LiFePO4 and fear of failure

[nmeyrick]

I realise this topic has probably been done to death but am stuck on one question and would love to hear people's thought process. I'm currently looking at replacing my lead acid bank with lithium, and am looking at drop in batteries. I'll likely end up with 4 drop in batteries, each individually fused. Talking to a friend in the anchorage yesterday he showed me how he uses a Bank Manager (from Emily & Clarke's adventures) to combine lithium and lead banks.

After going down the rabbit hole I really like the redundancy this provides and can see the argument for it, but suspect that given the size and power draw needs of my bank it would add a fair bit of complexity for relatively little cost saving in our case. I'm deliberately not going into the details of our set up at the moment as I'd prefer to focus on the general question.

So the part I'm left with is that I can find solutions for all the concerns I have around using lithium, for a purely lithium bank, with the exception of one question - how do you power the boat and keep things running if the lithium batteries fail or cut out, whether due to overheating, bad BMS etc. We are currently in the Med and heading across the Atlantic, so do want to be pretty self reliant. Our boat is an Amel Super Maramu and does have a big battery bank and some high draw equipment.

Our house bank is 24v so we can't fall back on the 12v engine start battery if all the lithium were to fail. We could add a dedicated lead "oh shit" battery, but to do this properly seems like it would need either something like the Bank Manager or DC-DC converters, so adding complexity. At the same time I'm figuring that having four batteries, separately fused does at least count for some scenarios where say a bad BMS on one battery would still leave us with three to use.

As far as I can tell there are lots of boats, including sister ships of ours (SV Delos, Mothership Adrift for a start) sailing around the world with fully lithium batteries and not seeming to worry unduly about the risk of the battery shutting down and leaving them dead.

How do others who have made the transition to LiFePO4 process and address this risk? Is it something that is worth investing in back ups for, or am I just over worrying about something that is more of a lithium bogeyman rooted in fear of the new technology?

Love any insight from those who have fitted lithium to their own boat, especially if you are sailing or planning to sail long distances.

Thanks
Neil

 

[Alex_Blackwood]

I realise this topic has probably been done to death but am stuck on one question and would love to hear people's thought process. I'm currently looking at replacing my lead acid bank with lithium, and am looking at drop in batteries. I'll likely end up with 4 drop in batteries, each individually fused. Talking to a friend in the anchorage yesterday he showed me how he uses a Bank Manager (from Emily & Clarke's adventures) to combine lithium and lead banks.

After going down the rabbit hole I really like the redundancy this provides and can see the argument for it, but suspect that given the size and power draw needs of my bank it would add a fair bit of complexity for relatively little cost saving in our case. I'm deliberately not going into the details of our set up at the moment as I'd prefer to focus on the general question.

So the part I'm left with is that I can find solutions for all the concerns I have around using lithium, for a purely lithium bank, with the exception of one question - how do you power the boat and keep things running if the lithium batteries fail or cut out, whether due to overheating, bad BMS etc. We are currently in the Med and heading across the Atlantic, so do want to be pretty self reliant. Our boat is an Amel Super Maramu and does have a big battery bank and some high draw equipment.

Our house bank is 24v so we can't fall back on the 12v engine start battery if all the lithium were to fail. We could add a dedicated lead "oh shit" battery, but to do this properly seems like it would need either something like the Bank Manager or DC-DC converters, so adding complexity. At the same time I'm figuring that having four batteries, separately fused does at least count for some scenarios where say a bad BMS on one battery would still leave us with three to use.

As far as I can tell there are lots of boats, including sister ships of ours (SV Delos, Mothership Adrift for a start) sailing around the world with fully lithium batteries and not seeming to worry unduly about the risk of the battery shutting down and leaving them dead.

How do others who have made the transition to LiFePO4 process and address this risk? Is it something that is worth investing in back ups for, or am I just over worrying about something that is more of a lithium bogeyman rooted in fear of the new technology?

Love any insight from those who have fitted lithium to their own boat, especially if you are sailing or planning to sail long distances.

