Lithium Batteries installation

[Roberto Conigliaro]

Hi everyone, as my AGM batteries, after many years of use, are not holding the charge anymore, I am keen on replacing them with Lithium batteries, at the moment I have 3 x AGM 230ah Xplorer batteries in parallel, charged either by the alternator or a solar power system (6 x 150w), a Victron inverter, which is used some time in the evening to charge the laptop and have extra lighting, not big appliances apart from a 12v fridge which in only switched on in the summer days.

 

I have some doubts and I wonder if anybody could please help with that. 

 

- I was reading that Lithium batteries even at lower capacity they offer more power compared to a AGM, is that correct? If so, I was planning to get 3 x Sterling Power 120ah Lithium batteries https://sterling-power.com/products/lithium-batteries?variant=50407892309

or shall I better get 1 x Victron Energy LiFePO4 Battery 12,8V 330Ah Smart https://www.visionmarine.co.uk/catalog/product/view/id/112065/s/victron-energy-lifepo4-battery-12-8v-330ah-smart-bat512132410-bat512132410/category/738/

what are the pro and cons in your opinion? 

 

- Can I charge / connect the lithium batteries same as I have the AGM ones connected at the moment? or do I need a different charging system or wiring?

 

any other general advice would be greatly appreciated, to follow some photos of what my system currently looks like.

 

Cheers! 

 

 

 

[Jen-in-Wellies]

You'll need to go through the manuals for each of your battery charging gadgets and see if they have a suitable Lithium charging algorithm. If not, then you'll have to budget for a replacement. The biggest question you've not asked is how are you going to safely disconnect the alternator from the batteries when they are fully charged, without damaging the alternator. Various ways of doing this. See multiple Li battery threads on here. 

[Tony Brooks]

1 minute ago, Jen-in-Wellies said:

You'll need to go through the manuals for each of your battery charging gadgets and see if they have a suitable Lithium charging algorithm. If not, then you'll have to budget for a replacement. The biggest question you've not asked is how are you going to safely disconnect the alternator from the batteries when they are fully charged, without damaging the alternator. Various ways of doing this. See multiple Li battery threads on here. 

 

And I would suggest ensuring the Li bank's propensity to draw maximum alternator current for as long as the battery is connected to the alternator does not burn out alternators in succession.

[Roberto Conigliaro]

14 minutes ago, Jen-in-Wellies said:

You'll need to go through the manuals for each of your battery charging gadgets and see if they have a suitable Lithium charging algorithm. If not, then you'll have to budget for a replacement. The biggest question you've not asked is how are you going to safely disconnect the alternator from the batteries when they are fully charged, without damaging the alternator. Various ways of doing this. See multiple Li battery threads on here. 

 

Hi, thanks for reply! what do you mean by the charging gadgets? is in general something easily doable switching to Li batteries or usually means also switching to different 'charging gadgets'? 

I didn't ask about alternator because I wasn't aware of the potential damaging issue, that's why I am here asking for advice

What about my first question, any advice on that? 

 

Thanks! 

16 minutes ago, Tony Brooks said:

 

And I would suggest ensuring the Li bank's propensity to draw maximum alternator current for as long as the battery is connected to the alternator does not burn out alternators in succession.

Thanks for your reply! unfortunately my level of knowledge on batteries doesn't allow me to follow what you're advising. Could you please explain in different words? 

 

Cheers!

[Alan de Enfield]

Basically you cannot just "plug & play" lithium batteries where previously you had FLA batteries.

 

You need different charging voltages, means of electrically disconnecting the alternator, and means of stopping the alternator 'melting' as the Lithiums will overload the alternator by making it run at 100% output for long periods.

[Tony Brooks]

A lead acid (AGM) battery allows a high current to flow for a short time and within, maybe 10 minutes, the current they will accept starts to fall, so for most of the time the alternator will be delivering lass and after maybe an hour, far less than its maximum output. However, an LI battery will take as much current as your charging system can deliver for many hours. Practically until the charge control system disconnects it from the alternator. This means the alternator runs at maximum output for hours, so it gets very, very hot. This is made even worse at low speed (waiting for a lock) when the cooling air flow through the alternator is reduced, allowing even more overheating. Now, the alternators most of us use were designed for automotive use with LA (AGM) batteries, so assume the current will start to fall within minutes of starting. If it does not, then they are very likely to suffer and eventually burn out. You can get high output alternators, but the cost is probably prohibitive for most boaters.

 

The need for very different charge control means that you would be well advised to do a lot more research before committing. There are enough LI battery threads on here for a start.

