DIY lithium for novices!

[pcatterall]

Just reading ( with interest) the thread from Neeves.
I have dipped into the comprehensive information from Poey50 and others and understand bits!!
I appreciate the idea that the DIY route has many rewards amongst them being the value of understanding this essential part of of our yachts.
What would be of immense value now would be a summary/guide which abstracts the essence of the great work done by our experts to act as a guide
for those of us who need a few prods and pokes in the right direction.
Poey50's tip/recommendation on sourcing batteries is a good example of the sort of experience that the rest of us would find very useful!
Thanks (in anticipation!?)

 

[geem]

It's the sort of thing that should appear in Practical Boat owner mag but they would probably get it wrong!
I think there is enough information in the posts from those that have gone the lithium route. I have posted some of the basics and kit used. There is a wealth of knowledge online. Trying to write the definitive guide would be a big undertaking. I would be reluctant to suggest it is the route everybody should take. A good understanding of electrics would be necessary otherwise get it done professionally. Some of the mistakes people have made dabbling in something they have no understanding of have lead to expensive and dangerous errors

 

[Pete7]

There is also the number of different possible reasons why people want to fit LifePO4 (LFP), the solutions and charging options. Off the top of my head do you want:

1. DIY pure lifePO4 (LFP) solution
2. "Drop In" manufactured batteries?
3. Hybrid LFP paralleled to lead acid batteries

Charged by some or all of:

1. Alternator
2. Solar and or wind
3. Shore power.

Finally, why do you want LFP?

1. To run a small open topped fishing boat and take the battery home when back ashore.
2. To save weight on a trimaran as we have discussed this evening.
3. To support a live aboard vessel off grid for days of poor weather.
4. To mix electric and gas cooking maximising sunshine as the main source of power.
5. To see what all the fuss is about.

Yes it does sound daunting at first, but is it? or is it just a battery, some wiring connecting some widgets to keep it all in check. The widgets mean you don't have to fret when the sun goes behind a cloud and the batteries start discharging below 99% state of charge (SOC) . That btw may be an imaginary problem, but we are so used to ensuring batteries need to be frequently fully charged or the world will end. Yes it does takes time and a change of mind set to chill out and not worry there is only 40% left in the batteries at bedtime and the fridge will be fine or can you boil the electric kettle in the morning with 33% SOC to make coffee and then use the electric toaster as well

This link needs a quiet room, large strong coffee and some concentration to get your head around the first time, easier on the second reading.

Lithium-Hybrid

This YT video makes it all sound quite easy and came out as I was sketching out diagrams of how we might do it therefore really helped confirm what I was doing was at least possible. The science project isn't over yet, but its been an interesting journey so far and yes we do like cooking off sunshine.

 

[Kelpie]

It's a bit of a rabbit hole and I spent about six months reading and researching before I made any decisions.

The system I ended up building is in some ways extremely simple. As I had a perfectly good lead acid system already installed, I left that alone and added a totally separate system with its own chargers (MPPT) and loads (fridge, freezer, most of the cabin lights).

This removed some of the more worrying aspects of lithium, but for many people it would be a compromise too far.

However I do think it's possible to over-complicate things and spend a fortune. If you're the kind of person who wants to know your SOC whilst you're down the pub, fine, but it's not necessary to add every widget available to have a basic working system.

 

[geem]

It's a bit of a rabbit hole and I spent about six months reading and researching before I made any decisions.

The system I ended up building is in some ways extremely simple. As I had a perfectly good lead acid system already installed, I left that alone and added a totally separate system with its own chargers (MPPT) and loads (fridge, freezer, most of the cabin lights).

This removed some of the more worrying aspects of lithium, but for many people it would be a compromise too far.

However I do think it's possible to over-complicate things and spend a fortune. If you're the kind of person who wants to know your SOC whilst you're down the pub, fine, but it's not necessary to add every widget available to have a basic working system.

Although my system is a little complicated, I share your views off simplicity. It would always be my first choice. But having a wind/water tubine and a diesel genset, things got more complicated than I planned initially. Diagrammatic attached. There are some bits missing such as the independent solar and MPPT for the engine battery.

