Fuses and circuit breakers for LiFePO4

[Statistical]

Originally Posted by dkenny64

you miss my point..fuses..blow once!!!. circuit breakers can be reset..
think circuit break on a windlass(over loads. trips..reset). FUSE REPLACE!!
fuses aren't always the best choice.. houses have circuit breaker not fuses anymore..
why should boats? get out of the 1950's
-dkenny64

Everyone understood the point. You missed the point that if the breaker doesn't have sufficient interrupt capacity it is pointless. It will trip and the circuit will not open and the circuit will remain energized potentially creating a fire or electrocution hazard as if the breaker didn't exist at all.

The required interrupt capacity for large LFP banks is incredibly high. The vast majority of circuit breakers are not going to have the required capacity. Using one without sufficient capacity is a potentially catastrophic mistake.

[hjohnson]

Originally Posted by dkenny64

you miss my point..fuses..blow once!!!. circuit breakers can be reset..
think circuit break on a windlass(over loads. trips..reset). FUSE REPLACE!!
fuses aren't always the best choice.. houses have circuit breaker not fuses anymore..
why should boats? get out of the 1950's
-dkenny64

Show me a DC breaker with a 20,000 amp interruption ability. That’s close to what my LFP can source if I mess up and dead short it. A class T fuse is far cheaper than a breaker that can do the same thing.

For the rest of my fuses, I’ve sized everything appropriately. The only fuse I’ve blown since I rebuilt my electrical system was for my macerator pump, because the shaft was frozen.

DC systems are fundamentally different than AC circuits as I’m not feeding any outlets with the DC system. On my AC system yes, I use breakers, but they’re feeding electrical outlets, and AC breakers have the zero crossing where they can trip.

[CaptainRivet]

Originally Posted by dkenny64

you miss my point..fuses..blow once!!!. circuit breakers can be reset..
think circuit break on a windlass(over loads. trips..reset). FUSE REPLACE!!
fuses aren't always the best choice.. houses have circuit breaker not fuses anymore..
why should boats? get out of the 1950's
-dkenny64

There are places where fuses are best and places where breakers are the best joice.
Windlass, also starter and watermaker i agree i breaker is a must and fuse a noGo
Fusing parallel batteries with mosfet BMS with 50% rating is smart and no overkill as its best practise to do so with a superfast rating. Here breakers or fuse make sense IF and thats the big IF they have the AIC rating needed. And i don't know breakers that have 15kA AIC IN DC current....but very happy to get to know which once do have so please post the breakers you are using.
And having a 15kA class T arced by a 400AH bank i only use now NH fuses with min 80kA AIC as battery fuses which you can also pull under full load acting as disconnect switch. Yes its for occasional disconnect, not frequent which is normally sufficient for most high current applications in boats (exceptions above). And yes if one of this big fuses blow i definitely not just replacing fuse=re-engage breaker...i check whats the root cause.
So i use NH for all high current applications.
on my boat the main battery fuse and all fuses located at load, charge and combo Multiplus busbar are NH fuses. Windlass and starter are connected with a motor type breaker directly after main battery bank fuse as i start from house.
Upstream as other stated, especially low current curcuits breaker/breaker switches is the better choice, i agree and use. Inverter draw far more then surge of starter or windlass, so the 500A NH3 fuse has no issue with that.
To make things simple i only have 16sqmm and 70sqmm cable in my installation till switchboard means i only have 200A NH2 and 63A NH0 fuses, so easy to store spares. Exception main battery fuse i have Nh3 fuse holder and 630A or 500A fuses. System is stress tested for 600A but i use the 500A as the max i pull is 400A to protect system and reduce voltage drop...the bigger a fuse rating is the more voltage drop you have on that fuse.

[CaptainRivet]

Originally Posted by dkenny64

you miss my point..fuses..blow once!!!. circuit breakers can be reset..
think circuit break on a windlass(over loads. trips..reset). FUSE REPLACE!!
fuses aren't always the best choice.. houses have circuit breaker not fuses anymore..
why should boats? get out of the 1950's
-dkenny64

Because there are applications a fuse has the needed short curcuit rating or AIC but a breaker by its construction cannot have. Thats the case for lithium batteries where AIC requirements is very high and a breaker can only be used for small capacity cells till around 150AH.

