Lithium Batteries installation

[dmr]

7 minutes ago, nicknorman said:

It works adequately and lots of people do it. It is reasonably safe.

However it is a bodge and may have a limited future because most Li battery manufacturers specify "do not mix with batteries of a different chemistry". And the BSS people don't like it and at some point it might (or might not) become a BSS fail. If you are non-compliant with BSS and have deliberately flouted manufacturers installation instructions, the insurance co are not going to want to pay out!

I explained earlier that although the batteries are fairly compatible and complement each other, the fine detail for long term is more problematic due to the differning charging requirements. So it remains a bodge that works after a fashion!

It is popular, its cheap, and it works.

I think those of us with an engineering background don't like it because its just not nice.

It is relying on what might be an emergency shutdown components to work on a routine basis.

My main concern is that its possibly not very kind to the lead-acid battery and it will not be obvious when this battery is getting into poor condition.

Worse case is the lead-acid failing with a shorted cell and all the lithiums energy dumping into it.

If you do go this route then I suggest routine replacement of the lead acid battery every two or three years.

[Alan de Enfield]

23 minutes ago, Roberto Conigliaro said:

Well I just finished chatting with a person in another group who was saying that hybrid solution is the best  : super safe and straight forward

 

If you search the internet for long enough you will find an answer that agrees with what you think is the best way.

 

Alternatively you can take the advice of others who are following the changes** being discussed for introduction in the UK by the manufacturers, the legislation, the insurers and the Boat Safety Scheme (BSS)

 

** Already being implemented by other countries.

[Roberto Conigliaro]

20 minutes ago, nicknorman said:

Energy efficiency is a good point. This is the product of the voltage and charge put in, vs that coming out. Both LA and Li have similar charge efficiencies (ie Ah out is about 95% of Ah put in). However when you take into account voltage, the energy efficiency of Li is much better because LA charges at 14.4v and discharges at (say) 12.5v. whereas Li mostly charges at 13.6v or less, and discharges at (say) 13.2v. And this is before you take into account the need to run an engine or generator for hours with just a trickle going in to get LA batteries up to 100%.

It works adequately and lots of people do it. It is reasonably safe.

However it is a bodge and may have a limited future because most Li battery manufacturers specify "do not mix with batteries of a different chemistry". And the BSS people don't like it and at some point it might (or might not) become a BSS fail. If you are non-compliant with BSS and have deliberately flouted manufacturers installation instructions, the insurance co are not going to want to pay out!

I explained earlier that although the batteries are fairly compatible and complement each other, the fine detail for long term is more problematic due to the differing charging requirements. So it remains a bodge that works after a fashion, but is not "the right way to do it"!

On your first point - do you think that mixing the Li with LA would compromise the efficiency of the Li? 

 

On your second point - I get it, it's not the 'right' way to do, but if enough people have done it and they say is efficient and safe (and I am not saying it is, just researching if it really is), the only issue remaining is passing the BSS really.. 

also in terms of costs, if a good 460ah Li is £1200 and 3 x 220ah AGM are roughly £1000, the difference is not even a big one

10 minutes ago, Alan de Enfield said:

 

If you search the internet for long enough you will find an answer that agrees with what you think is the best way.

 

Alternatively you can take the advice of others who are following the changes** being discussed for introduction in the UK by the manufacturers, the legislation, the insurers and the Boat Safety Scheme (BSS)

 

** Already being implemented by other countries.

 

Well I am trying to understand if it's the case of one reckless person going for it or many who can say it is safe and sound. On the other hand, I get it, at the moment it's basically illegal.. 

what about there solution of going fully Li with s 60a DC-DC to protect the alternator, which seems to be not too expensive 

[IanD]

4 minutes ago, Roberto Conigliaro said:

On your first point - do you think that mixing the Li with LA would compromise the efficiency of the Li? 

 

On your second point - I get it, it's not the 'right' way to do, but if enough people have done it and they say is efficient and safe (and I am not saying it is, just researching if it really is), the only issue remaining is passing the BSS really.. 

also in terms of costs, if a good 460ah Li is £1200 and 3 x 220ah AGM are roughly £1000, the difference is not even a big one

A mixed LA/LFP can be made to work/function, at least in the short term, and if you ignore implications with things like insurance.

 

How it works in the longer term is the question, because a lot of the people singing the praises of systems like this have no long-term experience about what happens to the lifetime/reliability of either the LA or LFP or both.

