Practical Questions about LiFePo4 Power Systems

[a64pilot]

I wouldn’t pour more money and effort into current Boat, I would the new one.
I’d assume you likely have to hire someone to supervise the build as you won’t have time for the details?
Anyway it would seem that your within the design window if that makes sense now, time to start designing, redesigning the new Boat?
Surely you spend considerable time with a statement of work, outlining priorities, the start specifying equipment / systems designers?
I assume you contract out the electrical system?

[Dockhead]

Originally Posted by a64pilot

I wouldn’t pour more money and effort into current Boat, I would the new one.
I’d assume you likely have to hire someone to supervise the build as you won’t have time for the details?
Anyway it would seem that your within the design window if that makes sense now, time to start designing, redesigning the new Boat?
Surely you spend considerable time with a statement of work, outlining priorities, the start specifying equipment / systems designers?
I assume you contract out the electrical system?

Yes, of course, new boat will not be built by me, but by actual skilled people, in an actual shipyard



I've done a lot of work on the design brief (some of it posted on here), and there's still a lot of work to do. But to do actual design, I'll have to hire a N.A., and I don't have the money for that at the moment, so I am kind of stuck in the design brief stage.

[a64pilot]

I didn’t know, but assumed if construction was to begin in a year or so, then you have a lot to work to do, unless of course you accept a “standard” boat, which there is nothing wrong with that, but I assumed you have other desires

[evm1024]

Right now I recharge my start and windless batteries with dedicated 10 Amp chargers (that do 3 stage). I run the chargers off the inverter when the engine is on.

Not very efficient, I know. I do get small gauge wires to the chargers and that is a plus.

One problem is that I do not have any solar at this time (still in the refit and full time cruising is a year out).

But when I get the solar installed I will run "raw" solar voltage out to the start and windless batteries and charge them through a victron MPPT 75/15 each.

The main LiFePO4 bank will have its own mppt controller. And will take the lions share of the solar output till it reaches a point where it is disconnected for the day.

I have done some small scale testing with 2 MPPT 75/15 on a single solar bank and not seen any "unexpected" events. It may not be as efficient as is could be but then again a single cloud will do that we well.

The idea is that after the main LiFePO4 bank has its AH replaced and disconnected the 75/15 will kick the 2 AGM batteries up where they need to be for long life.

That's the theory anyway.

If you all recall I posited this idea a while ago and ended up asking a Victron engineer if there would be any potential of destroying the solar MPPT controller. It is safe to do this but may not be as efficient.

And having a single 75 watt panel to play with I have not observed any issues. Of course 75 watts is a far cry from 1 kw of solar.

[rgleason]

connected with no battery to charge; at this point, an unregulated charging voltage usually gets fed straight through into the boat’s electrical system, leading to a memorably expensive wholesale fry up. The ultimate in terms of the depth of thoughts afforded by the incident is when it happens at sea.

This one is a. Overstatement.
Sterling pro ultra can be used w/o batts for house. Fry up ? What?

[john61ct]

Originally Posted by Dockhead

I think I would need the whole supply backed up. Perhaps running the loads bus off the lead and charging it via the lithium via a B2B charger might be the way to go. In normal conditions, the loads will be powered directly by the lithium bank.

In that case I'd put all charge sources especially the alt to the Main/House lead bank. Regular ACRs to Starters, any other lead banks.

One Sterling B2B, big as possible, to feed Reserve LFP at perfectionist setpoints, BMS protected as you like.

A second, smaller B2B to go the other way, keep the lead bank "long tail" charging from LFP once the primary charge sources are shut down. Of course only if needed, haven't been getting to 100% for a few days.

Or old school solution, cheap lead replaced more often, if that makes more sense for you.

[senormechanico]

Originally Posted by john61ct

I just meant the charging reconfiguration.

An Essentials circuit could easily have an A/B switch on it.

Really, how failsafe are most boats?

I just want to compensate a bit for the (maybe imaginary) added risk of LFP.

The "BMS cutting off loads" protects the bank. Without it the same thing would happen anyway just a bit later.

That's why I don't have a LVD.

