LFP FLA hybrid

[Qayaq]

Really, 80 amp windlass use 2 minutes = 2.6amps... I think.. Its not constant ,think you are going to find your fridge is going to use more in a day than your windlass

[mbartosch]

Originally Posted by Dockhead

My own case is unusual in that my boat is already configured with two banks, with technical loads connected to one (thruster, windlass, winches) and house loads to the other. If I go with a hybrid system, I would put the lithium in the technical load box, regulate the alternator for lithium, and connect it to the lithium bank, and charge the house bank with a B2B charger. That solves the problem of how to keep essential equipment working through a LVC event, but it leaves the issue of what to do to protect the alternator from a HVC event, but this can be done with other devices, such as the Sterling Alternator Lineariser.

A proper HVC on an alternator is quite easy. Field current to alternator goes through the NC contact of a standard 12 V automotive relay. This relay is then responsible for the HVC cutoff of the alternator and can be wired accordingly. If you are using a Balmar regulator it is recommended to interrupt the power supply to the regulator (which powers the field coil).

[john61ct]

Originally Posted by Dockhead

It is strongly not recommended to use HVC to regulate charging, in any case.

If you mean that there should be a multiple layered defence, and the protective final-level BMS should not be the daily-use mechanism to stop charging, I agree.

But my daily-use charging spec is "climb to 3.45Vpc then just stop"

That could mean "stop the charge source", or maybe "isolate the bank and let the charge source continue charging lead and/or carrying loads."

I see no need to duplicate charge sources of the same type, and works with an alt in either case.


> That might be a good way to do it if you have your loads connected to the lithium bank. But then you have the issue of what to do if the loads get disconnected by a LVC event.

Have that event "direct load" to the lead, rather than just isolate the LFP.

[Dockhead]

Originally Posted by john61ct

If you mean that there should be a multiple layered defence, and the protective final-level BMS should not be the daily-use mechanism to stop charging, I agree.

But my daily-use charging spec is "climb to 3.45Vpc then just stop"

That could mean "stop the charge source", or maybe "isolate the bank and let the charge source continue charging lead and/or carrying loads."

I see no need to duplicate charge sources of the same type, and works with an alt in either case.


> That might be a good way to do it if you have your loads connected to the lithium bank. But then you have the issue of what to do if the loads get disconnected by a LVC event.

Have that event "direct load" to the lead, rather than just isolate the LFP.

You touch on two different issues here --


One is control of charge source, to prevent over-charging.


I don't know who it was that explained it to me, but I found utterly convincing that the HVC should be left as an emergency fail safe device.



The other is alternator protection. Yes, of course, the easy way is to just leave the alternator connected to some kind of lead battery. If you have a starter battery of same voltage as your house bank, then that's a really easy way to do it. But some people will have trouble with this -- like me. So we explore other ways to deal with it, and there are other ways.

[Dockhead]

Originally Posted by john61ct

If you mean that there should be a multiple layered defence, and the protective final-level BMS should not be the daily-use mechanism to stop charging, I agree.

But my daily-use charging spec is "climb to 3.45Vpc then just stop"

That could mean "stop the charge source", or maybe "isolate the bank and let the charge source continue charging lead and/or carrying loads."

I see no need to duplicate charge sources of the same type, and works with an alt in either case.


> That might be a good way to do it if you have your loads connected to the lithium bank. But then you have the issue of what to do if the loads get disconnected by a LVC event.

Have that event "direct load" to the lead, rather than just isolate the LFP.

You touch on two different issues here --


One is control of charge source, to prevent over-charging.


I don't know who it was that explained it to me, but I found utterly convincing that the HVC should be left as an emergency fail safe device.



The other is alternator protection. Yes, of course, the easy way is to just leave the alternator connected to some kind of lead battery. If you have a starter battery of same voltage as your house bank, then that's a really easy way to do it. But some people will have trouble with this -- like me. So we explore other ways to deal with it, and there are other ways.

[Qayaq]

Originally Posted by Dockhead

Well, you should read back through this and other threads on the subject. We have gone into all of these issues, and there are some very knowledgeable people providing very useful information.



It is strongly not recommended to use HVC to regulate charging, in any case.


In my opinion, it is not possible to charge and discharge lead and lithium connected together, whatever diodes or other devices you have between them, and get a reasonable charging regime which suits both of them. Their needs are just totally different, and not only what regards voltage.