 

The LA is likely to get sulphated rapidly because it never gets cycled across any significant SoC range (LFP has much flatter voltage vs. SoC) and is never fully charged and equalised (too high voltage for LFP) -- but this may all be invisible because it's hidden by the parallel LFP.

 

The LFP may die sooner than expected if it does end up doing lots of low/high voltage disconnects because these circuits are designed to be "emergency-only" not switched on a regular basis.

 

End result : a sooner-than-expected death for LA, LFP, or both, and possibly with little or no warning until you suddenly don't have any power.

 

I'm sure the proponents will say this is all "Project Fear", but how many of them have used these parallel LA/LFP systems regularly for long periods of time, like a liveaboard boater? A lot of them have RVs which are used much less often, so if things are going to go wrong over time they probably haven't got there yet.

 

The issue with LFP on boats is no longer the cost of the batteries, especially when you consider usable capacity and lifetime and removing the need to charge for hours to get LA to 100% SoC. The issue -- apart from potentially insurance -- is that you can't just drop them in to a boat with charging systems designed for LA batteries, no matter how many people claim that you can... 😞

[Roberto Conigliaro]

13 minutes ago, IanD said:

A mixed LA/LFP can be made to work/function, at least in the short term, and if you ignore implications with things like insurance.

 

How it works in the longer term is the question, because a lot of the people singing the praises of systems like this have no long-term experience about what happens to the lifetime/reliability of either the LA or LFP or both.

 

The LA is likely to get sulphated rapidly because it never gets cycled across any significant SoC range (LFP has much flatter voltage vs. SoC) and is never fully charged and equalised (too high voltage for LFP) -- but this may all be invisible because it's hidden by the parallel LFP.

 

The LFP may die sooner than expected if it does end up doing lots of low/high voltage disconnects because these circuits are designed to be "emergency-only" not switched on a regular basis.

 

End result : a sooner-than-expected death for LA, LFP, or both, and possibly with little or no warning until you suddenly don't have any power.

 

I'm sure the proponents will say this is all "Project Fear", but how many of them have used these parallel LA/LFP systems regularly for long periods of time, like a liveaboard boater? A lot of them have RVs which are used much less often, so if things are going to go wrong over time they probably haven't got there yet.

 

The issue with LFP on boats is no longer the cost of the batteries, especially when you consider usable capacity and lifetime and removing the need to charge for hours to get LA to 100% SoC. The issue -- apart from potentially insurance -- is that you can't just drop them in to a boat with charging systems designed for LA batteries, no matter how many people claim that you can... 😞

 

They say you can drop them as long you use an AGM as a buffer, but I see your point, this system hasn't been tested long enough and it might destroy either or both in the long term, depending how long is the long term though, it might worth the risk, you still need to replace the LA batteries every 5 years or so anyways 

[nicknorman]

59 minutes ago, Roberto Conigliaro said:

On your first point - do you think that mixing the Li with LA would compromise the efficiency of the Li? 

 

On your second point - I get it, it's not the 'right' way to do, but if enough people have done it and they say is efficient and safe (and I am not saying it is, just researching if it really is), the only issue remaining is passing the BSS really.. 

also in terms of costs, if a good 460ah Li is £1200 and 3 x 220ah AGM are roughly £1000, the difference is not even a big one

 

Well I am trying to understand if it's the case of one reckless person going for it or many who can say it is safe and sound. On the other hand, I get it, at the moment it's basically illegal.. 

what about there solution of going fully Li with s 60a DC-DC to protect the alternator, which seems to be not too expensive 

 

I don't think the mix of Li and LA would significantly compromise the efficiency provided you didn't discharge the Li to the point where the LA starts discharging - which would be pretty low, probably below 10% SoC. This being because the Li voltage stays up around 13v or more until the battery gets very low. Effectively, there would be no current flowing into the LA during charge, no current flowing out of the LA during discharge. However I suppose if you were in the habit of putting on big loads like an electric kettle, this might dip the system voltage to the point the LA discharged a bit, and then you have the poor efficiency of LA recharging and difficulty of not being able to properly recharge the LA without overcharging the Li.

Also I suppose you would be holding the LA up at 13.3v and that might give rise to a bit of wasted current into the LA to compensate for self-discharge (something Li barely suffers from)

 

That said, a simple isolator switch between the LA and the Li would go a long way to making the "fudge" better. Switch closed when running the engine to recharge the Li, switch open to discharge the Li into the boat or if you need a long LA charge without overcharging the Li. But switches and people means finger trouble and at some point, having the switch in the wrong position! And potential to close the switch when the Li is very flat but the LA is full, which equals very large current flowing into the Li. Never underestimate the potential for human error to cause disaster!

