Lithium Batteries installation

[MtB]

40 minutes ago, magnetman said:

Oh maybe not then. Perhaps an inverter running off the AGM bank charged by the 175A Iskra alrernator powering a lithium specific charger. 

 

At the end of the day the issue is with inappropriate rotating electrics so perhaps this is where things need to change. 

 

I sometimes wonder about a permanent magnet alternator with a magnetic clutch. 

 

The best one would be running from the propshaft then you could pull some real power off it. 

 

 

There are four problems the 'drop-in' LFP user needs to understand, two of which s/he must do something about. 

 

1) The charging alternator can be wrecked when the drop-in decides its fully charged and disconnects. Fix = keep one LA batt in parallel with the LFP.

 

2) The charging alternator can be wrecked from overheating as the LFP will drag full output from the alternator for long periods, and the alternator is probably only rated for intermittent full load. Fix = add in a length of thin-ish wire to the charging circuit and adjust its length to limit the charge current to whatever the user can devine is appropriate for continuous loading.

 

3) The LA battery can have a cell fail, leading to it getting really hot as the LFP will discharge through it. Fix = there is no fix other than to be aware of this problem. Bit of a red herring though as it can happen just as easily on a 100% LA bank.

 

4) If the internal BMS in the drop-in LFP fails, the cells will be damaged from over or under charging. Another red herring as the LFP will have come with a guarantee. Hopefully. Fix = understand the risk and if you don't like it, install a second, external BMS set to wider parameters than the internal. 

 

 

My own view is until someone designs a BMS to go inside a 'drop-in' that addresses 1) and 2)*, calling them drop-ins is misleading and will eventually attract the interest of Trading Standards.  Or should anyway.

 

 

* Such a BMS will have a 'soft disconnect' feature to ramp down the alternator current slowly, and some sort of method of setting/adjusting/limiting the charging current. 

 

 

 

 

 

 

 

Edited February 9 by MtB
Add a bit.

[nicknorman]

7 minutes ago, MtB said:

 

* Such a BMS will have a 'soft disconnect' feature to ramp down the alternator current slowly, and some sort of method of setting/adjusting/limiting the charging current. 

Easy to say, not easy to achieve. It is easy to have a solid state switch that is either on or off, because in either state there is very little power dissipation.

 

But a switch half-on dissipates a huge amount of power as heat. So you need to add the sort of technology found in B2B converters. Switch mode buck converters. Which can be done, but at the sorts of currents involved is going to be very expensive and bulky.

 

All of which is why this would be a crazy way of doing it. The correct way to do it is to control the charge sources. Which is quite easy by comparison. No heavy current electronics required.

[magnetman]

13 minutes ago, MtB said:

 

 

My own view is until someone designs a BMS to go inside a 'drop-in' that addresses 1) and 2)*, calling them drop-ins is misleading and will eventually attract the interest of Trading Standards.  Or should anyway.

Drop In is definitely an interesting but of terminology. Obviously this is referring to the size of the battery blocks as provided and it is convenient to supply LFP battery blocks which have the same 'form factor' as normal '110 leisure' type Lead batteries. 

 

But... 

 

If one were to take the term 'drop in' literally it implies that the battery blocks may be released from a height. In some cases this could be quite handy as getting down into the engine 'ole is arduous. 

 

I think the suppliers probably ought to have specs for how high one can drop the battery in from. Is it one metre or two? 

 

 

 

Perhaps 'drop in' is referring to a casual medical facility. 

 

 

[MtB]

5 minutes ago, magnetman said:

Drop In is definitely an interesting but of terminology. Obviously this is referring to the size of the battery blocks as provided and it is convenient to supply LFP battery blocks which have the same 'form factor' as normal '110 leisure' type Lead batteries. 

 

Only half the story. "Drop-in" batteries are generally accepted to include an internal BMS.

 

 

[magnetman]

Yes but what does 'drop in' actually mean? 

 

It appears to be a meaningless term when it comes to batteries. A marketing term made up by someone at some stage. 

 

 

 

Was it Mr Sterling ? 

[MtB]

14 minutes ago, magnetman said:

Yes but what does 'drop in' actually mean? 

 

It appears to be a meaningless term when it comes to batteries. A marketing term made up by someone at some stage. 

 

 

 

Was it Mr Sterling ? 

 

 

Nope. "Drop-in" means a bunch of cells in a neat box with a Bluetooth BMS and an app, all looking a bit like a straight replacement for the LA battery. As opposed to a stack of Winston cells, a BMS screwed to the wall and a bird's nest of wires connecting it all up, which was my first way of doing it.

