LiFePO4 vs FLA - The Real Deal

[CatNewBee]

Lets stick to the car thing. Pick Up trucks and 4WD vehicles are for farmers, no one urban person need their features off road, but the US americans love them and drive them to the next Mc Donalds drive through and the shopping mall. Are they worth the money in this use case? I doubt it. On a farm, definitely, if you have to transport bulky stuff off road. But in the city? They are robust workhorses, no doubt about it, and they burn a lot of fuel.

So what, no Lamborghini, but completely out of place and people buy them, they are not cheap either.

Same for lithium, they have huge benefits for those people that appeciate them. Others may not understand or value them adequately.

There are so many obsolete things around people spent money on, like 3000$ mountain bikes in the city, iPhones an iPads, sneakers of a specific brand, you name it.

The buyer decides finally if a product is worth buying for the asking price.

For many it is, some want them, but cannot afford them, and some even neglect them, because they cannot afford them, secretly craving for, and others just not need them.

I am happy with my 6 years old android phone, i would not buy an Apple product anyway, nor spend money on a newer Android as long as the old one makes calls. I do understand you that you like your FLA and stick to them.

[daletournier]

"Same for lithium, they have huge benefits for those people that appeciate them. Others may not understand or value them adequately"

This is not correct, they have huge benefits for some that appreciate them but only small benefits for others that also appreciate them.

It depends on your usage and needs. It's not a matter of others not understanding them or appreciating them, it's how much extra value one gets over his current system. Some of us have very adequate and simple Fla systems that more than adequately cover their needs. Sometimes the "law of diminishing returns" comes into play.

Are LFP better? Yes, do they add much value above what I already have? No, not much.



Most of us here fully understand

[44'cruisingcat]

Originally Posted by ramblinrod

If one prefers solar and wind charging when available, the benefit of faster LiFEPO4 charge rate via alternator may be negligible.

In fact, the charge rate may be identical (alternator max output) over the charge cycle except the last 20%.

Simple solution, charge fully with wind and solar, whenever possible (and it usually will be using the ratios of charge sources I posted).

On rare occasions where it is not possible to charge fully via wind and solar, charge up to 80% SOC with the alternator early in the day, so the wind and solar that is available will charge the last 20% over the course of the day.

In reality, this will result in the same amount of ICE charging regardless of technology.


.

I'm sure you know this is completely wrong.

With lithiums you dont need to run the generator to fast charge for the first 80% of the charge cycle to allow for the slowness of the last 20%.

With LA you do.

Even better, with lithiums you dont even need to worry about getting that last 20% done.

With LA, you know that going to bed with the batteries at 80% is going to hurt them down the line. With lithiums it's no problem.

[newhaul]

Originally Posted by 44'cruisingcat

I'm sure you know this is completely wrong.

With lithiums you dont need to run the generator to fast charge for the first 80% of the charge cycle to allow for the slowness of the last 20%.

With LA you do.

Even better, with lithiums you dont even need to worry about getting that last 20% done.

With LA, you know that going to bed with the batteries at 80% is going to hurt them down the line. With lithiums it's no problem.

this is the part Rod doesn't seem to grasp
But to each his own.

[thinwater]

Originally Posted by john61ct

LFP's temperature compensation coefficient is so close to 1.0 I just disable that feature.

Most charge regulators don't even let you adjust it that finely anyway.

But if you have links to specs for the precise coefficient for the leading manufacturers, I'd like to check it out.

Obviously temperature **protection** is critical, but that's a very different topic.

http://www.cruisersforum.com/forums/...ge-206438.html


It's not that the coefficient is huge, but it is very important to batteries that require accurate charging voltages. We're talking about ~ 0.3V-0.5V different.

[thinwater]

Originally Posted by newhaul

this is the part Rod doesn't seem to grasp
But to each his own.

I'm pretty sure he grasps more than he's sayin' and you are rising to the bait. I'm also pretty sure everyone on this thread understand the concepts. They just value them differently.

[Dockhead]

Peace, guys


The premise of this thread ignores the great differences between different cruisers' use cases, and seems to want to say that there is only one right choice, which only smart people see.


This is just not true. Lead and lithium have different advantages and drawbacks and suit different use cases differently. People have different needs and different priorities. If lithium is the future, still lead is not dead yet, and lithium isn't fully developed, but for SOME cruisers there are huge advantages in lithium even at today's state of development. For others there's no point at all. Why do we want to impose our own choices and use cases, on others?