And above 100A a breaker needs to be that more beefy in construction with high quality material needed that the cost to produce and therefor sales price is very high.
A sufficient 150A breaker that really fully meet his specs is 300Euro and above...a 150A NH 2 is 8 Euro fuse and holder 80Euro, ANL or megafuse even cheaper.

In house you have breakers because current normally doesn't exceed 40A but your main house fuses from electric supply company or state is in europe typically either 3 phase 3x32/40A or if bigger 3x 63/100/125A NH0/1 fuses. Thats what in that metal box in the cellar installed by the electric supply company or state directly where the main power cable enters your house before the main counter.

[CharlieJ]

@dkenny64 #75

you miss my point..fuses..blow once!!!circuit breakers can be reset.

That is not much of a “point” as I would suspect that anyone searching this forum understands this basic idea.

think circuit break on a windlass(over loads. trips..reset).

Operating a piece of equipment (windlass) until it overloads and then depending on a circuit breaker to open as a control mechanism to correct improper equipment operation is not good operational or engineering practice.

fuses aren't always the best choice..

True. They can't be used as switches or to open more than one pole,

houses have circuit breaker not fuses anymore..why should boats?

Answer: Houses don’t generally have DC systems that carry hundreds of amps comes to mind.

get out of the 1950's

So, are you implying that the combined experience of thousands of marine electrical system designers, boat builders, electrical equipment manufactures, and marine electricians are wrong and need to “get out of the 1950’s” and that you are correct with your “point”. Sorry, I don’t think so.

[dkenny64]

so you want a DC breaker like this
https://www.amazon.com/DIHOOL-Circui...ZCJ717A91&th=1


yes they exist..for DC with 20kamp isolation?


agree running the load that far isn't the best..but series DC motors will run over rating.



-dkenny64

[CaptainRivet]

Originally Posted by dkenny64

so you want a DC breaker like this
https://www.amazon.com/DIHOOL-Circui...ZCJ717A91&th=1


yes they exist..for DC with 20kamp isolation?


agree running the load that far isn't the best..but series DC motors will run over rating.



-dkenny64

Exactly what i expected...Amazon and China brand with questionable certification for half the price that a proper certified unit cost. Buddy of mine is grid technician and he laughed about these breakers...they will trip at the stated rating or even a bit before or after as cable fuse but in a serious short of a big lithium bank won't hold up.
I would use it for a big inverter as cable fuse as the inverter has an internal device fuse or as cutoff switch to main busbar but not as last and only resort on a lithium bank to disconnects it from the installation in an internal bank short.
4mm silver plated copper bar on a 400A breaker compared to 7mmx30mm of NH fuse for that size is not so promising....only the sliver plated copper material needed for a proper 400A constant fuse or breaker costs more then this breaker....no documentation how the cable connection is dimensioned, what cable size fits and how connected. I don't see space for a beefy lug to connect.

I have a 600A stress tested install of 1088AH lithium bank with 6kw of inverter at 13V, so i know what i talk about. The smallest improper connection with over 300A constant current is very dangerous and can easly cause a fire. There is a reason proper certified stuff till 250A-300A is commonly available but bigger then that nearly nothing certified is openly available as only sold by specialst stores to certified technicians and costs go exponentially up. Same then with the rigg above 14mm wire size...

[s/v Jedi]

Originally Posted by CaptainRivet

Exactly what i expected...Amazon and China brand with questionable certification for half the price that a proper certified unit cost. Buddy of mine is grid technician and he laughed about these breakers...they will trip at the stated rating or even a bit before or after as cable fuse but in a serious short of a big lithium bank won't hold up.
I would use it for a big inverter as cable fuse as the inverter has an internal device fuse or as cutoff switch to main busbar but not as last and only resort on a lithium bank to disconnects it from the installation in an internal bank short.
4mm silver plated copper bar on a 400A breaker compared to 7mmx30mm of NH fuse for that size is not so promising....only the sliver plated copper material needed for a proper 400A constant fuse or breaker costs more then this breaker....no documentation how the cable connection is dimensioned, what cable size fits and how connected. I don't see space for a beefy lug to connect.

I have a 600A stress tested install of 1088AH lithium bank with 6kw of inverter at 13V, so i know what i talk about. The smallest improper connection with over 300A constant current is very dangerous and can easly cause a fire. There is a reason proper certified stuff till 250A-300A is commonly available but bigger then that nearly nothing certified is openly available as only sold by specialst stores to certified technicians and costs go exponentially up. Same then with the rigg above 14mm wire size...

