Hybrid or No Hybrid Power system?

[Dockhead]

I am planning to -- probably -- build a lithium system over this winter and am still struggling a bit with the architecture.


I have two battery boxes in different locations, each of which accommodates 4x 6v golf cart batteries. Just one of these boxes will fit 2x 280AH batteries made up of 8x 280K Eve cells, together with a couple of BMS's and other gear, for a total of 560AH @24v of capacity, which is a whole lot more usable capacity than I have now from 420AH of lead.


I was planning to get rid of all of the lead and use one of the battery boxes for additional storage space; always in demand on any boat, right?


But more and more I think about how I'm going to back up my nav/comms gear, and installing a backup battery of some kind and doing the wiring necessary for that would be one way of doing that.


But far simpler -- requiring no rewiring and no acquisition of anything except one B2B charger would be to just leave one of the lead banks, and feed all the house loads (including nav and comms) from that. Then the lithium would be connected to the heavy loads including winches, thruster, windlass, and inverter. My boat is already wired like that -- one bank was for house loads, the other for heavy loads -- so no reconfiguration of anything would be required.


I'm starting to think this could be a more elegant installation, and extremely robust against blackouts, and on top of that, I would gain another 210AH of capacity for truly huge power storage.


On the other hand, I wanted the storage space and would have been happy to get rid of any lead in the system.


I am probably the least knowledgeable person in this section so I would be really grateful for thoughts and ideas for the more knowledgeable among you.

[MWGDVC]

As I understand the differences between FLA and LiFePo, lead is better suited for the high current intermittent short term loads, such as engine starters, bow thrusters, windlasses, whilst Li is better suited for longer term loads, less voltage sag, for house and navigation electronics loads.
I configured my system using AGM for engine start and windlass, theory being I usually will start engine and warm up for a few minutes prior to hoisting anchor using windlass, keeping lead in it's happy place (fully charged). I haven't a bow thruster, but I envision most scenarios of it's use would be under motor as well.

Solar is my primary house charging supply, with a DC-DC charger as an option to supply charging current for house LiFePo.

[Renegde_Sailor]

Depending on where the loads are in your boat is the answer to that question.

Currently I have 2 8D AGM's under my V-berth and 2 pairs of 2/0 going back to my MELC where I have switches that can direct power.

I also have a stand alone 100ah AGM that is specifically tasked with running my windlass, and I have a start battery for starting the engine.

Then I have a set of switches that allow me to power anything from any battery bank, and they are isolated by Orion chargers to keep each topped off.

Currently I am about pull my engine and redo the engine room, but when I do I will be ditching the 8D's under the V-berth and reclaiming the storage, then I'll be installing 4x of the Victron 330ah lithiums (1056ah @ 80% DOD) in the engine room in a new box I am building in there and I will retain one pair of the 2/0 going forward to charge the windlass battery.

Doing this will leave me with a very robust system that can still operate the boat if 2 of the 3 battery banks crap out.

That being said, 2 battery banks in 2 different locations is having two for twice as much money, as they will need to be independently regulated and charged so keep that in mind as you are setting the system up.

[Dockhead]

I have completely separate engine and generator start systems, each with its own separate charger and alternator, so that's not at issue here.


HOWEVER, I do have a concern about my Sleipner bow thruster, which might need a motor rewind in order to be used with lithium.


So, it could be possible to swap this around from what I envisioned -- leave the lead in the "service bank" box, which serves thruster and other heavy loads, and put the lithium in the "house bank" box. I would need to have a switchover to bypass the lithium in case of emergency but that should be quite straightforward.


That would also protect the lithium from heavy loads, which would mean I could use cheap MOSFET BMS's rather than expensive REC ones.


Hmm. OK, you've given me some new ideas -- thanks!

[MWGDVC]

A couple more observations based upon my experiences with my configuration:
Lighting maintains a consistent brightness as Li voltage remains steady during all but the very tail end of discharge. Electronics are more reliable due to steady voltage supply as well.
LiFePo recharge faster than lead chemistries. Great for solar power harvesting.

I made the mistake of purchasing a 60A 12V B2B charger. I have a 120A alternator, external regulator, serpentine belt engine charging system. The B2B uses 75A to output 60A to the house. This causes the alternator to get warmer than I would like. Fortunately my B2B has a 50% output setting (30A). At this output the alternator runs at 185F/85C. If I were to replace the B2B, I would purchase a 40A instead.

In my use case, this works out as alternator is not my primary charge source.
I sized my shore power charger for the LiFePo house bank, at 75A, so I could use my 2KW/1.6KW continuous inverter generator to recharge if necessary. In 3 years I have not had to do so, but we go to sunnier locations...
Hope this helps,
Mike.

[Renegde_Sailor]

Originally Posted by Dockhead

I have completely separate engine and generator start systems, each with its own separate charger and alternator, so that's not at issue here.