[BEngo]

In answer to your first question the first:

 

Lithium  (meaning  Li FePO4 as other Liyhium types are not as safe,)  batteries have a wider no-damage discharge range than lead acids.  They can safely routinely be discharged to 20% SOC and below, whereas lead acids can only  go to about 50% to get the maximum life.

 

OTOH charging above about 90% is riskier and needs to be monitored carefully.

 

Leaving "full" lithium batteries on charge ( as in float charge like lead acid)  will probably wreck them quickly.

 

Lithiums  can be left partly charged without damage ( they should be stored at 30-50% SOC).  

 

Either of your suggested options will work.  3 x120 Ah lithiums will give you about 280 Ah useable.  One  330Ah is going to give you about 250 Ah useable.  Your current batteries, when new, would give you about 375 Ah "useable".

 

You should do a power audit to see what you actually need.

 

3 x120 Ah batteries may be easier to install than a single big one.  Fortunately LiFePo4 batteries are much lighter than lead based ones.

 

If you are installing batteries in parallel, check that their internal  BMS's are configured to be working  in parallel.

 

Other points:

 

Charging Lithium batteries is wholly different to charging lead acid.  They charge at a high rate right to 95% full. Then they chargecat constant voltage till full. Then you must STOP charging.  Unlike lead acids there is no need to charge them fully unless you want to store the  electricity, so you can cycle between 20% and 90% happily.

 

You have much to learn about Li batteries before it would be wise to take the ( expensive)  plunge.  Wonderful they can be, but they are not " what you currently know".  There are at least two mega threads on this site about the ins and outs of Li batteries - search for "Cheap DIY LiFePO4 BMS" to find one.  Make a large  brew and settle down for a read.  Once you have done that you will be much better informed.  

 

N

 

 

[Roberto Conigliaro]

38 minutes ago, Tony Brooks said:

A lead acid (AGM) battery allows a high current to flow for a short time and within, maybe 10 minutes, the current they will accept starts to fall, so for most of the time the alternator will be delivering lass and after maybe an hour, far less than its maximum output. However, an LI battery will take as much current as your charging system can deliver for many hours. Practically until the charge control system disconnects it from the alternator. This means the alternator runs at maximum output for hours, so it gets very, very hot. This is made even worse at low speed (waiting for a lock) when the cooling air flow through the alternator is reduced, allowing even more overheating. Now, the alternators most of us use were designed for automotive use with LA (AGM) batteries, so assume the current will start to fall within minutes of starting. If it does not, then they are very likely to suffer and eventually burn out. You can get high output alternators, but the cost is probably prohibitive for most boaters.

 

The need for very different charge control means that you would be well advised to do a lot more research before committing. There are enough LI battery threads on here for a start.

 

Thansk Tony, this makes a lot of sense now 

[magnetman]

It is worth remembering that the term 'drop in replacement' is a slightly deceptive marketing term. 

 

All it actually means is that the batteries are the same shape and can be 'dropped in' without modifying the battery tray or boxes. 

 

It gives the impression that the lithium batteries can be used instead of the lead acid batteries, with existing charging arrangements, but this is not what it means. 

 

 

 

The only really simple way to have lithium batteries is to have them charged by solar panels and a mains charger and not the engine.

 

Otherwise it gets more complicated because of their power demand when being charged by a rotating electrical machine. 

 

People do it but it is a bit awkward. 

 

 

Edited January 24 by magnetman

[Roberto Conigliaro]

9 minutes ago, magnetman said:

It is worth remembering that the term 'drop in replacement' is a slightly deceptive marketing term. 

 

All it actually means is that the batteries are the same shape and can be 'dropped in' without modifying the battery tray or boxes. 

 

It gives the impression that the lithium batteries can be used instead of the lead acid batteries, with existing charging arrangements, but this is not what it means. 

 

 

 

The only really simple way to have lithium batteries is to have them charged by solar panels and a mains charger and not the engine.

 

Otherwise it gets more complicated because of their power demand when being charged by a rotating electrical machine. 

 

People do it but it is a bit awkward. 

 

 

gotcha, thanks! 

[Jen-in-Wellies]

1 hour ago, Roberto Conigliaro said:

Hi, thanks for reply! what do you mean by the charging gadgets? is in general something easily doable switching to Li batteries or usually means also switching to different 'charging gadgets'? 

Gadgets, as in battery chargers, inverter/charger combis, solar charge controllers, perhaps an alternator controller. Any gadget that is used to charge the batteries. They need to be able to handle the different charging regime that Lithium batteries require. New ones are more likely to than older ones. Older ones from before when boat Li batteries were a thing will not. Ones from the early days of Li boat batteries, and that isn't long ago, may have a sub-optimal, or potentially damaging charging algorithm. 

