Lithium Batteries installation

[GUMPY]

14 minutes ago, PeterF said:

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.

When towing the caravan my alternator switches when it detects the caravan is there from being intelligent to being a dumb 14.4v alternator. There was no hardware added when the towbar was fitted merely some reprogramming of the ECU.

Is there a reason why an RV couldn't be reprogrammed to take account if the extra load when charging a Li battery in the same way my car does.

Thinking about this  as it stands an intelligent alternator is not going to fully charge an extra 100Ah LA battery so they must already  reprogram or similar when fitting an extra battery.

 

It's been interesting watching the alternator voltage curve when in intelligent mode, most of the time it sits, as you say, at about 13v however when on engine overrun/braking it reaches 14.4v that's about the only time it does apart from when the vehicle is first started.

[Lochwarden]

On 25/01/2024 at 16:44, 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 - just install a AGM batteries between the alternator and the Lifepo4 as a buffer and the trick is done. I feel like maybe some people would disagree with that, at least in terms of safety? 

That other group wouldn’t be the 12 volt boating group would it? As on here, there are some very knowledgeable people on there, and some not so knowledgeable as well. 

[MtB]

On 25/01/2024 at 16:44, 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 - just install a AGM batteries between the alternator and the Lifepo4 as a buffer and the trick is done. I feel like maybe some people would disagree with that, at least in terms of safety? 

 

It works fine for me. 

 

Most of the objections seem to revolve around potential future regulations, potential future insurance problems, and potential future FLA buffer failure.

 

Any or all of which may or may not come to pass in the fullness of time. But in the meantime, press on with what works I suggest. 

 

 

 

 

[Roberto Conigliaro]

1 hour ago, Lochwarden said:

That other group wouldn’t be the 12 volt boating group would it? As on here, there are some very knowledgeable people on there, and some not so knowledgeable as well. 

Yes I heard they give some good advice there, I asked to join the group a couple of days ago but the request is still pending 

1 hour ago, MtB said:

 

It works fine for me. 

 

Most of the objections seem to revolve around potential future regulations, potential future insurance problems, and potential future FLA buffer failure.

 

Any or all of which may or may not come to pass in the fullness of time. But in the meantime, press on with what works I suggest. 

 

 

 

 

Great to hear it works well for you  - I am fully convinced to do it, just need need some extra advice before ordering the batteries 

[IanD]

1 hour ago, MtB said:

 

It works fine for me. 

 

Most of the objections seem to revolve around potential future regulations, potential future insurance problems, and potential future FLA buffer failure.

 

Any or all of which may or may not come to pass in the fullness of time. But in the meantime, press on with what works I suggest. 

 

 

It works fine for you (and some other vloggers), but I believe you (and they) understand batteries -- LA and LFP -- and charging and what is needed to make the system work and keep them all healthy.

 

Going by the number of boaters who manage to kill off their LA batteries before their time, many are not technically minded, don't understand any of this and don't take much notice of what is going on with their batteries. They're quite likely to come a cropper one way or another, especially if they just drop-in LFPs to a system with an alternator -- and may end up with prematurely dead batteries, either LA or LFP or possibly both.

 

The insurance and regulations issue is a separate one, and it remains to be seen what the industry does -- but clearly they disapprove of parallel LA/LFP systems, as do all the battery manufacturers/suppliers. For the time being you're probably OK doing this, though given the LFP suppliers specifically say "don't do it!" it will be interesting to see what happens if something does go wrong with a system like this which results in an insurance claim -- maybe not common today, but it's going to happen sooner or later if more people keep going down this path.

 

I'm not saying people shouldn't do it, just that they should be aware of the potential problems and what care and maintenance is needed, and keep an eye on the insurance issue... 😉

Edited January 27 by IanD

[Alway Swilby]

On 27/01/2024 at 13:01, IanD said:

 

It works fine for you (and some other vloggers), but I believe you (and they) understand batteries -- LA and LFP -- and charging and what is needed to make the system work and keep them all healthy.

 

Going by the number of boaters who manage to kill off their LA batteries before their time, many are not technically minded, don't understand any of this and don't take much notice of what is going on with their batteries. They're quite likely to come a cropper one way or another, especially if they just drop-in LFPs to a system with an alternator -- and may end up with prematurely dead batteries, either LA or LFP or possibly both.

 

The insurance and regulations issue is a separate one, and it remains to be seen what the industry does -- but clearly they disapprove of parallel LA/LFP systems, as do all the battery manufacturers/suppliers. For the time being you're probably OK doing this, though given the LFP suppliers specifically say "don't do it!" it will be interesting to see what happens if something does go wrong with a system like this which results in an insurance claim -- maybe not common today, but it's going to happen sooner or later if more people keep going down this path.

