What size LiFEPO4 bank

[newhaul]

Originally Posted by ablefollower

I would, if the OP asked, but he didn't. You might google the voltage levels he quotes and the battery chemistry and SOC will be obvious, but I won't google it and link it here for you. You should do your own research and attend to your own education, it being your own responsibility.
.

ok you didn't understand .
Bluntly what size is your lifepo4 bank and what is / are your charging sources and sizes / setup of each .


Side note I am retired shipwright that installs / installed all of the above .

[john61ct]

Originally Posted by ablefollower

general disagreeableness

pot calling kettle black

For most boats, the weight/space available is 10 times that required to carry even 10x the most LFP Ah ever needed.

There are many other more critical needs like drinking water, food etc.

For PV past a certain point you're destroying sailing performance and the look of the boat.

On an RV, yes, maximize all available roof space, but the need for at least a small genset or big alternators kicks in earlier on a boat.

[newhaul]

Originally Posted by ablefollower

No, YOU didn't understand.

You are NOT the OP. I'm responding to the OP, not you. Start your own thread.

I will take that then to mean your experience is theoretical not practical.

[Josi2019]

A few facts on batteries:


- Energy is measured in Watt hours; Watt hours = Volt x Amperes x hours (for power factor =1); if your battery system is 12 V and 100 Ah, and you purchase a 6V 100 Ah battery, you will have half the energy. The reason why batteries are rated in Ah is because its output Ampere capacity is limited by its internal resistance.

- Lithium batteries start overheating after 80% discharge, so when it reaches 20% capacity it is best to shut down the system. Try sizing the battery system for 70% or lower discharge to give yourself at least a 10% margin.
- Lithium batteries must have a battery management system that limits the charge to the weakest cell's Voltage, in order to keep it from catching fire.

[KASHMIR]

I would be be going with 3x your charging capacity for LiFePO4, in order for maximum life. If you charge quicker, they can heat up and reduce the life. So it seems to me if you wish to have a balanced system and charge with 200A, then 600Ah would be the ideal size.
Just my thoughts

[newhaul]

Originally Posted by KASHMIR

I would be be going with 3x your charging capacity for LiFePO4, in order for maximum life. If you charge quicker, they can heat up and reduce the life. So it seems to me if you wish to have a balanced system and charge with 200A, then 600Ah would be the ideal size.
Just my thoughts

Yep a .3C is just about the perfect mix between rapid charging and longevity.

[john61ct]

Ah are a much better unit for energy consumed and battery capacity than Wh. Unless converting to and from different voltage levels.

Lithium is a broad umbrella term, different chemistries are widely varying, here we discuss LFP specifically, which have little risk of thermal runaway.

A good charger will keep OVP protection from ever triggering, BMS should be for failsafe only.

Yes approaching 10% SoC is not a good idea, but in a House bank scenario, nothing to do with heat.

[newhaul]

Originally Posted by Josi2019

A few facts on batteries:


- Energy is measured in Watt hours; Watt hours = Volt x Amperes x hours (for power factor =1); if your battery system is 12 V and 100 Ah, and you purchase a 6V 100 Ah battery, you will have half the energy. The reason why batteries are rated in Ah is because its output Ampere capacity is limited by its internal resistance.

- Lithium batteries start overheating after 80% discharge, so when it reaches 20% capacity it is best to shut down the system. Try sizing the battery system for 70% or lower discharge to give yourself at least a 10% margin.
- Lithium batteries must have a battery management system that limits the charge to the weakest cell's Voltage, in order to keep it from catching fire.

That is not correct in the least . We are talking lfp here they dont " catch fire " and a bms is not required however it is highly recomended for its hvc and its lvc bank protective fetures.

[john61ct]

Sizing the charge source to the bank size is better than v/v.