[mrsmelly]

While you are at it, get rid of those terrible pink plastic toggle type battery isolator switches.

[GUMPY]

For various reasons I would not get either a Sterling or a Victron battery.

I went for 

https://www.fogstar.co.uk/collections/lithium-leisure-battery

Good BMS and they just work.

@nicknorman did as well for his caravan.

There are various sizes in that link the 460Ah one should more than satisfy your needs. 

https://www.fogstar.co.uk/products/fogstar-drift-460ah-leisure-battery

You will have to create some way of protecting the alternator when the BMS says it's full and shuts off an old LA battery in parallel seems to work, mine is the engine start battery. 

 

[magnetman]

I agree. 

 

I am suspicious of Sterling products they apparently have a very good returns department. 

 

Victron batteries are far too expensive. 

Fogstar seem interesting and definitely what I would go for. 

 

 

[Roberto Conigliaro]

1 hour ago, GUMPY said:

For various reasons I would not get either a Sterling or a Victron battery.

I went for 

https://www.fogstar.co.uk/collections/lithium-leisure-battery

Good BMS and they just work.

@nicknorman did as well for his caravan.

There are various sizes in that link the 460Ah one should more than satisfy your needs. 

https://www.fogstar.co.uk/products/fogstar-drift-460ah-leisure-battery

You will have to create some way of protecting the alternator when the BMS says it's full and shuts off an old LA battery in parallel seems to work, mine is the engine start battery. 

 

Hi Gumpy, that's a nice positive piece of information and the battery cost within my budget. Could you explain more in depth what have you done to protect the alternator? looking at the equipment I have at the moment, would you have any idea of what should be done to switch to Lithium? cheers!

[nicknorman]

4 hours ago, Roberto Conigliaro said:

Hi everyone, as my AGM batteries, after many years of use, are not holding the charge anymore, I am keen on replacing them with Lithium batteries, at the moment I have 3 x AGM 230ah Xplorer batteries in parallel, charged either by the alternator or a solar power system (6 x 150w), a Victron inverter, which is used some time in the evening to charge the laptop and have extra lighting, not big appliances apart from a 12v fridge which in only switched on in the summer days.

 

I have some doubts and I wonder if anybody could please help with that. 

 

- I was reading that Lithium batteries even at lower capacity they offer more power compared to a AGM, is that correct? If so, I was planning to get 3 x Sterling Power 120ah Lithium batteries https://sterling-power.com/products/lithium-batteries?variant=50407892309

or shall I better get 1 x Victron Energy LiFePO4 Battery 12,8V 330Ah Smart https://www.visionmarine.co.uk/catalog/product/view/id/112065/s/victron-energy-lifepo4-battery-12-8v-330ah-smart-bat512132410-bat512132410/category/738/

what are the pro and cons in your opinion? 

 

- Can I charge / connect the lithium batteries same as I have the AGM ones connected at the moment? or do I need a different charging system or wiring?

 

any other general advice would be greatly appreciated, to follow some photos of what my system currently looks like.

 

Cheers! 

 

 

 

 

Li batteries are fantastic. However, there are a lot of pitfalls and it is not easy to put together an effective system.

Why fantastic? Well they are just like a big bucket of electricity. You can pour energy in as fast as the tap will run. You can discharge it way down to nearly 0% and still the voltage stays up around 13v. No need to fully charge between uses.

 

It is worth bearing in mind that Ah is not a unit of energy, because for that you need to mulitply by the voltage. So 100Ah of lead acid (LA), where the discharge voltage is 12 to 12.6, is worth less energy than 100Ah of Lithium (Li) where the discharge voltage is 13 - 13.3v. So more energy for the same Ah.

And that is before you remember that you shouldn't really discharge your LA below 50% Soc, whereas you can discharge the Li to 10% or lower quite happily. So 100Ah of Li is worth about 200Ah of LA.

 

That is the good news. The bad news is that, being a big bucket of electricity, a Li battery will hoover up 100% of the maximum output from an alternator until it is nearly full. Alternators fitted to boats are generally not rated for continuous operation at maximum output, and so they will fry themselves in fairly short order. There needs to be some means to limit the maximum alternator output, to protect the alternator.

Other things with Li:

They hate being overcharged or even held at charging voltage once they are full. The mantra is "charge to full, then STOP CHARGING". Full is defined as charge current reduced to 5% of capacity. This can be easier said than done because many charge sources don't recognise when the battery is full.

