Going from Lead to Lithium

[ksanders]

I ordered them directly from the manufacturer and had them delivered to San Diego and then CARLOS brought them down from DEKO MARINE

 

[dhays]

For my 2 LiFePo4 batteries I used equal length cables to a common connection point. Not necessary, but since this is all new to me, I decided that a little extra cable to the common connection point was worth being able to still have house power if one of the batteries decided to shut down.

OTOH, with my new AGM thruster bank of 3 Group 24 batteries, I just connected them in parallel and took the Post and Neg off of opposite ends. Not ideal, but given all the other potential losses going to a common bus bar, I figured it was "good enough".

 

[Marco Flamingo]

Re: Nigel Calder's video on parallel battery banks. He doesn't talk about the number of connections required for the various configurations (neither does this print article). Some examples show what looks like a single cable running between the batteries. I haven't seen lug fittings that would do that. My experience is that there would be 20 crimped-on lugs and 20 connection points used in the buss bar system, which gets you "closest" to perfect in theory. What are the chances of 20 fittings/connections all having the same resistance? I would think that a crimp/attachment point would likely be a larger factor than the resistance in a few extra inches of cable here and there. In the print article I cited, about the last paragraph states that for a two battery bank wired "fore and aft," there is no issue.

Here in lies the problem. Nobody, with all of their measurements and lab equipment have shown that I am going to significantly lower the life expectancy of my batteries by connecting them with whatever length cables work best for my boat. Yes, they make great measurements, and nifty looking graphs, but not one of them has shown any significant real world difference in my batteries that have what, a 5,000 cycle lifespan?

That's the same reasoning I'm using to eliminate a lead starter battery. Where are all the measurements and lab tests that show that I am going to significantly lower the life expectancy of my batteries by using a 4 battery bank of lithium to start my engine? How do we know if the only thing "new" about the new LFP combo/start batteries is the sticker on the side of the battery? I say this because I watched this happen to the Eco-Worthy 280Ah lithium. A year ago, the sticker on the battery said "Up to 15,000 cycles." Six months ago, the sticker said "Up to 6,000 cycles." Now the sticker doesn't say anything about cycles, but the specs that ship with the battery says "6,000 to 15,000 cycles" with no explanation. The spec sheet also state that peak discharge is 850 amps for 10 seconds. Time to put on a sticker that says combo/start battery?

I have found no real world testing, or even a plausible explanation, why 4 lithium batteries, each with a 250A continuous rating, can't be used to start a little diesel. Is that what drops the cycles from 15,000 to 6,000? That would still be about 6 times what a lead start battery can do. I'm beginning to see the wisdom of Will Prowse's recent statement to "smoke 'em if you got 'em" (that's my interpretation). It made sense to worry and baby-sit lithium batteries when they cost 5 times lead-acid. Now, I'm just as likely to see Davy Jones before I wear out 4 lithium batteries.

Ksanders' bluetooth app seems more sophisticated than mine, allowing to look at more than one battery at once. My app references WiFi, but the owner's manual says that feature isn't available yet from Eco-Worthy. I probably bought a few months too soon.

I believe Barking Sands started his motor a couple of times with a 120Ah lithium. He also said he tried to read peak amp draw when starting, but I don't know it that was using the lithium or his lead. I know my draw is somewhere around 500 amps, but I haven't sprung for a recording 1000A ammeter to get an accurate reading and probably won't. What I'm wondering about is the voltage sag and current draw differences between using a lead start battery and a lithium battery. Lead marine starting batteries are rated in Marine Cold Cranking amps. The allowable voltage sag is wild. A 750 MCC rating means that the battery can put out 750 amps for 30 seconds and stay above 7.2 volts. Most lithium have a BMS that would shut down at 10 volts, so they can't sag like lead even if they tried.

All of this got me wondering about just what is the amperage draw for my 4kw starter? I always assume that everybody knows more about Ohm's law than I do, so feel free to comment. Keep in mind that my last class on electronics was in 9th grade.