HOWEVER, I do have a concern about my Sleipner bow thruster, which might need a motor rewind in order to be used with lithium.

So, it could be possible to swap this around from what I envisioned -- leave the lead in the "service bank" box, which serves thruster and other heavy loads, and put the lithium in the "house bank" box. I would need to have a switchover to bypass the lithium in case of emergency but that should be quite straightforward.

That would also protect the lithium from heavy loads, which would mean I could use cheap MOSFET BMS's rather than expensive REC ones.

Hmm. OK, you've given me some new ideas -- thanks!

The thing to keep in mind with DC is it hates distance, I would run everything you are thinking of doing through the voltage drop calculator.

https://www.calculator.net/voltage-drop-calculator.html

On all of my systems I will not accept anything below 3% loss, they say you can go up to 10% on anything that is non critical, but I don't risk it.

On my setup it is about 25' from the batteries to the distribution which clocks in the following when the inverter throws a max 250a load at it if she is choochin at full tilt.

Voltage drop: 0.63
Voltage drop percentage: 4.91%
Voltage at the end: 12.17

That is why I am moving them back to the engine room with the new box to get back below that 3% loss.

[Hope123]

I really found it useful how you shared such descriptive insights on hybrid power systems. As your experience would be a guideline for readers. Keep sharing!!

[MWGDVC]

Renegde Sailor,
I agree that minimizing distance is very helpful, I wish I could do what you did.. Regrettably on my smaller boat, I have a chain locker with 280'/85M of chain, a 55lb/25KG anchor on the bow, and 70 gallons/265l. of water in the fwd. tank. I haven't the space, nor could I afford the additional weight forward to add 50-60 lbs more forward for a windlass battery. Not such an issue in larger boats.

Moving batteries to the engine room is probably fine for AGM,(that is where my start battery is, short cable run that way), but as I understand LiFePo is best stored at 73F/23C for maximum life.

[Dockhead]

Originally Posted by MWGDVC

A couple more observations based upon my experiences with my configuration:
Lighting maintains a consistent brightness as Li voltage remains steady during all but the very tail end of discharge. Electronics are more reliable due to steady voltage supply as well.
LiFePo recharge faster than lead chemistries. Great for solar power harvesting.

I made the mistake of purchasing a 60A 12V B2B charger. I have a 120A alternator, external regulator, serpentine belt engine charging system. The B2B uses 75A to output 60A to the house. This causes the alternator to get warmer than I would like. Fortunately my B2B has a 50% output setting (30A). At this output the alternator runs at 185F/85C. If I were to replace the B2B, I would purchase a 40A instead.

In my use case, this works out as alternator is not my primary charge source.
I sized my shore power charger for the LiFePo house bank, at 75A, so I could use my 2KW/1.6KW continuous inverter generator to recharge if necessary. In 3 years I have not had to do so, but we go to sunnier locations...
Hope this helps,
Mike.

Thanks. All this real experience is of course very helpful, since all I have is theory and fantasy.

My main engine has two alternators -- the stock Yanmar one which charges only the start battery and nothing else, and a Leece-Neville 110A 24v school bus alternator. I will not use a B2B there but rather regulate the alternator with a Wakespeed regulator wired to the BMS with CANBUS, and connect it directly to the lithium via a charge bus. This alternator is large case and hot rated, so it can be used continuously at its rated maximum output, unlike car alternators which are not designed for bulk power production.



I don't have solar because of windage and sailing performance (we race occasionally). Charging sources are the 2.5kW school bus alternator dedicated to house bank, and 6.5kW heavy duty low speed generator. I have the 3000VA/70A 24 volt Victron Multiplus. We consume a lot of electrical power with partial electric cooking, washer/dryer, extensive nav electronics, radar, etc.

I would charge the lithium directly from Multiplus (using either shore or generator power) and alternator. I realize I could use a bigger charger to shorten generator runs but compared to charging lead batteries it will be a paradise. The 70A charger in the Multiplus is only drawing 2kW and will take 8 hours to fully recharge a 560AH bank. But I'll be harvesting a lot of power from using the main engine so I think it's not so bad. Also I run the generator anyway for a couple of hours a day doing laundry etc. so it's not such a big deal.

If I keep one of the lead banks for backup power and bow thruster, that will get charged from a Sterling B2B charger from the lithium bank. Very little power (in terms of kWH) is used from those devices so the demand will be easily covered with a small B2B charger.

[Dockhead]

Originally Posted by Renegde_Sailor

The thing to keep in mind with DC is it hates distance, I would run everything you are thinking of doing through the voltage drop calculator.

https://www.calculator.net/voltage-drop-calculator.html

On all of my systems I will not accept anything below 3% loss, they say you can go up to 10% on anything that is non critical, but I don't risk it.

On my setup it is about 25' from the batteries to the distribution which clocks in the following when the inverter throws a max 250a load at it if she is choochin at full tilt.

