LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[Highland Fling]

Originally Posted by mcarling

The short answer is that they have incompatible voltages. One of the consequences is that if they are both fully charged and connected to each other, the lead-acid batteries (if they have enough capacity) will keep the LiFePO4 batteries above 3.4V per cell, which is likely to degrade their service life. How severe that effect would be depends on the relative capacity of the two banks. .

DON'T get that al all I stop charging my LIFePO4 ceels at 13.7V 3.425 a cell.

I am sure I could charge to 3.65 per cell 14.6V IF I wanted to get closer to the top knee which I don't want to do. I have yet to see the typcal LA boat battery that could hold 13.6V (your 3.4V per cell) for any length of time under load.

Maine Sail can tell us where the top knee is for Thundersky cells as I am sure that is what he has.

BUT from memory I think the specs say you can initially charge to 4V then 3.8V for inservice charging so that is well under your 3.4V figure.

Therefore I for one don't see any battery life problems or issues - the only one I see is why would you want to have the LIFePO4 batteries charging your LA one(s).

ME I have only kept the 8D AGM as it was a good battery and it seemed silly to bin it. Using it as the engine start battery seemed like an OK solution to keeping it on board.


LEAD IS DEAD and when the 8D AGM dies it will be binned and we will have only LIFePO4 batteries on board.

[Highland Fling]

Originally Posted by Jd1

Just keep in mind that if your BMS disconnects the LIFePO4 bank and you do not have a regular battery connected, you HAVE to insure the BMS disconnects the alternator field or else you will likely pop the alternator.

I have the LA and the LIFePO4 fed/charged via a diode block. so that is a NON issue.

IF however we go all LIFePO4 I don't really see that ocurring UNLESS we upgrade the alternator to a 200A Delco Remy 12SI model the present 60A alternator is never going to trip the HVC levels unless we were motoring for days on end.

99% of our charging is solar the rest Honda 20001 via a big old heart inverter charger.

[exMaggieDrum]

Originally Posted by Jd1

Just keep in mind that if your BMS disconnects the LIFePO4 bank and you do not have a regular battery connected, you HAVE to insure the BMS disconnects the alternator field or else you will likely pop the alternator.

And you want to disconnect the field before you disconnect the battery. Perhaps a relay could do it at exactly the same time and that would prevent blowing the alternator diodes but I would be reluctant to rely on that. That was the intent of my earlier question as to how to do that. I am leaning towards shutting off the alternator field with a relay that is tripped by the HV alarm of the BMS - but I need to dig in deeper to the BMS features and details to see if and how I could do this. I would disconnect the battery charge input circuit at the BMS HVC with a relay (or not). Putting in a LFP battery does not appear to be very KISS at this point.

[Highland Fling]

Originally Posted by exMaggieDrum

And you want to disconnect the field before you disconnect the battery. Perhaps a relay could do it at exactly the same time and that would prevent blowing the alternator diodes but I would be reluctant to rely on that. That was the intent of my earlier question as to how to do that. I am leaning towards shutting off the alternator field with a relay that is tripped by the HV alarm of the BMS - but I need to dig in deeper to the BMS features and details to see if and how I could do this. I would disconnect the battery charge input circuit at the BMS HVC with a relay (or not). Putting in a LFP battery does not appear to be very KISS at this point.

YOU CAN DO KISS.....I am not a fan of the HOUSE PRO bits the Ausie stuff is much more marine friendly......

Get back to basics you don't need fancy external alternator charging, a externally sensed alternator will do all you need and I still have that "HORRIBLE" diode charging block...yesterdays technology and bad for LA

BUT my LIFePO4 Batteeies DON'T care they love it. AND I love them even more......

BUT then IF you are not technically minded and cant sort out the wheat from the chaff (AND this is quite a task) then best get someone 'allegeldy professional' to instal your LIFePO4 batteries for you.

WE had the main charging wire snap (the connector fell off {a vibration issue I suppose} NO heatshrink over the joint) a few years ago on a 10 hour passge with no wind.....and it was only with the auto-helm saying low voltage did we find out.............

