Fuses and circuit breakers for LiFePO4

[Sailing Paul]

I have been thinking about potential problems connecting my new 280Ah LFP battery to my existing domestic circuit. This is protected by a 50A midi fuse and feeds through to the various circuit breakers in the panel. Some of the devices may have high inrush currents, such as the fridge compressor, autopilot and pumps. As the LFP can produce very high currents, could this lead to any problems? Could it cause frequent breaker tripping for example? I have tested with a 60Ah LFP and did not experience any problems, but the internal resistance of my 280Ah LFP is going to be much lower.

I don't have an inverter, but if I added one at some point what would I need to consider? Again I am thinking that a very high inrush current might present a problem.

[s/v Jedi]

Originally Posted by Sailing Paul

Interesting thanks, that makes sense.

I am not bothering with the shunt for the moment. I have ordered a JBD BMS which comes with Bluetooth. I will see what that tells me and how accurate it is before I invest in additional bits of kit.

If I ever buy a second battery I was thinking of using it as a reserve. Like our water tanks, use one until it dries, then swap over. That way if one blows up, I would still have the other. I do already have 2 smaller LFP batteries, 60Ah and 50Ah, that I use with an electric outboard/trolling motor. I have set the boat up so I could quickly attach these for domestic/nav use should I need to, but hopefully would never need to as our lead batteries will be the first option should the LFP fail.

LFP batteries should not be kept fully charged so the water tank system doesn’t work well. It’s best to use in parallel.

[CaptainRivet]

Originally Posted by Sailing Paul

Interesting thanks, that makes sense.

I am not bothering with the shunt for the moment. I have ordered a JBD BMS which comes with Bluetooth. I will see what that tells me and how accurate it is before I invest in additional bits of kit.

If I ever buy a second battery I was thinking of using it as a reserve. Like our water tanks, use one until it dries, then swap over. That way if one blows up, I would still have the other. I do already have 2 smaller LFP batteries, 60Ah and 50Ah, that I use with an electric outboard/trolling motor. I have set the boat up so I could quickly attach these for domestic/nav use should I need to, but hopefully would never need to as our lead batteries will be the first option should the LFP fail.

I would recommend a JK BMS with 200A and 2A active blancing,
https://es.aliexpress.com/item/1005003339311236.html
much better then the JBD BMS.
Costs are equal. Thats also capable of starting your engine incase the lead starter is dead. JBD won't handle that...
Are these 50Ah and 60AH really Lifepo4? Lithium batteries for trolling/epropulsion are in majority Li-ion due to power delivery and not lifepo4.
In case they are Lifepo4 i agree with jedi best paralleling them to your 280AH and use=cycle them too and not store them full. You can put a disconnect switch for the 280AH in so you can quickly just disconnect the 280AH and charge the trolling battery full when you need it for use with dingy.
In case Li-ion you can store them full and use as you suggested.

[Sailing Paul]

60Ah and 50Ah are both drop in LiFePO4. The 60Ah is a fairly expensive one with Bluetooth. 50Ah cheap eco-worthy. I also have a very portable 18Ah that I use for inflating and deflating the tender and kayak, and for recharging phones, but there should be no need for that with the new 280Ah LFP.

I have kept the batteries around 50% charged since October, but will fully charge in April or May for when we start sailing again. What is the problem charging until full between then and October?

[Sailing Paul]

Thanks for the tip about the JK BMS. I will look into sending back the JBD one. It is due for delivery tomorrow, so I could send it straight back.

[Sailing Paul]

For charging the 280Ah battery while we are away from it for a few days I am thinking of using a 3A charger as what I have read indicates slow charging is better for the cells and for rebalancing. Is this true? Or will the 3A not work properly on a 280Ah battery.