 

[Tintin]

Thanks for this. I've discarded lithium thoughts because I always assumed I'd be getting rid of a perfectly working system for no gain (before the cost side), but this thread has made me think about it some more. Thanks.

 

[Neeves]

Although my system is a little complicated, I share your views off simplicity. It would always be my first choice. But having a wind/water tubine and a diesel genset, thinks got more complicated than I planned initially. Diagrammatic attached. There are some bits missing such as the independent solar and MPPT for the engine battery.View attachment 158373

I see the advantage of a dual system but one reason for considering Lithium is the saving in weight and having lead and lithium seems to contradict that part of the reasoning.

We have a perfectly good lead installation, 2 x 200 amp/hr, but it has a finite lifespan so my reasoning is to investigate when we have time, ie now, and when the lead needs to be replaced - we will be ready. Usually when an item needs to be replaced it needs to be replaced NOW and this will also be the case when our Lead needs to be replaced - if the research is correct - we will have all the background and design ready.

Accepting that between now and then technology might have moved on.....

Jonathan

 

[Neeves]

Although my system is a little complicated, I share your views off simplicity. It would always be my first choice. But having a wind/water tubine and a diesel genset, thinks got more complicated than I planned initially. Diagrammatic attached. There are some bits missing such as the independent solar and MPPT for the engine battery.View attachment 158373

Geem - You have mentioned it in another post but include it in the diagram above - but why the emphasis on the Class T fuse at the Lithium battery and not for each segment of the charging circuit. The solar is unlikely to trigger a big Class T fuse, but the engine/battery might...... or am I being stupid? Why not different fuses for the different segments of the power input, smaller for solar, larger for the alternator etc (you could still have a big Class T at the battery (its not as if they are THAT expensive). Again - or am I being picky.

Given my ignorance - how did you decide how big the fuse would be.

Jonathan

 

[geem]

W

I see the advantage of a dual system but one reason for considering Lithium is the saving in weight and having lead and lithium seems to contradict that part of the reasoning.

We have a perfectly good lead installation, 2 x 200 amp/hr, but it has a finite lifespan so my reasoning is to investigate when we have time, ie now, and when the lead needs to be replaced - we will be ready. Usually when an item needs to be replaced it needs to be replaced NOW and this will also be the case when our Lead needs to be replaced - if the research is correct - we will have all the background and design ready.

Accepting that between now and then technology might have moved on.....

Jonathan

We had a perfectly good set of lead batteries. No reason to bin them. We are not a weight sensitive boat so they stay for now but I could just as easily add a second lithium battery in parallel. A failure on a BMS on one bank would then leave us with an intact backup. On a 12v boat it makes lots of sense to install two 12v batteries with their own BMS as you then drop the load on each battery to 50%. The BMS will live longer under light loads as you half the current through the BMS

 

[Pete7]

The solar is unlikely to trigger a big Class T fuse, but the engine/battery might...... or am I being stupid? Why not different fuses for the different segments of the power input, smaller for solar, larger for the alternator etc (you could still have a big Class T at the battery (its not as if they are THAT expensive). Again - or am I being picky.

Given my ignorance - how did you decide how big the fuse would be.

Jonathan

If a LFP battery system develops a fault and has a short circuit it is capable of discharging a huge surge of power. There is also a concern that mega or ANL fuses whilst they will blow, there is so much power flowing the arc will jump the blown fuse. Class T fuses are popular in the USA, but very expensive in the UK at £45 each for the fuse. In Europe there is an alternative NH type fuse at £5 each. That is a bit more acceptable particularly you may want to carry a couple of spares. I believe the fuse has silica or something inside, so in the event of a huge short the fuse blows but the arc across the fuse is also extinguished.

I have one of these in the circuit.

160A fuse NH00, 250VDC for NH00 DC Fuse Disconnect

 

[Neeves]

Another confession - I had to look with Google when Geem mentioned a Class T fuse on another, Lithium, thread about a week ago. It turned out I "knew' of them but had never realised they were called Class T.