That 200A was a typo, actually Ah per day usage, not amps charge rate

[senormechanico]

[QUOTE=newhaul;3025838so what you are saying is that I wasted 250 bucks on my Lfp bank ( 100ah) that has been performing wonderfully purely off grid charging on solar and wind ( renewable sources no ice used ) for the last year being a liveaboard At 48° north +/- ?]



You "wasted your money" but now you are in with the "cool" kids.

[newhaul]

[QUOTE=senormechanico;3028147]

Originally Posted by newhaul

so what you are saying is that I wasted 250 bucks on my Lfp bank ( 100ah) that has been performing wonderfully purely off grid charging on solar and wind ( renewable sources no ice used ) for the last year being a liveaboard At 48° north +/- ?

You "wasted your money" but now you are in with the "cool" kids.

Thats what i thought wait till i get my new 240ah bank takes up as much room as a single gc2 battery

[Delfin]

Originally Posted by Namoian

We upgraded our battery bank to lithium in 2011.

The old bank, consisting of four Trojan six-volt golf car batteries were replaced with four 160 AH LiFePO batteries. The Trojans provided 450AH and their lithium replacement 640 AH. We chose 640 AH as that number of batteries fitted the battery box perfectly.

The theoretical differential increase in capacity is nearly 3X due to larger capacity as well as the increased discharge levels and charge acceptance rates. We have never probed the discharge envelope and always maintained a minimum 50% state of charge.

So far, at nearly ten years of usage, no problems (knocking on wood). The LiFePO stay cool when being charged by either 200 amp alternator (derated to 160) or solar or Mastervolt charger. Do not miss the corrosion potential and low relative capacity of the old lead acid batteries.

+1, agreed.

[ramblinrod]

Originally Posted by Delfin

+1, agreed.

OK for the specific individual, but others may have better things to do with their time and finite boat maintenance/repair/upgrade budget.

[newhaul]

Originally Posted by ramblinrod

OK for the specific individual, but others may have better things to do with their time and finite boat maintenance/repair/upgrade budget.

A few things.
1 ) there is infinately more maintance required with fla banks.

2) when amounrorized over the full lifetime lfp batteries are wh for wh considerably cheaper.

3) the price of lead based batteries is fairly static . However the price of lfp batteries is declining rather rapidly as the chemistry becomes more mainstream.

Lastly there is no real difference wrt charging the batteries whether it be fla or lfp they both require simmilar charge voltages lfp just charges much faster.

[ramblinrod]

Originally Posted by newhaul

A few things.
1 ) there is infinately more maintance required with fla banks.

Oh really, top up FLA water level once or twice per year, 10 minutes per battery tops. Vs constantly monitoring LFP so you don’t over ornunder charge and wreck them completely.

2) when amounrorized over the full lifetime lfp batteries are wh for wh considerably cheaper.

Unless the LFP get damaged due to fault and one has to replace the bank in the first month or so, or if one sells the boat before 10 years or so and don’t get the benefit of longer life. (It is actually more likely the next owner will realize the financial gain when he buys the ~ 5 year old batteries at pennies on the dollar.

3)

the price of lead based batteries is fairly static . However the price of lfp batteries is declining rather rapidly as the chemistry becomes more mainstream.

Which including the initial and annual depreciation plus reduced price of new is why one will realize only pennies on the dollar.

Lastly there is no real difference wrt charging the batteries whether it be fla or lfp they both require simmilar charge voltages lfp just charges much faster.

Yeah right, until a HVD shuts the bank down and the alternator diodes blow, and leaves the boat stranded with no house bank power until the LFP batteries comes back on line, if they weren’t damaged by the FLA compatible absorption stage that can be held almost indefinitely by some chargers if the house load won’t let the charger go to float.


I’m not against LFP, just tired of hearing (a term derogatory of others has been removed by moderator) glossing over the very important details which mean they may not be right for everyone.


If any individual wishes to buy LFP after learning all pros and cons I could care less, but be aware, there are cons, there is to every boat decision one can make.