If, when I was looking at the 500 amp draw on my shunt when starting my 4 cyl diesel, the voltage sag on my old lead batteries could have been down to 8 volts (as deemed okay for MCC rating). That 500 amps would calculate out like this: (4,000W/8V=500A). If I changed to a four lithium bank for a starter, voltage sag might dip from 13V down to 12V (don't really know). 4,000W/12V=333A. From 500A to 333A, that's a 40% reduction just because a bank of lithium can't sag like lead. If the draw was 600A with lead, it could be 360A with lithium. That discharge is well within the "normal" parameters for discharge of 4 x 280Ah LFP. The four batteries combined have a 1,000 amp continuous discharge rating, so a kinda-sorta like having a 1000A MCC rated battery used to put out 360A. I just won't tell the batteries that the current is going to a starter.

 

[dhays]

Re: Nigel Calder's video on parallel battery banks. He doesn't talk about the number of connections required for the various configurations (neither does this print article). Some examples show what looks like a single cable running between the batteries. I haven't seen lug fittings that would do that. My experience is that there would be 20 crimped-on lugs and 20 connection points used in the buss bar system, which gets you "closest" to perfect in theory. What are the chances of 20 fittings/connections all having the same resistance? I would think that a crimp/attachment point would likely be a larger factor than the resistance in a few extra inches of cable here and there. In the print article I cited, about the last paragraph states that for a two battery bank wired "fore and aft," there is no issue.

[/QUOTE]

For that reason, on my 3 battery AGM bank, I made some copper bus bars with 1/4" x 1" copper flat bar stock. I was hoping to reduce the potential loss at crimps and lugs in the parallel connections.

 

[Barking Sands]

I'm beginning to see the wisdom of Will Prowse's recent statement to "smoke 'em if you got 'em" (that's my interpretation). It made sense to worry and baby-sit lithium batteries when they cost 5 times lead-acid. Now, I'm just as likely to see Davy Jones before I wear out 4 lithium batteries.

At the current cost.. the "smoke em if ya got em" view is much easier to adopt and I also subscribe to this view. Even though my batteries are not budget batteries, they arent deal breakers if I have to replace them at around $1500 each x2. Its very likely they will outlast my ownership of this boat. I am really not concerned about milking the last 100 cycles at all.

I dont think there should be much resistance to your starting your small diesel from a large bank with adequate load sharing. Load sharing is load sharing. There is nothing that I am aware of that makes lithium load sharing any different. Especially if you are well within the discharge ratings. Even though the official position at Epoch is that the standard models (non dual purpose) are not meant for starting....they know full well people are using them for this purpose. They have been doing this in the camper world with generators for years. I am not aware of any warranty denial or line of query regarding engine start when discussing possible failures.
I think the main disagreement may just be of not having a separate start bank for redundancy. It would be the same or similar argument between using your single large 8D bank for all purposes. I personally choose a separate start bank.
ABYC does state that lithium should have a backup power source for mission critical items. But that backup can be another lithium. So it would seem a bank of 4 will fit the bill. Keep in mind the most common issue is hitting overcharge protection. But also keep in mind having the charge mosfet shut down does not shut down the discharge mosfet. Its actually quite amazing that through a single pair of terminals the BMS can stop inflow at those terminals while still allowing outflow..lol.
But anyways it would be my personal preference to have a separate bank for starting as I think most want it that way. In short I am just saying I do not think you are wrong. But your thinking may not be optimal. Mainly because an accidentally depleted bank will leave you stranded. And as we all know..that does happen from time to time for reasons we never predict.

One other thing...as you can see in this discussion alone..the app info is invaluable for assessing your system for things like load sharing, hitting over currents or over voltage and checking cell balance issues. I am glad you got ones with the app.

Here is the video of my start testing with the 120ah dual purpose.. Please note this was actually the second and third start in the video. The initial cold start actually hit a bit over 600 amps peak. But the meter maxes at 600 so it may have been a bit higher but not likely by much since all subsequent starts were around 550-580.