I think a hybrid bank will need to have entirely separated charging systems. It's dead simple to have separate AC chargers, so that part of it is no challenge, but what you do with the alternator is a puzzle.


If you put the alternator on the lead bank, then you solve the issue of protecting the alternator from a HVC event, and you can charge the lithium with a B2B charger. So you regulate the alternator to give the lead what it wants and both banks get an ideal charging regime. That might be a good way to do it if you have your loads connected to the lithium bank. But then you have the issue of what to do if the loads get disconnected by a LVC event.


My own case is unusual in that my boat is already configured with two banks, with technical loads connected to one (thruster, windlass, winches) and house loads to the other. If I go with a hybrid system, I would put the lithium in the technical load box, regulate the alternator for lithium, and connect it to the lithium bank, and charge the house bank with a B2B charger. That solves the problem of how to keep essential equipment working through a LVC event, but it leaves the issue of what to do to protect the alternator from a HVC event, but this can be done with other devices, such as the Sterling Alternator Lineariser.

Well, you should read back through this and other threads on the subject. We have gone into all of these issues, and there are some very knowledgeable people providing very useful information.

Yep Have read those and a lot more besides, not totally convinced with the arguments put forward.

It is strongly not recommended to use HVC to regulate charging, in any case.

Think there is a reasoned argument that LFP like constant current until they hit HV knee and then the charge totally removed, may sound silly but that sounds a lot like an HVC to me.

In my opinion, it is not possible to charge and discharge lead and lithium connected together, whatever diodes or other devices you have between them, and get a reasonable charging regime which suits both of them. Their needs are just totally different, and not only what regards voltage.

Yes totally in agreement with that, my plan at the moment is going to boil my FLAs, need to come up with a solution to that. My intention is to keep them separate other than charge source.

I think a hybrid bank will need to have entirely separated charging systems. It's dead simple to have separate AC chargers, so that part of it is no challenge, but what you do with the alternator is a puzzle.

Could bolt on an extra alternator, use 1 FLA and 1 LFP?

If you put the alternator on the lead bank, then you solve the issue of protecting the alternator from a HVC event, and you can charge the lithium with a B2B charger. So you regulate the alternator to give the lead what it wants and both banks get an ideal charging regime. That might be a good way to do it if you have your loads connected to the lithium bank. But then you have the issue of what to do if the loads get disconnected by a LVC event.

Don’t really understand that, if you have an LVC, only the loads disconnect ,charge source would still be OK? HVC could trigger alternator field disconnect which should save the alternator diode pack.

My own case is unusual in that my boat is already configured with two banks, with technical loads connected to one (thruster, windlass, winches) and house loads to the other. If I go with a hybrid system, I would put the lithium in the technical load box, regulate the alternator for lithium, and connect it to the lithium bank, and charge the house bank with a B2B charger. That solves the problem of how to keep essential equipment working through a LVC event, but it leaves the issue of what to do to protect the alternator from a HVC event, but this can be done with other devices, such as the Sterling Alternator Lineariser.

What would worry me with your vessel, it sounds like you are reliant on winches for sail control? An LVC in the middle of an important tack could leave you vulnerable? Would you have some sort of emergency manual or auto switch to crossover to your domestic bank in the event of an LVC?

[john61ct]

Originally Posted by Dockhead

I found utterly convincing that the HVC should be left as an emergency fail safe device.

I agree if that disconnect is the final BMS defence layer.

My point is that high but-not-that-high voltages can trigger daily-use controls that are designed to stop further charging of the bank

without necessarily isolating the bank completely, nor necessarily shutting off the charge source

maybe just redirecting the charge current away from the LFP circuit, and on to the lead bank and/or carrying loads.

This may be **a** HVD based mechanism, without being **the** last ditch fail-safe one we call BMS functionality.

Just like an LVD can shut down a high-amp non-essentials circuit (no music) but leave the fridge going. Then another cuts off the fridge, but nav/safety still has 48 hours of juice left.


> The other is alternator protection. Yes, of course, the easy way is to just leave the alternator connected to some kind of lead battery. If you have a starter battery of same voltage as your house bank, then that's a really easy way to do it.

