LFP FLA hybrid

[Dockhead]

Originally Posted by Qayaq

This is the thread that I started about this project.

This thread is about the idea of LFP FLA hybrid in general. I would recommend starting a separate thread about building a home made BMS for lithium, which is a rather different subject and which I am sure will be of great interest to many who are not interested in using lead for anything.

[Qayaq]

Originally Posted by Dockhead

This thread is about the idea of LFP FLA hybrid in general. I would recommend starting a separate thread about building a home made BMS for lithium, which is a rather different subject and which I am sure will be of great interest to many who are not interested in using lead for anything.

Yep. However this thread is about how to create a LFP LFA hybrid as per my original post..
So the BMS to achieve this has to include the FLA as well.

Hence the use of any sort of gear that would enable this.

Which may be of interest to any body reading a thread about a Hybrid system.

Now if you just want to use off the shelf gear that might suit your vessel and systems... fair enough, but that's not everybodies cup of tea.

[Dockhead]

Originally Posted by Qayaq

Yep. However this thread is about how to create a LFP LFA hybrid as per my original post..
So the BMS to achieve this has to include the FLA as well.

Hence the use of any sort of gear that would enable this.

Which may be of interest to any body reading a thread about a Hybrid system.

Now if you just want to use off the shelf gear that might suit your vessel and systems... fair enough, but that's not everybodies cup of tea.

Well, you are welcome to post about it wherever you like, but I would recommend a new thread as you will get a lot more views that way. This is interesting to a lot more people, than those discussing this relatively narrow topic of hybrid power systems.

[Delfin]

I received a PM requesting that I describe our system, as it incorporates an LA battery as a component and it installed as close to a drop in system as I could have hoped for. So here 'tis with all voltages relative to our 24vdc system:

600 Ah Lithionics in 2 banks of 300 Ah @ replacing 1200 Ah Northstar AGM batteries. Kept 2 8D starter LA bank. Purchased the Lithionics BMS.

Already had installed a Balmar 624 regulator and a Link 20 amp counter, so no change there. Also had the earlier model of the ACR Catnewbe references above. Finally, the charge/inverter remains a Trace 4000.

Removed the AGM, dropped in the LFP bank in the same box, wired the LFP up to the BMS, ran the ignition wire on the 624 through the BMS port provided, reprogrammed the charge profile of the 624 and Trace and that was it. The LFP bank is wired as the house bank, as was the AGM bank.

Operation:

1. Isolate the LFP bank from all charge sources when charge acceptance rate begins to fall as indicated by the Link 20 in the pilot house.

2. This is done by switching off the BMS, which isolates the LFP bank, and switching the ACR to "manual combine", which directs the charge current only to the starter bank.

3. Charge the LFP bank at .33 C via the Trace charger and an Ample Power large frame alternator. As a practical matter, this takes about 1.5 hours with both the genset and main engine running to replace daily consumption, during which we also make water, do laundry, etc.

4. The Trace charger and Balmar are set to bulk voltage of 28.1 with minimum absorption time and float at 26.8 volts.

5. When at anchor, the LFP bank is brought online by switching on the BMS and putting the ACR into "auto combine", which as a practical matter means the starter bank is offline as soon as the LFP bank voltage drops below 27.2 volts, which happens as soon as it takes over the house loads.

6. When underway, the alternator provides house loads via the starter bank and inverter. Recently I installed a Balmar SmartGuage to monitor the SoC of the starter bank.

7. Throttle the alternator output to 80% via the Balmar.

8. When at the dock for a period of time, don't bother to recharge the LFP bank that day and store it at 50% or so of C.

Philosophy of operation:

1. Use the BMS as an emergency device that protects the LFP bank and a manual switch to disconnect it from charge sources. Never get into the voltages that trigger HVC or LVC.

2. Treat the LFP bank as a fuel tank. Fill it up, use it, re-fill. When a charge source is available and it is full, isolate it and use the charge source for house loads. When one is not, use the LFP after it has been filled.

3. The above means that just like I have to pay attention to a chart when underway, I also have to note when the charge acceptance rate of the LFP bank begins to drop so I can isolate it. Because of the flat acceptance rate of LFP, if it is down 300 amps I can set an alarm for 90 minutes later and that is the point in time when I am within 2 minutes or so of being able to observe a drop in the CAR. Virtually all of the angst surrounding control systems for LFP centers on being able to avoid this mundane task, which seems to me to be a total waste of time.