 

 

 

 

 

Edited February 9 by MtB
Fiddle with it

[magnetman]

I know what it is supposed to mean but in reality most people can't 'drop' one of these in to replace an existing Lead battery. It won't work. 

 

Well I suppose it is possible/probable that more people have shore power than don't but in that situation one would not be looking to maximise battery efficiency anyway. 

 

 

 

 

Presumably if it all gets regulated at some stage then terms like 'drop in' won't cut the mustard. 

They might even turn into 'drop out' when the arrangement is rejected on safety grounds. 

[MtB]

12 minutes ago, magnetman said:

I know what it is supposed to mean but in reality most people can't 'drop' one of these in to replace an existing Lead battery. It won't work. 

 

And yet, hundreds of thousands have been sold and most are working just fine. 

 

They must be or the returns would have bankrupted Fogstar , Life Batteries et al.

[magnetman]

Have they sold that many ? 

 

Warranty claims seem to not include burnt alternators. 

 

Also, as I have been saying all along, these things are great for solar panel use. 

I'm not remotely anti lithium batteries but I do question the drop in status. I guess a lot of these are sold to motorhome owners who are probably just a wee bit conservative and tie up their vans in nice safe camp sites with 6A mains supplies so they can charge their batteries up. 

 

 

[IanD]

11 hours ago, magnetman said:

Yes but what does 'drop in' actually mean? 

 

It appears to be a meaningless term when it comes to batteries. A marketing term made up by someone at some stage. 

 

Was it Mr Sterling ? 

 

The term "drop-in" suggests that you can just take out an LA and replace it with an LFP and not do anything else.

 

Which is literally true in the sense that they fit in the same size hole and have similar voltages, but is asking for trouble with things like BMS overvoltage disconnects when the alternator is charging (voltage spike kills alternator and/or anything else running off 12V) or a fried alternator as the new LFP battery accepts far more current for longer than the LA it replaced.

 

So it's an inaccurate marketing term, and using it by LFP sellers should really should be banned... 😉

[GUMPY]

Most of the marketing is aimed at caravans and mobile homes and not boats. In caravans and mobile homes it is pretty much drop in so not misleading. 

[MtB]

23 minutes ago, GUMPY said:

Most of the marketing is aimed at caravans and mobile homes and not boats. In caravans and mobile homes it is pretty much drop in so not misleading. 

 

 

I wonder how many off grid caravans there are out there, forming the main market for 'drop-in' LFPs.

 

My finger in the air guess is about a million. Against perhaps 30,000 liveaboard and holiday boats big enough to be charging an LFP from an engine alternator. Total guess.

 

 

[IanD]

19 minutes ago, GUMPY said:

Most of the marketing is aimed at caravans and mobile homes and not boats. In caravans and mobile homes it is pretty much drop in so not misleading. 

I disagree -- if you're going to market something as "drop-in" that clearly suggests you can safely do this anywhere an LA battery is used, just "drop-in" LFP as a replacement. Which is not the case... 😞

 

If the sellers also attached warnings about how these may not be suitable where alternator charging -- or any other "dumb" charging -- is used then maybe this would be OK. But they don't, do they?

 

It's a bit like promoting a novel foodstuff as a healthier replacement without pointing out that some people are allergic to it and might die as a result, except here the potential victims are equipment not people... 😉

 

Don't get me wrong, I think LFPs are great when used appropriately, otherwise I wouldn't have a boat with a huge bank of them. But like any new technology there are cases when care is needed, and some suppliers are ignoring this.

[MtB]

2 minutes ago, IanD said:

If the sellers also attached warnings about how these may not be suitable where alternator charging -- or any other "dumb" charging -- is used then maybe this would be OK. But they don't, do they?

 

 

Nope. Not a word about it came with either my Renogy Drop-In or my LifeBatteries Drop-In. 

 

Either the customers buying these things are better informed than we here think, or the manus have some rock-solid defences against people complaining their alternators have cooked or lost all their magic smoke. 

 

 

[IanD]

11 minutes ago, MtB said:

 

I wonder how many off grid caravans there are out there, forming the main market for 'drop-in' LFPs.

 

My finger in the air guess is about a million. Against perhaps 30,000 liveaboard and holiday boats big enough to be charging an LFP from an engine alternator. Total guess.