Voltage drop: 0.63
Voltage drop percentage: 4.91%
Voltage at the end: 12.17

That is why I am moving them back to the engine room with the new box to get back below that 3% loss.

I'm not changing anything about the original design, so I don't think any of this will be a problem.


The bow thruster has, for the last 15 years, been powered from 4 lead batteries located about 7 or 8 meters from the thruster, connected with fairly heavy cables. It's 24v and not 12, so that helps a lot. The thruster works fine and the only change this setup would create would be to allow me to switch to AGM batteries which have a lot more CCA than the golf cart batts I have now. I'm sure it will work fine.


I don't have any voltage drop issues anywhere else either. Lights never dim no matter what; never any problems with nav electronics. The boat's electrical system was well designed, and 24v greatly mitigates these problems in any case. That's why I want to change it as little as possible!

[Tupaia]

I am at a loss to understand why you are moving to Li?


You seem to be a adding an Li system to a perfectly working LA system.
What benefits are you trying to achieve?

[Nicholson58]

We used Hank at Starboard Landing who reps Blue Heron LiFePo.
The starting and house batteries were changed in November of 2023 to Blue Heron LiFePo, lithium iron phosphate. These are determined to be safe by ABYC. Contact Hank George at Blue Heron for help or assistance. hank@starboardlanding.com

Hank was fantastic in helping with the layout and engineering. No DC DC converters. All necessary software upgrades , dongles, patch cords etc were researched by Hank. All special hardware was in the boxes and the entire sister was dropped to Power Boats in Trinidad for us. Total installation in Trini was five days including physical modifications to the battery boxes. This system has been life changing.

House 3 X 210 amp hours = 630 AH@ nominal 24 volts.
Starting 110 amp hours @ 24 VDC
Total 740 AH.


There are two battery KEY switches on the main panel. Both are always be on. The combined house battery, while large, is not rated for the main engine starter instantaneous current. For this reason, the starting battery, two high output X 12 volts in series, was added. These are also by the same manufacturer and compatible for parallel connection.

The key switches permit separating the banks so motoring, motor-sailing we selectively isolate the banks and control which one gets the solar or the alternator. We can also switch off the alternator.

Solar 985 watts has us fully charged most days by noon, later if we make water.

[Dockhead]

Originally Posted by Renegde_Sailor

. . . That being said, 2 battery banks in 2 different locations is having two for twice as much money, as they will need to be independently regulated and charged so keep that in mind as you are setting the system up.

Indeed! My boat was built with two separate battery banks in completely different locations, so I'm well aware of this.


Actually 4 battery banks if you count the separate main engine/generator start systems.


There is an upside, however -- redundancy.

[Dockhead]

Originally Posted by Tupaia

I am at a loss to understand why you are moving to Li?

You seem to be a adding an Li system to a perfectly working LA system.
What benefits are you trying to achieve?

Great question!

Yes, my lead system are originally designed works pretty well. Yes, it would be cheaper and easier just to buy a new set of golf cart batts and add an alternator regulator to prevent a repeat of the recent incident.

And that's what I should do if I don't have an absolutely clear vision of the advantages of changing over.

The main advantages, as i imagine them:

1. Drastic reduction of generator usage as I will have more usable power, much more efficient charging, and no endless finishing charges. And because of more efficient harvesting of alternator power when motoring.

2. Much cheaper in the longer run, due to vastly greater cycle life.

3. Less trouble because vastly less frequent replacement of the actual batteries. These Eve cells should outlast the boat, if I don't kill them somehow. Humping out and disposing of 8 old golf cart batteries; receiving and humping in 8 new ones, weighing I don't know what large portion of a tonne, is a lot of hassle which I will be very happy to lose.

4. Easier management without the need to fret about finishing charges, over-discharging, etc.

5. Less weight and volume.

Voltage sag is not a big deal for me since I don't have that problem with lead either. For others this could be another motivator.

The economics look like this:

560AH of Eve cells, less than €1000.
A couple of Mosfet BMS's €500
Hardware to mount and compress the cells -- €300
Fuses and contactors -- €500
Some recabling.

So far that's about the cost of a new set of golf cart batts, where I live.

On top of that I will need to invest in:

Management/montoring systems, say Cerbo, Smartshunt, etc. €600 -- €1200
Alternator regulator €600

But this adds functionality whatever the chemistry and I would be doing this even if I change my mind and just replace the golf cart batts.

That's how it looks to me at this moment, but I'm still studying it.

[MWGDVC]

Dockhead,
I believe you have outlined the advantages of LiFePo very well, as so far as I understand them.
Two things that kill this chemistry I am told are heat and low current overcharge. Once any cell is charged to 100% stop the charge. No float of any kind. This will cause the Lithium Ion Salts to convert to Lithium metal. This is an unrecoverable condition that will reduce the capacity of the batteries. Keeping the cells top balanced means, ideally, they all reach 100% state of charge at the same time.