I'm debating switching to lithium myself, and for my particular use case, there is no clear answer. If I had space in my boat for a single bank of heavy duty FLA batteries with the capacity I need, I don't think I would be looking at lithium. But I don't -- my battery spaces are divided into two. If I had 1000 watts of solar, I don't think I would be looking at lithium -- but I don't, and have no place to put it which would not create unacceptable (to me and my own particular use case, which lately involves 1000 miles or more of upwind sailing every year) compromises to upwind sailing ability.



It's not correct to make all these blanket statements, either one way or the other. Even the idea of the "50% reserve" -- where did that come from? Who said? 50% of what? Some people might need that, but most people certainly not. Just as an example, I have 3 battery banks and two sources of high current charging on board, including a heavy duty, prime power rated generator. What do I need ANY reserve capacity for? Others for whom running the batteries down could be a problem -- say if you're on pure solar and have no heavy duty alternator, or no main engine at all -- might well need reserve capacity. And what are you calling "reserve capacity", anyway? You can't say arbitrarily what's reserve, and what's not without analyzing the particular use pattern of the particular cruiser, and the total capacity of the bank.



Some people hardly spend more than a weekend at a time off shore power; others spend months at a time or don't even have a shore power cord. Some people use a ton of electrical power on board; others hardly any. On top of that, people have different budgets. All these cases demand different solutions.



It's pointless criticizing each other's choices, when they are based on different use cases.





Interestingly, hardly anyone discusses using BOTH lead and lithium. For my particular use case, which is probably pretty unusual since it includes having two geographically separated battery compartments, a hybrid system could make a lot of sense. One of the biggest problems of lead is getting the finishing charge on if you have no solar and spend months at a time off grid, with only a generator to charge them. It's a huge waste of generator hours to keep running it half the day to get the last bit of charge into a lead bank. But if you have your capacity split between lead and lithium, you can easily do the finishing charge for the lead from the lithium bank. So the lead will get an absolutely ideal charging regime, which means it will work better, last much longer, and cause a lot less headache for the operator of a boat off shore power and without solar. At the same time, the lead solves a fundamental problem for the lithium, which is how to protect the alternator and other components, and how to be sure to have power to critical systems, in case the BMS makes an automatic decision to cut the charging source or loads.



So there might even be a third choice, which could be the right one for SOME use cases -- BOTH.

[john61ct]

Originally Posted by thinwater

http://www.cruisersforum.com/forums/...ge-206438.html


It's not that the coefficient is huge, but it is very important to batteries that require accurate charging voltages. We're talking about ~ 0.3V-0.5V different.

That thread has no mention of temp comp while charging.

I believe you've got your wires crossed.

As I mentioned I would be happy to read specific hard data from authoritative sources.

All the ones I know very clearly state to disable the temperature compensation feature on charge sources with that feature.

[newhaul]

Originally Posted by thinwater

http://www.cruisersforum.com/forums/...ge-206438.html


It's not that the coefficient is huge, but it is very important to batteries that require accurate charging voltages. We're talking about ~ 0.3V-0.5V different.

here is what I got for t105's
https://www.google.com/url?sa=t&sour...Voynp7Jbl-LjmG
Its not much of a difference so it seems it wouldn't make a difference in the real world.

[john61ct]

thinwater was asking about temp comp for LFP

[newhaul]

This is a rather interesting item I found
Useable energy and cost

It is generally accepted that the most economic and practical depth of discharge (DOD) for an AGM battery is 50%. For Lithium-iron-phosphate (LiFePO4 or LFP) which is the safest of the mainstream Li-ion battery types, 80% DOD is used.

How does this work out in the real world? Let’s take two Victron 24V battery examples and compare useable energy for a small yacht:

1 x Victron Lithium-ion 24 V 180 Ah
The nominal voltage of the LFP cell is 3.3 V. This 26.4 V LFP battery consists of 8 cells connected in series with a 180 Ah rating. The available energy is 26.4 x 180 = 4. 75 kWh. Useable energy is 26.4 x 180 x 0.80 = 3.8 kWh.

2 x Victron AGM 12 V 220 Ah
The nominal voltage of the lead-acid cell is 2.0 V/cell. Each 12 V monobloc battery consists of 6 cells connected in series with a 220 Ah rating. Connecting 2 x 12 V 220 Ah batteries in series to give 24V and 220 Ah, the available energy is 24.0 x 220 = 5.28 kWh. Useable energy is 24 x 220 x 0.50 = 2.64 kWh.

