Keeping the water off your Lifepo4 installation

[Pete7]

Originally Posted by CaptainRivet

you don't need ventilation for the LFP. Inverter as a heating source should be installed not in the same compartment anyhow

Well I disagree. I am quite happy keeping my LFP cool in the bilges, actually under the port saloon seat which have plenty of access to the bilge. The bilge is only 5" deep, but always dry if a little dusty occasionally.

No reason not to have the inverter in the same compartment, particularly since it keeps the battery cables short. As I said earlier, its about making the best use of the available space which is a priority on a smaller yacht. Proof in the pudding is that it has worked well for the past two seasons and as I type.

Pete

[Fuss]

Originally Posted by donradcliffe

LFP batteries are short protected by the BMS. Until you show me a Youtube with that causing a problem, I'm not going to install ANY fuses.

I also looked at the nice new BMS and I thought that this box, in catastrophic event, would probably explode… but as I’m not sure, I put the fuse in as well. I could imagine looking at the melted remains of the BMS after the event and checking the two negatives and finding them still to be connected…

[Fuss]

Originally Posted by Chotu

Completely agree!

How about making the boats themselves more safe so the batteries don't get splashed with water?

This seems to be such a non-problem. Why are so many people worried?

Well Chotu, you see, there are two types of water, one type is from the outside and the other type is from the inside. Now if some device from the inside starts spraying water around this called an inside water leak, and inside water leaks like to occur near expensive electronics if they can and as we now have BMS’s and shunts with circuit boards, this risk becomes more relevant.
Now if the water leak is from the outside, it is either due to some type of storm or to your lack of boat maintenance skills Chotu.
However, it is clear that you have never experienced any of these events, perhaps a sail around the harbour would help.

[CaptainRivet]

Originally Posted by Pete7

Well I disagree. I am quite happy keeping my LFP cool in the bilges, actually under the port saloon seat which have plenty of access to the bilge. The bilge is only 5" deep, but always dry if a little dusty occasionally.

No reason not to have the inverter in the same compartment, particularly since it keeps the battery cables short. As I said earlier, its about making the best use of the available space which is a priority on a smaller yacht. Proof in the pudding is that it has worked well for the past two seasons and as I type.

Pete

what happens if a seacock breaks, your bilge is not dry anymore and your batteries are wet...
2nd because your inverter is a heat source. eg on the last ocean crossing my buddy boat has the Multiplus 3000 in the rear cabin mostly used as storage. Well the other crew member was sleeping there and the multipus was quite a heating, especially when we used the mobile generator to charge the bank via its 120A charger. got really hot from comfy 20 to over 30 degrees celcuis. that in a battery compartment that is much smaller then a cabin is really bad.

mine bank sits in a watertide compartment under my bed, the one inverter/charger soon 2 sit on the watertide bulkhead directly above it, ressed 20cm back where a build in cabinet is where i have installed everything MPPTs/Inverters/DC2DC.... Cable length is 40cm bank-inverter, I have optimsed that too where i positioned the bank in the cabinet.

save and will deliver power till I have 80cm water standing in the hulls.

[newhaul]

Originally Posted by CaptainRivet

salt water or actually any water is one reason for a shortened bank.

So when bank get shorted by salt water the main battery fuse disconnects the whole installation properly and not anywhere else a fire in the boat gets started because the high current is distributed and melting cables.

You really don't understand lifepo4 battery setups do you.
The bms is a huge disconnecting device . I try to draw over 300 amps and it disconnects the battery from everything. No fuses involved. Fuses are to protect the wire upstream of a short not downstream of one

[newhaul]

Originally Posted by CaptainRivet

your BMS steers a relay or mosfets that prevents it from getting shortend by the battery cables on the input side. One protection you need but not the only one. But that relay or mosfet will melt close if the bank internally gets a short and faced with 10000A+, that the BMS cannot protect but a main battery fuse can.

well i have no youtube video but eg my buddy is a surveyor that lately inspected the leftover of a electric motorboat with shortend banks due to a water ingress. reason he found main Fuses where the lovely Megafuses ok speced for the battery cable but that got bridged and melted a lot other cables causing fire in the boat. Well the luck that this could be inspected is because fire brigade is 500m down the road of the habour. it would have also burned with AGMs...

put your bank in a bucket of water and it gets shortened. I don't try that but if you want feel free to do so and make a youtube video.
if you have prismatic cells with the thin blue insulation and that gets rubbed through due to constant vibrations on a boat you get a shortend bank. If you buy dropins from china, you don't know whats inside...
just 2 reasons and well there is no youtube video as the boat is burned to ground then.

