lithium cable size

[dreadnought]

hi,i`m thinking of going hybrid on my nb,if i do would i have to use the same size cable to connect the lithium battery to the LA`s. The cable is 95m on my battery bank. Many thanks

[ditchcrawler]

I would say yes

[nicknorman]

9 minutes ago, dreadnought said:

hi,i`m thinking of going hybrid on my nb,if i do would i have to use the same size cable to connect the lithium battery to the LA`s. The cable is 95m on my battery bank. Many thanks

Personally I don't think a hybrid setup is a good idea, and the BSS chaps don't seem to like it either. That said, I know it is very popular.

If you are going to do it then I would suggest that it is best to connect the loads directly to the Lithium (including the negatives), rather than keeping the loads connected to the lead acid and then connecting the Li via heavy cables. That way, if necessary, you can use the "long wire" method of reducing the load on the alternator to avoid cooking it- unless of course you have a decent alternator controller with temperature monitoring? My proposal above also allows for disconnecting of the Li from the LA (by means of an isolator switch) if you don't want to hold the Li at 14.4v or whatever, for a prolonged time after they are charged during a long cruise whilst still being able to power the services from the Li.

Edited March 29, 2023 by nicknorman

[MtB]

1 minute ago, nicknorman said:

and the BSS chaps don't seem to like it either.

 

Whether they 'like it' is neither here nor there, Shirley.

 

Is there some debate or doubt about hybrid LiFePoO4/LA installations breaching one or more of the BSS requirements? Which would they be? 

[IanD]

13 minutes ago, MtB said:

 

Whether they 'like it' is neither here nor there, Shirley.

 

Is there some debate or doubt about hybrid LiFePoO4/LA installations breaching one or more of the BSS requirements? Which would they be? 

 

If the lithiums are LFP and have an inbuilt (or external) BMS -- even if this is "emergency disconnect" only -- I can't see why there would be any safety issue, if anything they're safer than LA so BSS shouldn't have any reason to object to them even in a hybrid setup.

 

The dubious bit is all to do with over/undercharging the LFP and/or LA and reducing their life, or frying your alternator, or both. These are cost/lifetime issues for the boater, not safety ones for BSS.

 

P.S. Ex-EV lithium batteries like NMC are an entirely different kettle of fish due to the potential fire hazard, insurers (and potentially a BSS examiner) have good reasons to object to these if anyone's silly enough to use them on a boat just because they're available cheaply secondhand... 😉

Edited March 29, 2023 by IanD

[ditchcrawler]

3 minutes ago, IanD said:

 

If the lithiums are LFP and have an inbuilt (or external) BMS -- even if this is "emergency disconnect" only -- I can't see why there would be any safety issue, if anything they're safer than LA so BSS shouldn't have any reason to object to them even in a hybrid setup.

 

Remember the BSS insisted on flame traps in diesel tank vents for years

[MtB]

Well yes, this is the first I've heard of BSS inspectors being difficult about LiFePO4 batteries. Or as Nick appears to assert, hybrid installations specifically. 

 

I was just wondering how a hybrid installation breaks the BSS rules. Which rule(s) specifically. This seems important to get to the bottom of or there are going to be a lot of drop-in LiFePO4 hybrid installations being removed over the next few years. 

[IanD]

3 minutes ago, MtB said:

Well yes, this is the first I've heard of BSS inspectors being difficult about LiFePO4 batteries. Or as Nick appears to assert, hybrid installations specifically. 

 

I was just wondering how a hybrid installation breaks the BSS rules. Which rule(s) specifically. This seems important to get to the bottom of or there are going to be a lot of drop-in LiFePO4 hybrid installations being removed over the next few years. 

 

That seems unlikely since there are lots of LFP installations (very common nowadays, in fact almost standard) on lumpy water boats, I believe there are many thousands worldwide which is *far* more boats than are subject to BSS...

Edited March 29, 2023 by IanD

[MtB]

Just now, IanD said:

 

That seems unlikely since there are lots of LFP installations on lumpy water boats, I believe there are many thousands worldwide which is *far* more boats than are subject to BSS...

