Lithium for the love of God

[exMaggieDrum]

Originally Posted by CatNewBee

No problem with float on LFP, especially if you use power during the night, youll cycle the battery. It is only important to set it lower than a full cell would have in rest without charge, so there is no current going into the cells.

The main concern of the folks out there is, they want the LFP at 30% SOC (the recommended storage charge) for longitivity, that is a senseless approach. If you go for LFP, you do it on purpose and want the battery full in the afternoon and cycled during the night and morning. You want the power, and not just the storage 30% energy.

If you set the Float to 13.4...13.6V, the cells remain at 98%,while all current of the Float controller goes straight at the loads. Nothing wrong with that. At some point the voltage drops and the battery provides the missing energy.

Next day you simply re-charge what you have used.

It is not recommended to STORE LFP batteries at full charge, but you are not storing them,you are using them, so it is ok. It makes no sense to install a double size battery to just keep it at 50% SOC for longuitivity. This is a stupid approach. You buy the capacity you need and some extra for safety in cloudy days, you harge to full and use what you need. That is all.

What about the case of being off the boat for longer, for several days. If I didn't want to keep the refrigerator going I would shut off everything except the bilge pumps. They do automatically cycle several times a time but it would not be much of a load. From what you say, the reefer should keep some load on the battery but I think it cycles to bulk/absorption for X hours when the sun comes up each day, to whatever voltage I set. I just want to be clear on any issues.


Thanks for your comments.

[CatNewBee]

Originally Posted by exMaggieDrum

What about the case of being off the boat for longer, for several days. If I didn't want to keep the refrigerator going I would shut off everything except the bilge pumps. They do automatically cycle several times a time but it would not be much of a load. From what you say, the reefer should keep some load on the battery but I think it cycles to bulk/absorption for X hours when the sun comes up each day, to whatever voltage I set. I just want to be clear on any issues.


Thanks for your comments.

If you switch off everything and no energy is used, no energy is re-charged. the battery remains full. No cycles. You should not winterize it that way, but it will not hurt you for a couple of days or even weeks. Maybe you lose 10 cycles of the 5000 you supposedly have, but you saved 30 cycles during this time by not cycling every day. So what?

[exMaggieDrum]

For the times when I do not need to have any loads left on I am OK with leaving the battery at 50% SOC and checking it as often as I can, say in the summer (in the tropics) when not on the boat, or in the winter if in the higher latitudes. But if I am gone for just a week and want to leave the refrigerator on then I don't want to turn off all loads. I guess from what you saying it would be OK. I certainly would set my float at a lower level but the daily cycling at bulk/absorb would be a possible issue, or would it?


I hope I am not being too dense at this point. After this I will go off to other things.



Cheers

[CatNewBee]

Hi there. It is never a good idea to run electric devices unattended for a long time. Possible fire etc.

But back to your question.

When you stay on board and run yor fridges for a week, do you need a generator, alternator or shore power to recharge the battery or are you self-sufficient with battery and solar?

What about 2 or 3 cloudy days?

If you not need additional energy, your system may be fine.

If you have a BMS, that monitors the cell voltages and engages in case something goes wrong, you will be on the safer side. Worst case here potentially melting stuff in the fridge.

The risk of fire due to a failure in the compressor or corrosion is always present when running stuff.

Only you know your system and can make an educated decision what is feaseable.

[exMaggieDrum]

My bank can handle 7 days on my reefer at this location. I am not sure it could in a warmer location. My general practice would be to certainly turn off everything, including the reefer unless that would be very inconvenient while living aboard and then I would make a decision based on what would have to be disposed of if it were shut down.


Boats are always a potential risk. The risk of unintentional sinking is far greater than the risk of a fire in my experience. In my area, owners routinely leave devices running on their boats, some DC but mostly AC. The fires that happen are 90% from AC heaters and/or battery chargers. Of these I suspect (but don't have direct forensic evidence) those are mostly from loose wiring connections or wire corrosion issues.


But your concern is a good one. I wouldn't hesitate to leave my new reefer compressor running for a few days if need but, but as you say, that is my personal decision. I would be more likely to do that when in a marina rather than anchored out since there are other issues then such as dragging anchor, storms, theft, etc.


What I am trying to address is the issue of how well the chargers themselves can be regulated so that the BMS should normally never have to disconnect anything.