 

Oh and I wouldn't say it is "illegal" at the moment, it just has the potential to become "illegal" in the future.

Edited January 25 by nicknorman

[MtB]

39 minutes ago, IanD said:

I'm sure the proponents will say this is all "Project Fear", but how many of them have used these parallel LA/LFP systems regularly for long periods of time, like a liveaboard boater? A lot of them have RVs which are used much less often, so if things are going to go wrong over time they probably haven't got there yet.

 

Is that really true? 

 

I get the impression there might be just as many liveaboard RVs as there are liveaboard boats. Administrative reasons not to use a hybrid system (insurance, BSS) are trumped by the absence of a significant number of users reporting fires in their RVs or boats. In fact I've yet to read about of a single incident. 

 

I would imagine there is a large body of 'drop-in' LFP users reporting goosed alternators, but there doesn't seem to be an emerging problem with hybrid installations. Or maybe there IS? I don't know, I only know I'm not seeing reports of them. 

 

 

[BEngo]

I think DMR has identified one of the bigger risks in a direct hybrid.  Sooner or later the lead acid battery which is there to absorb the load dump will shed enough materual from thevplatescthat one cell will short put.  This is a common  failure in 'conventional ' battery systems where it causes real problems for sytems with continuous charging ( solar or  shoreline).  I do not think the consequences of discharging say 460 Ah from a lithium battery into a defective lead acid would be very good, though I doubt the current would get high enough to trip the excessive discharge rate protection in the BMS.  Much will depend on the internal resistance on the knackered LA and the connection and cable resistance

 

A BtoB charger is an improved solutio  over hybrid.  It solves the back discharge problem above, and to some extent addresses alternator overload. It is cheaper thsn a new charging control set-up.

 

It still relies on some of the emergency disconnects for normal operation and it is not efficient.

 

N

  

[GUMPY]

If the Li batteries are treated like a normal LA domestic battery bank and fed by a VSR from the starter battery then there is the same risk of the Li dumping into a shorted cell  as there is of the alternator doing it.

I would suspect that is how most RV are wired as often there will only be one alternator on an RV and definitely only one in a car towing a caravan.

 

The charger and the MPPT have been set for Li in my van and it all works as it should the charger reaches the end of bulk and switches to float about the same time as the LI are 100%. 

 

and the BMS then disconnects the charging leaving discharge on.

[IanD]

23 minutes ago, MtB said:

 

Is that really true? 

 

I get the impression there might be just as many liveaboard RVs as there are liveaboard boats. Administrative reasons not to use a hybrid system (insurance, BSS) are trumped by the absence of a significant number of users reporting fires in their RVs or boats. In fact I've yet to read about of a single incident. 

 

I would imagine there is a large body of 'drop-in' LFP users reporting goosed alternators, but there doesn't seem to be an emerging problem with hybrid installations. Or maybe there IS? I don't know, I only know I'm not seeing reports of them. 

 

 

 

I didn't say all, I said that "A lot of them have RVs which are used much less often (than liveaboard boaters)" which I'm pretty sure is true. Most of the RV/boat proponents of parallel LA/LFP say how brilliant they are but are strangely quiet about how many years they've been running these for -- there might be some out there who've been successfully cycling them for years, but I didn't find any.

 

AFAIK there have been few or no reports of *battery* fires anywhere -- boats, RVs, or houses -- with LFP batteries. Which is as expected, battery fire risk is *not* a good reason to be scared of LFP batteries, they don't really burn. However they're perfectly capable of setting other components on fire like alternators and wiring... 😉

 

46 minutes ago, Roberto Conigliaro said:

 

They say you can drop them as long you use an AGM as a buffer, but I see your point, this system hasn't been tested long enough and it might destroy either or both in the long term, depending how long is the long term though, it might worth the risk, you still need to replace the LA batteries every 5 years or so anyways 

 

If the LA batteries are in parallel with the LFP so they don't get cycled over SoC range (little voltage change) and never get charged to 100% SoC and equalised/desulphated at high voltage, they probably won't last 5 years, sulphation is likely to kill them *long* before that... 😞

Edited January 25 by IanD

[Roberto Conigliaro]

18 minutes ago, IanD said:

 

I didn't say all, I said that "A lot of them have RVs which are used much less often (than liveaboard boaters)" which I'm pretty sure is true. Most of the RV/boat proponents of parallel LA/LFP say how brilliant they are but are strangely quiet about how many years they've been running these for -- there might be some out there who've been successfully cycling them for years, but I didn't find any.