[more]

i have 10 x 310 ah lifepo4 battery.
boatname is oman of dubai . 22 ft long superyacht.
factory put 95mm2 1 meter long 200a fuse,disconect to board with factory fuse 10/16/60A depend end user,cabel size. i use only eletric for fridge danfoss 35w
with huge inrush of 10A by specification and for led light 20W and for charging phone.

what you ting by power of battery bank,name of boat what extra expensive t-fuse i buy 1000A or 600A

[CaptainRivet]

Originally Posted by Sailing Paul

60Ah and 50Ah are both drop in LiFePO4. The 60Ah is a fairly expensive one with Bluetooth. 50Ah cheap eco-worthy. I also have a very portable 18Ah that I use for inflating and deflating the tender and kayak, and for recharging phones, but there should be no need for that with the new 280Ah LFP.

I have kept the batteries around 50% charged since October, but will fully charge in April or May for when we start sailing again. What is the problem charging until full between then and October?

You are welcome regarding BMS.
Lifepo4 chemistry doesn't like to be stored or kept at 100%.totally different to lead. With lifepo4 min 3000cycles, some speced to do 8000 your major factor of degreation is age and spec that aftrr that 3000 till 8000 cycles still 80% Capacity is left means 10 years easily. Storing at 50% is perfect.
But they don't like to stay at 100%SoC and you can kill them in 3-4 years like that, its for them the same then keep a lead at 60%SoC they die much faster. A lead must be full and best floated to achieve a long life, a lifepo4 is exactly the opposite likes the most if cycled between 50 and 80% (but you can cycle them from 20 to 100%daily and won't matter as speced for that) and get charged to 100% from time to time to balance the cells but never kept for long at 100%.

So i would simply parallel both to your 280AH and use them, they will last longer then kept at 100% and used from.time to time.
I would install it the following:
Take a busbar for positive and negative battery, then busbar,
1) disconnect switch, nh 63A fuse, 280AH to poistive terminal. Negative directly to negative busbar
2) disconnect switch, Anderson connector (positive, neative cable direct to negative busbar) <-> anderson connector with cable length you need for the motor setup in your dingy-mrbf fuse spec for the cable you use- 60AH battery
3) same then 2) with 50AH battery
Like this if you wanna charge your trolling battery full you just disconnect with switch the other 2, charge full then disconnect with switch, disconnect anderson plug, put into your dingy, connect anderson plug and use it. Connect back the other 2 batteries and use them as house.
If empty connect back and the battery will take charge from other 2 as much as it needs...assume 50-60A range. They are small and you can do this, nothing will happen.
Not recommended to do this with Lifepo4 batteries bigger then 100AH!!!! as the current that can flow then is potentially huge. in most cases not but there can be unlucky combos and then the **** hits the fan...Murphy is waiting...

[more]

Originally Posted by Sailing Paul

For charging the 280Ah battery while we are away from it for a few days I am thinking of using a 3A charger as what I have read indicates slow charging is better for the cells and for rebalancing. Is this true? Or will the 3A not work properly on a 280Ah battery.

this is to week when you recive JK-BMS 4S-8S Edition plug some 20-30-100A charger and leave 2 days for balacing

[more]

Originally Posted by CaptainRivet

You are welcome regarding BMS.
Lifepo4 chemistry doesn't like to be stored or kept at 100%.totally different to lead. With lifepo4 min 3000cycles, some speced to do 8000 your major factor of degreation is age and spec that aftrr that 3000 till 8000 cycles still 80% Capacity is left means 10 years easily. Storing at 50% is perfect.
But they don't like to stay at 100%SoC and you can kill them in 3-4 years like that,.

od agm C20 125a c5 100A 960 W price for chinese brend 125-160€ + varta 200€ + expensive delivery last maybe 500 cycle very hard to maintane on boat need quick charge after discharge 20-80% after charge to 80% terible effiency charging maybe only 10-20% in reality need for finish charging solar

lifepo4 90a 1000W easy cost 120-160€ + bms easy maintain high efficiency charging and discharging and this pice is on door
last 2000 cycle easy

in begining we dont have any BMS but we use calb or winston,also Victron in begining dont have BMS. lot this battery still work from 2005

[CaptainRivet]