As others have noted the BMS should be the safety device protecting the batteries of last resort.

[CatNewBee]

Originally Posted by exMaggieDrum

My bank can handle 7 days on my reefer at this location. I am not sure it could in a warmer location. My general practice would be to certainly turn off everything, including the reefer unless that would be very inconvenient while living aboard and then I would make a decision based on what would have to be disposed of if it were shut down.


Boats are always a potential risk. The risk of unintentional sinking is far greater than the risk of a fire in my experience. In my area, owners routinely leave devices running on their boats, some DC but mostly AC. The fires that happen are 90% from AC heaters and/or battery chargers. Of these I suspect (but don't have direct forensic evidence) those are mostly from loose wiring connections or wire corrosion issues.


But your concern is a good one. I wouldn't hesitate to leave my new reefer compressor running for a few days if need but, but as you say, that is my personal decision. I would be more likely to do that when in a marina rather than anchored out since there are other issues then such as dragging anchor, storms, theft, etc.


What I am trying to address is the issue of how well the chargers themselves can be regulated so that the BMS should normally never have to disconnect anything.



As others have noted the BMS should be the safety device protecting the batteries of last resort.

no problem with the Victron MPPT, you can set them to pretty low voltages. They never trip the BMS. More concern about deep discharge, there the BMS will definitely help throw the loads if necessary.

[Nicholson58]

Originally Posted by john61ct

Too strong.

Had a poster assembling packs from small cylindricals, DIY Tesla style, say that accidentally puncturing them did cause a brief flash-flareup type fire.

Did not ignite others though.

So, yes, very safe, maybe as safe as lead, safer than gas or propane.

But "You cannot make it burn" is overstating.

"Much less subject to thermal runaway" is how I'd put it.

You are correct.
These guys put a torch to them, bullets, shorts, etc. never self-ignited despite terrible abuse.

https://marinehowto.com/lifepo4-batteries-on-boats/

YouTube

https://m.youtube.com/watch?v=aQs7L5...mTpf_xVUPbTWwg

Highly unlikely any of the legendary lithium run aways. Makes one wonder what the aircraft makers used for common sense.

[exMaggieDrum]

I am relocating my Outback solar charge regulator, and, as I always do, I took a second look at the wire sizing.

My 2000W inverter/charger puts out a solid 100A to my 400Ah LFP bank when it is at 13.7V and it does not slow down as long as I run it. The fan starts running after about 10 minutes and then the fan goes in to high speed 5-10 minutes after that. I have a relatively short run of 3/0 cable from it to the battery so it is sized well for the current.


My solar charger and panels were put on by the OP (as was the I/C) but he undersized the wiring even for AGM batteries. The wire runs are longer. From the panels to the old charger location is 8-2 duplex wire and it goes up and through the stanchions. The regulator was in a potentially wet spot in a cockpit lazerette right under the hatch so I did not want to leave it there.


I am moving it to a dry location that is also closer to the battery but still a 16 foot round trip for the cables to the battery. The previous cables were 6ga. Of course the solar panel is 50V so the potential 60A current to the regulator was probably safe since the previous AGM batteries would push back fairly quickly, slowing down the current on the cables fairly quickly. But they were significantly less than required for full output over a long charge cycle. Still too small in my opinion but I was not going to redo until I put in the LFP bank.
But watching how my LFP battery just sucks up any and all juice without any pushback made it very obvious how important safe wire size is. So I have to assume that the panels and regulator will put out full charge until voltage setpoints are reached.


That means I really need 6ga from the panels to the regulator and 4ga from the regulator to the battery. That is a huge increase in wire size. I am putting in my new 60A AC charger and am also using 4ga for it (as recommended by the installation and ABYC guidelines). I know the wiring will have substantial current for potentially hours.

This is emphasized in most of the LFP threads but also shows how important it is to review existing wiring for all previous charge sources with LFP upgrades.
I am also replacing my 4ga alternator wiring with 2ga for a relatively short roundtrip. This isn't easy to do (as on many boats) but very important.


Those of you who have been looking at this for awhile, and those who have paid attention to the voluminous threads on LFP installations, this is nothing new. But I suspect some have taken are will take the easy route and just change the charger setpoints and call it good, assuming the old wiring was good enough for the old batteries it will be good enough for the new.