 

AFAIK there have been few or no reports of *battery* fires anywhere -- boats, RVs, or houses -- with LFP batteries. Which is as expected, battery fire risk is *not* a good reason to be scared of LFP batteries, they don't really burn. However they're perfectly capable of setting other components on fire like alternators and wiring... 😉

 

 

If the LA batteries are in parallel with the LFP so they don't get cycled over SoC range (little voltage change) and never get charged to 100% SoC and equalised/desulphated at high voltage, they probably won't last 5 years, sulphation is likely to kill them *long* before that... 😞

 

I see, I wonder though if having to replace a 100ah AGM battery every couple of years still worth the advantages of having the Li on board..

 

whoever wrote the following has a huge believe in the hybrid   https://www.zwerfcat.nl/en/lithium-hybrid.html

[dmr]

36 minutes ago, BEngo said:

I think DMR has identified one of the bigger risks in a direct hybrid.  Sooner or later the lead acid battery which is there to absorb the load dump will shed enough materual from thevplatescthat one cell will short put.  This is a common  failure in 'conventional ' battery systems where it causes real problems for sytems with continuous charging ( solar or  shoreline).  I do not think the consequences of discharging say 460 Ah from a lithium battery into a defective lead acid would be very good, though I doubt the current would get high enough to trip the excessive discharge rate protection in the BMS.  Much will depend on the internal resistance on the knackered LA and the connection and cable resistance

 

A BtoB charger is an improved solutio  over hybrid.  It solves the back discharge problem above, and to some extent addresses alternator overload. It is cheaper thsn a new charging control set-up.

 

It still relies on some of the emergency disconnects for normal operation and it is not efficient.

 

N

  

The Victron BtoB devices have a charge enable input and this could be fed from the Victron BMV relay to stop charging at about 90%. This should prevent any over charge disconnects, but does rely on keeping the BMV correctly synched to the true battery SoC.

 

I still prefer the proper Zeus type alternator controller approach but a well thought out BtoB system is a good second best.

[BEngo]

The other thing to be aware of is that the emerging US requirements call for their to be alarms /warnings in good time before the battery protection system shuts off the power.  This is obviously lumpy water driven as no one wants to find themselves in mid shipping lane, at night with no power.  Not so much of a problem on our cut, except perhaps in a long tunnel, but anything the BSS requires will have to be vonsistent with a lumpy water position.

 

  A drop-in solution with most of today's batteries cannot meet that.  One reason is that their BMS only does cut-off and not warnings followed by cut-off.  The other is that few batteries enable access to the BMS except through an app.

 

N

[dmr]

2 minutes ago, BEngo said:

The other thing to be aware of is that the emerging US requirements call for their to be alarms /warnings in good time before the battery protection system shuts off the power.  This is obviously lumpy water driven as no one wants to find themselves in mid shipping lane, at night with no power.  Not so much of a problem on our cut, except perhaps in a long tunnel, but anything the BSS requires will have to be vonsistent with a lumpy water position.

 

  A drop-in solution with most of today's batteries cannot meet that.  One reason is that their BMS only does cut-off and not warnings followed by cut-off.  The other is that few batteries enable access to the BMS except through an app.

 

N

 

Maybe this will drive the providers of the lithium BMS systems to give us a couple of simple "relay" type outputs:

90% please stop charging

95% sound alarm, internal cut-off approaching.

 

This would be a good halfway house for those (many) who don't want to go the full CANbus route.

[IanD]

2 hours ago, dmr said:

 

Maybe this will drive the providers of the lithium BMS systems to give us a couple of simple "relay" type outputs:

90% please stop charging

95% sound alarm, internal cut-off approaching.

 

This would be a good halfway house for those (many) who don't want to go the full CANbus route.

The alarm doesn't have to be CANbus, a Bluetooth alert to a phone app costs far less, doesn't need any external hardware, and meets the requirements. 

[nicknorman]

35 minutes ago, IanD said:

The alarm doesn't have to be CANbus, a Bluetooth alert to a phone app costs far less, doesn't need any external hardware, and meets the requirements. 

What exactly are the requirements? Anyone of engineering competence designing a warning system would not rely on the recipient having a phone, a phone that is on, a phone not selected to “silent” mode, a phone that has a non-flat battery and a phone that is currently running the relevant App.

[blackrose]

10 hours ago, nicknorman said:

The only thing wrong with your post is that you have this fantasy that at some point, everyone will agree on how to do it. Never going to happen!!!