 

They (hopefully) have a built in battery management system (BMS) that is there to protect the cells by disconnecting the battery if a cell voltage gets too high or too low or too cold. However if the BMS decides to disconnect the battery when it is being charged by an alternator, a massive voltage spike will ensue which can damage the alternator and other equipment connected to the electrical system.

So IMO one should avoid triggering the "battery emergency disconnect" algorithm in the BMS. ie set a charge voltage that is somewhat lower than the BMS cutoff voltage. The BMS protection should be considered "last resort" not "day to day control".

For the solar, you can set a fairly low charge voltage around 14.1v or so (which will still get the battery nearly full) and a float voltage much lower, say 13.3v so that no more current flows into the battery. The absorption time (time between reaching the charging voltage, and going to float) should be very short, maybe 10 minutes.

 

It is a bit problematic in summer if the boat is not being used - every day the batteries are pushed up to their charged voltage, without anything being taken out. This is not very good for them. So not much of an issue if you are aboard permanently, but if you leave the boat unattended with no loads on, disconnect the solar panels.

 

 

1 minute ago, Roberto Conigliaro said:

Hi Gumpy, that's a nice positive piece of information and the battery cost within my budget. Could you explain more in depth what have you done to protect the alternator? looking at the equipment I have at the moment, would you have any idea of what should be done to switch to Lithium? cheers!

He and I both have the Fogstar in a caravan! But the Fogstar is good for a caravan because it has the built in heating element. If you try to charge the battery at too low a temperature, the charge is diverted to heating elements until the battery is warm enough. However on a boat, where the canal water is a great temperature stabiliser, low battery temperature is unlikely to be much of an issue especially as you can site the Li battery within the cabin where it is hopefully warm!

Otherwise, the Fogstar seems well put together but it does have quite a conservative BMS so it would be inportant to make sure the charge voltage doesn't trigger the BMS shutoff.

[GUMPY]

Nick has explained it better than I can.

If I was doing it in a boat I would have a single alternator system charging the starter battery and a VSR feeding the LI batteries. When the BMS disconnects then the starter battery is still there loading the alternator.

I can shut off charge and discharge remotely on my system using apps* on my phone. 😉

 

 

* Victron Connect, eWeLink and the Fogstar app.

[Lochwarden]

Run your new LiFePO4 in parallel with some LA. A lithium/ Lead acid hybrid set up will negate the need for any fancy charging gadgets and will protect your alternator once the LFP is fully charged and the BMS stops accepting the charge current from the alternator. It’s as simple as that. On my boat I have one 300ah LiFePO4 and 3 x 110ah lead acid in parallel. They work just fine together. 

[BEngo]

Sorry, but I think that relying on  the internal  BMS  to shut off charging is risking rather a lot of money on the reliability of some Chinese electronics that were built down to a price.

 

The JBD (xiaoxang)   BMS  (used by Fogstar and sold by Overkill and others)  has a decent reputation, but they all are mostly newish.  When they get to be 4 or 5 years in use  I would like to have some redundant  automatic backup .  The time to put that in is at the start.

 

The other cloud  on the horizon is the BSS.  They have asked the IEE to look at the electrical parts of the BSS, with focus on Lithium batteries (and 240 V systems).  It seems that the review body are following in the footsteps of the USA's insurance led standards bodies and are not keen on mixed battery types ( hybrid installations), because a failure of the charge separator will lead to overcharging.  Overcharging Lithium batteries increases the risk of a battery fire.

 

N

 

 

[David Mack]

1 hour ago, BEngo said:

The other cloud  on the horizon is the BSS.  They have asked the IEE to look at the electrical parts of the BSS, with focus on Lithium batteries (and 240 V systems).  It seems that the review body are following in the footsteps of the USA's insurance led standards bodies and are not keen on mixed battery types ( hybrid installations), because a failure of the charge separator will lead to overcharging.  Overcharging Lithium batteries increases the risk of a battery fire.

Do the US bodies or BSS have a view on how you can protect the alternator if they ban you from having a LA battery permanently connected to it?

[dmr]

I don't have Lithium but am doing my research and electrical upgrades heading in that direction.

I also really do not like the (popular)  idea of relying on the emergency disconnect in the BMS to give day to day charging control, and I also don't like the idea of using a parallel lead acid as a surge suppresor (and a long cable as a current limiter).

 

There is a new alternator controller that appears to solve all the problems by correct engineering. This is the Arco Zeus.