Did the alternator blow up did a diode pop....NOPE it lasted a few more years and then the internal rectification diode block nuts came loose and the voltage went carzy......did that pop the diodes NOPE....but we did replace the alternator before stripping it down to find out what the problem was.

Theory and practise don't always agree, that is not to say you should not understand the theory and possible issues of course, then decide which ones are critical to you and your mindset and try and manage your way around these 'possible' issues. Apart from the cell boards and the BMS's my system could not be much simpler and it is now one year old and counting.

[Maine Sail]

Originally Posted by exMaggieDrum

And you want to disconnect the field before you disconnect the battery. Perhaps a relay could do it at exactly the same time and that would prevent blowing the alternator diodes but I would be reluctant to rely on that. That was the intent of my earlier question as to how to do that. I am leaning towards shutting off the alternator field with a relay that is tripped by the HV alarm of the BMS - but I need to dig in deeper to the BMS features and details to see if and how I could do this. I would disconnect the battery charge input circuit at the BMS HVC with a relay (or not). Putting in a LFP battery does not appear to be very KISS at this point.

With a Balmar or Xantrex alternator regulator you cut the red B+ wire to the regulator not the blue field wire.... With an internally regulated alt you would simply tap into the brush wire and cut the field.... Ideally your HVC is set to trip before the banks main oh $hit/ejector seat relay does.

[alctel]

Does anyone have any good sources for cells in Canada? Buying stuff from the US just got real expensive

[hellosailor]

Dunno, but it seems that an "automotive" alternator with typical internal regulator is actually within acceptable parameters for a lithium battery, given the way most boats would use them. That is, often drained less than 50% d-o-d and often recharged only to around 90-95% d-o-d. The alternator will typically be putting out 14.4 volts, well under the maximum that the battery can be safely and regularly brought up to, and it will taper off the charge as the battery approaches that voltage--which will leave the lithium battery perennially undercharged, but that's apparently also the preferred charging parameter according to many sources including some of the automakers.
Is it perfect? Hell no. Is it within and similar to the optimal charging routines that a lot of the really big, well-funded, well-established companies are using for the mass market?
I'd suggest, surprisingly so.
If battery makers are suggesting vaguely a 3.6v charge for cells that are rated for 4V charge...they are in fact condoning the 14.4 volts from a typical alternator/regulator, right on the nose. As opposed to the 16 volts that their own data say are a maximum charge.


Of course the down side is that something so simple would negatively impact BMS sales and "special" status of lithium batteries.(G)

[SV THIRD DAY]

Originally Posted by hellosailor

Dunno, but it seems that an "automotive" alternator with typical internal regulator is actually within acceptable parameters for a lithium battery, given the way most boats would use them. That is, often drained less than 50% d-o-d and often recharged only to around 90-95% d-o-d. The alternator will typically be putting out 14.4 volts, well under the maximum that the battery can be safely and regularly brought up to, and it will taper off the charge as the battery approaches that voltage--which will leave the lithium battery perennially undercharged, but that's apparently also the preferred charging parameter according to many sources including some of the automakers.
Is it perfect? Hell no. Is it within and similar to the optimal charging routines that a lot of the really big, well-funded, well-established companies are using for the mass market?
I'd suggest, surprisingly so.
If battery makers are suggesting vaguely a 3.6v charge for cells that are rated for 4V charge...they are in fact condoning the 14.4 volts from a typical alternator/regulator, right on the nose. As opposed to the 16 volts that their own data say are a maximum charge.


Of course the down side is that something so simple would negatively impact BMS sales and "special" status of lithium batteries.(G)

While I agree totally the HS's view that complexity sells...

I want to give a warning about using a "standard" automotive alternator to charge these LiFePO4 batteries. In short you should really have a high output alternator and then de-rate it with your alternator regulator. Otherwise you will be burning through alternators like candy out of a Pez dispenser. I don't care what brand of alternator you use they are not built for their full load output for anything more than 15-30minutes.

I'm living on a Mooring at the moment and besides motoring to the pump out dock once a week I have not been charging with my alternator, but I know that if I was motoring more frequently I would need to do something to keep my 100A alternator from melting down....