Well you say that but you don’t know that. I expect them to work conform it’s specifications. The time to ridicule Chinese components has passed because they do produce top quality products today. Like your iPhone, or the robot on the dark side of the Moon

But the lack of a UL listing is worrying for such an important component. I have Chinese breakers on my AC system that do have an UL listing so I wouldn’t be surprised to find those exist for this as well.

[CaptainRivet]

Originally Posted by s/v Jedi

Well you say that but you don’t know that. I expect them to work conform it’s specifications. The time to ridicule Chinese components has passed because they do produce top quality products today. Like your iPhone, or the robot on the dark side of the Moon

But the lack of a UL listing is worrying for such an important component. I have Chinese breakers on my AC system that do have an UL listing so I wouldn’t be surprised to find those exist for this as well.

Read again my post, as i wrote to produce a 400A with silver plated copper allready the raw materials cost more then the sales price they are asking. Additionally 4mm thick is appropriate for 200A but not 400A. These are my buddies 2 points why this is already clear its inappropriate and the stated CE certification is fake for sure. He is the pro and i have no reason to mistrust him. He is a non BS talker and advised me on a lot high current builds that all work flawlessly.
He also said till around 200A they look appropriate and eg he would also use them for eg inverters. He also stated for aprox 10kA that look sufficent from his experience but not 20kA. He works since 30years with that stuff, is often at courts as expert, so i trust his expertise.
He wouldn't source breakers that cost him 400Euro when he could get the same for 170Euro but he has to sign off the installation and is in liability for it.

I am fully aware that a huge amount is produced in china and they produce crap and top notch. I also have chinese made breaker in my installation for the solar panels and 230V switchboard which is a known Spanish brand and each breaker had a copy of the certification with it.
The key for chinese stuff if they have a legal subsidary in a EU country or not. If they do you can assume to a high degree they are legit and what you get is really certified, if they only sell from china and via aliexpress and alike i would be very suspicious.

[CaptainRivet]

Originally Posted by s/v Jedi

Well you say that but you don’t know that. I expect them to work conform it’s specifications. The time to ridicule Chinese components has passed because they do produce top quality products today. Like your iPhone, or the robot on the dark side of the Moon

But the lack of a UL listing is worrying for such an important component. I have Chinese breakers on my AC system that do have an UL listing so I wouldn’t be surprised to find those exist for this as well.

Read again my post, as i wrote to produce a 400A with silver plated copper allready the raw materials cost more then the sales price they are asking. Additionally 4mm thick is appropriate for 200A but not 400A. These are my buddies 2 points why this is already clear its inappropriate and the stated CE certification is fake for sure. He is the pro and i have no reason to mistrust him. He is a non BS talker and advised me on a lot high current builds that all work flawlessly.
He also said till around 200A they look appropriate and eg he would also use them for eg inverters.down the stream as there you won't get anything above 5kA but directly at an LFP noGo. He also stated for aprox 10kA that look sufficent from his experience but not 20kA. He works since 30years with that stuff, so i trust his expertise.
He wouldn't source breakers that cost him 400Euro when he could get the same for 170Euro but he has to sign off the installation and is in liability for it.

I am fully aware that a huge amount is produced in china and they produce crap and top notch. I also have chinese made breaker in my installation which is a known Spanish brand and each breaker had a copy of the certification with it. But the main AC breaker and PCB is Moeller that cost double.
The key for chinese stuff if they have a legal subsidary in a EU country or not. If they do you can assume to a high degree they are legit and what you get is really certified, if they only sell from china and via aliexpress and alike i would be very suspicious.

[Sailing Paul]

I thought I would give an update on my experience with the 280Ah DIY LFP battery system I put together with help from this board and thread. I am very pleased, the LFP has exceeded my expectations. Throughout the summer we left the fridge on all the time, used the auto helm frequently, charged phones, etc. The battery was only charged on shore power and at no point did I become concerned about it running too low. We never needed to use the lead bank, other than for the windlass. So hopefully the lead batteries should last a long time, which was part of the objective of installing the LFP.

The minimum SOC was about 25% and on several occasions I only charged to about 80% SOC, using my cheap mains timer plug to turn off the the battery charger at the appropriate time.