4. If I am distracted and don't notice that the charge acceptance rate has begun to drop, then the voltage regulation of the Balmar 624 and the Trace charge will handle the situation just fine without the slightest damage to the bank, unless charging to 28.1 volts is a problem once in about 60 cycles, which no one whose opinion I respect thinks it is.

5. Don't draw the LFP bank below around 50% of C, which should extend the life of the bank to close to 6,000 cycles. I won't live that long.

Suggested disadvantages of this system:

1. If you are using the small LA bank + alternator for house loads, when large inverter draws happen you may hurt the LA bank. As a practical matter, this never seems to happen to us, mostly because when docking we start the genset so it provides supplemental oil flow for thrusters to the main at idle. If we had electric thrusters the genset would fill that gap as well. Other house loads, like the water maker, can still be run when just the LA bank is online via the alternator output.

2. Expense of buying factory assembled pack from Lithionics rather than building your own. Yep. No question about that.

3. You have to throw two switches twice a day when charging for a time investment of 1 minute or so. Since my BMS and ACR switches are in the ER, it takes this long. An improvement would be to place them in the pilot house for remote operation.

4. This approach won't work as simply if you have separate busses/charge sources for technical and house loads. However, my guess is that the reason why dual busses were installed in the first place was to avoid voltage sag and its effect on sensitive electronics when heavy house loads kick in. Since LFP isn't affected by voltage sag, at least as far as I can see in operation, I don't know why you wouldn't combine those dual busses and just power everything with LFP, or if it is off line with the alternator putting out 26.8 volts.

This is just one possible approach to using this technology, which IMO is so far superior in performance to LA that it is worth the effort to lose the LA mindset and learn how to manage a new system.

[tanglewood]

Thanks for that description, Delfin.


One question. There has been lots of talk about the hazards of disconnecting the battery (regardless of type) from the alternator while underway. How do you handle this in your system? Do you always connect the other battery bank before disconnecting the other, such that at least one is always connected?

[Qayaq]

Many thanks for that Delphin, interesting to See how you have made that work in a practical way.
Cheers
Simon

[Delfin]

Originally Posted by tanglewood

Thanks for that description, Delfin.


One question. There has been lots of talk about the hazards of disconnecting the battery (regardless of type) from the alternator while underway. How do you handle this in your system? Do you always connect the other battery bank before disconnecting the other, such that at least one is always connected?

There are two layers of protection. First, yes, when taking the FLA offline via the ACR, I first switch to "manual combine". Second, the Balmar is programmed for a soft ramp so it doesn't kick in for 15 seconds in any case. I also seem to recall that when I bought the Ample Power alternator, it had protective diodes (?) that prevented a disconnect from a destination battery causing any harm, but I can't remember the details....

[john61ct]

Originally Posted by Dockhead

No, I was talking about amp/hours in vs. amp/hours stored. I don't have the literature right to hand, but I understand that this ratio approaches infinity at the end of the tail charge. What we would want to know is how many amp/hours of power would it take to go from 85% or whenever we shut off the generator, to a nice full 100%. If it's a 200 amp/hour bank, then 15% of that is 30 amp/hours. I guess that will be something well above double, or 60 amp/hours, if not triple, then you have to add the efficiency losses in the charger, which are not trivial. I can easily imagine 100 amp/hours being needed which is, for God's sake, equal to the whole usable power of a 200 amp/hour lead bank

Yes if that is indeed the case the idea is useless.

Easy enough to test, I would not rely on a general paper.

I agree with the rest, just note boats with low usage do often get by fine with only 400-600W, rarely needing supplementing with ICE.

But winter far from the equator, not as much.

[newhaul]

Originally Posted by john61ct

Yes if that is indeed the case the idea is useless.

Easy enough to test, I would not rely on a general paper.

I agree with the rest, just note boats with low usage do often get by fine with only 400-600W, rarely needing supplementing with ICE.

But winter far from the equator, not as much.

at 47°N I'm doin ok with 400 solar for now.
All led.

[john61ct]

Cross fertilizing http://www.cruisersforum.com/forums/showthread.php?p=2777319

[john61ct]

More cross pollination LFP's Charging Voltage and State of Charge - Cruisers & Sailing Forums

[rgleason]

Cpt Pat wrote:
My own design places my LFP in parallel with my pre-existing lead-acid batteries, so there is no interruption to bus operation at the charged/discharged thresholds of the LFP. I place the LFP on the bus when the bus (lead-acid batteries) voltage declines to 13.2 volts, and float the lead-acids on shore power at 13.4 volts (temp compensated) with the LFP off the bus.

This approach is interesting:

1. The separate control of LFP with a regulator and relay, to disconnect and reconnect to the FLA-Alternator at the proper times and charge levels.