I now understand why Geem has specifically mentioned them and why they would be installed close to the battery.

Thanks Pete7

Jonathan

 

[Poey50]

Just reading ( with interest) the thread from Neeves.
I have dipped into the comprehensive information from Poey50 and others and understand bits!!
I appreciate the idea that the DIY route has many rewards amongst them being the value of understanding this essential part of of our yachts.
What would be of immense value now would be a summary/guide which abstracts the essence of the great work done by our experts to act as a guide
for those of us who need a few prods and pokes in the right direction.
Poey50's tip/recommendation on sourcing batteries is a good example of the sort of experience that the rest of us would find very useful!
Thanks (in anticipation!?)

I'm a bit late to this. I did a PowerPoint presentation for the Cruising Association on the pros and cons of LFP including 5 model plans for installation. If you - or anyone - wants a copy feel free to PM me with an email address.

 

[geem]

Another confession - I had to look with Google when Geem mentioned a Class T fuse on another, Lithium, thread about a week ago. It turned out I "knew' of them but had never realised they were called Class T.

I now understand why Geem has specifically mentioned them and why they would be installed close to the battery.

Thanks Pete7

Jonathan

The recommendation is to have a class T fuse, or equivalent spec fuse, within 7" of the positive terminal. This is to reduce the risk of a direct short. Another tip when building a battery is to insulate the spanner you are using to tighten cell nuts. Wrap the whole spanner in tap apart from the very end. If you drop it, it will vastly reduce the risk of a direct short and many thousands of amps running through the spanner.
I mounted a sheet of perspex over the finished battery to stop anything falling on the battery terminals.

 

[Kelpie]

The recommendation is to have a class T fuse, or equivalent spec fuse, within 7" of the positive terminal. This is to reduce the risk of a direct short. Another tip when building a battery is to insulate the spanner you are using to tighten cell nuts. Wrap the whole spanner in tap apart from the very end. If you drop it, it will vastly reduce the risk of a direct short and many thousands of amps running through the spanner.
I mounted a sheet of perspex over the finished battery to stop anything falling on the battery terminals.

I did the same, also wrapped the cell connection bars, again to reduce opportunities for shorts.

 

[Stemar]

I knew someone who dropped a small spanner across the terminals of his car battery. Apparently It glowed quite nicely before he was able to knock it off. I hate to think what would happen with LiFePO batteries

 

[Kelpie]

I knew someone who dropped a small spanner across the terminals of his car battery. Apparently It glowed quite nicely before he was able to knock it off. I hate to think what would happen with LiFePO batteries

This thing is, with a drop in battery, not much is likely to happen. The over-current feature will trip in the BMS and it will just shut down.

(I'm not advocating that anybody tries this!!)

Shorting across the cells themselves is different... literally thousands of amps can be generated. I had one such accidental short whilst top balancing my pack- butterfingers moment with a bus bar- and it was like a welding spark. Quite impressive really.

 

[pcatterall]

I know an idiot who shorted and melted his metal watch strap while jumping across a dud solenoid. I still have the scar!!

 

[geem]

I know an idiot who shorted and melted his metal watch strap while jumping across a dud solenoid. I still have the scar!!

I was mid Atlantic in 2005 tightening a squeeling alternator belt and shorted a metal watch strap across the terminals. It glowed red hot and left a lovely burn. It welded the hasp shut. I had to lever it off with a screwdriver. The watch still worked though!

 

[Neeves]

Leather still has its uses, even in the 21st century

J

 

[Poey50]

I was mid Atlantic in 2005 tightening a squeeling alternator belt and shorted a metal watch strap across the terminals. It glowed red hot and left a lovely burn. It welded the hasp shut. I had to lever it off with a screwdriver. The watch still worked though!

Yikes!

Because my Balmar alternator charges the LFP direct on its own circuit (i.e. not connected to starter) I installed an 'Alternator Service Switch' to isolate the alternator when working on the engine. The only thing I have to remember is to use the switch - not obvious as it only gets used about once a year.