Pulled the trigger on the cheapest LiFePO4 batteries anywhere. And I have a question.

[Cpt Mark]

A lot of good info here. What you choose to do with it is up to you. History lesson. Gel batteries were all the rage when they 1st came out much like Lifepo4 is today. People installed them on their boats, drop in. and within a very short lifecycle those batteries all died an early, expensive death. The owners blamed crappy batteries. Truth was, crappy installation. Yes, they were 12 v batteries that were the same size and shape as the lfp's they were replacing but the batteries required charging upgrades which people did not do. My prediction is Liepo4's are going to be suffering this exact fate as well.

I made the decision to go Lifepo4 a few years ago. Talked friends of mine about it who are extremely knowledgeable about electrical things. My buddy has a masters in electrical engineering, his response was, "it would take me a year to understand how that works". Nope, no way I thought. Yep. It took us a year to figure it out and I'm still not happy. Every cable coming out of those batteries needs to be upgraded. The level of power potential between lfp and lifepo4 is very different. Fusing needs upgrading, cable lengths need to be he same. This is not easy. You have a lot to learn to get what you want out of lifepo4. Read everything you can.

[Mr. Kevin]

Mark, why would you not stay with something somewhat more mainstream tried and true until their is a sufficient critical mass of knowledge on the technology/best practices published? The risk of getting it wrong and having your batteries die seems to be a substancial one. One that if I was leaving my home port for a period of time, I would probably not feel was worth it...

Originally Posted by Cpt Mark

A lot of good info here. What you choose to do with it is up to you. History lesson. Gel batteries were all the rage when they 1st came out much like Lifepo4 is today. People installed them on their boats, drop in. and within a very short lifecycle those batteries all died an early, expensive death. The owners blamed crappy batteries. Truth was, crappy installation. Yes, they were 12 v batteries that were the same size and shape as the lfp's they were replacing but the batteries required charging upgrades which people did not do. My prediction is Liepo4's are going to be suffering this exact fate as well.

I made the decision to go Lifepo4 a few years ago. Talked friends of mine about it who are extremely knowledgeable about electrical things. My buddy has a masters in electrical engineering, his response was, "it would take me a year to understand how that works". Nope, no way I thought. Yep. It took us a year to figure it out and I'm still not happy. Every cable coming out of those batteries needs to be upgraded. The level of power potential between lfp and lifepo4 is very different. Fusing needs upgrading, cable lengths need to be he same. This is not easy. You have a lot to learn to get what you want out of lifepo4. Read everything you can.

[Cpt Mark]

Originally Posted by Mr. Kevin

Mark, why would you not stay with something somewhat more mainstream tried and true until their is a sufficient critical mass of knowledge on the technology/best practices published? The risk of getting it wrong and having your batteries die seems to be a substancial one. One that if I was leaving my home port for a period of time, I would probably not feel was worth it...

Very good question. The potential benefits of Lifepo4 are amazing. I no longer have any propane on my boat. An all electric kitchen I love and soon, solar powered to run it all. Building the batteries is easy. Putting together all of the bits and pieces to make a system out of it was the challenge. And that's what this whole lifepo4 thing is about. It's not just a battery, it's an entire system that needs to be evaluated, upgraded etc. I also expect these batteries to outlive me. True they may be obsolete n the next 5 years but it won't matter to me because mine will still be going strong. I upgraded every part of the system to match what Liepo4 needs to work.

I am confident that the system we designed and put in exceeds ABYC standards whatever those mysterious standards are. That, is an issue I have with ABYC. They have these standards that you can only access by paying a lot of money to them. These "standards" should be public . Then you can hire a certified ABYC electrician to do the work, check the work etc. BTW, my buddy has asked a few ABYC electricians about lifepo4 and they say, they don't know, don't understand it. I'm sure some do so maybe they need an additional certification for those who are fully trained in this technology.

[billyehh]

Looking through the website of the battery seller, nowhere could I find the capacity of the BMS. In fact the only reference was on the side of the battery which stated that it had an internal BMS. I suspect being a cheap battery that the BMS is only 50 amps. No wonder that it shut down the battery when it was used to try to start the engine.

The website as well as most experts emphatically state that LiFePo batteries are not to be used as starting batteries.

[mcon12000]

Hi OP,

ABYC tech here.

This thread is a bit nuts as it’s rare to see so much good information ignored. Kinda feel like the whole thread is a setup. Anyway that said I’m going to address one serious issue that has still not been resolved in the comments.

You can not have any washers between the battery terminal and the cable lug if you need a washer it should be placed on top of the lugs where it’s job is to be a spacer and provide clamping force. The correct material for this washer would be stainless steel as softer materials can deform and lead to loosening of the terminals. This loosening will cause resistance which will then cause heat followed by damage to the post, lug or wire.

On a personal note it appears you’re polling or looking for one person to agree with you and call this project complete. That’s not going to happen because there’s simply too many things wrong in fact so many I’m wondering if this was written for a laugh. If it wasn’t please no offense and take less time than it took to read all these comments and google “marine how to” website there you will find the information you need to continue this project.

[Nicholson58]

Originally Posted by jcapo

Others will delve more deeply but the battery internal BMS disconnected the battery due to current load. The website says 100A max load but they lied or the starter current exceeded 100A.

Parallel all 4 batteries for the house bank and retain one AGM, or buy another, for the starting battery.

LFP batteries are not drop in direct replacements for lead acid batteries. You have a lot of studying to do re: LFP on boats.