2. ..Distinct from the FLA batteries and alternator regulator settings which control charge settings.

I think we would need a two level regulator for the alternator-FLA particularly to protect LFP when the LFP is connected, otherwise the LFP might get damaged.

The other alternative is to alternator charge the LFP only with the proper regulater settings.

Then charge the small reserve FLA with occassional shore power or a small solar PV and regulator that are separate and only connected by the emergency switch.

[newhaul]

Originally Posted by rgleason

Cpt Pat wrote:
My own design places my LFP in parallel with my pre-existing lead-acid batteries, so there is no interruption to bus operation at the charged/discharged thresholds of the LFP. I place the LFP on the bus when the bus (lead-acid batteries) voltage declines to 13.2 volts, and float the lead-acids on shore power at 13.4 volts (temp compensated) with the LFP off the bus.

This approach is interesting:

1. The separate control of LFP with a regulator and relay, to disconnect and reconnect to the FLA-Alternator at the proper times and charge levels.

2. ..Distinct from the FLA batteries and alternator regulator settings which control charge settings.

I think we would need a two level regulator for the alternator-FLA particularly to protect LFP when the LFP is connected, otherwise the LFP might get damaged.

The other alternative is to alternator charge the LFP only with the proper regulater settings.

Then charge the small reserve FLA with occassional shore power or a small solar PV and regulator that are separate and only connected by the emergency switch.

or you could charge the Fla with a small charger on a 150 watt inverter will easily run a small maintenance charger with minimal power from the primary Lfp bank. Which I assume in this scenario is being charged off alternative energy sources.

[Delfin]

Originally Posted by rgleason

This approach is interesting:

1. The separate control of LFP with a regulator and relay, to disconnect and reconnect to the FLA-Alternator at the proper times and charge levels.

I do that with the BMS and an ACR. When the LFP is "full", as in CAR < 5% of C, the BMS gets switched off and this isolates the LFP bank from charge sources. I then use a Blue Seas ACR to manually combine the LA starter bank and LFP bank, which, since the LFP bank is offline means all charge current goes to the LA bank.

Originally Posted by rgleason

2. ..Distinct from the FLA batteries and alternator regulator settings which control charge settings.

I think we would need a two level regulator for the alternator-FLA particularly to protect LFP when the LFP is connected, otherwise the LFP might get damaged.

That's really the BMS's job. The BMS I have - Lithionics - will kill the alternator in the event the BMS disconnects the bank from the charge source due to a HV event. Since I monitor the charge cycle (only takes <2 hours), this is unlikely to happen, but the BMS is there if needed.

Originally Posted by rgleason

The other alternative is to alternator charge the LFP only with the proper regulater settings.

Then charge the small reserve FLA with occassional shore power or a small solar PV and regulator that are separate and only connected by the emergency switch.

You certainly could if what you are looking for is set and forget charging where the alternator stays connected to the LFP bank and you don't want to be bothered with disconnecting it as described above.

For us, lacking solar, recharging the LFP at anchor means noting the draw down from the coulomb counter, dividing by 200, which is my charging output on the genset, and setting an alarm for that many hours - usually 90 minutes or so. Alarm goes off, genset gets turned off. Done.

The alternator is set to LA parameters with the exception of the absorption time, which via a Balmar 624 is set to 20 minutes. Under power and wishing to charge the LFP bank just means keeping an eye on the coulomb counter, and when it falls to < 5% C, flip the Blue Seas to manual combine and turn off the BMS, isolating it in a state of full charge, ready for the next night at anchor.

If we're headed back to the barn, don't recharge the LFP - just leave it around 50% SoC until you head out the next time, then recharge as above before you get to anchorage.

The above isn't appropriate if you believe any of these spurious notions:

1. Storing an LFP bank at full charge for a day (or a week) is harmful.
2. Storying an LFP bank for a month (or months) at 40-50% is harmful.
3. Disconnecting the charge source when the charge voltage reaches around 28.2 - 28.4vdc and CAR is <5% (both happen at the same time) is harmful to longevity.

[rgleason]

Delfin wrote:
I do that with the BMS and an ACR. When the LFP is "full", as in CAR < 5% of C, the BMS gets switched off and this isolates the LFP bank from charge sources. I then use a Blue Seas ACR to manually combine the LA starter bank and LFP bank, which, since the LFP bank is offline means all charge current goes to the LA bank.

This seems practical. Do you trust the BMS to shut off properly? I assume so because your BMS is programmed by you.
How do you know it is shut off, so that you can manually switch the ACR? Also what switch do you use for the LFP BMS.