Thanks
Neil

How do you power your boat if the current set up fails? I know that may not be helpful, But! I am not, by the way, trying to be funny.

 

[mattonthesea]

Off the top of my head: if you had two LA in parallel for starter and then, if you had a total BMS shutdown, you could rig them in series to get you by.

 

[nmeyrick]

How do you power your boat if the current set up fails? I know that may not be helpful, But! I am not, by the way, trying to be funny.

No I completely agree! The argument that has been put to me is that lead batteries are dumb and don’t tend to fail without good cause, while lifepo4 depends on electronics in the BMS that could either cut it off, or fail altogether.

I do not yet fully understand how much this is a real risk, and how much simply fear of the unknown / new technology hence hoping others who have made a similar decision can shed some light

 

[nmeyrick]

Off the top of my head: if you had two LA in parallel for starter and then, if you had a total BMS shutdown, you could rig them in series to get you by.

Thanks Mattonthesea, yes this is something I’m considering. It wouldn’t be automatic and not ideal but it’s at least an opportunity to jury rig. I may settle on this as it seems the simplest way to have some degree of redundancy - unless someone can tell me a reason that it’s not a good idea

 

[RunAgroundHard]

You can sail and navigate without power. If you need a plotter to navigate then a low cost tablet with solar charger deals with that issue. If you need a water maker you maintain and emergency stock of water. If. You cook on electric, you keep a low cost camping style gas cooker for an emergency. Buy a battery powered night vision monocular and that takes care of failed navigation lights.

The point is, it’s not an issue, you should be able to deal with power outages mid ocean in order not to be a victim.

 

[Refueler]

If I am considering offing into the unknown - first thing is I do not saddle myself with systems or setups that I am unfamiliar with. I prefer to stick with tried and tested that I can handle reasonably.

 

[Sea Change]

Which 24v systems are actually critical? I'd expect all of your navigation equipment and lights to be perfectly happy running off 12v. In which case it's not hard to get them switched over to the lead acid.

That's how my boat is set up, although without the complication of different voltages. My 'critical' circuit can be powered from either bank. I found out hard to get 1-off-2 switch so I use a pair of keyed isolators, with only one key. Turn one off, remove the key, turn the other one on. Very simple and cheap.

 

[geem]

Firstly. Are you sure you want four lithium batteries in parallel? Some drop in lithium battery manufacturers don't recommend paralleling this amount of batteries.
3 batteries would normally be plenty in parallel if going for lithium. You just need bigger capacity batteries. We opted for two batteries.
The risk of all your lithium batteries simultaneously failing is remote beyond belief in a properly designed system. Each battery will have its own bms, and isolator. I have a shunt for each of my batteries as well. I can run on one battery if I had a bms failure on the other battery.
If you are going for reputable lithium batteries with Bluetooth and active balancers, the risk if total system failure is negligible.
To stop cell damage by over charging, uncharging or over heating, the bms will isolate and protect the cells, so if the bms is good the cells will never get damaged.
We can charge our lithium with solar, diiesel generator, dc/dc chargers, towed turbine or wind turbine. So many ways to keep them charged

 

[Trident]

I currently have 7 Renogy batteries in parallel - all have their own built in BMS so it would take 7 failures to cause any issue and in 4 years of full time use I have had none.

If you're replacing LA with LIfePo4 there is realistically nothing to worry about on the failure front if you do it properly but if you use multiple batteries , just as you would with LA to build a big enough bank, then you need all to fail to be left without power and the chances of that are tiny.

The other option is build a bank based on EVE cells and separate BMS systems. You can build say two large 24V banks with 2 separate BMS so there is built in redundancy and then why not buy a spare BMS for an extra £100 so you have the part in board to swap out in the unlikely event of electronics failure. With this kind of set up it take minutes to swap out a BMS - a negative in and out , as many connectors to cells as for balancing as there are cells (probably 8 in a 24v set up) and most these days just on normal screw connections, no soldering etc.