Originally Posted by more

i have 10 x 310 ah lifepo4 battery.
boatname is oman of dubai . 22 ft long superyacht.
factory put 95mm2 1 meter long 200a fuse,disconect to board with factory fuse 10/16/60A depend end user,cabel size. i use only eletric for fridge danfoss 35w
with huge inrush of 10A by specification and for led light 20W and for charging phone.

what you ting by power of battery bank,name of boat what extra expensive t-fuse i buy 1000A or 600A

Each of the 310AH batteries should have a class T or NH battery fuse with min 20kA speced for cable used (if 70sqmm cable a 200A fuse with min 20kA short curcuit rating) then connected to a battery bus bar. Then battery busbar with a main battery bank fuse via 95sqm cable to main switchboard. The main battery fuse due to >3000AH min needs 40kA short curcuit capability, 95sqmm is 200 or 250A fuse rating for cable so you need a class T or NH 200 or 250A fuse with short curcuit capability of >= 40kA

Any other fuse type would be arced and useless with this huge bank. I learned it the hard way...400A 10kA speced class T fuse arced by a 400AH LFP bank due to internal bank short and burned a car down...enough proof for me to play 100% safe...
20kEuro in batteries i don't cheap out on the battery fuses...and NH till Nh1 costs the same then good ANL or Megafuse bs but is 1000% more safer, only by the fact no fakes exists.
NH00 or 0 can do max 125A, fuse holder 30Euro, fuse 5-10Euro
Nh1 till 200A, fuse holder new 50Euro, used for 20Euro
NH2 till 250A fuse holder new 80-120Euro, used for 30-40Euro
NH3 till 630A fuse holder new 250Euro, used 50-80Euro
Nh4 till 1500A fuse holder new 450Euro, used 100-150Euro.
And the specs means you can run 200A over a 200A NH fuse 24/7/365 and its max 10 degrees over ambient temp...do this with ANL or megafuse BS and latest after 30min the cable isolation or fuse holder is melting because the fuse emits so much heat into surrounding installation...NH not.

[Sailing Paul]

Originally Posted by CaptainRivet

You are welcome regarding BMS.
Lifepo4 chemistry doesn't like to be stored or kept at 100%.totally different to lead. With lifepo4 min 3000cycles, some speced to do 8000 your major factor of degreation is age and spec that aftrr that 3000 till 8000 cycles still 80% Capacity is left means 10 years easily. Storing at 50% is perfect.
But they don't like to stay at 100%SoC and you can kill them in 3-4 years like that, its for them the same then keep a lead at 60%SoC they die much faster. A lead must be full and best floated to achieve a long life, a lifepo4 is exactly the opposite likes the most if cycled between 50 and 80% (but you can cycle them from 20 to 100%daily and won't matter as speced for that) and get charged to 100% from time to time to balance the cells but never kept for long at 100%.

So i would simply parallel both to your 280AH and use them, they will last longer then kept at 100% and used from.time to time.
I would install it the following:
Take a busbar for positive and negative battery, then busbar,
1) disconnect switch, nh 63A fuse, 280AH to poistive terminal. Negative directly to negative busbar
2) disconnect switch, Anderson connector (positive, neative cable direct to negative busbar) <-> anderson connector with cable length you need for the motor setup in your dingy-mrbf fuse spec for the cable you use- 60AH battery
3) same then 2) with 50AH battery
Like this if you wanna charge your trolling battery full you just disconnect with switch the other 2, charge full then disconnect with switch, disconnect anderson plug, put into your dingy, connect anderson plug and use it. Connect back the other 2 batteries and use them as house.
If empty connect back and the battery will take charge from other 2 as much as it needs...assume 50-60A range. They are small and you can do this, nothing will happen.
Not recommended to do this with Lifepo4 batteries bigger then 100AH!!!! as the current that can flow then is potentially huge. in most cases not but there can be unlucky combos and then the **** hits the fan...Murphy is waiting...

Thanks, I was thinking about how to charge my small batteries away from shore power.