[daletournier]

Hi, I understand the advantages of Lifepo BUT how great are they really compared to the simplicity of a decent size Fla? If a Fla bank is meeting your electricity needs easily and without a great deal of fuss how much improvement is left?

I'm not trying to start a debate or argument just pointing out that my experience with my main bank of 660ah (900ah when combined) is more than adequate, I hardly ever see less than 12.6v first thing in the morning unless on passage, it's simple, robust and can absorb mistakes, it does everything that a battery bank should do, with ease. I just can't see what more is nessacary?

Change the boxes and you can then have a very simple solid system that dosent cost a great deal.

I top up with water once a mth, that's the only area I see upgrading to Lifepo would improve my life.

I suppose my point is, how much improvement, how much extra happiness do you get for the money and energy spent? Law of diminishing returns.

[CatNewBee]

Originally Posted by daletournier

Hi, I understand the advantages of Lifepo BUT how great are they really compared to the simplicity of a decent size Fla? If a Fla bank is meeting your electricity needs easily and without a great deal of fuss how much improvement is left?

I'm not trying to start a debate or argument just pointing out that my experience with my main bank of 660ah (900ah when combined) is more than adequate, I hardly ever see less than 12.6v first thing in the morning unless on passage, it's simple, robust and can absorb mistakes, it does everything that a battery bank should do, with ease. I just can't see what more is nessacary?

Change the boxes and you can then have a very simple solid system that dosent cost a great deal.

I top up with water once a mth, that's the only area I see upgrading to Lifepo would improve my life.

I suppose my point is, how much improvement, how much extra happiness do you get for the money and energy spent? Law of diminishing returns.

They are simply awesome and superior to any FLA technology.

You ALWAYS can override the BMS on a proper design of course, than you have just a simple, mega powerfull battery until you kill it on purpose Just use ML-RBS solenoids, they have a manual switch, so you simply push the button like on a automatic breaker. You even can install the remote battery switch in parallel to the BMS, and override it from the helm if necessary.

But you newer will. A good BMS will keep you safe all the time. BTW. I use the REC ABMS, no cell modules, less clutter and so less potential failures, totaly configurable. I use 1000Ah Winston LiFeYPO4 cells.

Advantages: endless power, no voltage drop, no gasing, no boiling batteries due to cell shorts, no top up with water, totaly maintenance free, full capacity usable a nominal 1000Ah cell delivers 1000Ah (they are over provisioned to meet 5000 cycles at 80% nominal capacity, so in fact my cells have initially 1200Ah - measured in the lab) A FLA 1000Ah bank delivers only useable 400...500Ah before the voltage drops below 11.6V

LFP charge faster, they are unimpresst with 1C continous charge or discharge rate, they stay cool.
*

[daletournier]

Originally Posted by CatNewBee

They are simply awesome and superior to any FLA technology.

You ALWAYS can override the BMS on a proper design of course, than you have just a simple, mega powerfull battery until you kill it on purpose Just use ML-RBS solenoids, they have a manual switch, so you simply push the button like on a automatic breaker. You even can install the remote battery switch in parallel to the BMS, and override it from the helm if necessary.

But you newer will. A good BMS will keep you safe all the time. BTW. I use the REC ABMS, no cell modules, less clutter and so less potential failures, totaly configurable. I use 1000Ah Winston LiFeYPO4 cells.

Advantages: endless power, no voltage drop, no gasing, no boiling batteries due to cell shorts, no top up with water, totaly maintenance free, full capacity usable a nominal 1000Ah cell delivers 1000Ah (they are over provisioned to meet 5000 cycles at 80% nominal capacity, so in fact my cells have initially 1200Ah - measured in the lab) A FLA 1000Ah bank delivers only useable 400...500Ah before the voltage drops below 11.6V

LFP charge faster, they are unimpresst with 1C continous charge or discharge rate, they stay cool.
*

Hi, I understand the advantages you speak of and don't dispute these are true BUT they make such little difference to my life, my battery bank already 100% forfills my needs for a much lower price and does so as part of a simple system.

My bank reaches acceptance rate of approximately 1% of total capacity each day via solar, my voltage is always above 12.5v (mostly 12.6v), the gassing causes no problem that I can see in my ventilated bilge, the weight is of no concern due to boat size, the fla battery explosion thing is very very rare, T105's will absorb charge regulator problems in their stride etc etc.

