LiFePO Batteries ???

[tpenfield]

I always follow your threads with interest, and here again I think you mis titled your previously posted thread "My boat is being a boat" would make more sense to me as "my computer is being a boat". Just sayin..

Or . . . My boat is being a computer

 

[Scott Danforth]

alternators don't like that . . . it basically turns the alternator into an ignition system

The blue glow only lasts a few moments before the magic smoke

 

[tpenfield]

The blue glow only lasts a few moments before the magic smoke

That's the part that I was not quite understanding about the LFP batteries . . . that the LFP batteries actually shut off. So, the 5,10, 20 or even 40 amps of charging current coming from the alternator instantaneously has to find a place to go when the battery shuts off.

 

[sam am I]

I think most modern alt's these days have clamp circuitry to protect "over shoot" when and if the alt's load suddenly disconnect, BUT also there is still loads (passive and active loads) that remain the alt's charge path even if the BMS opens itself from the alt. So in reality, the alt doesn't see a pure "open circuit" per-se, it see's only a "battery-less" load when and if the BMS open circuits its cells............If you are still worried it has to have a battery among its many loads , why not just hang a cheapy small'ish 5'ish lbs ATV AGM off the alt as well? That way if the BMS opens the Lithium, the ATV AGM remains put as normal.

 

[tpenfield]

I think most modern alt's these days have clamp circuitry to protect "over shoot" when and if the alt's load suddenly disconnect, If you are still worried it has to have a battery among its many loads , why not just hang a cheapy small'ish 5'ish lbs ATV AGM off the alt as well? That way if the BMS opens the Lithium, the ATV AGM remains put as normal.

I was thinking about that. . . Wondering if it will work

 

[Scott Danforth]

I think most modern alt's these days have clamp circuitry to protect "over shoot" when and if the alt's load suddenly disconnect, BUT also there is still loads (passive and active loads) that remain the alt's charge path even if the BMS opens itself from the alt. So in reality, the alt doesn't see a pure "open circuit" per-se, it see's only a "battery-less" load when and if the BMS open circuits its cells............If you are still worried it has to have a battery among its many loads , why not just hang a cheapy small'ish 5'ish lbs ATV AGM off the alt as well? That way if the BMS opens the Lithium, the ATV AGM remains put as normal.

I believe its the BCM controlled relay and the power distribution box sitting on top the battery in your car or truck you are describing. the BCM controls the field on the alternator as well as the power relays. most alternators are still dumb, and the marine world doesnt use power relays or BCM controled alternators yet.

 

[sam am I]

I believe its the BCM controlled relay and the power distribution box sitting on top the battery in your car or truck you are describing. the BCM controls the field on the alternator as well as the power relays. most alternators are still dumb, and the marine world doesnt use power relays or BCM controled alternators yet.

Maybe we're on two different pages? I was referring to the "BMS" which resides internal to the Lithium battery.........Nothing from the battery runs to the alt cept the normal charge wire, hooks up with two posts just like a AGM, Flooded.

What Is A BMS (Battery Management System)?

A battery management system is the "brain" of battery, which is critical for safety and operation. Here's a deep dive on the BMS.

battlebornbatteries.com

100Ah 12V LiFePO4 Deep Cycle Battery

The 100Ah 12V LiFePO4 Deep Cycle battery is the pinnacle of battery technology and the lightweight drop-in replacement for lead acid batteries.

battlebornbatteries.com

 

[tpenfield]

I just replaced the Alternator on my Ford Explorer . . . $600 for the part + $200-ish in labor

So, not taking any chances with the boat engines. I figure that I can go with more minimal lead-acid batteries, and as needed, there is a 'parallel solenoid' with a helm switch to combine the starting batteries during cranking.

Here is my current & proposed schematics.

Current System: (OEM + my modifications)

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Proposed System:

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This would reduce the weight by about 350 lbs. I plan on having the LFP batteries more forward in the boat, rather than in the engine bay (my understanding is the the LFP batteries don't like heat (or extreme cold) ).