 

The only thing wrong with your post is that you think you can predict the future. I'm not saying that everyone will agree on everything related to using lithium batteries on boats, but I certainly think they're will be greater consensus as new batteries and new management systems emerge. I  don't think that's a fantasy.

 

As I said, these days everyone more or less agrees on how best to apply "conventional" battery technology on boats and I doubt that was always the case. We didn't always have smart chargers or split charge relays for example, so it wasn't that long ago that many people weren't charging their batteries very effectively. 

 

Basically you're all early adopters of lithium battery technology on boats which is why there are several different ways of doing it most of which don't seem entirely satisfactory. I can't predict the future either, but my hunch is that if I returned to these discussions in 5 or 10 years time some of these disagreements will have been settled.

Edited January 26 by blackrose

[BEngo]

5 hours ago, blackrose said:

if I returned to these discussions in 5 or 10 years time some of these disagreements will have been settled.

I am sure that is true.  Whether it will be  by consensus and best practice or through regulation I am not sure.

 

N

[nicknorman]

6 hours ago, blackrose said:

 

The only thing wrong with your post is that you think you can predict the future. I'm not saying that everyone will agree on everything related to using lithium batteries on boats, but I certainly think they're will be greater consensus as new batteries and new management systems emerge. I  don't think that's a fantasy.

 

As I said, these days everyone more or less agrees on how best to apply "conventional" battery technology on boats and I doubt that was always the case. We didn't always have smart chargers or split charge relays for example, so it wasn't that long ago that many people weren't charging their batteries very effectively. 

 

Basically you're all early adopters of lithium battery technology on boats which is why there are several different ways of doing it most of which don't seem entirely satisfactory. I can't predict the future either, but my hunch is that if I returned to these discussions in 5 or 10 years time some of these disagreements will have been settled.

Sorry, I had temporarily forgotten that my and your senses of humour are not compatible.

[MtB]

24 minutes ago, nicknorman said:

Sorry, I had temporarily forgotten that my and your senses of humour are not compatible.

 

For there to be a sense of humour incompatibility, the other party needs to have one in the first place.

 

 

[nicknorman]

Just now, MtB said:

 

For there to be a sense of humour incompatibility, the other party needs to have one in the first place.

 

 

I was trying to be polite, you’ve blown it now!

[MtB]

16 minutes ago, nicknorman said:

I was trying to be polite, you’ve blown it now!

 

Pleased to have been of assistance  

 

 

 

[IanD]

11 hours ago, nicknorman said:

What exactly are the requirements? Anyone of engineering competence designing a warning system would not rely on the recipient having a phone, a phone that is on, a phone not selected to “silent” mode, a phone that has a non-flat battery and a phone that is currently running the relevant App.

The requirements are the insurance ones that the BMS should be capable of alerting the steerer/boat owner when things go wrong, not just silently take action -- which means some link to the outside world not a standalone isolated internal BMS.

 

Many (most?) people nowadays are more likely to have their phone with them than be next to a warning buzzer or flashing light somewhere on the boat, possibly the other side of a couple of closed doors. And if you're not on the boat then a phone can still warn you, assuming remote access.

 

No solution is perfect and guaranteed to always work, either phone or buzzer/light, there will always be cases where an alert gets missed. The insurance requirement is that the BMS communicates with the outside world to warn of problems; how these are communicated to the boater/owner is a separate problem.

 

The phone solution has the advantages that the cost is effectively zero and no wiring or warning lights/buzzer need to be installed, so there's nothing to stop lazy people installing it -- and the battery doesn't need CANbus or any connectors adding to it. But if you don't like this, by all means adopt any other solution you want -- however battery manufacturers are unlikely to adopt a hardware trigger solution, cheapo ones will use Bluetooth and expensive ones will use CANbus -- and this is already exactly what they do... 😉

 

15 hours ago, Roberto Conigliaro said:

 

I see, I wonder though if having to replace a 100ah AGM battery every couple of years still worth the advantages of having the Li on board..

 

whoever wrote the following has a huge believe in the hybrid   https://www.zwerfcat.nl/en/lithium-hybrid.html

 

He does indeed, and waxes lyrical about the advantages, while carefully avoiding several potential problems...

 

The first is that to stop the LA dying of sulphation it's down to the user to deliberately and regularly run charging for long enough that the voltage goes up and the LFP BMS disconnects due to overvoltage, so that the LA can get into the equalisation mode -- and this has to be done for some time, typically at least a couple of hours. You can bet that most can't-be-bothered users won't do this, they'll just run with the LFP providing power most/all of the time, and end up with dead LA batteries.