 

[Marco Flamingo]

Went to the boat yesterday to get the cable ratings, something I forgot when drawing out my existing electrical. Since I was crawling around, I decided to water my lead-acids. Since I was watering, I decided to use my new hygrometer as I was alway suspicious of the old one. One batt had a dead cell. In the other bank, one batt had three dead cells. And that is with only letting the batts rest for an hour after taking them off charge.

What I realized is that with using two banks to start, I can use my 600 amp meter on each leg and then total the amperage. Big issue is as I stated above, voltage sag is liable to be huge, especially in the "deader" bank, giving me a wonky amp reading. Odd that the old Lehman fired right up.

I also looked into solid bar stock between the batteries. What makes me pause is having looked at a couple tear downs of the lithium batteries. They use solid bars between the individual internal cells, but the bars are slightly corrugated to allow for vibration and heat expansion that will occur between the cells. A solid bar between external battery posts might have the same issue. Slight push and pull on the battery posts over the years even if the batteries are perfectly secured. Might be a non-issue, but the posts on lithium are skimpy in comparison to lead. I've used the old-school battery handles for lifting out lead batteries that attach to the posts. Would never think of lifting lithium by the terminals.

I think I see a thermal camera in my future even though I'm looking at relatively few connections for my 2 banks of 2 batteries. Lead-acid is forgiving when charging/discharging (as I found out with my hygrometer). With lithium, a 10th of a volt matters. Sometimes less. The lithium system might benefit from the same care and cleanliness as the diesel lines. That means the lowest possible resistance (and equal resistance) at every connection.

 

[Barking Sands]

Yes..thermal cam and lifepo4 apps are your best friends. Like having super powers.

 

[Mambo42]

I changed to LiFePO4 for several reasons.
I had 4 x 250 Ah AGM at 12 V, but then rewired the boat to 24 V, so basically only had 250 Ah usable at 24 V, which was not enough for our boat needs.
I could have bought another 6 or 8 additional 250 Ah to bring the usable Ah to about 750, but did not have the space for that in the lazarette.
So I changed to 7 x 200 Ah at 24 V Victron LiFePO4, but kept the starter batteries at 4 x Optima red top (12 V) and 6 x Optima yellow top for the bow and stern thruster.
The start batteries get charged through the 12 V alternators on the engines and the 24 V bow and stern thruster batteries get charged via a 220 V to 24 V 30 A Victron charger, which basically runs off the inverter........read house bank.

To charge the house bank I have 2 x 200 A alternators on the engines (so each engine has 2 alternators). On top of that I can charge them through my solar panels or via my generator.

Changing from AGM to LiFePO4 has given me so much more usable power, which means that in the summer time, even if I use 400 or 500 Ah in one day, I don't need to run the generator at all. The solar panels will top up the batteries.
Safety wise I am not afraid. LiFePO4 is the safe version of Lithium, it is actually safer than Lead acid. It is lithium ion you should be worried about, that is the type of battery you don't want to have onboard.
As for the BMS, am not worried about that either, if the BMS might fail I still have the MPPT controllers, the wakespeed controllers to stop the charging. On top of that each battery has an internal BMS.
The only thing I am worried about are the sh*tty connections Victron came up with. In fact, the reason they are now changing them in MC4 connecters is proof to me they agree with the assesment that the old connectors were dangerous. They will never admit it since that would open up pandora's box in litigation.

 

[dhays]

I also looked into solid bar stock between the batteries. What makes me pause is having looked at a couple tear downs of the lithium batteries. They use solid bars between the individual internal cells, but the bars are slightly corrugated to allow for vibration and heat expansion that will occur between the cells. A solid bar between external battery posts might have the same issue. Slight push and pull on the battery posts over the years even if the batteries are perfectly secured. Might be a non-issue, but the posts on lithium are skimpy in comparison to lead. I've used the old-school battery handles for lifting out lead batteries that attach to the posts. Would never think of lifting lithium by the terminals.

That is definately a consideration.