Pricing this out, it looks more do-able as all the bits and pieces would run about $2,000. Probably will be a project for over the winter 2023-24.

Thanks everyone for your comments so far.

 

[airshot]

When I upgrade my TM batteries to lifepo4 I will use dedicated chargers to keep them full. No way would I use an alternator to charge one. My starting battery will remain an agm until alternator issues on lipos are fixed for sure. These lipo type batteries are designed for long drains with high draws, where the problems generally arrise is during the charge cycles. A dedicated charger is the safer bet until these new type batteries get figured out. That is my two cents and I am sticking to it !!

 

[Scott Danforth]

@sam am I I was referring to the BCM (Body Control Module) that controls the alternator in my car and truck

The sense wire no longer is connected to the ignition.

Most marine alternators are a simple Mando, Delco, or Bosch 3-wire running off the ignition sense wire

 

[tpenfield]

I am wondering if the BMS will eventually be modified so they don't do a hard shut off. Something more gradual would probably work for the alternators.

 

[909]

I have never run a BMS and my batteries are always perfectly balanced after charging. I use a simple inexpensive balance charger ( Imax B6) but yours could be scaled for your application.

 

[sam am I]

@sam am I I was referring to the BCM (Body Control Module) that controls the alternator in my car and truck

Got ya....

The sense wire no longer is connected to the ignition.

Most marine alternators are a simple Mando, Delco, or Bosch 3-wire running off the ignition sense wire

So yes, complicating things by adding or having a BCM or such, and as you mentioned, the marine alt's are still relitively simple, so why make it worse when running lithium? I think the manu's have it right w putting a/the BMS internal to the battery where it manages itself regardless of the outside world makes the most sense, ya just drop one in, it keeps itself maintained, keeps the install stupid simple and runs SAFE.

 

[tpenfield]

One additional thing to consider is temperature . . . I would float charge the batteries over the winter, but it might be too cold to do so. I think it is OK for charging down to about 0˚F, but not so sure about -10˚F

 

[sam am I]

Yes, charging Lithium's at too low of temp(chem makeup can vary it somewhat) isn't good for them, I used Polymide heaters on a LiPo starting battery design for my snowblower so the batt c/would safely charge at lower ambient temps. Dewalt etc, even inhibit charging for their Li-ion's below some preset.

The BMS in LiFePO's above for example, is meant to automagic'ally take care of that for ya no matter where it is and when voltage is applied to its terminals.

 

[airshot]

One additional thing to consider is temperature . . . I would float charge the batteries over the winter, but it might be too cold to do so. I think it is OK for charging down to about 0˚F, but not so sure about -10˚F

Great reason to put a heater in your barn/ garage !!

 

[alldodge]

Why worry about charging in the winter. Keep hearing they can go to near zero volts without damage. Why charge at all when not in use?

 

[airshot]

When I move over to them in the future, I will pull rhem and store them in my heated garage. If we were to get a chilly night before time for winter storage, then the old conventional

Why worry about charging in the winter. Keep hearing they can go to near zero volts without damage. Why charge at all when not in use?

There is a minium voltage that must be maintained or the battery will die. Not sure what the lifepo4 requires but on a regular lipo battery it is 3.7 volts per cell x how many cells the battery has. Dropping below 3.7 volts voids all warranties and usually kills the battery. They have there best storage life when stored at just above the 3.7 per cell, never store fully charged ( 4.2 volts per cell) for long periods of time as this can shorten life expectancy. LifePO4 are a little different but not sure how....yet...will be researching this when time to upgrade mine.

 

[tpenfield]

Great reason to put a heater in your barn/ garage !!

I wish I had a barn . . . the boat is bigger than the garage

 

[airshot]

I wish I had a barn . . . the boat is bigger than the garage

Yep, so was mine so I built a bigger barn !! A man has gotta do what a mans gotta do !! Lol...