Alternator Size with LiFePo4

[nebster]

For what it's worth, I am floating at 3.375 and I see the pack stabilizing to zero current at around 65-68% SOC in this configuration.

My float value is measured at the bus bar, not the terminals, and I may have as much as 50mV of measurement inaccuracy as well, both of which could be enough to matter. (One day I need to pop the compartment and put the Fluke on the terminals when floated and see what we get.)

[tanglewood]

Originally Posted by nebster

For what it's worth, I am floating at 3.375 and I see the pack stabilizing to zero current at around 65-68% SOC in this configuration.

My float value is measured at the bus bar, not the terminals, and I may have as much as 50mV of measurement inaccuracy as well, both of which could be enough to matter. (One day I need to pop the compartment and put the Fluke on the terminals when floated and see what we get.)

Great data point. Who's cells? Not sure it matters, but just for completeness.

[kmacdonald]

Originally Posted by rgleason

A gentle reminder to all folks, this thread is about "Alternator Size with LiFePo4". It appears FLA and Equalization is taking over this thread in a huge thread contamination.

Little if any of the posts in this thread address alternator size for LiFePO4. It mainly consists of WAG's and inaccurate, incoherent babble. If you need to ask a forum what size alternator you need, you certainly aren't a candidate for LiFePO4. Most if successful LiFePO4 installs start with individuals taking the initiative to research the issues adequately to form their own decisions based on their own needs. Spoon feeding from an open forum won't deliver good results.

[Q Xopa]

Originally Posted by kmacdonald

Little if any of the posts in this thread address alternator size for LiFePO4. It mainly consists of WAG's and inaccurate, incoherent babble. If you need to ask a forum what size alternator you need, you certainly aren't a candidate for LiFePO4. Most if successful LiFePO4 installs start with individuals taking the initiative to research the issues adequately to form their own decisions based on their own needs. Spoon feeding from an open forum won't deliver good results.

Woooha, thats quite an extreme reaction.
Perhaps you could enlighten us ignorant forum participants what you're purpose for the forum and post is?
Im at a bit of a loss to see what positve contribution your post is.
Im sure like many, I am here to learn. I certainly dont know it all like it sounds like you do.
Yes there is a lot of chaf, in between scatterd gems.
I dont know how you, or anyone can know about a subject without learning from others. Perhaps you are more gifted than the rest of us.
Thanks for your contribution.

[kmacdonald]

Originally Posted by Q Xopa

Woooha, thats quite an extreme reaction.
Perhaps you could enlighten us ignorant forum participants what you're purpose for the forum and post is?
Im at a bit of a loss to see what positve contribution your post is.
Im sure like many, I am here to learn. I certainly dont know it all like it sounds like you do.
Yes there is a lot of chaf, in between scatterd gems.
I dont know how you, or anyone can know about a subject without learning from others. Perhaps you are more gifted than the rest of us.
Thanks for your contribution.

You're welcome.

It was an attempt to lead capable and interested parties to search out information from reliable sources. This being one of the most reliable:Lithium Battery Systems | Nordkyn Design
MaineSail also has excellent information on his site.

[newhaul]

Originally Posted by kmacdonald

You're welcome.

It was an attempt to lead capable and interested parties to search out information from reliable sources. This being one of the most reliable:Lithium Battery Systems | Nordkyn Design
MaineSail also has excellent information on his site.

and if you hadn't noticed rod is rather active in this thread as well

Also I have learned from this thread that my 65 amp alternator is to big for charging my Lfp bank wrt the correlation between C rates and longevity

[Q Xopa]

Originally Posted by kmacdonald

You're welcome.

It was an attempt to lead capable and interested parties to search out information from reliable sources. This being one of the most reliable:Lithium Battery Systems | Nordkyn Design
MaineSail also has excellent information on his site.

Appologies for misreading your intent as 'condecending'. Im obviously a bit slow on the uptake. You perhaps should have just mentioned those sources directly, my bad.

Agreed that these are both excellent resources. However are you saying they are the only ones with anything to contribute? They are not the be all, end all.

Im pretty sure most of the contributers here have actually read them. I know I have, but like I assume most here, I want to be informed as I can. My guess is you might even be here for the same reason?

However since they were written some more up to date things have also been and continue to be added to the collective knowledge base. MS, you reference, regularily contributes here with some of his new information, and also tries to steer some people back that wander off on tangents.

Keep up the good work.

Cheers.

[CatNewBee]

Originally Posted by newhaul

and if you hadn't noticed rod is rather active in this thread as well

Also I have learned from this thread that my 65 amp alternator is to big for charging my Lfp bank wrt the correlation between C rates and longevity

What battery size do you have? LFP with less than 65Ah?

There is no such thing TOO BIG for LFP. Do you have a mobile phone? It has a LiPo battery. Do you think a nuclear power plant is too big to charge it?

Anyway. The size of the alternator does not matter. What matters is the quality of the regulator and the protection of both alternator and battery, e.g. by an adequate charge controller.

The C-Rate control is subject to the regulator and/or charge controller, LFP batteries are recommended to be charged continuously at 0.5C, and the alternator rarely outputs the nominal current, it does so at a specific high RPM, also there are other loads connected, so you cannot expect it to deliver 65A all the time, charging current will be probably in the 40es, also there is usually an overheat protection that may limit the current and the voltage drop comes also into play, the current is also limited by the voltage difference between battery and alternator output. You can safely charge any LFP battery with the right regulator. A LFP can be charged even with 1C continuously and short time with up to 3C btw.

The main concern of LFP batteries and alternators is, that cheap automotive alternators do not have sufficient heat protection and over current protection, they are designed to charge a 65Ah LA start battery and some headlights. A big LFP bank can easily overwhelm them and the result are burned coils, rectifiers etc.

