LiFePo4 Power -- Controlling Alternator and Inverter/Charger

[Dockhead]

Do we need to control the charging sources with the BMS, or not?


It would seem prudent to me to be able to force the charging sources into float when the battery is full as determined by amp/hour-counting. Or do we think this is unnecessary?


I note that the Batrium BMS system can be connected to the Victron Multiplus by Canbus, but it's not clear to me exactly what it does:


https://secondlifestorage.com/t-Batr...24561#pid24561


This:



https://support.batrium.com/article/...-with-watchmon


seems to suggest that the BMS can control the charging profile.






What concerns Balmar, this:


http://www.balmar.net/wp-content/upl...re-7-19-17.pdf


strongly warns that the alternator should be shut down before a HVC is activated, which should be done by interrupting power to the brown ignition wire. Interesting question whether there needs to be a small time delay between this interruption, and activation of the HVS, and whether an alternator protector like the Sterling one makes this irrelevant.


I don't see anyway for the BMS to force the Balmar into float, but I note that the default LFP program in the Balmar has "absorption" voltage at 13.6, which is basically float I think, so it seems the Balmar automatically drops the voltage when the acceptance tapers off. Don't know if that is an adequate control and will be glad to be educated.

[Viking Sailor]

DH,

Some BMS's will disconnect if the battery gets too hot. Thus, the APD.

[Delfin]

With the caveat that I am just a user, not an expert, perhaps the following will be useful:

Originally Posted by Dockhead

Do we need to control the charging sources with the BMS, or not?

Not under normal conditions. The BMS handles high and low voltage issues, overheating, etc.

Originally Posted by Dockhead

It would seem prudent to me to be able to force the charging sources into float when the battery is full as determined by amp/hour-counting. Or do we think this is unnecessary?

I'm not sure anyone has figured out how to drop to float based on amp hours replaced, but I am also not sure why you would need to. I started out managing my bank to avoid overcharging and theoretically reducing cycle life manually via amp hour counting, but the thread on memory effects and other user reports convinced me that isn't of anymore benefit than letting regulated charge sources manage the charging.

FWIW, here is how I am managing my bank after reading everything I can on the subject with an eye towards ease of management, reasonable longevity and maintaining the capacity of the bank. Since mine is a 24v system, that is the reference voltage.

1. Cruising from anchorage to anchorage: The Balmar 624 and Ample Power 160 Ah alternator are used as the only charge source. The Balmar is set to depower the alternator to 80%, and with house loads underway I get 100 amps more or less flowing into the bank. CV is set at 28.2 and absorption at around 30 minutes. When the Balmar flips to float, I depower the BMS, which takes the LFP bank offline and divert charge current to the LA starter bank. This is done via a Blue Seas ACR. I believe this fully charges the bank as it rests at 27.2+ volts after an hour, or 4 hours if you believe there is much of a difference, and this, at least according to Lithionics indicates a fully charged battery. Rinse and repeat.

2. At anchor for 2+ days: The genset powers a 100 Ah charger in the inverter, and I have another 90 Ah charging from Sterling 30 Ah chargers connected in parallel. We'll draw the bank down by 75% or so, then depending on long the genset needs to run to wash clothes, make water, etc., the LFP bank is recharged either at 100 Ah, or around 175 Ah, depending on whether the Sterlings are engaged. Not sure why I can't get more than 75 Ah out of the Sterlings, but I can't. I have the inverter charger and Sterlings set for CV of 29.2 and absorption of 30 minutes. I have measured the temperature of the bank many times and never detected any heat at the bank, and in any case, Lithionics recommends 29.2 for charge voltage anyway. I believe this routine eliminates the potential for the dreaded memory effect.

3. Underway for long distances or connected to shore power: If the boat is going to be at the dock or underway for a couple of weeks or more, I don't bother recharging the LFP bank and store it at 50% or so SoC. If we are at a marina for a couple of days, I recharge the LFP bank per #2 the day before we leave, but otherwise, charge sources are connected to the starter bank and the BMS is depowered.

Since I have no solar and I know that introduces other issues, this may not work for many. However, if you have a two bank system, and externally regulated charge sources via dino, managing the LFP bank is no more complex than managing an LA bank, with the added benefits of LFP.