 

I'm not saying people shouldn't do it, just that they should be aware of the potential problems and what care and maintenance is needed, and keep an eye on the insurance issue... 😉

The LFP/LA hybrid is ideal for people who don't have a clue about looking after batteries. The BMS looks after the LFP batteries for them. They are impossible to over charge or over discharge. Impossible to chronically under charge. The LA battery is kept fully charged nearly all the time which is just what LAs  like. The system looks after itself and just works.

There is a company called Life Batteries (https://www.lifebatteries.co.uk/) who sell LFP batteries and will set them up for a hybrid system before sending them out. They are fully aware of how the hybrid set up works and are very happy to sell you LFP batteries for use in a hybrid system. Their web site has a section explaining it all. https://www.lifebatteries.co.uk/blank-page

 

 

Edited January 29 by Alway Swilby
Links added

[magnetman]

Interesting read. 

 

Are the BMS circuits designed to be used as on/orf switches? I don't know, presumably they are but its possible they are only meant for unexpected outcomes rather than being used routinely. 

 

He doesn't say what happens if the BMS over voltage disconnect fails to operate. 

 

Website needs proof reading. 

Also the website pages need sorting out. Calling it 'blank page' is a bit naff. 

[Alway Swilby]

12 minutes ago, magnetman said:

Interesting read. 

 

Are the BMS circuits designed to be used as on/orf switches? I don't know, presumably they are but its possible they are only meant for unexpected outcomes rather than being used routinely. 

 

He doesn't say what happens if the BMS over voltage disconnect fails to operate. 

 

Website needs proof reading. 

Also the website pages need sorting out. Calling it 'blank page' is a bit naff. 

Yes, he is aware his web site is a bit naff. It's on his list to sort out.

I don't see a reason why the BMS shouldn't be used as an on/off (its easier to type off than orf 🙂) switch. The supplier sells the batteries fully expecting them to be used as such and gives a 10 year guarantee whilst connected in a hybrid system.

 

[MtB]

10 hours ago, Alway Swilby said:

The LFP/LA hybrid is ideal for people who don't have a clue about looking after batteries. The BMS looks after the LFP batteries for them. They are impossible to over charge or over discharge. Impossible to chronically under charge. The LA battery is kept fully charged nearly all the time which is just what LAs  like. The system looks after itself and just works.

There is a company called Life Batteries (lifebatteries.co.uk) who sell LFP batteries and will set them up for a hybrid system before sending them out. They are fully aware of how the hybrid set up works and are very happy to sell you LFP batteries for use in a hybrid system. Their web site has a section explaining it all.

 

This post perfectly illustrates the schism that exists between old skool dinosaur engineers on here who see the switches in the BMS (any BMS) as a last ditch backstop and the vast numbers of real world users out there who say the BMS (the JBD specifically) is ultra-reliable and use it on a daily basis for charge control with no problems arising.

 

I think it is partly if not wholly due the the plummeting price of LFP batteries. Back in the day when LFP batteries cost multiple £ks and BMS designs were not so reliable, it made sense to have separate cell charge control and charge protection devices. But now LFP batts cost hardly any more than decent LAs, the occasional loss of a cheap LFP bank is no longer the big deal it used to be. Hence the willingness to rely on the JBD device to control charge, along with a carefully selected length of thin(ish) wire to cut down alternator current and an LA in parallel to protect the alt when the JBD disconnects.

 

 

 

 

 

Edited January 29 by MtB
Grammar!

[nicknorman]

1 hour ago, magnetman said:

Interesting read. 

 

Are the BMS circuits designed to be used as on/orf switches? I don't know, presumably they are but its possible they are only meant for unexpected outcomes rather than being used routinely. 

 

He doesn't say what happens if the BMS over voltage disconnect fails to operate. 

 

Website needs proof reading. 

Also the website pages need sorting out. Calling it 'blank page' is a bit naff. 

The BMS switches are not mechanical, they are MOSFETs (transistors if you like) so there is no concept of mechanically wearing out. More ageing will occur from high charge and discharge currents than from switching on and off.

34 minutes ago, MtB said:

 

This post perfectly illustrates the schism that exists between old skool dinosaur engineers on here who see the switches in the BMS (any BMS) as a last ditch backstop and the vast numbers of real world users out there who say the BMS (the JBD specifically) is ultra-reliable and use it on a daily basis for charge control with no problems arising.