My point with the above is that the LFP bank's charging can be terminated when it hits the target voltage,

while the lead & loads continue to receive current, going to the higher V the lead requires, and

all from the same charge source.

Not saying **your** use case should go that way, just correcting overgeneralization, making the above points for everyone's consideration.

[Dockhead]

Originally Posted by john61ct

I agree if that disconnect is the final BMS defence layer.

My point is that high but-not-that-high voltages can trigger daily-use controls that are designed to stop further charging of the bank

without necessarily isolating the bank completely, nor necessarily shutting off the charge source



maybe just redirecting the charge current away from the LFP circuit, and on to the lead bank and/or carrying loads.

Yes, of course.


HOWEVER, here's a puzzle for you:


What do you do if you want to stop charging the lithium but you want the alternator online to power ongoing loads?


This is not a problem with a hybrid bank where the alternator is connected to the lead. But how about the other way around? I hadn't thought of this issue, but it must be a basic question for lithium only banks. What is the answer? Is there a voltage at which the alternator can be regulated to, which will allow it to take loads without putting charge into the lithium?

Originally Posted by john61ct

This may be **a** HVD based mechanism, without being **the** last ditch fail-safe one we call BMS functionality.

Sure, but I think by convention we are referring to HVC as the high voltage cutoff in the BMS. Whatever functionality in the control system external to the BMS probably should be referred to in a different way, no?

Originally Posted by john61ct

My point with the above is that the LFP bank's charging can be terminated when it hits the target voltage,

while the lead & loads continue to receive current, going to the higher V the lead requires, and

all from the same charge source.

Not saying **your** use case should go that way, just correcting overgeneralization, making the above points for everyone's consideration.

Well, sure -- that's the easy solution already mentioned. But what do you do if you can't do it that way?




And how do mains chargers with a lithium profile work? How do they handle loads AND a full lithium bank?




To deal with the alternator, note that the Sterling Alternator Lineariser has a specific function of allowing a B2B charger to be powered directly from the alternator with no battery in the circuit. I bet that is specifically designed for this case -- so you can disconnect the lithium from the alternator bus while leaving the alternator connected to the B2B charger and hence powering loads connected to that. Could be just the thing for my application, and for others maybe too.

[tanglewood]

Originally Posted by Dockhead

Yes, of course.


HOWEVER, here's a puzzle for you:


What do you do if you want to stop charging the lithium but you want the alternator online to power ongoing loads?

This is not a problem with a hybrid bank where the alternator is connected to the lead. But how about the other way around? I hadn't thought of this issue, but it must be a basic question for lithium only banks. What is the answer? Is there a voltage at which the alternator can be regulated to, which will allow it to take loads without putting charge into the lithium?

Ah, this links back to the LFP Float discussion. I think the answer is to program your charge controller (this assumes you have or install one for the alternator) to enter it's Float mode, but program the Float voltage to act as a Standby power source for the LFP, not as an on-going charging source as you would for LA. No hybrid system, and associated complexity required.




And I think the preferred solution to all this HVC discussion is, as you mentioned earlier, the two stage control found in better BMSes. There is a charging control signal that, well, controls charging. It is used to shut down chargers that can't or won't otherwise back off on their own. And it does this when the battery reaches an operating full charge level of 80%-90% of nameplate SOC. This is well before 100% nameplate SOC, and well before any need to disconnect the battery.


The HVC is the action of last resort when things have gone astray and the battery is threatened. Disconnecting the battery, especially on a boat, is a really, really harsh action, and something you never want to do unless absolutely necessary. A two stage control solves this problem, and disconnects only happen where there is actually a serious malfunction.


And this now links back to the drop-in battery discussion, since one of the downsides to a drop-in is that you can't have a two stage control without redoing the charging control systems, and that's contrary to being a "drop in" solution.

[ramblinrod]

Originally Posted by Qayaq

I’ve looked at LFP for a long time.
FLA heartily sick of them. Good for starting engines but degrade quickly if you actually deep discharge them. And I’ve had enough of diesel use and engine wear trying to keep them from sulfating.

I have an electric bike and I’m thoroughly impressed with that battery.

LFP stumbling block is the expense and it’s a bit of an experiment. FLA one thing good about them they are reliable and cheap…..ish.

So why not marry them together, FLAs are great at short big bursts of power, don’t like being discharged or charged but are super reliable. So just keep them charged up & ready for back up when the LFP goes flat.