Well for 50Euro i can prevent that and easly disconnect my whole bank when boat stored for longer periodes.to me a good investbut your boat, your decision.

That is called a disconnects switch .

[CaptainRivet]

Originally Posted by newhaul

You really don't understand lifepo4 battery setups do you.
The bms is a huge disconnecting device . I try to draw over 300 amps and it disconnects the battery from everything. No fuses involved. Fuses are to protect the wire upstream of a short not downstream of one

oh i do. Look at your BMS with its mosfet, 300A is no problem but 10000A of a shortend bank rushing in is...mosfets or relays used to disconnect will melt close with everything latest above 2000A, most likely much earlier.
the correct setup of a battery fuse is battery pole, battery fuse, BMS (for mosfet BMS) or disconnect relay (for BMS steer via relay) then battery cable and battery cable fuse.
so if the bank gets internally shortend, first the battery fuse blows and isolates the battery so your BMS and all what comes after is not fried or burns.
the battery cable fuse is there to prevent the cables from battery to main busbar or sources due to current overload or when the cable shortens which would shorten the poles and create a shortend bank externally.

The BMS steers the mosfet to disconnect from overload measured pulled of the battery but that is NOT a short curcuit protection, if you shorten that under high load eg close to your cont rating of your BMS your mosfets are fried and mosfets tend to fry close in most cases. so no short curcuit protection.

[s/v Jedi]

No, MOSFET’s don’t melt closed, they vaporize under those conditions.

For a solenoid this is true, they can fail to interrupt. But that’s why there must be a class-T fuse with it’s 20kA AIC rating. This is also why the ANL fuse isn’t good enough.

As per the graph I posted earlier, nuisance blows of class-T fuses don’t happen.

[newhaul]

Originally Posted by CaptainRivet

oh i do. Look at your BMS with its mosfet, 300A is no problem but 10000A of a shortend bank rushing in is...mosfets or relays used to disconnect will melt close with everything latest above 2000A, most likely much earlier.
the correct setup of a battery fuse is battery pole, battery fuse, BMS (for mosfet BMS) or disconnect relay (for BMS steer via relay) then battery cable and battery cable fuse.
so if the bank gets shortend, first the battery fuse blows and isolates the battery so your BMS and all what comes after is not fried or burns.
The BMS steers the mosfet to disconnect from overload pulled of the battery but that is NOT a short curcuit protection, that the job of a fuse.

What a word salad . Now what are the actual chances of a battery getting wet enough to cause a short and you don't have bigger issues than that happening ? Like grabbing your ditch kit and stepping up into your liferaft.

[CharlieJ]

@CaptainRivet:
What is "lightbow"?

[s/v Jedi]

Originally Posted by CharlieJ

@CaptainRivet:
What is "lightbow"?

I guess he means arcing. Still, the class-T fuse is the correct one to use exactly because it has a better rating but he doesn’t get it.

[CharlieJ]

@Jedi:
That is what I surmised.

I am perplexed by his stand on OCPD placement.

the correct setup of a battery fuse is battery pole, battery fuse, BMS (for mosfet BMS) or disconnect relay (for BMS steer via relay) then battery cable and battery cable fuse.
so if the bank gets internally shortend, first the battery fuse blows and isolates the battery so your BMS and all what comes after is not fried or burns.

Since all the OCPD's that I am familiar with respond to an overcurrent event downstream from their installation position, an internal bank short circuit, upstream from the "battery fuse" will not cause the "battery fuse" to open. Or am I just missing something?

[Pete7]

Originally Posted by CaptainRivet

what happens if a seacock breaks, your bilge is not dry anymore and your batteries are wet...

You keep saying this, but since the three underwater seacocks were replaced within the last two years, it isn't going to happen. The LFP is drop in, so sealed and the FLA (in parallel) isn't mission critical.

Originally Posted by CaptainRivet

2nd because your inverter is a heat source.... multipus was quite a heating, especially when we used the mobile generator to charge the bank via its 120A charger. got really hot from comfy 20 to over 30 degrees celcuis. that in a battery compartment that is much smaller then a cabin is really bad.

For once I agree, which is why mine are under the saloon seat with plenty of ventilation, not in a confined battery compartment or the engine space.

[s/v Jedi]

Originally Posted by Pete7

You keep saying this, but since the three underwater seacocks were replaced within the last two years, it isn't going to happen. The LFP is drop in, so sealed and the FLA (in parallel) isn't mission critical.

Yes, I didn’t even respond to that yet. We have three watertight compartments with two watertight bulkheads and no seacocks at all in the center compartment with batteries… a concept he must be unfamiliar with

[CaptainRivet]

Originally Posted by newhaul

That is called a disconnects switch .

really