 

 

By far the biggest market for "drop-in" LFP batteries -- what they were originally made for, in massive numbers at minimum cost -- are solar backup batteries mounted on lighting poles in the Far East. All that's needed here is the lowest possible price and relatively low current capability and adequate lifetime, which is exactly what some of the cheapest "drop-ins" provide with a cheap nasty internal BMS -- stick a new label on ("marine" or "heavy duty" or whatever) and get them out of the door. They're not designed to play nicely with alternators -- or high-current loads, like some on a boat -- because they don't have to for the application they were originally intended for.

 

https://marinehowto.com/drop-in-lifepo4-be-an-educated-consumer/

https://marinehowto.com/dont-get-scammed-buying-lifepo4/

Edited February 10 by IanD

[BEngo]

4 minutes ago, IanD said:

If the sellers also attached warnings about how these may not be suitable where alternator charging -- or any other "dumb" charging -- is used then maybe this would be OK. But they don't, do they?

 

But it is not the alternator ( or other dumb)  charging in itself that is a problem.  The problem is the effect of relying on the BMS ( a battery protection device) to be a charge control device and of using an inappropriate alternator ( not able to providea suitable continuous output)  as charge source.

 

Neither is difficult to solve safely though charge control solutions are somewhat limited options.

 

N

[Alan de Enfield]

11 minutes ago, MtB said:

 

 

I wonder how many off grid caravans there are out there, forming the main market for 'drop-in' LFPs.

 

My finger in the air guess is about a million. Against perhaps 30,000 liveaboard and holiday boats big enough to be charging an LFP from an engine alternator. Total guess.

 

 

 

I think that is likely to be an gross exageration - I doubt there are more than a few dozen (maybe just those who are on hard times) who are off-grid at any one time. Caravans do not have much battery capacity to stay off-grid. I reckon the vast majority, by far, are plugged in everynight when touring.

[IanD]

16 minutes ago, MtB said:

 

Nope. Not a word about it came with either my Renogy Drop-In or my LifeBatteries Drop-In. 

 

Either the customers buying these things are better informed than we here think, or the manus have some rock-solid defences against people complaining their alternators have cooked or lost all their magic smoke. 

 

 

But it's not their fault if you fry your alternator by loading it heavily for ages, it's yours for not keeping it cool enough or limiting the charging current. And it's not their fault if the voltage spike when it overvoltage disconnects blows up either your alternator or other stuff on the boat, they told you the BMS would do this at high voltage so it's up to you to deal with the consequences. They'll just say "We can't possibly know how you're going to use our battery, we just provide it".

 

Plenty of cases of killed/fried alternators, see marinehowto or any of the yachting forums... 😞

 

10 minutes ago, BEngo said:

But it is not the alternator ( or other dumb)  charging in itself that is a problem.  The problem is the effect of relying on the BMS ( a battery protection device) to be a charge control device and of using an inappropriate alternator ( not able to providea suitable continuous output)  as charge source.

 

Neither is difficult to solve safely though charge control solutions are somewhat limited options.

 

N

 

Correct, but these problems don't happen with LA do they? So if you tell people that your LFP is a "drop-in" replacement so they do exactly that, whose problem is it?

 

Many people don't have a clue about battery chemistry or charging or alternators or BMS or charge control, they just connect something up as the suppliers suggest -- so "drop-in" means just that, nothing else is changed.

 

This isn't a "nanny state" thing, I'm not saying LFP batteries shouldn't be sold as modern replacements for LA -- but it's dishonest for the suppliers to use the term "drop-in" with no warnings about what the (expensive!) consequences of doing this can be in some -- not all! -- cases.

Edited February 10 by IanD

[magnetman]

It would be fun if a court had to decide what 'drop in' means. 

They might come to the conclusion it just means two items the same shape. 

'Drop in replacement'

 

Not 'drop in alternative'. 

 

 

[IanD]

9 minutes ago, magnetman said:

It would be fun if a court had to decide what 'drop in' means. 

They might come to the conclusion it just means two items the same shape. 

 

If somebody whose electrics were damaged ever sued an LFP "drop-in" battery supplier for using the term, I suspect the supplier would lose -- because the potentially damaging consequences of naive "LFP drop-in" are well known, and normally manufacturers have to warn of any known consquential risks of using their products as sold and advertised. And the courts have often found that a disclaimer in the small print of an page 37 of the user manual is not sufficient if the consequences can be severe -- in this case, hundreds of pounds worth of damage, maybe more if a load dump kills other 12V gear not just the alternator.