 

I think it is partly if not wholly due the the plummeting price of LFP batteries. Back in the day when LFP batteries cost multiple £ks and BMS designs were not so reliable, it made sense to have separate cell charge control and charge protection devices. But now LFP batts cost hardly any more than decent LAs, the occasional loss of a cheap LFP bank is no longer the big deal it used to be. Hence the willingness to rely on the JBD device to control charge, along with a carefully selected length of thin(ish) wire to cut down alternator current and an LA in parallel to protect the alt when the JBD disconnects.

 

 

Not dinosaurs IMO, just cautious based on decades of engineering experience that says a single point of failure shouldn't cause a catastrophe.

 

That said, it is interesting that they mention the BMS is configured to be used as a hybrid system. I think traditionally, battery manufacturers have set the BMS limits on charge and discharge to be the absolute limit, in order to maximise the claimed capacity. The "dinosaurs" were concerned that taking the cells routinely up to the limit for "just not quite doing serious damage" was a bad thing.

 

But of course there is nothing to stop a manufacturer from moving the BMS settings to more conservative values and thus one doesn't routinely approach and only just dodge the "death to Lithiums" conditions. This is what these folk have done, and same applies to Fogstar who have set fairly conservative limits in their BMS.

 

Downside of that is if you want to use the battery in a "proper" system whereby charging is properly controlled and the BMS shutoff is considered the last resort protection - instead of the charging system controlling the charging, the battery BMS might decide to jump in first and thus the concept of "last resort protection" is nullified.

 

The other thing to mention about the website is no mention of alternator overheating. I guess that doesn't concern them too much because their battery won't be damaged, but it is interesting they have not mentioned the slightly dodgy tactic of the "long wire".

 

[magnetman]

1 hour ago, nicknorman said:

The BMS switches are not mechanical, they are MOSFETs (transistors if you like) so there is no concept of mechanically wearing out. More ageing will occur from high charge and discharge currents than from switching on and off.

 

 

I know they are MOSFETS. These can fail. Well at least they do in brushed motor speed controllers but that can be related to motor noise. 

 

I expect its fine. 

 

I have a LA / LFP hybrid setup on one of the Boats but the other Boat has LTO batteries as does the electric canoe. 

 

 

1 hour ago, nicknorman said:

The BMS switches are not mechanical, they are MOSFETs (transistors if you like) so there is no concept of mechanically wearing out. More ageing will occur from high charge and discharge currents than from switching on and off.

 

 

 

A question for you Nick as you seem 'up' on electronics. 

 

I know a little bit but not a lot. 

 

What I am intrigued about is the potential high current degradation of FETS. 

 

IF the alternator was providing a high charge rate lets say 1C to the lithium battery then the BMS suddenly switches off could this cause degradation of the FETs? 

 

What I am getting at is the BMS has originally been engineered as a rarely used backup for cell protection rather than an 'on/off' switch. 

 

If the original design had been intending to regularly cut off a high current would the specification of the FETs be the same? 

Heating and cooling (thermal management) of FETs is a significant issue when large currents are being switched. 

Edited January 29 by magnetman

[nicknorman]

2 hours ago, magnetman said:

A question for you Nick as you seem 'up' on electronics. 

 

I know a little bit but not a lot. 

 

What I am intrigued about is the potential high current degradation of FETS. 

 

IF the alternator was providing a high charge rate lets say 1C to the lithium battery then the BMS suddenly switches off could this cause degradation of the FETs? 

 

What I am getting at is the BMS has originally been engineered as a rarely used backup for cell protection rather than an 'on/off' switch. 

 

If the original design had been intending to regularly cut off a high current would the specification of the FETs be the same? 

Heating and cooling (thermal management) of FETs is a significant issue when large currents are being switched. 

 

The devil is in the detail. At a high current, provided the gate drive voltage is adequate, there is fairly low power dissipation. Obviously you would choose MOSFETS that have sufficiently low Rds(on) (on resistance) to keep power dissipation to a safe limit at max rated current - and taking regard for the relevant temperature range.

 

When the MOSFET is off, there is no significant current and thus no power dissipation.

Bearing in mind  power = V*I, you can see that when on we have lots of I but no (very little) V, and when off we have lots of V but no I.

But half on we have quite a lot of V and I and thus a very large power dissipation. So it is important to drive the MOSFET hard and fast to pass through this "partially on" phase as quickly as possible. Bearing in mind the actual semiconductor junction is very small and its thermal capacity is very low.