Regarding 100% charge, our usage pattern of the boat would typically mean no more than 100 days sailing between May and October, with frequent marina stops and probably no more than 50 cycles per year. Would it really be a problem charging to 100% for each cycle? The battery would be left for no more than 2 weeks at 100% SOC.

[more]

Originally Posted by CaptainRivet

Each of the 310AH batteries should have a class T or NH battery fuse with min 20kA speced for cable used (if 70sqmm cable a 200A fuse with min 20kA short curcuit rating) then connected to a battery bus bar. Then battery busbar with a main battery bank fuse via 95sqm cable to main switchboard. The main battery fuse due to >3000AH min needs 40kA short curcuit capability, 95sqmm is 200 or 250A fuse rating for cable so you need a class T or NH 200 or 250A fuse with short curcuit capability of >= 40kA

Any other fuse type would be arced and useless with this huge bank. I learned it the hard way...400A 10kA speced class T fuse arced by a 400AH LFP bank due to internal bank short and burned a car down...enough proof for me to play 100% safe...

ussualy all european boat producer use nh 50ka fuse., you dont need nothing also betwen battery you dont need fuse by law.i dont reed certification books,becouse this is not my job .but if boat producer dont use fuse betven batery i also dont use. iaam not sure for big disconector but for off grid use i like use MCCB Moulded Case Circuit Breaker Battery with termal protection.also this is ussualy 25ka

[s/v Jedi]

Originally Posted by Sailing Paul

Would it really be a problem charging to 100% for each cycle? The battery would be left for no more than 2 weeks at 100% SOC.

You want him to give in and say that what you want is just fine? The answer was no, don’t.

For charging, do you have solar, generator etc. ? You must realize that you must produce all the power you use every day. You can’t just bring a bag of full batteries to use during the sailing and then recharge them later. You cycle daily when living aboard.

Also, your idea of a 3A battery charger indicates you are on the wrong path and not ready for any of this. Do you have a specific LFP 3A charger in mind for this? Did you research how to deal with electrical energy generation and storage on boats, how to calculate needed capacity etc.?

[Sailing Paul]

Originally Posted by s/v Jedi

You want him to give in and say that what you want is just fine? The answer was no, don’t.

For charging, do you have solar, generator etc. ? You must realize that you must produce all the power you use every day. You can’t just bring a bag of full batteries to use during the sailing and then recharge them later. You cycle daily when living aboard.

Also, your idea of a 3A battery charger indicates you are on the wrong path and not ready for any of this. Do you have a specific LFP 3A charger in mind for this? Did you research how to deal with electrical energy generation and storage on boats, how to calculate needed capacity etc.?

I want to know the impact on the battery given our proposed usage pattern. I would like the battery to be useful for 10 years (no more than 500 cycles). After that I suspect I would be able to replace with twice the capacity at half the price. The cost is about £400, for DIY build, with components and case from a reliable UK supplier.

Our daily usage is about 40Ah, maybe 50Ah in hot weather for the fridge, less if just sitting at anchor as no autopilot or nav instruments in use. So a 280Ah battery should go 5 days and we have 2X90Ah lead to push another day should we need it. This summer it is unlikely we would be away from shore power for more than 3 days, so initially we plan just to charge on shore power. Depending on how things go, I may buy some solar, although if prices keep falling adding another 280Ah LFP might be more cost effective and less hassle. I really cannot forsee us ever being away from shore power for 10 days. Alternator charging would be the last thing we added after more battery capacity and/or solar.

I currently have a couple of 3A LFP chargers and a 10A charger. I will look for a 20-30A charger for faster charging, but my question was really about whether it would be better for the battery to charge at 3A when we are in no hurry, as indicated by the manufacturer of my 60Ah battery, or does it really not matter?

If we are away from the boat for a couple of days, a 50Ah top-up to 80% SOC might also be preferable to using a 30A charger that takes it to 100% in a few hours.

Edit: what would the impact on the battery be if I did leave it at 100% SOC for 2 weeks?