 

The second is that this needs to be done regularly to keep the LA healthy, which means the LFP is regularly charged past 100% SoC and (slowly) up to the emergency disconnect voltage, and this by definition is not a state that the internal cells are happy with for any length of time -- going above 100% SoC should only happen in emergencies, not regularly, and battery life is likely to be reduced as a consequence. There's also the question about how reliable the LFP is when a circuit intended for occasional emergency use (overvoltage disconnect) is used regularly.

 

The first one means short LA life, the second one means short LFP life. Neither will show up for some time, maybe a year or more depending on how often the boat (or RV) is used -- but at this point you're faced with unexpected and expensive battery replacement, both of the LA bank and also not the 10 years lifetime you were expecting from expensive LFP and used to justify buying them... 😞

 

And there's the problem in a nutshell -- how many of the proponents of these systems have used them heavily for years to hit these reduced lifetime problems?

 

In contrast, there's no doubt that a properly-designed LFP system will outlast most boats (and probably boaters) -- see here for example...

 

https://marinehowto.com/agm-vs-lifepo4-longevity/

 

This was my own personal bank that I built in 2009 and began using in the spring of 2010. This bank was built as an educational /experimentation tool for myself and our employees. As such, each cycle was carefully recorded and documented. I specifically ran each discharge to 80% DoD, occasionally 0% if needed.  I also ran full 0% SoC capacity tests every 50 cycles. Once the bank broke 1000 80% DoD cycles I switched to capacity testing every 100 cycles (capacity just was not changing enough in 50 cycles to waste the time/energy).. At the time of testing this bank had just turned 13 years old and had exceeded 2200 cycles. It served summers (April to Nov) on our 36ft cruising sailboat and it spent winters as the “load bank” for our alternator test bench and also powered a large 2000W Inverter /charger in the shop that we ran an electric heater from…. This meant the battery was often sitting at 80% DoD or lower to serve as the load for alternators as large as 200A.

 

For the  cells 13th birthday I tested each 400Ah cell individually. As can be seen the lowest capacity cell was 417.02 Ah. With LFP banks the lowest capacity cell determines bank capacity as this cell will cause the entire bank to disconnect the minute it his the low voltage cut off. For 13 year old cells the Ah capacity still matches to within 3Ah..It was slightly tighter when new but not bad for 13 years old and in excess of 2000 cycles!

Edited January 26 by IanD

[nicknorman]

12 minutes ago, IanD said:

The requirements are the insurance ones that the BMS should be capable of alerting the steerer/boat owner when things go wrong, not just silently take action -- which means some link to the outside world not a standalone isolated internal BMS.

 

Many (most?) people nowadays are more likely to have their phone with them than be next to a warning buzzer or flashing light somewhere on the boat, possibly the other side of a couple of closed doors. And if you're not on the boat then a phone can still warn you, assuming remote access.

 

No solution is perfect and guaranteed to always work, either phone or buzzer/light, there will always be cases where an alert gets missed. The insurance requirement is that the BMS communicates with the outside world to warn of problems; how these are communicated to the boater/owner is a separate problem.

 

The phone solution has the advantages that the cost is effectively zero and no wiring or warning lights/buzzer need to be installed, so there's nothing to stop lazy people installing it -- and the battery doesn't need CANbus or any connectors adding to it. But if you don't like this, by all means adopt any other solution you want -- however battery manufacturers are unlikely to adopt a hardware trigger solution, cheapo ones will use Bluetooth and expensive ones will use CANbus -- and this is already exactly what they do... 😉

 

I did. There is a sounder on the BMS board that makes a fairly piercing shriek! BMS board is in the "engine room" area, ie close to the engine panel etc so it should be reasonably audible when driving the boat. As disconnect approaches, it starts to beep with increasingly long beeps until finally it sounds continuously for a few seconds and then disconnects. In the mean time of course it has sent an "imminent disconnect" message to the alternator controller which, if the engine is running, goes to a zero current voltage.

[PeterF]

Several posts ago raised the issue of RVs and lithium. Modern RVs can not use the direct hybrid charging route from the alternator because modern vehicles have "smart" alternators where often the voltage being generated may well be 13.0V or so during periods of time, so the lithium house bank can not get charged. Modern vehicles with lithium house batteries either need to have a second alternator fitted or to use BtoB chargers. Older vehicles with permanent 14.4V alternator output can use direct hybrid.