 

Then we have the possibility of avalanche breakdown, which occurs when Vds is too high. No problem you say, we are using MOSFETS rated at 25v and the system voltage is never more than 14.6v. Except that we have to take into account inductance. Even a wire leading from a cell to the BMS  board has some inductance, and the wires leading from the alternator to the battery, a lot more. The property of inductance is to resist rates of change of current, by creating an opposing voltage. V = LdI/dt. So with a fast dI/dt, which you need to avoid the power dissipation problem, you can generate a momentary transient voltage that exceeds the MOSFET rating. By "momentary" we are talking a few microseconds.

 

"But I have a LA battery in parallel" you say. Yes, but again we have inductance in the wires and the battery will take more than a few microseconds to absorb the transient as a result.

 

Well you did ask!
 

So to answer your question, if the system is properly designed the MOSFETs won't be degraded by high current switching. If it is not properly designed, each time the MOSFETs switch off there could be a transient that takes the MOSFET into avalanche just for a few microseconds. And each excursion into avalanche takes a little bit of life away.

Edited January 29 by nicknorman

[TheBiscuits]

2 hours ago, nicknorman said:

we have inductance in the wires

 

You wouldn't recommend the long thin wire is coiled up then?

 

[IanD]

4 minutes ago, TheBiscuits said:

 

You wouldn't recommend the long thin wire is coiled up then?

 

 

Yes if you do it properly to avoid inductance -- loop the spare length of cable into a hairpin shape so the two ends are together, and then coil the hairpin up. Then the opposing currents out and back are adjacent and there's far less inductance. Incidentally this also avoids twisting the cable. Taught to me by a sound engineer at the BBC whose motto was "Tidy cables are happy cables"... 🙂

 

(there's a more complex figure-of-eight coiling method too, but this one is harder to explain...)

Edited January 29 by IanD

[dmr]

Another issue and a growing one, is relying on Chinese electronics of unknown quality and quality control with very little detailed technical documentation and specification.

Have a look at the Fogstar website, they sell BMS systems and state that the documentation is minimal.

Also have a look on eBay for cheap electronics, maybe a dc-dc converter, and see how many almost identical devices are for sale with different names. Maybe some are good and genuine and others are copies from somebodies garden shed operation. We are totally dependant on the BMS importer understanding the Chinese way of doing things and keeping on top of the quality control. 

[magnetman]

Indeed. 

 

I'm a little surprised the Lifebattery gentleman has suggested the LFP/LA hybrid setup with BMS to cut off the LFP is All Good. 

 

I wonder if he has done his homework. 

 

 

Also slightly bizarre on one of the web pages it refers to LIFOS. Obviously one can work out what chemistry this refers to but LIFOS is an existing brand of consumer batteries. 

 

https://www.lifos.co.uk

[GUMPY]

 

[Jen-in-Wellies]

On 29/01/2024 at 09:37, MtB said:

This post perfectly illustrates the schism that exists between old skool dinosaur engineers on here who see the switches in the BMS (any BMS) as a last ditch backstop and the vast numbers of real world users out there who say the BMS (the JBD specifically) is ultra-reliable and use it on a daily basis for charge control with no problems arising.

Alternatively, it is the difference between those who have actual engineering experience designing, or maintaining complex systems and know that if it can possibly go wrong, it almost certainly will and those that haven't. If you are of the former school, then single points of total failure for the system from an aging component makes you jumpy.

[IanD]

9 minutes ago, Jen-in-Wellies said:

Alternatively, it is the difference between those who have actual engineering experience designing, or maintaining complex systems and know that if it can possibly go wrong, it almost certainly will and those that haven't. If you are of the former school, then single points of total failure for the system from an aging component makes you jumpy.

 

There are almost always single points of failure in any system unless you can have a complete second independent means of delivery, which means it will spend 99% of its time doing nothing except costing money -- most boats don't have a backup engine or generator or batteries or inverter or toilet or water tank or...

 

But at least it makes sense -- especially with electrical systems -- to try and design them properly in the first place to try and fend off things which make them less reliable or shorten lifetime, to put safeguards in should anything go wrong, and stuff to monitor the health to check that everything is OK and spot problems before they become critical. And part of this is to not abuse the components, especially batteries...

 

In "old-school" boats this includes treating the batteries properly (charging regimes), having fuses/emergency switches, and something to monitor SoC/voltage/current. On "new-school" boats with LFP this includes monitoring the batteries and having notification of what the BMS is doing, dealing with charging properly whether from solar or shore or alternator, and often remote control/monitoring when away from the boat.

 

None of which stops some people with LA batteries killing them off quickly through ignorance or inattention, and I would be surprised if the same approach doesn't do the same with LA/LFP hybrids. A lot of these systems smack of the "suck it and see" approach, cutting corners to try and minimise cost -- which is all fine and good so long as you're aware that there are risks with doing this, which is unlikely to be the case for naive users who don't understand the ins-and-outs of batteries, and who I suspect will be the majority of users.

