LiFePO4 vs FLA - The Real Deal

[ramblinrod]

Hi All,

I have a fair bit of experience with FLA batteries and am trying to figure out what all the hype is about over LiFePO4.

What I have heard so far about LiFePO4 is:

Pros:

Higher energy density. How much? For a given dimension of battery case, lets say equal to a FLA Grp 27 100 A-hr battery, how many more A-hrs capacity does a LiFePO4 have?

Higher Usable Capacity. I hear people tout 80% (charge cycle from 90 - 10%).

Wait a mintute!

Shouldn't we design for 50% reserve capacity?

What if there is no sun or wind one day?

What if the girlfriends hair gets longer and she needs to run the blow drier another 5 minutes per day?

So if we design for 50% reserve capacity of 80% max capacity (so we don't hurt the battery), we're talking cycling the battery from 90-50%.

Wait a minute!

We were cycling our FLAs from 100-50%, and if on occasion we had to dip into the reserve, say to 20%, no biggy as long as we charged right back up again.

We could have design for 100% - 20% charge cycle on our FLAs too. They probably wouldn't last as long, but isn't that a fair weight/capacity trade-off?

Faster Charging: Sure, pound the Amps into that puppy.

Wait a minute!

Where are they going to come from?

The 400W wind genny and the 400 W solar panels will only deliver a high of about 30 A max.

So we are going to be forced to run ICE (Internal Combustion Engine) to gain any benefit of the fast charging capability.

Isn't the goal for most cruisers to avoid running the ICE when it isn't necessary?

Reduced Voltage Sag.

The output remains constant right down to 10% DOD.

Wait a minute!

Voltage sag is never really a problem when using a properly sized FLA bank.

So it seems the only time LifePO4 would really be a benefit if one is going to throw on a thruster, windlass, or huge inverter with heavy load, when the FLA bank is really low.

Is that the only real benefit?

CONS:

Expensive. By the time the batteries are purchased, higher output shore power and ICE charging is included. This "upgrade" will be many thousands of dollars.

Wait a minute!

Wouldn't it be a lot more economical to just use a smaller bank of FLAs with design charge cycle of 100-20%, and replace them more often?

Limited Availability. There are only a few suppliers with limited distribution channels with very limited (if any) stock at the retail level.

Wait a minute!

One can get a replacement FLA battery anywhere.

Consequence of Failure:

If something goes wrong, like the batteries get trashed by an incorrect charge or discharge incident, how much will it cost and how long will it take?

OK, I think that about sums up my thoughts.

To me, the only real benefit I see to switching from FLA to LifePO4 is the ability to say, "I have LiFePO4s".

Am I missing something?

[senormechanico]

Enjoy your Buggy Whip Batteries.

[CatNewBee]

wait a minute...

use the search function.

wait a minute...

Why Elon uses Lithium batteries and not FLA for the Tesla?

wait a minute... Cars can tow anexes, why tot loading one of those with FLA batteries and charge them for a weak before driving?

Wait a minute...

why have heavy duty tools not heavy FLA?

[ramblinrod]

Originally Posted by senormechanico

Enjoy your Buggy Whip Batteries.

Wait a minute!

You would recommend LiFePO4, just because they supposedly make the purchaser “cool”, even though the cost/benefit justification doesn’t seem to be anywhere near?

That kinda smacks of a 10 year old little girl in the school yard with the latest iPhone her Dad stood in line for. ;-)

[CatNewBee]

wait a minute...

I would buy them because they are yellow and look so pretty under the berth...


But if you really look for an answer, 4 times the nominal capacity and 6..8x the usable capacity of a FLA regarding weight and space, 10 times the life expectancy (cycles).

And there is no Absorption Amp drop while charging. A LFP 1000Ah battery can be charged from empty to full in 1h with a 15kWh generator, a 1000Ah Fla will still need the whole day to recharge with the same generator. Got the point?

[daletournier]

As i said on another thread, I cant justify the cost for the potential gains above what I already have , as the gains arent big enough to improve my cruising life that much, hardly at all actually, BUT there would be some gains that I could appreciate.

* no battery gassing. Gassing dosent seem to be causing me any issues BUT none would still be better.

*heat my hot water from batteries, the power would be replaced by my solar due to LiFepo4 being able to accept everything my solar can throw at them. Possibly run water maker forvlimited time more frequently from batteries, but this is questionable with my current solar set up.