 

But they are not subject to BSS.

 

If there are really BSS bods out there refusing BSS tickets because of hybrid installations, we need to know on what grounds.

[rusty69]

6 minutes ago, MtB said:

Well yes, this is the first I've heard of BSS inspectors being difficult about LiFePO4 batteries. Or as Nick appears to assert, hybrid installations specifically. 

 

I was just wondering how a hybrid installation breaks the BSS rules. Which rule(s) specifically. This seems important to get to the bottom of or there are going to be a lot of drop-in LiFePO4 hybrid installations being removed over the next few years. 

The rules they are going to introduce after thousands of people have installed them, and before my next BSS exam probably.

[MtB]

Just now, rusty69 said:

The rules they are going to introduce after thousands of people have installed them, and before my next BSS exam probably.

 

This is exactly my concern too!

 

Still at least they are relativly easy to remove and lug outside to the van if necessary, before the BSS geezer rocks up....

 

 

[rusty69]

Just now, MtB said:

 

This is exactly my concern too!

 

Still at least they are relativly easy to remove and lug outside to the van if necessary, before the BSS geezer rocks up....

 

 

It would make more sense to unbolt them after he's failed it if there is no retest fee. My install recently passed the dreaded inspection, so they are bound to change the goal posts before the next one.

[IanD]

6 minutes ago, MtB said:

 

But they are not subject to BSS.

 

If there are really BSS bods out there refusing BSS tickets because of hybrid installations, we need to know on what grounds.

What I meant is that there are thousands of boats out there around the world with LFP installations with no real safety issues from insurance companies or regulation authorities, so there seems no reason that there should be any valid objections from BSS -- and if they did come up with any it would be very easy to challenge them as unfounded and against all the evidence.

[MtB]

1 minute ago, rusty69 said:

It would make more sense to unbolt them after he's failed it if there is no retest fee. My install recently passed the dreaded inspection, so they are bound to change the goal posts before the next one.

 

It would make more sense for them to stop being so bloody silly and just pass them in the first place. 

 

If Nick is right about it, that is. 

[IanD]

8 minutes ago, rusty69 said:

The rules they are going to introduce after thousands of people have installed them, and before my next BSS exam probably.

If they tried that they'd get shot down in flames -- not from the LFP batteries, obviously -- by all the evidence from the field (sea?) that shows they're not a safety risk...

Edited March 29, 2023 by IanD

[rusty69]

4 minutes ago, IanD said:

If they tried that they'd get shot down in flames -- not from the LFP batteries, obviously -- by all the evidence from the field (sea?) that shows they're not a safety risk...

I can see them introducing, at the very least, stipulations based on the so called 'long cable' method, and approriate cable support,and fusing, if the scheme doesn't already cater for such matters. Maybe it does, I haven't actually read it.

Edited March 29, 2023 by rusty69

[Tony1]

3 minutes ago, MtB said:

 

But they are not subject to BSS.

 

If there are really BSS bods out there refusing BSS tickets because of hybrid installations, we need to know on what grounds.

 

I couldn't agree more. My BSS is due in December and if they are making comments or raising common concerns about any aspects of lithium setups, we need to know the details asap. 

I'm hoping that since I use a B2B in between each lead acid and the lithiums, I have an additional degree of control over the lithium charging, and perhaps thus extra safety, but I'm no expert and I have no real idea. 

 

 

 

[Alan de Enfield]

38 minutes ago, IanD said:

What I meant is that there are thousands of boats out there around the world with LFP installations with no real safety issues from insurance companies or regulation authorities, so there seems no reason that there should be any valid objections from BSS -- and if they did come up with any it would be very easy to challenge them as unfounded and against all the evidence.

 

My 'lumpy water' insurers ask if you have lithium batteries, if you say 'yes' the next question is details on type / chemistry,

 

Don't know if they refuse to offer cover or load the premium if you say LFP (or other nasties).

