house bank on our 42 foot ketch to lithium.

This is what I came up with for a general plan. I already have the lithium batteries (1x460ah, 1x100ah), 30 amp Victron Orion DC-DC charger, inverter, wire, terminals, and the solar on the boat in the Bahamas.

I'll be bringing the on/off switch, echo charger, and bus bars from the US.

What worries me about this drawing now is the little 100ah lithium battery on the port side near the solar controller. My concern is this battery will be overcharged and under-utilized with the loads all being closer to the 460ah battery on the starboard side. The batteries are arranged as they are due to the size and location of the boxes.

The boat is rarely, if ever, plugged in. It spends most of its time on a mooring or at anchor when we are not on the move.

I wanted to add an emergency engine start switch to start off lithium if it's absolutely necessary. The 460AH house battery has a 600A (3 sec peak) and 200A continuous BMS.

In this setup, the windlass battery in the bow will remain an AGM fed off an echo charger and the start battery will remain a Group 27 FLA.

I am not an electrical engineer (clearly) so please don't flame me too bad.

Thanks in advance for any help.
I agree with others - you need bus bars, fuses, etc as noted.

You cannot expect 350 watts of solar to keep things charged. And your Victron 75/15 is only good for 220 watts anyway. You need more solar and larger controllers - for 350 a Victron 100/30 is a good match.

I would sell the 100 AH battery. The wire and fuse alone to properly connect it will be pricey. It will be more a hindrance than a help.

Unless as posted you use it for the windlass and charge it with a DC-DC.
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