New Boat: Lithium Now or Later

[fxykty]

Originally Posted by SV Confianza

I will second that! I really wish when we did our refit we went 24v instead of 12... I didn't want to replace the other 12v stuff, but I have since replaced a lot of it anyway. If I had to do it again, I would certainly go 24v in a heartbeat. I'm already reaching limitations of 4/0 cable with the lithium setup.

I will third that! At the time we planned our LFP conversion I just didn’t consider changing to 24V. Sigh.

We’re about to double our LFP capacity and need to decide between keeping to 12V (building a second same-size 4S battery and running the two in parallel, giving us some nice redundancy) or building a 24V 8S battery using a combination of new and old cells.

But the big cables are already led where they’re needed and we’d also need to replace our inverter/charger, our two external alternator regulators, and our windlass motor, and of course install a large 24-12 converter to power everything else that’s 12V. So not worth it at this point I think.

[Adelie]

Originally Posted by SV-Viento

Op here - and you are correct the builder is at this time supplying FLAs for the house bank. I would prefer AGMs if not lithium but they have strong opinions that differ from mine and simply have two options FLA or lithium.

Why do you prefer AGM over FLA?

For short high current loads such as windlass and bow thruster AGMs are the better choice. They are better able to deal with the high current demand. Since they are not drawn down very far they aren’t damaged by not having high current charging sources at all times.

For house loads where it can be expected that the bank will be drawn down past 65% SoC then you need to have and always use high current charging for the absorption phase. AGMs need to be charged at 0.2C minimum while in absorption, 0.3-0.4C is better. For a 600Ahr bank that means 120A minimum alternator, 180-240A would be better. To get that you need to pony up for a high output alternator, regulator and a serpentine belt system.

If you want to rely primarily on solar for recharging then you should use FLAs or Gels or install an AGM bank so large compared to normal daily loads that you almost never go below 70%.

[rslifkin]

Originally Posted by Adelie

Why do you prefer AGM over FLA?

For short high current loads such as windlass and bow thruster AGMs are the better choice. They are better able to deal with the high current demand. Since they are not drawn down very far they aren’t damaged by not having high current charging sources at all times.

For house loads where it can be expected that the bank will be drawn down past 65% SoC then you need to have and always use high current charging for the absorption phase. AGMs need to be charged at 0.2C minimum while in absorption, 0.3-0.4C is better. For a 600Ahr bank that means 120A minimum alternator, 180-240A would be better. To get that you need to pony up for a high output alternator, regulator and a serpentine belt system.

If you want to rely primarily on solar for recharging then you should use FLAs or Gels or install an AGM bank so large compared to normal daily loads that you almost never go below 70%.

TPPL AGMs like Odyssey do need those fast recharges. But other heavy duty AGMs don't necessarily. In fact, my Fullriver AGM bank doesn't like being charged at or above 0.2C. At or above that point, the batteries heat up significantly during charging (the one time I tried feeding them 0.25C they got over 120* and triggered the charger high temp cut-off). Below that, they only warm up a little, and below about 0.1C, there's minimal (if any) temperature increase. That said, the temp sensor in my setup is on one of the battery terminals, so the temperature there likely comes up a bit faster than the actual cell temperature at high currents.

[Statistical]

Originally Posted by Adelie

Why do you prefer AGM over FLA?

For short high current loads such as windlass and bow thruster AGMs are the better choice. They are better able to deal with the high current demand. Since they are not drawn down very far they aren’t damaged by not having high current charging sources at all times.

Is it even better for that?

AGM sustain higher peak current at lower SoC. FLA deliverable current falls off rather quickly as the SoC% declines as evident by a deeply discharged FLA starter battery struggling to deliver power to a starter. However do bow thrusters, windlasses, (and starters) ever pull the SoC% low enough for that technical difference to matter?

If you have a 1500W windlass (~120A @ 12V) and you run it for 5 minutes it will use about 10 Ah. If your windlass battery is 200Ah that is a 5% reduction in SoC. A DC to DC charger can top that back up in under an hour so you are really just cycling from 100% Soc to 95% SoC back to 100% SoC. Would AGM provide any benefit for the higher cost? You don't even need deep discharge FLA a "starter" bat would work fine.

In the LFP world AGM feel like a chemistry looking for a niche. For anything AGM does well LFP does it better. For the few things LFP are not as ideal doing FLA is cheaper.

[Adelie]

Personally if I had a high load at the bow like a windlass, I would run massively oversized cables to power it from the house bank figuring that the voltage drop of a 100Ahr AGM at the bow was going to be worse than from the 600Ahr bank at the stern end of the cabin.

Between extra battery (or 2), cabling and special charging arrangements its going to cost about the same as just installing oversized cables.

2-25’ rolls of 1/0 tinned cable is about $500.
4 terminals is $14, $15 with heat shrink.

AGM is $300 https://www.batteriesplus.com/produc...hoCo_AQAvD_BwE
Echo charger $193 https://www.westmarine.com/xantrex-d...BoCrgcQAvD_BwE
25’ 12ga duplex l tinned. $35
Lugs $10, maybe more depending on what the echo charger needs.


And all the batteries are in one place simplifying maintenance. Also there’s less to go wrong with cable than with batteries and the electronics in an echo charger.

[rslifkin]

Originally Posted by Adelie

Personally if I had a high load at the bow like a windlass, I would run massively oversized cables to power it from the house bank figuring that the voltage drop of a 100Ahr AGM at the bow was going to be worse than from the 600Ahr bank at the stern end of the cabin.

Between extra battery (or 2), cabling and special charging arrangements its going to cost about the same as just installing oversized cables.