*more storage space. 900ah lead takes up a lot of space BUT i have it.

*and yes they are cool

But the two deterents for me are, cant justify cost (cost vs gain) , and my fla's can take a kicking.

[ramblinrod]

Originally Posted by CatNewBee

wait a minute...

I would buy them because they are yellow and look so pretty under the berth...


But if you really look for an answer, 4 times the nominal capacity and 6..8x the usable capacity of a FLA regarding weight and space, 10 times the life expectancy (cycles).

And there is no Absorption Amp drop while charging. A LFP 1000Ah battery can be charged from empty to full in 1h with a 15kWh generator, a 1000Ah Fla will still need the whole day to recharge with the same generator. Got the point?

So if one has a 1000 A-hr LiFePO4 bank, I assume they have about 300 A-hr daily draw.

So a 400 W wind generator and 1000 W solar charging system on a 600 A-hr FLA bank could handle that most days. Zero generator. Wouldn’t that be mo’ better?

[ramblinrod]

Originally Posted by ramblinrod

So if one has a 1000 A-hr LiFePO4 bank, I assume they have about 300 A-hr daily draw.

So a 400 W wind generator and 1000 W solar charging system on a 600 A-hr FLA bank could handle that most days. Zero generator. Wouldn’t that be mo’ better?

Let’s see, 600 A-hr FLA bank plus 400W wind generator plus 600W flexi panels weights about 500 lbs.

1000 A-hr LiFePO4 bank and 5kW generator plus big charger to charge 300 A-hrs in an hour weighs about 700 lbs. Nope, still no major advantage.

[a64pilot]

As a lead acid battery users myself, I have to say arguing they they are “better” than Lithium is a lot like arguing that wood is a better boat building material than fiberglass.
I just don’t have that kind of money, and don’t want to have to become a lIthium expert either, so I’ll stay in my old wooden boat, but I recognize fiberglass is superior for most.
Let the early adopters find out and fix any traps, and hopefully by the time my lead dies, it’s not such a Science project, and less expensive.

[ramblinrod]

Originally Posted by a64pilot

As a lead acid battery users myself, I have to say arguing they they are “better” than Lithium is a lot like arguing that wood is a better boat building material than fiberglass.
I just don’t have that kind of money, and don’t want to have to become a lIthium expert either, so I’ll stay in my old wooden boat, but I recognize fiberglass is superior for most.
Let the early adopters find out and fix any traps, and hopefully by the time my lead dies, it’s not such a Science project, and less expensive.

If LiFePO4 were the same price, or even 50% more than FLA, I’d be tempted.

But after weighing pros and cons, I think it is about a wash. Trading one set of problems for another.

My fear is that folks are being sold on exaggerated claims of how much better they are by telling them they have substantially more usuable capacity.

From what I can tell, that’s BS if one includes a reasonable amount of reserve capacity, one really can’t really do that.

So the benefit is really how many more total a-hrs per battery for equal size and weight, one really gets.

It will also be interesting to find out how many years the average
person gets out of them.

I’ll be surprised if they live up to all the hype.

[missourisailor]

Even though I have reconfigured the current boat for a LiFePo bank ( Dual buss, RBS’s, Charge sources that are customizable..etc), I chose to go with FireFly instead.

Two main reasons:
1) Lack of reliable source for 400Ah cells. I can get 180Ah cells pretty easily. But the higher Ah cells are just not available in the US market.
This is without ordering them directly from China. Which seems to be problematic at best.
Way to many bad customer service reviews, to risk $2000+.

2) Lack of a real, marine BMS.
Most of the BMS’s are made for land based banks and/or vehicles.
Nordkyn Design ,was at one time, designing a marine specific BMS. But I have not heard from him for quite some time, so even his project seems to be dead.

FireFlys offer the same charge/discharge advantages as LiFePo’s, but from a some what more reliable, US based source.

Infact, IMHO, the only advantage that LiFePo have over FireFlys is weight and size. And since my 6ea FireFlys are occupying the same space that my 8ea LifeLines came out of , space is not really a factor.

Until the previous two issues have been resolved, it FireFlys for me.

[jkleins]

Originally Posted by ramblinrod

Hi All,



I have a fair bit of experience with FLA batteries and am trying to figure out what all the hype is about over LiFePO4.