 

If it's ever going to happen, I expect it would happen first in the USA -- and shortly afterwards LFP advertising would change tone... 😉

Edited February 10 by IanD

[Tony1]

16 hours ago, MtB said:

 

 

There are four problems the 'drop-in' LFP user needs to understand, two of which s/he must do something about. 

 

1) The charging alternator can be wrecked when the drop-in decides its fully charged and disconnects. Fix = keep one LA batt in parallel with the LFP.

 

2) The charging alternator can be wrecked from overheating as the LFP will drag full output from the alternator for long periods, and the alternator is probably only rated for intermittent full load. Fix = add in a length of thin-ish wire to the charging circuit and adjust its length to limit the charge current to whatever the user can devine is appropriate for continuous loading.

 

3) The LA battery can have a cell fail, leading to it getting really hot as the LFP will discharge through it. Fix = there is no fix other than to be aware of this problem. Bit of a red herring though as it can happen just as easily on a 100% LA bank.

 

4) If the internal BMS in the drop-in LFP fails, the cells will be damaged from over or under charging. Another red herring as the LFP will have come with a guarantee. Hopefully. Fix = understand the risk and if you don't like it, install a second, external BMS set to wider parameters than the internal. 

 

 

My own view is until someone designs a BMS to go inside a 'drop-in' that addresses 1) and 2)*, calling them drop-ins is misleading and will eventually attract the interest of Trading Standards.  Or should anyway.

 

 

* Such a BMS will have a 'soft disconnect' feature to ramp down the alternator current slowly, and some sort of method of setting/adjusting/limiting the charging current. 

 

 

 

Obviously I'm no expert, but my hope/expectation is that placing a B2B charger between the LA and the lithium bank will resolve point 3.

I use victron 30 amp B2Bs, and my understanding is that no current can flow from the lithium back into the LAs.

 

The fourth issue is managed by setting a safe bulk charging voltage on the B2B, e.g. 13.8 or 13.9v.

From what I've observed, when the lithium gets up to about 90% full its voltage will start to rise above the bulk charging voltage in the B2B, and this causes the B2B to go into float mode.

If you set float voltage to something like 12.5v, it means effectively no further current will pass into the lithiums.

 

So maybe a B2B does provide a step up in terms of safety from a simple 'long wire' setup?

Certainly it allows more precise control of the charging that is done to the lithiums.

On the downside, as has been said here many times, B2Bs are very inefficient, and not really very a cheap solution, and who knows whether they will be deemed acceptable by potential future regulations?

 

 

 

 

 

 

[IanD]

52 minutes ago, Tony1 said:

 

Obviously I'm no expert, but my hope/expectation is that placing a B2B charger between the LA and the lithium bank will resolve point 3.

I use victron 30 amp B2Bs, and my understanding is that no current can flow from the lithium back into the LAs.

 

The fourth issue is managed by setting a safe bulk charging voltage on the B2B, e.g. 13.8 or 13.9v.

From what I've observed, when the lithium gets up to about 90% full its voltage will start to rise above the bulk charging voltage in the B2B, and this causes the B2B to go into float mode.

If you set float voltage to something like 12.5v, it means effectively no further current will pass into the lithiums.

 

So maybe a B2B does provide a step up in terms of safety from a simple 'long wire' setup?

Certainly it allows more precise control of the charging that is done to the lithiums.

On the downside, as has been said here many times, B2Bs are very inefficient, and not really very a cheap solution, and who knows whether they will be deemed acceptable by potential future regulations?

 

 

A decent B2B isn't inefficient (well over 90%?), and should be accepted by future regulations since you're treating the LFP properly/safely, not connecting it in parallel with LA and charging from an alternator. Make sure the B2B does have settings suitable for charging LFP not just LA.

 

Not sure that 30A will be enough though if you want to minimise engine running time when charging, something that can use more of the alternator's output (without overheating it!) would be better, so long as it doesn't exceed the maximum charge current of the LFP. What size alternator do you have, and what's the LFP charge current rating?

Edited February 10 by IanD

[magnetman]

30 amps seems quite a low charge rate. 

Is it also the point at which Victron B2B hardware gets a lot more expensive? 

 

 

I do idly wonder if my 50A Victron MPPT for the solar panels could be repurposed and used as a B2B in winter if I wanted to charge batteries using the main engine. 

 

Sun is predictable due to seasonal changes so there would be a certain point where whipping out the 50A and replacing with a 20A MPPT (observing input voltage) could make some sense. 