It is going to take me about two weeks full time to redo all this given the wire run difficulties of taking out old wire and replacing with new, plus the money for the wire. I'm reusing the old wire for some of the new wire runs where I can but I have had to buy several 25' rolls of 4ga and 6ga wire now. I am not going to replace the 8ga duplex going to panels that goes through the bimini tubing (yet) but will connect 6ga for most of the new wire run from the closest point to the bimini tube end points.

[john61ct]

While it is true that few electrons are flowing when a charge source drops to Float with a fully charged batt

that does not mean there is no longevity-reducing effect of leaving the LFP connected to that charge for long periods of time, even if voltage is set very low. That factor is as yet unknown, so best to ensure the bank is isolated once full from any charge sources.

More importantly, remember that LFP should **only** get charged to a high SoC just before the loads come online to start depleting them.

When they are not being actively cycled, SoC should be reduced to as low a level as possible, consistent with not risking self-discharge will bring them anywhere near dead flat.

IOW there is not only **no reason** to Float LFP, you are drastically shortening their lifespan by keeping them in a Full state for more than a few minutes.

Float is Lead Thinking.

[john61ct]

Originally Posted by exMaggieDrum

What I am trying to address is the issue of how well the chargers themselves can be regulated so that the BMS should normally never have to disconnect anything.

As others have noted the BMS should be the safety device protecting the batteries of last resort.

For large / pricey banks, there needs to be a "middleware" defense layer controlling relays to isolate the bank in daily use, separately for charging vs loads buss.

Do not trust the charge sources' regulation.

That approach will also save money, let you use any old dumb charge source without worry.

Keeping the BMS as a failsafe fallback defense layer.

[exMaggieDrum]

As much as I would love to not install a BMS I am going to do it.



I would like an option on charge regulators so that they get to some absorption voltage point and then shut down without float, as you say. Then wake up and recharge at some lower voltage set point.

[OceanPlanet]

Originally Posted by exMaggieDrum

As much as I would love to not install a BMS I am going to do it.



I would like an option on charge regulators so that they get to some absorption voltage point and then shut down without float, as you say. Then wake up and recharge at some lower voltage set point.

You're in Anacortes? We've starting selling Li systems to Betts Enterprises there, where they have some pretty impressive projects going. Starting with a small battery/charger/monitoring kit for the nifty Bieker 35 "Terramotto". But I digress.

Wanted to point out that we often use Victron inverter-chargers with which you can program a very low Float, and then a periodic repeated absorption every 1-30 days (we usually go for every couple weeks). So, if you set the Float low enough you essentially have what you're looking for.

[exMaggieDrum]

Originally Posted by OceanPlanet

You're in Anacortes? We've starting selling Li systems to Betts Enterprises there, where they have some pretty impressive projects going. Starting with a small battery/charger/monitoring kit for the nifty Bieker 35 "Terramotto". But I digress.

Wanted to point out that we often use Victron inverter-chargers with which you can program a very low Float, and then a periodic repeated absorption every 1-30 days (we usually go for every couple weeks). So, if you set the Float low enough you essentially have what you're looking for.

Bob Perry designed a four boat commission for Betts. He said he would give me a tour if I wanted when he was visiting. I got to meet Jim Betts and his crew and see the facility. They seem to be doing very well. We are all happy the boatbuilding industry is still going here.


If I have to replace my old Trace I/C, I think I would put the Victron at the top of my list based on all the kudos it has received for lithium setups. Thanks for the info. By very low Float you mean low voltage?

[OceanPlanet]

Originally Posted by exMaggieDrum

Bob Perry designed a four boat commission for Betts. He said he would give me a tour if I wanted when he was visiting. I got to meet Jim Betts and his crew and see the facility. They seem to be doing very well. We are all happy the boatbuilding industry is still going here.


If I have to replace my old Trace I/C, I think I would put the Victron at the top of my list based on all the kudos it has received for lithium setups. Thanks for the info. By very low Float you mean low voltage?

Yes, low Float means low Float voltage setting. We sell & set up the Victron Multis & Quattros often here as part of the complete system packages we ship out: Lithionics batteries, inverter-chargers, monitoring (Simarine, Victron, Philippi, etc.), HO alternators with pulley kits & regulators, solar with controllers, B2B chargers, etc. Then everything in the system is programmed appropriately when it arrives.

[N1EYO]

Following - with interest.