�� max output current for a starter will often exceed battery capability. Also, starters may demand more than their published data. My Blue Heron set included 630 AH @ 24 VDC but I still had to add in 110 AH starting set in parallel. My starter is nominally 80 amps but can suck almost double that as inrush.

If you didn’t add an alternator suppressor such as sold by Balmar please consider. This will protect your alternator if the BMS cuts out.

[Colin Stone]

Just had my insurance renewal and my insurer drew this guidance to my attention -
https://www.havenkj.com/guides-and-t...tery-guidance/

Point 5 - fire protection is I think quite difficult to achieve. It could easily require LFP batteries to be in a floodable tank. Certainly the FirePro technician I was talking about LFP onboard was thinking along those lines even though his product can put out a Li fire but not stop a thermal runaway.

[wholybee]

Originally Posted by Colin Stone

Just had my insurance renewal and my insurer drew this guidance to my attention -
https://www.havenkj.com/guides-and-t...tery-guidance/

Point 5 - fire protection is I think quite difficult to achieve. It could easily require LFP batteries to be in a floodable tank. Certainly the FirePro technician I was talking about LFP onboard was thinking along those lines even though his product can put out a Li fire but not stop a thermal runaway.

That guidance doesn't distinguish between different Lithium Chemistries, simply grouping them together as "Lithium Ion." I would toss out and disregard any guidance that fails to acknowledge the differences between Lithium Chemistries. Importantly, Lithium Iron Phosphate batteries are (in the words of another forum member) safer than a 2x4.

LFP batteries are very difficult to set fire. When they do burn, when the cause is removed (for example a direct electrical short, or if there is something else burning near them) they will self-extinguish and go out on their own. The don't go into thermal runaway except under controller lab conditions where they force it to happen. Testing by the ABYC doing everything bad they could think of could not get them to burn. When the whole boat was set on fire, the LFP batteries did not contribute to making the situation any worse.

What I just said is not true generically of "Lithium Ion" which has many variant chemistries, and are fire hazards in cars, e-bikes, and cell phones. Which is why when we talk of LFP batteries on boats, we need to understand that guidance for "Lithium Ion" is wrong.

[Nicholson58]

ABYC has approve LiFePo for boats. I don’t recall any crazy restrictions. They are just about ignition proof. Many insurers have not got the message.

Watch out for all other big lithium devices such as surfboards, dive scooters, E bikes, hover boards, outboards. BOAT 23 Feb issue has an article noting many superyacht fires from these devices. They list special precautions but not for properly installed house and starting banks.

[The Sun King]

I agree with the notion that the BMS is shutting you down when trying to start the motor, due to overcurrent. Somewhere in the fine print you can find the various BMS ratings and settings. Some BMS units are programmable, but I don't know on the drop-ins.


I put 2 x 320 ah 24v LFP batteries in parallel aboard Sun King to replace FLA batteries and quickly found that they are not the same. I now have much greater range (electric propulsion) but weird things happen when the two BMS controllers interact, or fight. I can set these to a max of up to 300 amps each, but they do not exhibit normal parallel battery operation. One supplies all the load for a while, minus whatever solar is making. Then, without warning, the other decides that it will discharge to run things AND since the 1st battery is down a little, it tries to charge it, too, resulting in huge currents. Normally the biggest load is from the galley and the old 100 amp breakers were plenty. I doubled to 200 amp breakers and can still manage to pop them if I am using the boat to charge my EVs, even though the inverter could not possibly pull 200amps.


LFP batteries with BMS are a different animal.

[KingRichard]

Rohan, thanks for taking the punishment on this one, I learned a lot. Read almost everything.

I think Nicholson58, a few posts back, was onto your initial question/problem. That is inrush or starting current for most electric motors is 2-3x operating current. I think you posted the discharge current at 100A for these batteries, that's not a lot. I think the old lead acid starting batteries are in the 500-800A range. Under perfect conditions 100A and change might be just enough, but often times won't be.

I do like the idea of using a lead acid or AGM as a sort of buffer or capacitor with the charging systems and/or alternator feeding into it, but I'm not sure if this would work the way I'm imagining...

I do have a question, when you said that you ran the alternator into your charger... I assumed it was something like a solar charge controller? Obviously not AC, but that was funny

Best

[Jweyndling]

Lithiums are not designed as cranking batteries. As others have said the BMS limits the current you can draw from
Any one battery. When you connect three together you can draw three times the current. Best to stay with lead acid for starting if you want to have a separate start battery.

[KingRichard]

Forgot, second on the guy that said not to use zinc plated washers for conduction, tracking down a handful of copper will be worth the time. You'll have that same type of crappy connection like the solar panels

[team karst]

Originally Posted by Rohan

The washers, bolts and nuts I used are all zinc,

.

Highly unlikely. They are zinc plated, still poor conductor. If u need to send hundreds of amps thru metal, do as the man said copper. Or brass.

[mvweebles]

Originally Posted by Tupaia

FWIW I recently replaced 2 banks of 3 AGM's with one bank of 4 Lithiums. I got round the start issue by using a couple of Racing Series batteries these are very small, weight approx 6kg and are designed for starting so have excellent cranking ability.

Anti-Gravity makes LFP (LiFePO4) starting batteries that are pretty slick. I use one in my Tohatsu 20hp with electric tilt/start. Weighs 3lbs. Automotive sized are available.....for a price

https://antigravitybatteries.com/pro...m/atx12-hd-rs/