For the bus bars that I made, they are 15". They connect three batteries together. The end holes for the terminals are around 14" apart. The copper is 110 copper and has a coeficient of linear expansion of ~.0000177 for temps above 20°C and ~.000017 below 20°C. I installed them at 50°F or 10°C. So the amount that those bars would lengthen between the terminals on either end of the bar at 100°C (or 212°F) would be a bit less than .6 of a mm. The amount that they would shorten at 0°C is vanishingly small at only .06mm.

FWIW, the .6mm expansion in length is smaller than the clearance between the hole in the bus bars and the diameter of the terminals.

So while the expansion is real, I don't think it is likely signficant. Of course, my math has been known to be faulty in the past.

 

[Marco Flamingo]

But your thinking may not be optimal. Mainly because an accidentally depleted bank will leave you stranded. And as we all know..that does happen from time to time for reasons we never predict.

I've been thinking a bit more about an accidentally depleted bank. I have the NOCO jump starter aboard. I have the dinghy battery and jumper cables. I have a separate 120Ah lithium for the stove (and the jumper cables). But the main reason an "accidentally depleted bank" is of little concern is because of our usage. We check the SOC meter several times in the evening and morning when at anchor. From anchor drop to anchor up (dinner and breakfast), we tend to use 100-120Ah of our 245Ah available from or present lead-acid. That is a little tight, and was another reason for moving to lithium.

To "accidentally deplete" a 1,120Ah lithium bank on our boat would be very difficult. I would likely hear the crackling of the arcing short or smell the burning of wire insulation. Since we got rid of the generator, there is nothing aboard that makes any noise at anchor. Again, our boat/use specific, but accidentally using 1,000Ah isn't too concerning. I guess I'll find out. Hopefully the jumper cables will continue to sit unused for another decade.

 

[SteveK]

Marco, you will be OK until you are not.
Then you will share with others what not to do.
Carry on.

 

[Pau Hana]

Wow- crazy thread. LFP has become the new “what anchor” question…

 

[Marco Flamingo]

Marco, you will be OK until you are not

Then you will share with others what not to do.
Carry on.

Redundancy #1 is switch to one bank when anchoring and saving 560Ah in second bank. Redundancy #2 is NOCO portable jump starter good for multiple starts of a 7 liter diesel. Redundancy #3 is dinghy battery and jumper cables. Redundancy #4 is stove lithium with jumper cables. I can also mix and match these redundancies for more options.

I can share now. Don't be afraid to the point of paralysis.

 

[ksanders]

I don't see the difference between accidentally depleting your lithium batteries, and accidentally depleting your flooded lead acid batteries.

It can happen if you're inattentive or if your boat becomes unplugged while you're gone, and you don't have any monitoring system in place.

But I don't see any difference between the two technologies for reinitializing.

If the battery voltage on my inverter charger goes below 10.5 V, then my inverter charger will not work. I have a backup charger. That is the one that keeps my engine and generator batteries topped off that with the flip of a breaker will connect to my house bank as well.

I also have a on off switch that I can use to connect my house battery to my port engine start battery. This would immediately provide voltage to the system and allow the chargers to come online.

But again lithium doesn't change that.

 

[Bud]

Great thread! I too have replaced house bank with LiFePO4. It has been 4 years and I am very pleased. My 3 start 8D batteries I have replaced with 3 group 27 marine start lead acid batteries in parrallel with bus bars as shown by dhays. I have three groups. Two to start port and starboard 3208's and the third to start 16kw northern lights gen set. No problems to date. I will pay attentioin for info on using lifePO4 for starting.

 

[J.T kearney]

I don't see the difference between accidentally depleting your lithium batteries, and accidentally depleting your flooded lead acid batteries.

It can happen if you're inattentive or if your boat becomes unplugged while you're gone, and you don't have any monitoring system in place.

But I don't see any difference between the two technologies for reinitializing.

If the battery voltage on my inverter charger goes below 10.5 V, then my inverter charger will not work. I have a backup charger. That is the one that keeps my engine and generator batteries topped off that with the flip of a breaker will connect to my house bank as well.

I also have a on off switch that I can use to connect my house battery to my port engine start battery. This would immediately provide voltage to the system and allow the chargers to come online.

But again lithium doesn't change that.