LFPs Are great for discharge, re charge really efficiently.
So all the stuff that normally drags down my FLA goes on that circuit.

So being that I want to keep my cash for cruising vouchers and that my boat has some good FLA charging gear. Here's my thoughts, drawing attached

Charging sources
Alt max 50amp, dialed back on Balmar 614. (single belt)
4 x 100W solar
Wind generator
Pro mariner 30-amp 240v charger

The idea is to lower the voltage from charge Bus to LFP by fitting an old style splitter diode pack which also stops feedback from LFP to FLA, may be able to pick one that has just right voltage drop. And they are cheap.

If it turns out that the FLA tries to charge the LFP through the diode splitter then maybe a Schottky diode could be put on that line

LVC. Because my LFP load is light approx. total worse case about 25amps, the LVC contactor could even be a 40amp NC/NO relay for testing, would prefer to find a better low current unit, also need something that would switch it at specified voltages, perhaps a Raspberry? Hopefully something easier..

HVC, Poss max on HVC could be as high as 90/100amps on a windy sunny day just after starting the engine so would need to look into a suitable unit for that. Again need to find something to switch at specified voltages. The reason I would want the HVC is to prevent float on the LFP.

So in the event of an LVC event which I would expect to happen occasionally, it simply switches the switch board back from being split LFP/FLA back to all FLA. Win Win.

OK the radar and auto pilot etc would reset but that’s not a major.

Can you see holes in this idea?

Would appreciate your input

Drawing attached.

Cheers
Simon

So here is my question.

If you have ample wind and solar to meet your charging needs most days (regardless of bat technology), why do you need all this LFP cost and complexity?

I assume your average daily consumption is about 100 A-hrs (at anchor) and 200 A-hrs (underway).

So 300 A-hrs of FLA, 80 A stock alternator, 200 W solar, and 200 W wind should be more than enough to charge the FLA to full about 5 days out of 7.

If the other 2 days at anchor, you may need the alternator for an hour in the morning.

Underway, just motor sail for 2 hours.

In this case, even the cheapest FLA should last 5 +/- 1 years.

It doesn't get easier than this.

[Dockhead]

Originally Posted by tanglewood

Ah, this links back to the LFP Float discussion. I think the answer is to program your charge controller (this assumes you have or install one for the alternator) to enter it's Float mode, but program the Float voltage to act as a Standby power source for the LFP, not as an on-going charging source as you would for LA. No hybrid system, and associated complexity required.




And I think the preferred solution to all this HVC discussion is, as you mentioned earlier, the two stage control found in better BMSes. There is a charging control signal that, well, controls charging. It is used to shut down chargers that can't or won't otherwise back off on their own. And it does this when the battery reaches an operating full charge level of 80%-90% of nameplate SOC. This is well before 100% nameplate SOC, and well before any need to disconnect the battery.


The HVC is the action of last resort when things have gone astray and the battery is threatened. Disconnecting the battery, especially on a boat, is a really, really harsh action, and something you never want to do unless absolutely necessary. A two stage control solves this problem, and disconnects only happen where there is actually a serious malfunction.


And this now links back to the drop-in battery discussion, since one of the downsides to a drop-in is that you can't have a two stage control without redoing the charging control systems, and that's contrary to being a "drop in" solution.

OK, but I don't understand your answer -- so there is a voltage at which the charger can support loads but current is not accepted by the cells?




As to drop-in lithium batteries -- I'm convinced that the only thing this approach brings is an illusion of simplicity and a superficial imitation of lead-acid batteries.



If I had to guess how lithium power is going to develop --


I believe that it will eventually be normal and standard and not terrifying to technophobic people to buy individual LiFePo4 cells, and they will be generally sold in this form.


The industry will start to produce really good and mass produced BMS systems.


Someone will make battery boxes in a variety of shapes with proprietary bus bars and connectors which will make it easy to integrate these systems.


Boats will start to be designed from scratch with the necessary contactors and bus arrangements.


Marine electricians will get used to these systems.



At which point even accountants will be able to start using lithium power on their boats.


The terrifying question of "did you top balance your cells this year?" will eventually be as common and normal and unintimidating as "is your electrolyte topped off?" is today.