Originally Posted by Dockhead

What concerns Balmar, this:


http://www.balmar.net/wp-content/upl...re-7-19-17.pdf


strongly warns that the alternator should be shut down before a HVC is activated, which should be done by interrupting power to the brown ignition wire. Interesting question whether there needs to be a small time delay between this interruption, and activation of the HVS, and whether an alternator protector like the Sterling one makes this irrelevant.

My BMS, and I believe it would be common for other types, has a disconnect for the alternator during a HV situation. I don't think a time delay is needed.

Originally Posted by Dockhead

I don't see anyway for the BMS to force the Balmar into float, but I note that the default LFP program in the Balmar has "absorption" voltage at 13.6, which is basically float I think, so it seems the Balmar automatically drops the voltage when the acceptance tapers off. Don't know if that is an adequate control and will be glad to be educated.

As noted above, yes, I think this is adequate. If I forget to switch over to the LA bank once float is tripped, no big deal since the open circuit voltage is 27.2/13.6 anyway. I'd personally program the Balmar rather than use the defaults.

Hope that helps.

[john61ct]

If you accept the premise that your LFP bank should not be floated

there is no need to complicate things by varying voltage levels.

It is just a question of isolating the bank from charge sources when it gets to your desired "working Full" definition whatever that is.

Then bringing the LFP bank online to the loads buss when charging source input current is lower than what loads require.

None of this implies a "float voltage" different from the charging setpoint.

[toddster8]

I sent email to Battle Born, pretending to be even more confused than I am, (in case some of the things that I know turn out to be wrong...). They phoned me up shortly after, told me to buy the Sterling APD and Don't Worry.

[Q Xopa]

Originally Posted by john61ct

If you accept the premise that your LFP bank should not be floated

there is no need to complicate things by varying voltage levels.

It is just a question of isolating the bank from charge sources when it gets to your desired "working Full" definition whatever that is.

Then bringing the LFP bank online to the loads buss when charging source input current is lower than what loads require.

None of this implies a "float voltage" different from the charging setpoint.

Im pretty sure everyone agrees 'its just a question of isolating the LFP from the charging source'.
How is the question being asked. I assume you are suggesting manually with s switch.

[Dockhead]

Originally Posted by john61ct

If you accept the premise that your LFP bank should not be floated

there is no need to complicate things by varying voltage levels.

It is just a question of isolating the bank from charge sources when it gets to your desired "working Full" definition whatever that is.

Then bringing the LFP bank online to the loads buss when charging source input current is lower than what loads require.

None of this implies a "float voltage" different from the charging setpoint.

Well, how can you "isolate the bank from charge sources" if you want to power the loads from those charge sources, and use Power Boost to deal with a shore power connection which is not quite adequate to your loads?


Or when motoring when you want to be using inverted power from the alternator.



You can't. So the answer is to set a float voltage which does not charge the bank. With a manual control which will allow you to stop the charging anywhere in the cycle and go to non-charging float, as for example when you are on shore power for a long time and don't want the battery to be held at full charge.



Can this not be done with LiFePo4?


If not then this will vastly complicate the architecture of yacht systems. Then you would simply have to use a hybrid bank of some kind, or else give up Power Boost and give up using AC power while motoring except when you are either charging or drawing down the bank without using any alternator power -- all of which is just ugh.


Similar to Power Boost, I want to be able to for example cook electrically or do laundry while motoring, and have the battery periodically make up the difference between the loads and alternator output whenever the loads exceed what the alternator can make. So I need BOTH battery AND alternator connected during this process. Some kind of float voltage is the only answer to this.




For my specific application, working within certain existing systems architectural features which are impractical to change, if it is impossible to use LiFePo4 like this, I will need a third charger/inverter for the vestigial lead bank and a way to switch between it and the other two -- ugh! So that the lead bank can be used for Power Boost on shore power (and generator) and for using AC power while motoring.

Originally Posted by Q Xopa

Im pretty sure everyone agrees 'its just a question of isolating the LFP from the charging source'.
How is the question being asked. I assume you are suggesting manually with s switch.

Well, not me. See above.