I'm sticking with my original plan of a 4d agm for start with on/off switch and lithium bank for house and bow thruster. When I get to my destination, start battery is switched off and no worries about starting up the next time. Pretty simple. All I have to think about is if I have enough power to run my coffee maker,refer,and blender!!
Cheers and Happy New Years everyone J.T.

 

[Marco Flamingo]

I don't see the difference between accidentally depleting your lithium batteries, and accidentally depleting your flooded lead acid batteries.

The difference for me is that my present lead-acid banks can run my primary bilge pump for maybe 8 hours straight. My proposed LFP bank about 15 days straight. So if one is has amperage anxiety, LFP is the way to go.

Having the boat accidentally disconnected from shorepower is something I'm still thinking about. LFP doesn't like to stay at 100%, so I'm wondering if turning off the charger while not at the boat is better. Will have to see what the charging parameters actually do and whether connected or disconnected is better. That will probably cause some anxiety, but I lived aboard for years without shorepower, so I guess it isn't as worrisome to me.

JT: What is the draw of your bow thruster on the lithium bank? More than a starter?

Just heard that a 2024 Tesla just exploded in Las Vegas, killing one. Blame lithium.

 

[BVrolyk]

All,

A good friend of my (and serious engineer), Stan Honey, build the first LFP controller I'd ever seen for his Cal-40 years ago. It is still working great now. My son owns that boat. Stan bought the Peters designed fast cruiser SARISSA and his now rebuilt the entire electrical system. Along the way he built the battery stack, from cells. It's an interesting read and he addresses the specific way to protect the alternator from No-Load failure.

The link is: LFP battery | Stan Honey and Sally Lindsay Honey's files

 

[Barking Sands]

I've been thinking a bit more about an accidentally depleted bank. I have the NOCO jump starter aboard. I have the dinghy battery and jumper cables. I have a separate 120Ah lithium for the stove (and the jumper cables). But the main reason an "accidentally depleted bank" is of little concern is because of our usage. We check the SOC meter several times in the evening and morning when at anchor. From anchor drop to anchor up (dinner and breakfast), we tend to use 100-120Ah of our 245Ah available from or present lead-acid. That is a little tight, and was another reason for moving to lithium.

To "accidentally deplete" a 1,120Ah lithium bank on our boat would be very difficult. I would likely hear the crackling of the arcing short or smell the burning of wire insulation. Since we got rid of the generator, there is nothing aboard that makes any noise at anchor. Again, our boat/use specific, but accidentally using 1,000Ah isn't too concerning. I guess I'll find out. Hopefully the jumper cables will continue to sit unused for another decade.

I understand. And when I say "your thinking may not be optimal" I really mean optimal. That's different than acceptable or even adequate. How many people ran around for years and years on their large 8 D banks used for everything. Tons. Sounds like you have several back up sources too. I think you generally have all your bases covered.

 

[J.T kearney]

The difference for me is that my present lead-acid banks can run my primary bilge pump for maybe 8 hours straight. My proposed LFP bank about 15 days straight. So if one is has amperage anxiety, LFP is the way to go.

Having the boat accidentally disconnected from shorepower is something I'm still thinking about. LFP doesn't like to stay at 100%, so I'm wondering if turning off the charger while not at the boat is better. Will have to see what the charging parameters actually do and whether connected or disconnected is better. That will probably cause some anxiety, but I lived aboard for years without shorepower, so I guess it isn't as worrisome to me.

JT: What is the draw of your bow thruster on the lithium bank? More than a starter?

Just heard that a 2024 Tesla just exploded in Las Vegas, killing one. Blame lithium.

Mark, It's a 5hp marine hardware unit. I talked with Epoch about using 4 100 amp lithium batteries in parallel and said it wood work fine, which it has. I believe it's because each battery has it's own bms. I recall the amp draw was 300 amps for the thruster. The boat was originally set up with a battery bank in the bow but the 2nd owner didn't want to sleep on the batteries and moved to the house bank (6 6volt cc batteries) powering the thruster. Cheers J.T.