[kmacdonald]

IMHO we are looking to use the wrong lithium battery chemistry. LiFePO4 won't make it through the sieve. Their properties vary too much from battery to battery and don't have the energy density of other chemistries. We will end up having to adopt whatever chemistry the EV car industry uses even though they may not be optimal for our particular use profile. Several marine providers have already figured this out. I guess time will tell with Trojans entry into lithium. They seem to be proceeding very cautiously though, as if unsure of the product.

[kmacdonald]

Watch the Battery Energy Storage Systems (BESS) market for more info. Electric utilities are starting to use the technology for peak demand periods. It is one reason why the price of lithium batteries has been slow to come down----the demand is rapidly rising and capacity hasn't kept pace.

[tanglewood]

Originally Posted by kmacdonald

IMHO we are looking to use the wrong lithium battery chemistry. LiFePO4 won't make it through the sieve. Their properties vary too much from battery to battery and don't have the energy density of other chemistries. We will end up having to adopt whatever chemistry the EV car industry uses even though they may not be optimal for our particular use profile. Several marine providers have already figured this out. I guess time will tell with Trojans entry into lithium. They seem to be proceeding very cautiously though, as if unsure of the product.

I don't really agree. I do agree with your implication that the majority market gets to write the rules, and in this case that's likely EVs. But I don't agree that we will all end up with one chemistry, driven by EVs. Just look at the diversity of chemistries today, and not because of rapid development. NiCad and NiMHi are still abundant, as of course is LA. All have their place and fit, apparently enough so to create a viable market for them.


As for power density, that matters a lot in many applications, but matters very little in others, including boating (other than perhaps competitive racing). Yet in boats, fire protection is paramount, and LFP has much better characteristics compared to other Li chemistries. I'll take fire protection over power density any day. I personally think that NMC and some others have no place on a boat, and am quite surprised that some vendors are pushing them. If a car starts to smoulder and catch fire, you can pull over, get out, and walk away. No so much with a boat...


And I'm not sure where you are seeing wide variation in properties between vendors. I've seen just the opposite.


As for Trojan and other "drop-in" vendors, I think they are smart to go slow. Many of us think there are one or more train wrecks waiting to happen with such products. I only hope they have a net positive on the overall market, rather than tarnishing it.

[newhaul]

Originally Posted by CatNewBee

What battery size do you have? LFP with less than 65Ah?

There is no such thing TOO BIG for LFP. Do you have a mobile phone? It has a LiPo battery. Do you think a nuclear power plant is too big to charge it?

Anyway. The size of the alternator does not matter. What matters is the quality of the regulator and the protection of both alternator and battery, e.g. by an adequate charge controller.

The C-Rate control is subject to the regulator and/or charge controller, LFP batteries are recommended to be charged continuously at 0.5C, and the alternator rarely outputs the nominal current, it does so at a specific high RPM, also there are other loads connected, so you cannot expect it to deliver 65A all the time, charging current will be probably in the 40es, also there is usually an overheat protection that may limit the current and the voltage drop comes also into play, the current is also limited by the voltage difference between battery and alternator output. You can safely charge any LFP battery with the right regulator. A LFP can be charged even with 1C continuously and short time with up to 3C btw.

The main concern of LFP batteries and alternators is, that cheap automotive alternators do not have sufficient heat protection and over current protection, they are designed to charge a 65Ah LA start battery and some headlights. A big LFP bank can easily overwhelm them and the result are burned coils, rectifiers etc.

I am running 100ah lfp and the general consensus is the optimum charge rate for longevity is between .2C and .3C
My primary charge sources are my 400w solar and or my 400w wind.
Now my battery specs call for .5C with burst up to 5.0C however I'm talking about longevity charging C rates not absolute rates.

[kmacdonald]

Originally Posted by tanglewood

As for Trojan and other "drop-in" vendors, I think they are smart to go slow. Many of us think there are one or more train wrecks waiting to happen with such products. I only hope they have a net positive on the overall market, rather than tarnishing it.

LiFePO4 has been available for a LONG time. Most vendors of marine battery systems using that technology have gone out of business or stopped selling it or support for it. I don't know if Trojan will be the needed life support for marine LiFePO4 or not but the odds a against it. Even Boeing failed on it's first feeble attempt with lithium. (different chemistry that LiFePO4) On paper LiFePO4 looks like a marine battery dream come true but has turned into a nightmare for many.

[rgleason]

Newhaul:
The 62% of banks total capacity is really from me, using 20%SoC as the lowest which is xx vpc and highest voltage 13.88v (3.47vpc) using a charge rate of 0.35C.
and the charge curve from the Lund Co Powermiser website that I linked to.

The 7000 cycles is just from winston battery specs and John suggesting to use that as the bottom. Should I be using cell voltage?

In your experience actually using LiFePo4 what do use as top and bottom and what are the SoC?
And what do you think is the no cycles?

[tanglewood]

Originally Posted by kmacdonald

LiFePO4 has been available for a LONG time. Most vendors of marine battery systems using that technology have gone out of business or stopped selling it or support for it. I don't know if Trojan will be the needed life support for marine LiFePO4 or not but the odds a against it. Even Boeing failed on it's first feeble attempt with lithium. (different chemistry that LiFePO4) On paper LiFePO4 looks like a marine battery dream come true but has turned into a nightmare for many.

I’m still not seeing it. Victron, Lithionics, and Mastervolt all seem to be growing and likely here to stay. Lots of little garage shops have failed, but I’ve seen nothing to suggest it was because or their choice of LFP over other variants. And Battleborn seems to be getting some traction in the drop-in market.

Just curious, what marine vendors started with LFP and have dropped it for something else?