[Dockhead]

This suggests that floating a LiFePo4 battery at any given partial SOC is possible:


"The LFP battery will have a no-load voltage that varies a bit with SOC. Let's say your LFP sits idle at 13.30 volts when it's 80% charged and you want to keep it there. You could float it at 13.30V and no charging would occur beyond compensating for the slight self-discharge that would otherwise cause voltage to drop slightly (over some months). Ditto for other SOC levels. This approach would be suitable for a battery connected to some load but you want your charger to carry that load, not the battery. Again, you would set the charger to float the battery at that voltage (13.30 in the above example) and the charger will carry the load without charging the battery. But, if there will be no load on the battery, there is no point to floating it because the self-discharge rate is very small. Even a six month idle period will not drop the charge much; maybe a percent or two. An LFP SOC monitor will usually be a coulomb or AH counter and will not record the self-discharge."

https://electronics.stackexchange.co...-i-charge-them


If that is true, then it would seem to be pretty elementary for the charging system controls to allow you force them into partial SOC float at any given level. 70% or 80% might be quite suitable for most cases, no?


The main thing is you will need a manual control to allow you to charge full if you are going to need all the capacity, or charge to 70% or whatever and stop, if you are not going to need all the capacity and don't want the battery sitting fully charged.


Is this possible with available charging control gear? For me, that is the very question.

[Kenomac]

I don’t wanna sound flippant, so please take this as constructive.

We own two boats, one with a 450Ah house bank and 10kw 120/240v 60hz Westerbeke generator, and another with a 840Ah bank and Onan 12.5kw 230w 50hz genset. Both 24v and flooded lead acid batteries.

I have zero problems, and spend zero amount of time fussing with electrical power and power storage issues. Zero... ongoing costs, everything works as it should. Air conditioning and all electric cooking, both boats function in the Americas and Europe, and the battery banks return to 100% nearly every day.

Would you like some help with yours, you seem to be struggling through trying to get to the point where we are? And throwing money at a possible solution rather than solving the root problem.

[Dockhead]

Originally Posted by Kenomac

I don’t wanna sound flippant, so please take this as constructive.

We own two boats, one with a 450Ah house bank and 10kw 120/240v 60hz Westerbeke generator, and another with a 840Ah bank and Onan 12.5kw 230w 50hz genset. Both 24v and flooded lead acid batteries.

I have zero problems, and spend zero amount of time fussing with electrical power and power storage issues. Zero... ongoing costs, everything works as it should. Air conditioning and all electric cooking, both boats function in the Americas and Europe, and the battery banks return to 100% nearly every day.

Would you like some help with yours, you seem to be struggling through trying to get to the point where we are? And throwing money at a possible solution rather than solving the root problem.

It's a perfectly reasonable question, and probably what I would do myself IF the architecture of my existing system were ok -- since I won't own this boat that much longer.


If I had 600 amp/hours or so of 2volt industrial Rolls lead-acid cells, I would be quite happy with lead. Or even a bunch of Trojan T-105's.

HOWEVER, that is not what I have or can have, and in general the architecture of my existing system is not OK, therefore it would be nearly as costly to reconfigure it for a proper lead system with proper deep cycle lead batteries.


ALSO, I'm doing lithium and working out these issues for the fun of it, for learning, and for experience which will be applicable to the next boat.





What is not OK about the present system is a lot more than just lack of ventilation in the aft bank. It is the fact that the bank is separated into two separated by probably 6 meters of distance, which makes it impossible to perfectly balance them, plus the spaces for the two banks are too shallow and too small for proper deep cycle lead batteries.



The original idea of the two banks was that one would be used for "services" -- thruster, windlass, winches -- and the other for house. I combined them because the "house" bank was not large enough for using an inverter and being off grid a lot. The designer specified a heavy duty continuous rated generator and assumed that would be running most of the time.



So what I have pretty much sucks for my purposes -- remember I spent three months last year not hooked up to anything! So I'll be very happy to wipe the slate clean and get a really nicely functioning system, ripping out all the crappy interconnection system I put in some years ago.


Maybe now the appeal is more clear? Lithium is especially elegant and cool on my particular boat because I can fit 300 (or even 500) amp/hours of lithium into the space of just one of the previous lead banks. I put that in place of the former "Service" bank, leave lead batteries in the original "House" bank, and I restore almost the entire original architecture of the original system, just adding a B2B charger between Service and House. So I even gain redundancy in the very unlikely event of some kind of failure of the lithium bank, I still have the lead "House" bank in commission.

[Delfin]

Originally Posted by Kenomac

I don’t wanna sound flippant, so please take this as constructive.

We own two boats, one with a 450Ah house bank and 10kw 120/240v 60hz Westerbeke generator, and another with a 840Ah bank and Onan 12.5kw 230w 50hz genset. Both 24v and flooded lead acid batteries.