 

[Barking Sands]

Having the boat accidentally disconnected from shorepower is something I'm still thinking about. LFP doesn't like to stay at 100%, so I'm wondering if turning off the charger while not at the boat is better. Will have to see what the charging parameters actually do and whether connected or disconnected is better. That will probably cause some anxiety, but I lived aboard for years without shorepower, so I guess it isn't as worrisome to me.

Some thinking out loud for storage or sitting at the dock longer term.....

You can just float at 13.3 or 13.4 volts. Take a look at Ben Steins outstanding testing (linked below) done on charged voltage VS measured capacity. Scroll down to see the chart of charge voltage vs measured capacity. As you can see 13.5 is the first sign of any capacity loss and its very very minimal, so its effectively 99.8%. 13.4 is around 98.5%, but 13.3 is a significant step down to the mid 60%. So how you want to "maintain" your status at the dock is dependent on the status of SOC/ships readiness vs potential capacity loss over time. Especially when you mention things like bilge pump back up power. 13.3 to 13.5 is actually quite a large difference in capacity. 13.4 does not really split the difference and ends up being just a hair below 13.5 as far as SOC is concerned. How much degradation above standard calendar degradation occurs holding the pack at 13.5, which is still essentially 100% capacity is hard to pin down. But its nothing compared to the recent past (that is still occasionally present) of floating at 13.8 volts+. You can still find batteries that state charge parameters of 14.6 absorb and 13.8+ float with claims of 8k cycles..lol.

But at the dock one of the main concerns, as you point out, is reserve capacity for systems like bilge pumps in case of power loss and mission readiness to head out quickly.. with a full pack or close to it. So IMO the choices are essentially 13.3 (~65%), 13.4 (~98.5%) or 13.5 (~99.8%) with each successive increase adding to some theoretical amount of degradation that may or may not amount to a hill of beans in the overall perspective. FYI, many storage mode settings, including Victron believe, is 13.3. I think 13.5 could be eliminated since 13.4 is so close in capacity. So my view is pick your poison...13.3 or 13.4 for storage based on what you feel is important. At least this is my current thinking...always subject to change in light of new information.

I have either been at 13.4 or 13.5 most of the time because I think i might take the boat out tomorrow.....lol. That has been a few months.

In my defense I have been still doing upgrades and just got done installing the Garmin autopilot yesterday, up to completing the dockside wizard. So now I have no choice but to go out to finish the Sea Trial wizard. But the battery bank will be full!

Charging LiFePO4, what's the impact of lower voltages?

What voltage should I charge my LiFePO4 batteries? That seems like a simple question likely to have a single, direct answer. But, the actual answers are often unclear. Many LiFePO4 battery manufacturers recommend 14.6 volt absorption. But, that singular recommendation doesn't account for...

panbo.com

 

[Marco Flamingo]

Mark, It's a 5hp marine hardware unit. I talked with Epoch about using 4 100 amp lithium batteries in parallel and said it wood work fine, which it has. I believe it's because each battery has it's own bms. I recall the amp draw was 300 amps for the thruster.

That's the kind of logic I was looking for. The thruster draws 300A. Epoch 100A each probably have a continuous discharge rating of 100A, for a total of 400A continuous. Epoch says it is okay because there is enough cushion between thruster draw and the 4 battery's discharge rating; a 300 amp momentary draw on 400 amp continuous rated supply. My LFP battery bank will have a 1,000A continuous discharge capacity on a starter motor that has a momentary draw of 500A. The wild assumption that I am making in my install is that an electron doesn't know the difference between a thruster motor and a starter motor.

I think some of the reluctance to use LFP batteries for engine starting is the admonition on some battery stickers that reads "DO NOT USE AS A STARTER BATTERY." That sounds authoritative enough, but it reminds me of this picture that circulated on the web:

Despite what an LFP battery sticker says, it doesn't always means that LFP can't be used as a starter battery. What it means is that a single LFP battery is unlikely to have the rating required for a starter motor as most motor vehicle applications (i.e., under a hood) don't have room for a bank of LFP batteries. But this short blurb on a sticker has been misinterpreted to mean "DO NOT USE THIS BATTERY AS PART OF A BATTERY BANK OF SUFFICIENT SIZE SUCH THAT THE STARTER (OR THRUSTER) DRAWS ONLY 50% OF THE BANK'S CONTINUOUS RATING." Epoch has cleared this up.