2-25’ rolls of 1/0 tinned cable is about $500.
4 terminals is $14, $15 with heat shrink.

AGM is $300 https://www.batteriesplus.com/produc...hoCo_AQAvD_BwE
Echo charger $193 https://www.westmarine.com/xantrex-d...BoCrgcQAvD_BwE
25’ 12ga duplex l tinned. $35
Lugs $10, maybe more depending on what the echo charger needs.


And all the batteries are in one place simplifying maintenance. Also there’s less to go wrong with cable than with batteries and the electronics in an echo charger.

Agreed. I prefer that method as well. The only time I'd do otherwise is if there's an issue with excessive voltage sag on the house bank when using the windlass or something (not an issue with LFP and it hasn't been an issue on my boat with the windlass on the house bank).

[Adelie]

Yeah, but what’s going to sag more?

600Ahr FLA house bank under 120A windlass + 20A house load

OR

130Ahr AGM under 120A windlass load

AGM will sag more.

Even if it was 200Ahr of AGMs the sag would probably be close to even. But you would have paid 50-75% more with 2 AGMs.

[rslifkin]

Originally Posted by Adelie

Yeah, but what’s going to sag more?

600Ahr FLA house bank under 120A windlass + 20A house load

OR

130Ahr AGM under 120A windlass load

AGM will sag more.

Even if it was 200Ahr of AGMs the sag would probably be close to even. But you would have paid 50-75% more with 2 AGMs.

Exactly. The big house bank certainly won't sag enough to be a problem for the windlass. It's just a question of whether anything else will be bothered by the sag. Probably not unless it's a huge windlass on a small house bank.

[sailorboy1]

Considering $30k ..................I would just go with the builder standard and worry/change it later when needed.

If not for how inexpensive drop in LFPs have become I would have gone back to FLA after my expensive FireFly experiment failed 6 months ago.

[SV-Viento]

Originally Posted by Adelie

Why do you prefer AGM over FLA?.

I guess my answer is more subjective than the data driven objective reasoning you laid out. And to be clear the preference is lithium if cost not an issue. Given that, my preference for AGMs is 1) minimal to no maintenance, 2) minimal to no off gassing 3) limited risk of costic spills. 4) generally faster charging times.

In the end the builder does not offer an AGM option for the house bank only FLA or lithium.

[geoleo]

Originally Posted by SV-Viento

New 40' mono build for weekend to multi month cruises. Demand side of system will have fridge, full electronics with radar and autopilot, etc but at this time no AC or water maker. These items will be serviced by house bank either FLA or Lithium LiFePo.

Other demands loads include windlass, electric headsail furling, and electric primary winches and starter to be serviced by Separate AGMs via DCtoDC relays.

Shore power, 2 alternators (one to starter and one to house and AGM loads). Future solar is also planned.

THE QUESTION: should we have the House System Set up with lithium now or later and the real question is cost. The entire system is a Mastervolt system. To add Lithium, the builder charge is close to 30K. But my simple math indicates we can add later for roughly half of that. What are we missing? and should we simply move forward with it now or later?

You seem to be ;guilding a Lily. Why not just get couple Full River Agm s and enjoy sailing?

[AKA-None]

Originally Posted by SV-Viento

I guess my answer is more subjective than the data driven objective reasoning you laid out. And to be clear the preference is lithium if cost not an issue. Given that, my preference for AGMs is 1) minimal to no maintenance, 2) minimal to no off gassing 3) limited risk of costic spills. 4) generally faster charging times.

In the end the builder does not offer an AGM option for the house bank only FLA or lithium.

Then consider putting in the equipment that can do lithium and set it to work with fla
You can upgrade at any point

[SV-Viento]

Originally Posted by geoleo

You seem to be ;guilding a Lily. Why not just get couple Full River Agm s and enjoy sailing?

A bit pithy but actually appreciated the thought.

[SV-Viento]

Originally Posted by AKA-None

Then consider putting in the equipment that can do lithium and set it to work with fla
You can upgrade at any point

One of the two options we are considering.

[stormalong]

Originally Posted by Adelie

Personally if I had a high load at the bow like a windlass, I would run massively oversized cables to power it from the house bank figuring that the voltage drop of a 100Ahr AGM at the bow was going to be worse than from the 600Ahr bank at the stern end of the cabin.

Between extra battery (or 2), cabling and special charging arrangements its going to cost about the same as just installing oversized cables.

2-25’ rolls of 1/0 tinned cable is about $500.
4 terminals is $14, $15 with heat shrink.

AGM is $300 https://www.batteriesplus.com/produc...hoCo_AQAvD_BwE
Echo charger $193 https://www.westmarine.com/xantrex-d...BoCrgcQAvD_BwE
25’ 12ga duplex l tinned. $35
Lugs $10, maybe more depending on what the echo charger needs.


And all the batteries are in one place simplifying maintenance. Also there’s less to go wrong with cable than with batteries and the electronics in an echo charger.

I agree entirely with Adelie's post. That is what I did 30 years ago and it works well. In addition, most of the time you are operating a windlass the engine will be running and most of the power will come from the alternator. Also, even though it is a 1500 watt electric motor you will rarely use that much power.


As for the decision to go LFP, IMO don't do it.

My reasoning is that battery technology is rapidly changing. Different chemistries will be coming out in the next few years that will be better. The global demand for electric vehicles is driving a huge amount of R & D.

FLA is long proven technology. I use 6 Trojan T-105s for 660 AH at 12 volts. I have 390 watts of solar and two alternators. My loads include refrigeration and a windlass. I get about ten years from a battery bank. The batteries are seldom discharged more than 20%.

Considering the cost and potential obsolescence, again, IMO it is a poor investment.