[exMaggieDrum]

Originally Posted by Highland Fling

YOU CAN DO KISS.....I am not a fan of the HOUSE PRO bits the Ausie stuff is much more marine friendly......

Get back to basics you don't need fancy external alternator charging, a externally sensed alternator will do all you need and I still have that "HORRIBLE" diode charging block...yesterdays technology and bad for LA

BUT my LIFePO4 Batteeies DON'T care they love it. AND I love them even more......

BUT then IF you are not technically minded and cant sort out the wheat from the chaff (AND this is quite a task) then best get someone 'allegeldy professional' to instal your LIFePO4 batteries for you.

WE had the main charging wire snap (the connector fell off {a vibration issue I suppose} NO heatshrink over the joint) a few years ago on a 10 hour passge with no wind.....and it was only with the auto-helm saying low voltage did we find out.............

Did the alternator blow up did a diode pop....NOPE it lasted a few more years and then the internal rectification diode block nuts came loose and the voltage went carzy......did that pop the diodes NOPE....but we did replace the alternator before stripping it down to find out what the problem was.

Theory and practise don't always agree, that is not to say you should not understand the theory and possible issues of course, then decide which ones are critical to you and your mindset and try and manage your way around these 'possible' issues. Apart from the cell boards and the BMS's my system could not be much simpler and it is now one year old and counting.

David, many thanks for your thoughts and philosophy. I agree with you on KISS. I am trying to sort out the wheat from the chaff. There are several opinions about all this and it will be up to me to make decisions based on what I know, or imagine. It seems many LFP adopters have forgone the solenoids and relays to turn off the battery ins and outs for LVC and HVC. I'm still learning from all of you. If I plunk down US$2400 for new batteries (plus US$xxx for other gear) I want to keep them alive without going overboard on it all. If it is too hard to figure out it is too hard to monitor and manage. But looks to me that all is doable right at the moment, and I trust myself to get it approximately right in the end. Thanks to all.

Joe

[exMaggieDrum]

Originally Posted by Maine Sail

With a Balmar or Xantrex alternator regulator you cut the red B+ wire to the regulator not the blue field wire.... With an internally regulated alt you would simply tap into the brush wire and cut the field.... Ideally your HVC is set to trip before the banks main oh $hit/ejector seat relay does.

Thanks Maine Sail. In all the boat systems I have worked on I have never had a reason to disconnect an alternator while the engine was running for any purpose. I have seen, but never designed in, 1-2-3-All switches with a field disconnect feature to prevent potential problems by manually turning off the batteries under charge. I like having the alternators going to the house with separate switches to all batteries.....as you do.

So it had not occurred to me that the B+ wire to the regulator would be a better place to discontinue the field to an alternator, e.g. a Balmar 612 or 614 regulator. I can see that would work. The user/install manual does not even bring that up. I have a new 614 that I have not yet installed for my system upgrade.

I just took another look at the House Power BMS manual and circuit diagrams. I initially expected to find a separate circuit for HV alarm and LV alarm, in addition to the HVC and LVC cutoff leads. I am going to go back and reread/study your thoughts and musings on your website and the BMS instructions and make sure I understand what is there. My question is how to do the final Oh S**t battery shut off on the charging side after the HVC alarm has already been tripped and the alternator shut down from the relay there. I'll look more and see if I missed something about how to determine a HVE or a LVE after the HVC/LVC levels have been reached and what was suggested as to how to trip a main cable battery disconnect.

[Highland Fling]

Originally Posted by SV THIRD DAY

While I agree totally the HS's view that complexity sells...

I want to give a warning about using a "standard" automotive alternator to charge these LiFePO4 batteries. In short you should really have a high output alternator and then de-rate it with your alternator regulator. Otherwise you will be burning through alternators like candy out of a Pez dispenser. I don't care what brand of alternator you use they are not built for their full load output for anything more than 15-30minutes.

Alternators dont give full load (max output) for more than a few minutes this is the same warning that we heard when AGMs were going to drive our alternators crazy sucking every last amp out of them.

After almost a year with a massive 600AH LIFePO4 house bank my alternator is fine not even too hot to hold after 45 minutes of motoring.