I have zero problems, and spend zero amount of time fussing with electrical power and power storage issues. Zero... ongoing costs, everything works as it should. Air conditioning and all electric cooking, both boats function in the Americas and Europe, and the battery banks return to 100% nearly every day.

Would you like some help with yours, you seem to be struggling through trying to get to the point where we are? And throwing money at a possible solution rather than solving the root problem.

Anyone satisfied with running their genset hours per day can be quite happy with any type of inexpensive battery bank. For those that don't want to, not so much. You are projecting your use patterns onto others, and since preferences may differ your generalization is an over simplification.

[Dockhead]

Originally Posted by Delfin

Anyone satisfied with running their genset hours per day can be quite happy with any type of inexpensive battery bank. For those that don't want to, not so much. You are projecting your use patterns onto others, and since preferences may differ your generalization is an over simplification.

Ken can speak for himself, but I think he gets most of his power from solar.


In an application where you get most of your power from solar, lead acid batteries are quite a bit more satisfactory, than they are in applications like mine where you get your power from running diesel engines.


Solar power, which can give long sustained finishing charges, makes it vastly easier to operate lead-acid batteries in a regime which is healthy for them.

[Delfin]

Originally Posted by Dockhead

Ken can speak for himself, but I think he gets most of his power from solar.


In an application where you get most of your power from solar, lead acid batteries are quite a bit more satisfactory, than they are in applications like mine where you get your power from running diesel engines.


Solar power, which can give long sustained finishing charges, makes it vastly easier to operate lead-acid batteries in a regime which is healthy for them.

Solar is certainly preferable. My point is that energy is not free. Lots of solar panels, gensets, inverters, batteries, wiring, etc. are all possible components, so pick your poison. Not wanting to festoon my boat with solar panels while cruising in areas with 100 days of sun a year, my choices for not running a big genset for 6 hours a day to top off LA was to install a small second genset or go LFP. The cost was about the same, so the choice was easy. I've run my big genset two hours over the last two days at anchor, so as I said, generalizing that one approach to having the energy that makes life on a boat even more pleasant is over simplifying.

[Dockhead]

Originally Posted by Delfin

Solar is certainly preferable. My point is that energy is not free. Lots of solar panels, gensets, inverters, batteries, wiring, etc. are all possible components, so pick your poison. Not wanting to festoon my boat with solar panels while cruising in areas with 100 days of sun a year, my choices for not running a big genset for 6 hours a day to top off LA was to install a small second genset or go LFP. The cost was about the same, so the choice was easy. I've run my big genset two hours over the last two days at anchor, so as I said, generalizing that one approach to having the energy that makes life on a boat even more pleasant is over simplifying.

Sure, and this was also my point. Different use cases indicate different optimum solutions. If you've got a lot of solar, then lithium has some benefits but is not so overwhelmingly attractive like it is if you are getting your power from diesel engines.



My use case is similar to yours -- long distance sailing yacht optimized for sailing upwind, and used in latitudes without huge amounts of sun -- so no way to mount solar panels (windage kills upwind sailing ability), not as much benefit even if I could, and I'm dependent on running a genset or using the main engine. Here lithium is enormously beneficial because it drastically shortens the hours you need to run those engines. On top of the various other benefits.

[Kenomac]

Originally Posted by Delfin

Anyone satisfied with running their genset hours per day can be quite happy with any type of inexpensive battery bank. For those that don't want to, not so much. You are projecting your use patterns onto others, and since preferences may differ your generalization is an over simplification.

Originally Posted by Delfin

Solar is certainly preferable. My point is that energy is not free. Lots of solar panels, gensets, inverters, batteries, wiring, etc. are all possible components, so pick your poison. Not wanting to festoon my boat with solar panels while cruising in areas with 100 days of sun a year, my choices for not running a big genset for 6 hours a day to top off LA was to install a small second genset or go LFP. The cost was about the same, so the choice was easy. I've run my big genset two hours over the last two days at anchor, so as I said, generalizing that one approach to having the energy that makes life on a boat even more pleasant is over simplifying.

I only run my generator 1-2 hours per week, the rest is supplied by 450w of solar. And no... solar doesn’t cover up the entire boat, just the bimini where nobody can even see it.

And yes... I have other energy saving/producing ideas which can help Dockhead achieve his goals too, but he seems to have his mind already made up, which is his perogative.