 

Don't know if it would work and I think perhaps there is a problem with voltage needing to be higher than the battery. Maybe Victron have already thought of that and designed it out of their products. 

 

Been here before I seem to recall. 

24v alternator is the thing. 

Edited February 10 by magnetman

[Tony1]

27 minutes ago, IanD said:

 

A decent B2B isn't inefficient (well over 90%?), and should be accepted by future regulations since you're treating the LFP properly/safely, not connecting it in parallel with LA and charging from an alternator. Make sure the B2B does have settings suitable for charging LFP not just LA.

 

Not sure that 30A will be enough though if you want to minimise engine running time when charging, something that can use more of the alternator's output (without overheating it!) would be better, so long as it doesn't exceed the maximum charge current opf the LFP. What size alternator do you have, and what's the LFDP charge current rating?

 

I can say the B2B units get very hot in use, so there's certainly a lot of heat energy wasted, although I've not measured the current going into them, only that coming out- so I cant say for sure. The previous Sterling unit I used seemed to waste at least 15% of the input current as heat, and maybe as much as 20% at times.

 

My starter and domestic alternators are rated at 70 amps and 100 amps respectively, but they cant keep that up without overheating.

To keep their temp below 100 degrees, I can't take more than about 30 and 35 amps from them respectively, so the victron units are a pretty good match for their safe current output level.  So I get about 60amps into the lithiums in total.

 

I did also install a third smaller B2B, with 18 amps output. I sometimes use the third B2B when I'm doing a static charge, because when doing that I can keep the revs up at 1300 rpm, which helps cool the alternators.  So flat out I can get almost 80 amps of charge, but I don't always use the third B2B.

Mine is a canaline 38 and it has narrow V belts- not poly V-  and I feel like I might be straining the belts and the crank more I really should, when I'm doing a 90 minute battery charge at the full 80 amps.

So I tend to stick to using two B2Bs for most of the time. 

 

I cant remember the max charge of the lithiums, but its certainly much more than I ever do to them! Even when cruising in high summer, with maybe a further 90 amps of solar coming in for long periods of the day, the charge current is only around 150 amps max. 

Tbh in those high solar months, I tend to leave the B2Bs switched off for most of the time, even when the engine is running, since the solar does everything I need and more.

(Speaking of which, I've had 1100 Wh of solar today, so I feel like we may be starting to get into the period where it gets useful again)

 

 

 

25 minutes ago, magnetman said:

30 amps seems quite a low charge rate. 

Is it also the point at which Victron B2B hardware gets a lot more expensive? 

 

 

I do idly wonder if my 50A Victron MPPT for the solar panels could be repurposed and used as a B2B in winter if I wanted to charge batteries using the main engine. 

 

Sun is predictable due to seasonal changes so there would be a certain point where whipping out the 50A and replacing with a 20A MPPT (observing input voltage) could make some sense. 

 

Don't know if it would work and I think perhaps there is a problem with voltage needing to be higher than the battery. Maybe Victron have already thought of that and designed it out of their products. 

 

Been here before I seem to recall. 

24v alternator is the thing. 

 

I can't understand why some wizard doesnt design something like that- a charging unit that will accept the output from an alternator, and transform that into charging current for lithiums. 

You've almost got that with the MPPT units, as you say - they just need adapting to accept the alternator input current at lower voltages than solar panels. 

Obviously an ignorant chimp like myself couldn't do it, but on the face of it, it sounds like a simple task for an electronics wizard?

 

 

 

Edited February 10 by Tony1

[cheesegas]

9 minutes ago, Tony1 said:

I can't understand why some wizard doesnt design something like that- a charging unit that will accept the output from an alternator, and transform that into charging current for lithiums. 

You've almost got that with the MPPT units, as you say - they just need adapting to accept the alternator input current at lower voltages than solar panels. 

Obviously an ignorant chimp like myself couldn't do it, but on the face of it, it sounds like a simple task for an electronics wizard?

They exist already, there's just not much market for them so they're expensive. It's called an alternator regulator and there's not many models to choose from, Arco Zeus, Wakespeed WS500, Mastervolt Alpha, Balmar 618.

 

The decent ones keep an eye on the alternator temperature and RPM, and vary the field current to keep the alternator at a safe temperature and to alter the output voltage by dropping to float etc. Advanced ones like the Wakespeed communicate with a CANbus system and will reduce charging current if something happens like one of three battery BMses goes offline, to avoid exceeding the max charge current of the batteries.