What I have heard so far about LiFePO4 is:



Pros:



Higher energy density. How much? For a given dimension of battery case, lets say equal to a FLA Grp 27 100 A-hr battery, how many more A-hrs capacity does a LiFePO4 have?



Higher Usable Capacity. I hear people tout 80% (charge cycle from 90 - 10%).



Wait a mintute!



Shouldn't we design for 50% reserve capacity?



What if there is no sun or wind one day?



What if the girlfriends hair gets longer and she needs to run the blow drier another 5 minutes per day?



So if we design for 50% reserve capacity of 80% max capacity (so we don't hurt the battery), we're talking cycling the battery from 90-50%.



Wait a minute!



We were cycling our FLAs from 100-50%, and if on occasion we had to dip into the reserve, say to 20%, no biggy as long as we charged right back up again.



We could have design for 100% - 20% charge cycle on our FLAs too. They probably wouldn't last as long, but isn't that a fair weight/capacity trade-off?



Faster Charging: Sure, pound the Amps into that puppy.



Wait a minute!



Where are they going to come from?



The 400W wind genny and the 400 W solar panels will only deliver a high of about 30 A max.



So we are going to be forced to run ICE (Internal Combustion Engine) to gain any benefit of the fast charging capability.



Isn't the goal for most cruisers to avoid running the ICE when it isn't necessary?



Reduced Voltage Sag.



The output remains constant right down to 10% DOD.



Wait a minute!



Voltage sag is never really a problem when using a properly sized FLA bank.



So it seems the only time LifePO4 would really be a benefit if one is going to throw on a thruster, windlass, or huge inverter with heavy load, when the FLA bank is really low.



Is that the only real benefit?



CONS:



Expensive. By the time the batteries are purchased, higher output shore power and ICE charging is included. This "upgrade" will be many thousands of dollars.



Wait a minute!



Wouldn't it be a lot more economical to just use a smaller bank of FLAs with design charge cycle of 100-20%, and replace them more often?



Limited Availability. There are only a few suppliers with limited distribution channels with very limited (if any) stock at the retail level.



Wait a minute!



One can get a replacement FLA battery anywhere.



Consequence of Failure:



If something goes wrong, like the batteries get trashed by an incorrect charge or discharge incident, how much will it cost and how long will it take?



OK, I think that about sums up my thoughts.



To me, the only real benefit I see to switching from FLA to LifePO4 is the ability to say, "I have LiFePO4s".



Am I missing something?

You missed the most important pro. No PSOC issues. The ability to not worry about charging to 100% and being able to stay at 30-40% (if that is what the sun, and your motoring, and the wind gives you) is golden. It is the only reason I would go with them. I am getting the same out of Firefly right now so no urgent need but I would never go back to FLA or AGM just due to this issue.
But you knew that. [emoji3]

Jim

[jkleins]

Originally Posted by missourisailor

Infact, IMHO, the only advantage that LiFePo have over FireFlys is weight and size. And since my 6ea FireFlys are occupying the same space that my 8ea LifeLines came out of , space is not really a factor.

Until the previous two issues have been resolved, it FireFlys for me.

There is one other advantage and that is more reliable voltage. My Firefly’s do get pretty low under a good load when below 50%. It hasn’t affected me yet but I never have any critical instruments on usually during this time. LFP do seem better in this regard.

Jim

[ramblinrod]

Originally Posted by jkleins

You missed the most important pro. No PSOC issues. The ability to not worry about charging to 100% and being able to stay at 30-40% (if that is what the sun, and your motoring, and the wind gives you) is golden. It is the only reason I would go with them. I am getting the same out of Firefly right now so no urgent need but I would never go back to FLA or AGM just due to this issue.
But you knew that. [emoji3]

Jim

Good point.

Yup that is a bonus.

But if one is chronically undercharged with FLAs, it is generally cause there is something wrong with the charging system. ((Too light.)

No matter what technology, one has to be able to put back in what they take out.

[ramblinrod]

Originally Posted by jkleins

There is one other advantage and that is more reliable voltage. My Firefly’s do get pretty low under a good load when below 50%. It hasn’t affected me yet but I never have any critical instruments on usually during this time. LFP do seem better in this regard.

Jim

Thanks, but voltage sag was covered in the original post. You are correct though, far less sag with LiFePO4.