I have no idea what the chopping board warning means and I'm sure some would assert that a chopping board can never be used as a chopping board. It says it right on the sticker.

 

[Marco Flamingo]

After +50 posts, I'm ready to begin the project. First, I removed the old lead acid. Four 260Ah 6V batteries dated June of 2017. They had special caps on the cells that supposedly reduce the amount of water they off-gassed. I don't know if they worked as I still put water in the batteries regularly. Even with the caps, liquid occasionally came out sufficient to drip down the sides of the batteries. As a result, the nice plastic battery box had accumulated about half an inch of what I presume was battery acid. After lifting the batteries out, I could only remove the box through the engine room hatch by tilting it in a manner that emptied the acid into the bilge. I had to rinse and pump the bilge. I slept on the boat waiting for high tide in the morning so that I could get the batteries up the gangway. Fun. I can still feel it in one shoulder. The good news is that the recycle yard gave me $55 for the cadavers.

I had hoped to use the old battery cables again to connect the new batteries but on close inspection I decided to order new cable and lugs. I may be cheap, but not that cheap. Plus, I kind of wanted to upgrade the cable size. When shopping, I found some cable that was heat-rated at 200C (old is 105C 2/0) and that gave me enough of a safety increase without paying for 4/0.

The existing fuses are an 250 ANL fuse for each bank, and that won't be enough for LFP batteries, so I have different fuses on order. In researching Class T fuses, I was surprised to find some 10k interrupt Class T. I thought they were all 20K, so be careful when ordering. I ordered 35/50k breakers.

With the battery box removed (the new batteries won't fit and don't need to be in the acid-resistant battery box), I am free to create a new hold down system/shelves. I am planning on stacking the batteries in order to save space in the engine room. I decided not to move the batteries out of the ER because LFP charging doesn't seem to be effected by temperature like lead acid (except extreme high and low). I monitored my ER temp and it went from 45F in the winter to 93F when cruising in the summer. I have empty space in the ER from removing the generator that will now be home to LFP. Tomorrow's chore will be a cardboard mockup.

 

[luna]

The existing fuses are an 250 ANL fuse for each bank, and that won't be enough for LFP batteries, so I have different fuses on order. In researching Class T fuses, I was surprised to find some 10k interrupt Class T. I thought they were all 20K, so be careful when ordering. I ordered 35/50k breakers.

I think this says you have different fuses on order, some ClassT are only rated at 10kA AIC and that you ordered 35/50k breakers.

So, what fuses did you order and what are the 35/50 breakers? Do you have product name and model number?

 

[Marco Flamingo]

I read a lot of fine print to find what I thought would work best. MCCB (Molded Case Circuit Breaker) come in various configurations. The ones I bought to replace my 250A ANL fuses are single pole DC rated Taxnele brand. They are thermal magnetic breakers rated at 35k AIC for the breaker switch and 50K AIC for the non-reset fusable link. If the 250A breaker trips and the short circuit current is 35k or less, it can be reset. If the breaker trips and there is a continuing current arc, the MCCB still has an AIC of 50k, but will need replacement like any fuse . Probably overkill (but better than underkill) and about half price compared to 20k Class T and holders. I am concerned that two 280 amp LFP batteries in parallel might be too close to the Class T 20k AIC limit. As noted in another thread, the new Epoch 460Ah has an internal 50k AIC fuse, so I thought that would be nice for my 560Ah. I think 35k breaker likely has me covered and I only need to flip a switch (after sussing out the issue).

I wasn't able to locate a time/amp curve for any of the MCCBs. They claim that they are "fast acting," but that doesn't have an industry wide meaning. I need to get greater than 250 amps through them for a fraction of a second to handle the starter motor inrush. The existing 250A ANL fuses did this without issue. Most fast acting fuses will pass their rated amperage for at least a few seconds. Won't know for sure until I try the MCCB.