We have a French METO AMBER WARNING here for nothern facing anchorages BIG BIG Swells from a dirstubance up in Florida. So we moved into the Lagoon at Marigot that took 45 or so minutes of motoring to get down to our fave spot......at the end of that wee trip our 60A alternator was outputting 39A with an under charge house bank voltage of 13.46V.....now with only lights and the F/F running it sitting at its 'normal' 13.22V.

[SV THIRD DAY]

Originally Posted by Highland Fling

at the end of that wee trip our 60A alternator was outputting 39A with an under charge house bank voltage of 13.46V.....now with only lights and the F/F running it sitting at its 'normal' 13.22V.

Your alternator was at 1/2 load right...39A out of a 60A alternator.
So I wouldn't expect it to have a problem there.
From your voltages it looks like you tweaked down the voltage of the reg already? Maybe I'm confused (which happens easily) or just missing something. When my 400AH LiFePO4 bank is down on charge, my 100A alternator with will run at 100A until it drags the voltage up or until it melts down, which ever comes first. But of course if you dial down your alt regulator to a lower voltage set-point that will save that from happening. The caution is using an alternator with the standard internal regulator...I've only seen 5 Alternator melts downs with the folks I know that have LiFePO4 batteries...but being my friends maybe there were bozos like I am....who knows....?

[hellosailor]

If you out an external regulator on an unprotected alternator, you don't have a typical marine installation. You may have a more proper one--but it isn't typical. The typical mass-market installation uses a conventional automotive alternator with a fixed internal regulator, and TYPICALLY there is no overheat protection involved. The "alternator" (meaning, alternator with internal regulator) protects itself against overheat simply by ramping down the output as the battery voltage rises. Of course, all you have to do is add a second battery, or a bigger battery, and pull more than an SLI load from it, and you may find the voltage rising slowly enough to damage the alternator, yes.


Which is why the better automotive regulators actually DO have internal thermal protection, and if the engine bay is too hot, or the ambient temperature too hot, or the radiator and fan are blocked off...for whatever reason, they will throttle back their output to reduce their operating temperature. No, I have no idea which ones do this, there are hundreds if not thousands of designs on the market and the makers keep creating new ones.
In fact, simply installing an automotive regular in a boat's engine bay, without the massive cooling air from the front grill and big fan, would violate the manufacturer's recommendations unless there was some other means of positive airflow, wouldn't it? Regardless of the battery and regulator.


Just saying, there are situations which are not perfect, which are anything but ideal, but which are "good enough for government work".


Oh, you should hear a proper German Volkswagen mechanic throw a truly ballistic fit upon finding out that someone dared to replace a broken throttle cable with a piece of picture hanging wire, and then continue to USE IT THAT WAY for almost a year.


But as Galileo supposedly said, "Nevertheless, it turns."


Ever see a picture of a B17 or a "Warthog" shot full of holes, looking like a pile of scrap metal, that still managed to bring everyone home in one piece? Right, damn few aircraft are built that way, but somehow, a lot of folks accept lesser standards. And the fact that they usually work "good enough for government work".

[NahanniV]

I don't think thermal protection in internal alternator regulators is uncommon at all.

All these ones have some form of thermal protection:
Alternator Regulators - STMicroelectronics

Abd these:
Alternator Regulator - Infineon Technologies

Could you point out a particular internal regulator that has no thermal protection ?

It's a little more difficult in external regulators.

What kind of failures are you seeing Rich ?

Cheers,
JM.

[hellosailor]

"Could you point out a particular internal regulator that has no thermal protection ?"
Can you find a single alternator (remember, I've been clear to say this is about automotive alternators with internal regulators) where the shop manual shows, or even mentions, that there IS such a component? In how many of their hundreds of models?


Those companies you mention may MAKE such parts, but now let's get back to the real world. Does Delphi (which spun off the Delcos), or Leece-Neville, or Hitachi, or Denso, built in such a component?


Maybe nowadays they do, but I'd never heard of it being done. In their conventional mass-market installation, there simply was no cost justification for it.


There could be an elephant on the pool table, but you'll have to show me more than some lumps under the green felt.