 

It's noticeable that few of the LA/LFP hybrid enthusiasts -- especially the followers not the vloggers -- have been using their systems long enough and intensively enough to see problems of reduced lifetime or failures, where there are plenty of properly-designed LFP systems that have been running for many years (more than 10 in some cases) and which have shown that battery degradation is negligible and the projected long lifetime can be achieved -- which is often used to justify buying the LFP in the first place.

 

Caveat emptor then... 😉

[David Mack]

10 minutes ago, IanD said:

there are plenty of properly-designed LFP systems that have been running for many years (more than 10 in some cases) and which have shown that battery degradation is negligible and the projected long lifetime can be achieved

And where can I buy such a system off-the-shelf at a reasonable price, to install myself, and which will keep insurers and safety authorities happy?

 

... I thought not! ...

[MtB]

20 minutes ago, IanD said:

A lot of these systems smack of the "suck it and see" approach, cutting corners to try and minimise cost --

 

I think this understates the case.

 

To bung a "Drop-in" LFP battery into an existing system as a hybrid and configure a long piece of wire to limit the charge current to protect the alternator can be done for £350 and an afternoon's work. Yes this is a fine ol' bodge but it brings most of the benefits of lithium batteries to yer average boater boating/living on a shoestring.

 

To do it 'properly' would firstly be way beyond the technical capability of yer average boater so they would be into having it done professionally. Yes? Which would cost what? I really have no idea but I'd imagine a quote from Ed Shiers would be several £k.

 

Lets guess £3k for a stand-alone LFP system with separate charge controller, cell protection and perhaps a new, appropriate alternator. A sum few boaters of modest means are going to spend especially when they can get nearly the same benefits for 10% of that price.

 

So in summary, the real-life reality for yer average boater is a choice between a slightly-less-than-techncally-perfect LFP/LA hybrid which works fine and doesn't bust the bank if it goes wrong, or nothing. 

 

 

 

 

Edited February 8 by MtB

[nicknorman]

1 hour ago, MtB said:

 

I think this understates the case.

 

To bung a "Drop-in" LFP battery into an existing system as a hybrid and configure a long piece of wire to limit the charge current to protect the alternator can be done for £350 and an afternoon's work. Yes this is a fine ol' bodge but it brings most of the benefits of lithium batteries to yer average boater boating/living on a shoestring.

 

To do it 'properly' would firstly be way beyond the technical capability of yer average boater so they would be into having it done professionally. Yes? Which would cost what? I really have no idea but I'd imagine a quote from Ed Shiers would be several £k.

 

Lets guess £3k for a stand-alone LFP system with separate charge controller, cell protection and perhaps a new, appropriate alternator. A sum few boaters of modest means are going to spend especially when they can get nearly the same benefits for 10% of that price.

 

So in summary, the real-life reality for yer average boater is a choice between a slightly-less-than-techncally-perfect LFP/LA hybrid which works fine and doesn't bust the bank if it goes wrong, or nothing. 

 

 

I think Ian's point is that your "works fine" needs to be defined. Do you mean works fine right now. In that case, yes. Do you mean will still work fine after 10 years of long summer cruising days with batteries already fully charged by solar? Well we don't know that, but the suspicion is it probably won't.

The difficuly with something with a projected life of well over 10 years, is that it takes a long time to discover that you have done something that in fact has reduced the expected life to half what it should be.

[MtB]

2 minutes ago, nicknorman said:

 

I think Ian's point is that your "works fine" needs to be defined. Do you mean works fine right now. In that case, yes. Do you mean will still work fine after 10 years of long summer cruising days with batteries already fully charged by solar? Well we don't know that, but the suspicion is it probably won't.

The difficuly with something with a projected life of well over 10 years, is that it takes a long time to discover that you have done something that in fact has reduced the expected life to half what it should be.

 

 

All true, but when the outlay is £350 not £3,500, nobody is going to care that much.

 

 

[Rob-M]

1 hour ago, MtB said:

Lets guess £3k for a stand-alone LFP system with separate charge controller, cell protection

More like £6k when I discussed with Ed, I would have to replace alternator and battery charger and included upgrading inverter.

[MtB]

2 minutes ago, Rob-M said:

More like £6k when I discussed with Ed, I would have to replace alternator and battery charger and included upgrading inverter.

 

Thanks. That's actually what I thought but didn't want to have people say I was overstating the case. 

 

 

So spend £6,000 to get it exactly right or £350 to get it pretty close. 

 

Hmmm.... now which option will the average tightwad boater think looks better value?