 

[luna]

It appears that the Taxnele brand is not the only Brand of these dc rated circuit breakers. This would lead me to believe that none of the Brands listed on the internet sites are the actual manufacturer of this breaker.
If so, getting additional information like the trip delay curve could be difficult.

A few other thoughts.

- Although these breakers display the CE mark, there is no indication that they are UL or CSA listed. As the OCPD on your LFP battery, do you think your US based Surveyor/Insurance provider will accept only a CE designation?

- It is not uncommon for high amperage cheap dc breakers to have a resistance of about 4mΩ. If you are running things at 100 Amps, the voltage drop through the breaker will be 0.4 V. Are you OK with that?
In addition the breaker will dissipate 40 watts and if it is mounted in an enclosure you may well need to move the air around it, to cool it.

- Some dc breakers are polarized, meaning that they can only trip with the current running through them one way.
The Taxnele breakers I saw have on the case in raised letters, Line and Load which may indicate a polarized breaker.
You want a non-polarized breaker. How do you confirm this?

Rather than go the breaker route I would use a Mersen (a worldwide manufacturer of electrical products) A3T Class T fuse of the appropriate amperage rating, that also has an IR rating for 50k Amps.
It also looks like it will fit in my Blues Seas Class T fuse holder.

https://us.mersen.com/sites/default/files/medias/PIM/files/DS-A3T-A6T-Class-T-Fast-Acting-Mersen.pdf

Good luck with whatever you chose.

 

[Marco Flamingo]

Here is the best independent info I've found on the Taxnele MCCB, and I think that it is in Russian. The main market for this brand, based on the manufacturer's website and certifications, seems to be Europe and Asia. I don't think they have been rebranded in the US (yet). I haven't run down all of the certifications that are listed on the Taxnele website. The YouTube video is a comparison of several different brands/sizes of DC breakers and the author concludes that even though they look almost identical they are from different manufacturers. I went with Taxnele because it had the most certifications and available specifications. It also lists the AIC right on the MCCB. Some don't and when researching I found that manufacturers often had what appeared to be identical breakers but in various ratings. That's when I zoomed in on some Class T fuses and saw that some had a 10K AIC.

The Taxnele brand MCCB is dissected in the video at 46:45, along with a Tomzn brand MCCB that has a higher DC rating than needed for 12V (as do most of these). The resistance and voltage drop through the breakers is done at the start of the video and Taxnele is fine. He talks quite a bit about the plus and minus designations on the terminals, but in Russian and the captioning is difficult to follow. At 53:30, the author starts running tests on this breaker. First thing he finds using an IR thermo is that his cable lugs are an issue and are getting hot. But then the results are about what I expected. Testing a 150A MCCB, he finds that it will pass 300A for 30 seconds before tripping and it gets slightly warm. That looks to be inline with many fuses that will pass 3x their rated amperage for a couple seconds. And that is what I need in order to fuse my entire system, including starter cable and still handle the starter motor inrush of +500A for a fraction of a second.

The video also tests and dissects one of the cheapo little black box breakers found allover on Amazon and it is not recommended. The dissections of the MCCBs are interesting and he discusses the rare earth magnets used in the arc suppression chamber. Who knew?

I can't think of a scenario where I would need a non-polarized breaker. I thought it is the enormous potential from the LFP batteries that is the necessity for a fuse with a high AIC. Neither my 100A alternator (derated with a Balmar external regulator) nor my 60A shore power charger are likely to suddenly produce +35,000 amps going back into the batteries. My charger is fused such that it can't and think that my alternator would fail trying to feed 300 amps back into the batteries. If there is some reason to need a UL listed breaker, I need to know. I'm afraid to ask my surveyor (he was an idiot) or my insurer (he might realize that my boat was made in China).

 

[OldDan1943]

I remember when AGM were thought to be the perfect solution

 

[OldDan1943]

I remember when AGM were thought to be the total solution

 

[tiltrider1]

AGM’s are the perfect solution for starting batteries.