This begs the question, what Ah rating of AGM batteries would be the equivalent of the 3.8 kWh useable energy of the Lithium-ion battery? To get 3.8 kWh of useable energy from an AGM battery it would need to be twice that size to start with due to the 50% DOD economy rule i.e. 3.8 x 2 = 7.6 kWh. At 24V that would mean 7,600/24 which gives us a battery rating of 316.66 Ah, which is moving closer to twice the rated capacity of the Lithium-ion 24 V 180 Ah. Note this does not take into account, the ageing of the batteries, temperature derating or the effect of higher loads. For AGM batteries, higher loads have a greater effect than on Lithium. See the section – Useable energy: effect on discharge capacity and voltage with differing loads, below. Based on all this it is reasonable to say that an AGM battery will need to be twice the Ah rating of a Lithium one.

From https://www.victronenergy.com/blog/2...um-ion-vs-agm/
Where it also mentions temperature compensation for the agm but not for the Lfp.

[thinwater]

Originally Posted by john61ct

That thread has no mention of temp comp while charging.

I believe you've got your wires crossed.

As I mentioned I would be happy to read specific hard data from authoritative sources.

All the ones I know very clearly state to disable the temperature compensation feature on charge sources with that feature.

I would love to see good data too. That is EXACTLY why I started that thread.



The temperature thing is boiled into the physical chemistry of batteries and there is no way around it. I suspect it is simply less than LA and it is being overlooked, since very, very few sailors are interested in Li in cold temperatures. That is really a small subset... but I'm in that subset. There is also data that shows that over charging is specifically damaging to Li batteries, far more so than LA. And thus...



From what I'm reading, charging Li below freezing is a dodgy area, and yet my boat (and many others) will it at dock in those conditions for months. I also cruise some in the winter.

[CatNewBee]

@Dockhead...

regarding LFP and alternator and BMS....

One fact is, LFP can absorb much more current, and this puts more / longer high load on the alternator, usually the alternators are designed to re-charge a start battery after cranking the engine and provide some Amps for the bord electric system, like lights, fans, fuel pump etc.

They are not meant to charge empty house banks of any chemistry. The regulators are set to 14.2V, safe for lithium, the BMS would cut-off at 15+ Volt according to the specs, they can be charged up to 4V per cell, so 16V is the upper limit, however this is not good for long lasting batteries, LFP are fully charged at 3.65V, what is 14.6V in a 4 cell system.

A FLA battery has a higher inner resistance, so the voltage rises quicker than the voltage of a LFP, BUT, LFP has in general a higher cell voltage, so the battery rarely drops below 13.4V, the voltage difference is not so high to the alternator output to draw too much current on startup as with FLA.

So a properly working alternator will never turn off the BMS, also in most installs, there is a small AGM start battery per engine, it will remain connected in case the BMS cuts off (e.g. because of temp issues or out of balance drifted cells), so again no problem for the alternator.

You can overload the alternator with a empty FLA bank of a significant size too, LFP is not the sole problem for dying alternators anyway, but often blamed for it.

In most cases it is just coincidence, your system comes to age, yor FLA were dying maybe the second time and you are sick of investing again in an old technology, the alternator brushes are wearing out in the mean time, then you drop in fresh LFP batteries eventually with a higher capacity and the alternator just degrades faster and needs a service / replacement.

[a64pilot]

Dockhead,
In your case I’m still thinking that a fuel call and LA make sense, the generator can hammer in the amps when the bank can take it, and the fuel cell dribble it in after the acceptance rate drops, just it requires a fuel cell that can handle the house load, and have room left over to top off the batteries.
Same if you use a Lithium bank to finish charge, and I take it, your house loads are large.

[CatNewBee]

Originally Posted by a64pilot

Dockhead,
In your case I’m still thinking that a fuel call and LA make sense, the generator can hammer in the amps when the bank can take it, and the fuel cell dribble it in after the acceptance rate drops, just it requires a fuel cell that can handle the house load, and have room left over to top off the batteries.
Same if you use a Lithium bank to finish charge, and I take it, your house loads are large.

There are fuel cells running on methanol out there, a waste product of moonshining on the first few litres...

This gives this thread a surprising turn I guess... [emoji12]