My point is I just don't see at this stage how Lifepo4 batteries make my life measurably better although they most likely are better.

I don't believe I'm just defending my choice, and I also, as stated understand the qualities of your battery choice, it's just that it dosent translate into anything more than I currently have from a day to day cruising perspective. I have as much power as I could possibly need.

Also I truly expect to get 6-8 years out of this bank based of my previous experiences and the experiences of other cruisers I travel with, time will tell.

[Dockhead]

Originally Posted by daletournier

Hi, I understand the advantages you speak of and don't dispute these are true BUT they make such little difference to my life, my battery bank already 100% forfills my needs for a much lower price and does so as part of a simple system.

My bank reaches acceptance rate of approximately 1% of total capacity each day via solar, my voltage is always above 12.5v (mostly 12.6v), the gassing causes no problem that I can see in my ventilated bilge, the weight is of no concern due to boat size, the fla battery explosion thing is very very rare, T105's will absorb charge regulator problems in their stride etc etc.

My point is I just don't see at this stage how Lifepo4 batteries make my life measurably better although they most likely are better.

I don't believe I'm just defending my choice, and I also, as stated understand the qualities of your battery choice, it's just that it dosent translate into anything more than I currently have from a day to day cruising perspective. I have as much power as I could possibly need.

Also I truly expect to get 6-8 years out of this bank based of my previous experiences and the experiences of other cruisers I travel with, time will tell.

I've often said -- solar and lead-acid batteries go together like cookies and cream. If you have a decent solar installation, then there is little to gain from lithium. Your use case is different from mine.


I don't have and won't have solar on this boat as I regularly have to do 1000 miles upwind in a given year, so the boat is on a strict windage-free diet.


The next one might have some solar built into the roof of the pilot house.

[CatNewBee]

So, stay with FLA, no question about it.

We chose LFP because we need them, the GEL bank 4x120Ah was too small, one battery boiled and smelled like rotten eggs, the other was just dead. 100Ah useable left.

We go all in, throw the GELs out, throw propane cooktop and oven out, converted galley to electric, topped up solar, inverter. No more generator usage. That was the taylored setup for us. Totally self-sufficient energy, water etc. It was a large project, but worth it.

[Dockhead]

Originally Posted by john61ct

In that case I'd put all charge sources especially the alt to the Main/House lead bank. Regular ACRs to Starters, any other lead banks.

One Sterling B2B, big as possible, to feed Reserve LFP at perfectionist setpoints, BMS protected as you like.

A second, smaller B2B to go the other way, keep the lead bank "long tail" charging from LFP once the primary charge sources are shut down. Of course only if needed, haven't been getting to 100% for a few days.

Maybe. But can there be two B2B chargers on at the same time, pointed in opposite directions? How would that work?

Originally Posted by john61ct

Or old school solution, cheap lead replaced more often, if that makes more sense for you.

Definitely under consideration.


Another reason to do lithium now is to gain experience and get the learning curve out of the way, before the next boat. This is actually a really good reason, given the "science experiment" aspects of lithium today (as A64 puts it ).

[Dockhead]

Originally Posted by a64pilot

I didn’t know, but assumed if construction was to begin in a year or so, then you have a lot to work to do, unless of course you accept a “standard” boat, which there is nothing wrong with that, but I assumed you have other desires

I will use a standard hull design but everything inside, and the rig, etc. will be designed from scratch.



The build itself won't start in a year; I've got to earn some money before I can start the design work, which will go on for a while. It's a long term project, and so I don't want to waste a couple (or few) of prime cruising years waiting for the new boat, when I still have a pretty decent one which just needs a few tweaks.

[daletournier]

The point I was trying to make is, how much do you gain in real life by going the lithium way? I used my own experience as an example, on paper I could see all these wonderful advantages BUT the longer I thought about it the more I realised it wouldn't change or improve my cruising at all, or at least very little.

Catnewbee determined it would and did improve his cruising considerably.

You have all the information you could possibly want regarding this subject, only you can decide if or how much of an improvement it will make to your cruising life and if that improvement is worth the cost and energy of instalation.
No wrong decision here, just cost VS returns.