The fact is, there is nothing simple about lead acid batteries; we are just familiar with them. I don't think it will take a whole generation for us to get familiar enough with lithium for the great mass of people to be comfortable with it.



Progress is not served by trying to make lithium look, feel, or behave like lead. It's different in fundamental ways.

[mbartosch]

Originally Posted by ramblinrod

So here is my question.

If you have ample wind and solar to meet your charging needs most days (regardless of bat technology), why do you need all this LFP cost and complexity?

I assume your average daily consumption is about 100 A-hrs (at anchor) and 200 A-hrs (underway).

So 300 A-hrs of FLA, 80 A stock alternator, 200 W solar, and 200 W wind should be more than enough to charge the FLA to full about 5 days out of 7.

Amazingly the OP message which you conveniently full-quoted states that the OP already does almost exactly what you recommend - and yet Simon is not satisfied with the results (emphasis mine):

Originally Posted by Qayaq

I’ve looked at LFP for a long time.
FLA heartily sick of them. Good for starting engines but degrade quickly if you actually deep discharge them. And I’ve had enough of diesel use and engine wear trying to keep them from sulfating.

I have an electric bike and I’m thoroughly impressed with that battery.

LFP stumbling block is the expense and it’s a bit of an experiment. FLA one thing good about them they are reliable and cheap…..ish.

So why not marry them together, FLAs are great at short big bursts of power, don’t like being discharged or charged but are super reliable. So just keep them charged up & ready for back up when the LFP goes flat.

LFPs Are great for discharge, re charge really efficiently.
So all the stuff that normally drags down my FLA goes on that circuit.

So being that I want to keep my cash for cruising vouchers and that my boat has some good FLA charging gear. Here's my thoughts, drawing attached

Charging sources
Alt max 50amp, dialed back on Balmar 614. (single belt)
4 x 100W solar
Wind generator
Pro mariner 30-amp 240v charger

As we can see Simon's setup exceeds your recommendation for the solar/wind charging side while being a little weak on the ICE charging side. But with enough solar and wind, you say, this will not be a problem. Batteries are full, ice is cold, as you say. Or not, as reported by Simon.

Now, the next argument will probably be that he exceeds your assumed 100 Ah per day usage, no problem, just add more wind and solar.
As far as I can see this is a 32' boat. So we add some balconies for even more solar, right...?

Well, his idea of using a LFP bank makes total sense in his case. With 400 Wp solar and a wind generator (power not specified) he should easily net 200+ Ah per day, 99% of which would be usable with a LFP only bank of sufficient size to average out the energy balance over time.

The proposed LFP/FLA hybrid will have losses, so I guess it would be more like 90 % of the available energy harvest, but if he pursues the idea of filling the FLA bank from a "breathing" LFP bank (be it via a relay or better yet via a B2B charger) the FLA bank will certainly last much longer. (I would just not do that, throw out the FLA instead and go pure LFP, but I am a special case as has been remotely diagnosed previously in a previous discussion on the same topic)

[tanglewood]

Originally Posted by Dockhead

OK, but I don't understand your answer -- so there is a voltage at which the charger can support loads but current is not accepted by the cells?

Yes, precisely my point.


A disconnected LFP battery rests at some voltage. No current in, and no current out, because it's disconnected.


Now connect a charger to it that is operating at the exact same voltage. Because the charger and battery are at the same voltage, there will continue to be no current in, and not current out. You program your charger's Float Voltage to this resting voltage of the battery, and presto. And just so you don't think I'm a wacko alone in the woods on this (well, I might still be) this is exactly what Victron says to do with all their chargers when used with LFP. And it's what CALB says to do in a standby power application, which is exactly what a baot is while it's got an engine running, or shore power, or active solar.



Now along comes a load. That load causes a voltage drop, and both the battery and charger respond because they are both connected. The load will be served by some combination of the two, and the batter charge level will drop some with the loads, but it won't go very far before the charger is carrying more and more of the load.


Make sense?

[mbartosch]

Originally Posted by tanglewood

A disconnected LFP battery rests at some voltage. No current in, and no current out, because it's disconnected.

Now connect a charger to it that is operating at the exact same voltage. Because the charger and battery are at the same voltage, there will continue to be no current in, and not current out. You program your charger's Float Voltage to this resting voltage of the battery, and presto. And just so you don't think I'm a wacko alone in the woods on this (well, I might still be) this is exactly what Victron says to do with all their chargers when used with LFP. And it's what CALB says to do in a standby power application, which is exactly what a baot is while it's got an engine running, or shore power, or active solar.