[IanD]

2 minutes ago, Alan de Enfield said:

 

My 'lumpy water' insurers ask if you have lithium batteries, if you say 'yes' the next question is details on type / chemistry,

 

Don't know if they refuse to offer cover or load the premium if you say LFP (or other nasties).

 

They certainly refuse/reduce cover if you say NMC or other similar chemistries, LFP are fine -- but like anything high-power and electrical have to be properly installed (fuses, cables sizes etc) and protected (BMS).

38 minutes ago, rusty69 said:

I can see them introducing, at the very least, stipulations based on the so called 'long cable' method, and approriate cable support,and fusing, if the scheme doesn't already cater for such matters. Maybe it does, I haven't actually read it.

All electrical installations -- LA, LFP or hybrid -- have rules about cable sizing, fuses, terminals, protection/insulation and so on. There's no reason a hybrid installation should be any different, there may be specific rules but I doubt that BSS have caught up with this setup yet. Similarly the BSS section about electrical propulsion is pretty much blank... 😉

Edited March 29, 2023 by IanD

[ditchcrawler]

47 minutes ago, IanD said:

What I meant is that there are thousands of boats out there around the world with LFP installations with no real safety issues from insurance companies or regulation authorities, so there seems no reason that there should be any valid objections from BSS -- and if they did come up with any it would be very easy to challenge them as unfounded and against all the evidence.

As I posted before, they have only just remover the requirement for a flame arrester on a diesel tank vent, as someone who has a diesel cooker I know how hard it is to set fire to diesel, let alone any fumes coming out of a half inch vent. So its seams its just their idea of a hazard and who can afford to challenge them, I cant.

46 minutes ago, rusty69 said:

I can see them introducing, at the very least, stipulations based on the so called 'long cable' method, and approriate cable support,and fusing, if the scheme doesn't already cater for such matters. Maybe it does, I haven't actually read it.

An alternator cable is not fused now with perhaps 550Ah of lead acid sitting on the end of it. They can pump a lot of current down into the alternator if you get a fault or short on the cable so why should  suitable lithium Life batteries be different ?

[rusty69]

11 minutes ago, ditchcrawler said:

 

An alternator cable is not fused now with perhaps 550Ah of lead acid sitting on the end of it. They can pump a lot of current down into the alternator if you get a fault or short on the cable so why should  suitable lithium Life batteries be different ?

I would suggest that some alternator cables probably do have a fuse. I guess the risk of having one though,is that it may wreck the alternator should the fuse ever blow.  Given the choice of a wrecked alternator, or a potential fire, which method then becomes the safest?

 

Perhaps, as you suggest, the BSS office have already decided.

[TheBiscuits]

1 hour ago, rusty69 said:

I can see them introducing, at the very least, stipulations based on the so called 'long cable' method, and approriate cable support,and fusing

 

I suspect this is exactly it.  I've seen too many numpties posting their setups using dangerously thin cables (10mm² or less!) because it's cheaper and you don't need as much of it.  Directly to a lithium battery bank, unfused.

 

Handy as a hot wire for cutting polystyrene, not great as your main electrical charging circuit!

[nicknorman]

2 hours ago, MtB said:

 

Whether they 'like it' is neither here nor there, Shirley.

 

Is there some debate or doubt about hybrid LiFePoO4/LA installations breaching one or more of the BSS requirements? Which would they be? 

The new ones which they are thinking of creating.

 

As communicated to me in response to a letter I had published in NABO news from NABO chairman who also sits on the BSS technical committee. He said that some lithium batteries are safe provided they are correctly installed and not mixed with older, more conventional batteries. I take that to mean his input to the BSS technical committee will be anti-hybrid setups.

Edited March 29, 2023 by nicknorman

[MtB]

10 minutes ago, nicknorman said:

The new ones which they are thinking of creating.

 

 

Ah, so Rusty was on the right track. Pass this time, fail next eh?! 

[nicknorman]

2 minutes ago, MtB said:

 

 

Ah, so Rusty was on the right track. Pass this time, fail next eh?! 

See my edit, but yes, maybe.