Downsides are its quite expensive (but then so are destroyed lithiums) and is very very new so not proven in the field, and a little effort to install including alternator modifications. I also think that ideally one should choose a lithium battery that is compatible with CANbus though these are still quite rare.

 

[Tony Brooks]

20 minutes ago, David Mack said:

Do the US bodies or BSS have a view on how you can protect the alternator if they ban you from having a LA battery permanently connected to it?

 

I doubt it, but it would not be too difficult to simply shut the alternator down by isolating the rotor currant on most alternators. That would not cause the voltage surge mentioned above, and I think @nicknorman and possibly others here have made their own alternator controller. For optimum Li performance and life, the standard alternator controller is not really up to the job because I think it regulates at too high a voltage, although the high currant LIs allow to flow will mitigate this to a degree.

Edited January 24 by Tony Brooks

[nicknorman]

28 minutes ago, David Mack said:

Do the US bodies or BSS have a view on how you can protect the alternator if they ban you from having a LA battery permanently connected to it?

The problem arises when one uses an alternator designed for charging lead acid, to charge lithium. Not using a device for its intended purpose is always likely to be problematic! The answer is to use an alternator designed for charging lithium. Simple! And that would include having communication between the BMS and the alternator such that the latter would know if the former were about to isolate itself.

 

Another, or possibly additional, method is to have a load dump absorber. Sterling sell one, although they are a bit scant on the detail of what size of alternator it would cope with, and just how high a transient would be produce from a full output load dump.

I made one out of a bunch of high power Tranzorbs, it was not expensive although I have never actually put it to the test! Mostly for peace of mind just in case the bistable relay I use as the battery isolator/protector, ever goes open circuit on its own.

 

10 minutes ago, Tony Brooks said:

 

I doubt it, but it would not be too difficult to simply shut the alternator down by isolating the rotor currant on most alternators. That would not cause the voltage surge mentioned above, and I think @nicknorman and possibly others here have made their own alternator controller.

Yes so for instance one could use a BMV712 battery monitor, which has a built in configurable relay, to shut down the alternator field current when some specified SoC (80, 90, 100% or whatever is configured) was reached. It would need an intermediary relay due to the current involved. Quite doable I think, but people seem a bit scared of opening up their alternators to intercept the field current.

14 minutes ago, dmr said:

I don't have Lithium but am doing my research and electrical upgrades heading in that direction.

I also really do not like the (popular)  idea of relying on the emergency disconnect in the BMS to give day to day charging control, and I also don't like the idea of using a parallel lead acid as a surge suppresor (and a long cable as a current limiter).

 

There is a new alternator controller that appears to solve all the problems by correct engineering. This is the Arco Zeus.

Downsides are its quite expensive (but then so are destroyed lithiums) and is very very new so not proven in the field, and a little effort to install including alternator modifications. I also think that ideally one should choose a lithium battery that is compatible with CANbus though these are still quite rare.

 

 

Its a shame because there are a number of alternator controller chips around - every modern car uses one - that are adjustable via some sort of computer interface. The chips can be had for a few £. All the hard work is done for you. You just need to send it the right data in terms of regulated voltage and field current limit plus optionally a few more subtleties like field current ramp rates. Not difficult for some small electronics company to take on. I guess the market is just too small to make it worthwhile.

Edited January 24 by nicknorman

[BEngo]

29 minutes ago, David Mack said:

Do the US bodies or BSS have a view on how you can protect the alternator if they ban you from having a LA battery permanently connected to it?

I doubt it and I would not expect them too.

There are readily available engineering solutions available which do not involve  bodges such as  just dumping the load on the alternator and then  trying to deal with the aftermath or adding in extra cabling to create resistance and reduce charge current.  The problem is that they are expensive and more complicated than the "drop-in" market wants to understand.  That does not worry the underwriters- their concern is for their money,  not the boaters' money.

 

N

[David Mack]

6 minutes ago, BEngo said:

I doubt it and I would not expect them too.

There are readily available engineering solutions available which do not involve  bodges such as  just dumping the load on the alternator and then  trying to deal with the aftermath or adding in extra cabling to create resistance and reduce charge current.  The problem is that they are expensive and more complicated than the "drop-in" market wants to understand.  That does not worry the underwriters- their concern is for their money,  not the boaters' money.

 

N

I understand where the insurance underwriters are coming from. But I get the feeling that the BSS people are a bit more pragmatic. I feel they would be happier if there were a suitable commercial product (properly designed and tested) which could be used on a plug and play basis, whereas they may be less happy with individual boaters creating their own bespoke solutions or modifying standard components which will create a situation that BSS inspectors cannot realistically assess.

Edited January 24 by David Mack