Now along comes a load. That load causes a voltage drop, and both the battery and charger respond because they are both connected. The load will be served by some combination of the two, and the batter charge level will drop some with the loads, but it won't go very far before the charger is carrying more and more of the load.

That's what I observe as well. If I allow my bank to reach 100 % SoC I can see it's approaching the 13.8 V set point, then the chargers drop to float (set to 13.3 V in my case) and resting voltage drops quickly as well.

Resting voltage of the bank will come down to 13.3 V quickly under load and more or less stay there. I observe that for some time all power is first delivered by the LFP battery, almost none by the MPPT chargers. While discharging further, the floating MPPT charger current ratio increases up to a point where it carries the majority of the load, with the bank only contributing a little trickle current. However, this happens well within the high SoC 90s, and as we all know this should be avoided.

So normally I do not allow this to happen with the exception of long offshore cruising legs (e. g. when running the engine in a calm), because as we say: charge to 100%, then stop and use the battery.
This contradicts floating, because the system will find an equilibrium where the battery still sits at high SoC.

In order to provide a better usage profile I have the habit of either manually cutting the charging source (flip of a switch which simulates a BMS HVC and isolates the charging sources from the bank - oh, btw, no voltage spike!) or letting my system work in what I call "lazy charging mode". For this mode I have programmed my BMV 700 battery monitor to close its relay at 80 % SoC and open it at 70 % SoC (can be reconfigured arbitrarily). This relay can also create the artificial HVC event which blocks all charging.

In this "Lazy Mode" (which we normally use when not on a long sailing leg, e. g. at anchor or in a marina) the battery SoC will not get higher than 80 % and happily be recharged when it reaches 70 % SoC.

[ramblinrod]

Originally Posted by mbartosch

Amazingly the OP message which you conveniently full-quoted states that the OP already does almost exactly what you recommend - and yet Simon is not satisfied with the results (emphasis mine):

Sticking to the facts as presented and using logic and reasoning (as I always do)...

Incorrect.

1. The OP stated that he is not currently satisfied with his FLA.

2. The OP posted a system solution specifying various charging sources.


The OP did not state that he currently employs any or all of those charging sources. He may, or he may not, we don't know, hence my question posted directly to the OP.

Perhaps we should allow the OP to speak for themselves, rather than post assertions on their behalf, which may be incorrect, based on your personal assumptions, interpretations, and opinions.

As we can see Simon's setup exceeds your recommendation for the solar/wind charging side while being a little weak on the ICE charging side.

Not necessarily. See post above.

But with enough solar and wind, you say, this will not be a problem. Batteries are full, ice is cold, as you say.

Exactly why I posed the question to the OP.

Now, the next argument will probably be that he exceeds your assumed 100 Ah per day usage, no problem, just add more wind and solar.
As far as I can see this is a 32' boat. So we add some balconies for even more solar, right...?

Why not? I have 400W of semi-flex solar on my personal 32 foot cruising sailboat (very narrow transom) on a very light Nidacore hard bimini.

As a DIY project, total cost around C$1500.

I don't have wind yet as we are in the Great Lakes and in 1000 Island anchorage rarely have enough wind to be productive. Before we head south to Bahamas and possibly beyond, 400W of wind will be going on.

Presently, just the 400 W of solar meets my total need (about 5 days out of 7) at extended anchor. A combination of wind (where appropriate) and solar may improve this to 6 out of 7.

Well, his idea of using a LFP bank makes total sense in his case. With 400 Wp solar and a wind generator (power not specified) he should easily net 200+ Ah per day, 99% of which would be usable with a LFP only bank of sufficient size to average out the energy balance over time.

Perhaps.

In fact we don't know until we find out what he currently truly has, hence my question...to him.

Based on the information I currently have, I believe all of his needs would be just as adequately met, by the system I proposed, except for the exercise of implementing an expensive LFP bank, and the associated complexity.

The only significant difference regarding end user "benefit", is that he may extend battery life a little, or then again, maybe not. Perhaps he has an unforeseen incident or makes a mistake and trashes the LFP bank in short order. In which case, he reduces battery life.