At one time, with the battery down to 36% SOC, I did try charging with the alternator, by connecting it up in parallel with the lead house bank. The LFP was separated from the alternator by about 12m of 10mm cable, 6m each red and black and my calculations indicated the resistance would be sufficient to limit the current from the alternator, given the expected voltage of the alternator and LFP (13.0V) at the time. With the engine running at 2800RPM the charge current to the LFP was 14A, so well within the capabilities of the alternator. I tested for about 20 minutes and there was no discernible change in the temperature of the alternator.

Alternator charging is not something I ever plan on doing, but I thought it was interesting to try it. In an emergency, such as unexpected power failure at a marina where we expected to recharge, this would give another option, albeit one that would require careful monitoring.

We don't plan on any more long trips this summer, but next year intend heading over to France and the Channel Islands. I need to read up on likely availability of shore power there and might go for a solar panel if this looks like it might be worthwhile. The way the price of the panels is dropping it is getting to the point where it doesn't make much sense not to have solar!

[CaptainRivet]

Great to now all worked well Paul.
You can run the windlass of the LiFePO4 too it has a much smaller voltage sag when under high load and the windlass motor has it easier and lifes longer.
Solar is always a good idea on a boat, every AH harvested extends your time between habour stays. And as you said they are very cheap now, so I highly recommend doing it.
Your lead won't live significantly longer as you don't cyling it, there is a good chance it will die sooner as the Lead will get sulfaltation. Only a sofisticated 5 stage charger with automatic storage mode will prevent that.

[Sailing Paul]

Originally Posted by CaptainRivet

Great to now all worked well Paul.
You can run the windlass of the LiFePO4 too it has a much smaller voltage sag when under high load and the windlass motor has it easier and lifes longer.
Solar is always a good idea on a boat, every AH harvested extends your time between habour stays. And as you said they are very cheap now, so I highly recommend doing it.
Your lead won't live significantly longer as you don't cyling it, there is a good chance it will die sooner as the Lead will get sulfaltation. Only a sofisticated 5 stage charger with automatic storage mode will prevent that.

All really interesting thanks.

At the moment the windlass is connected to the starter battery (battery - breaker - windlass), but the lead house bank connects to the starter battery via a charge relay when the engine is running. So in essence, the windlass runs off the alternator, lead starter and lead house bank. I would have to do some tricky rewiring to switch the LFP in instead. How would it be if I simply connected in the LFP as well in parallel when using the windlass? As I mentioned above, I can connect both the lead and LFP house banks together in parallel should I need to, but most of what I have read advises against this on safety grounds. Another concern is that the LFP is connected using 10mm cable, passing through a 50A circuit breaker. I would not want to trip that breaker when anchoring as all the NAV instruments would go off*

Interesting point about the sulfation and lead batteries. I think the next time I need to replace I will just buy 1 lead house battery instead of 2. The LFP has worked out so well I don't feel the need for more than 1.

*Edit - I got that bit wrong. The NAV would not go off of course as it the lead and alternator would still be feeding it!

[CaptainRivet]

Why do you need a lead house when you have a lifepo4 house?

Total waste of money and raising complexity. Running lead and LiFePO4 as house is just worst of both worlds.
As long as it lives, ok use it as is but as soon as this dies get a 2nd 280AH LiFePO4 or a smaller whatever your needs are as replacement. Connect that in parallel to existing lifepo4 and all thats on the lead house to lifepo4 too. Will cost the same money and you eliminate a lot of weight, failure points, complexity, bad reliability and maintainance.
Get a small 20A DC2DC charger from renogy that charges the lifepo4 from lead starter when motor/alternator running, thats 100Euro. Means take the cable that connects starter and lead house, disconnect it from the house, move it as close as possible to lifepo4 the connect the DC2DC with the input and output to a fuse speced for the cable with a new cable to lifepo4 house, done.
Connect the windlass directly to lifepo4 house terminal with its own breaker, so you can use it also when engine not running and you don't trip the 50A fuse.

Otherwise charge your lifepo4 bank via shorepower as its now.

[The Yacht Rigger]

Our electrical team recently made a video on this subject, lots of interesting comments and discussion in the video comments - they are going to do some follow up videos going into more detail on these questions in the coming weeks.

https://www.youtube.com/watch?v=2r6NbG73qZg