No offence but I think you are maybe over thinking something that really is unlikely to be a problem and if it were its just solved by spares or redundancy like everything for ocean crossing boats .

 

[nmeyrick]

Thanks all, appreciate the feedback here. Yes absolutely battery failure is a challenge rather than an emergency, and we would keep sailing the boat without power just as we would if say hit by lightning. While Amels have a lot of power systems they do all have manual backups so that is all doable. Of course I’d rather avoid the problem in the first place but I’m not hearing from anyone that loss of power seems significantly more of a risk on a lithium bank rather than a lead set up.

Geem & Trident yes this is very much what I’m hoping that having multiple batteries with independent BMS internal to each provides redundancy; so that while one may fail it would be unlikely for all to fail at the same time. This seems logical to me but glad to hear it borne out by your experience

Thank you

 

[Sea Change]

Just a note, having seven batteries in parallel doesn't make your system seven times more resilient.
A lithium battery can go off-line for a number of reasons, including:
- over current discharge
- under voltage through deep discharge
- over voltage when charging
- over temperature
- out of cell voltage balance

Almost all of these would occur at the same time to batteries working in parallel. Only the last one on my list would likely be restricted to one battery only.
If you have configurable BMSs, you could tweak the settings so that batteries don't all go offline at the same time, but personally I would have them all set the same unless there was a very good reason.

You won't actually know if one battery has gone offline anyway, so in practice it makes no difference if the whole bank has the same settings.

Final point- the only time my lithium has ever gone offline has been when I've tried to draw too much current at once. And that was me running an electric galley through a 120A BMS. I can now draw 400A and don't expect to get that problem again.

In theory you could get a bad cell or dead BMS but in a well built system using decent quality components, that's really not very likely, and I wouldn't worry about it any more than I'd worry about a lead acid system going bad though e.g. a corroded component. Incidentally that's happened to me when my 1-2-both switch had a bit of corrosion on the contacts.

 

[geem]

I currently have 7 Renogy batteries in parallel - all have their own built in BMS so it would take 7 failures to cause any issue and in 4 years of full time use I have had none.

If you're replacing LA with LIfePo4 there is realistically nothing to worry about on the failure front if you do it properly but if you use multiple batteries , just as you would with LA to build a big enough bank, then you need all to fail to be left without power and the chances of that are tiny.

The other option is build a bank based on EVE cells and separate BMS systems. You can build say two large 24V banks with 2 separate BMS so there is built in redundancy and then why not buy a spare BMS for an extra £100 so you have the part in board to swap out in the unlikely event of electronics failure. With this kind of set up it take minutes to swap out a BMS - a negative in and out , as many connectors to cells as for balancing as there are cells (probably 8 in a 24v set up) and most these days just on normal screw connections, no soldering etc.

No offence but I think you are maybe over thinking something that really is unlikely to be a problem and if it were its just solved by spares or redundancy like everything for ocean crossing boats .

Spot on.
We have a 24v boat with two batteries using a 200A JK bms on each battery. I built my own batteries. We have a spare jk bms. We use CATL cells on my 24v, 280Ah battery and EVE cells on my 105Ah battery. It works beautifully

 

[Trident]

Just a note, having seven batteries in parallel doesn't make your system seven times more resilient.
A lithium battery can go off-line for a number of reasons, including:
- over current discharge
- under voltage through deep discharge
- over voltage when charging
- over temperature
- out of cell voltage balance

Almost all of these would occur at the same time to batteries working in parallel. Only the last one on my list would likely be restricted to one battery only.
If you have configurable BMSs, you could tweak the settings so that batteries don't all go offline at the same time, but personally I would have them all set the same unless there was a very good reason.

You won't actually know if one battery has gone offline anyway, so in practice it makes no difference if the whole bank has the same settings.

Final point- the only time my lithium has ever gone offline has been when I've tried to draw too much current at once. And that was me running an electric galley through a 120A BMS. I can now draw 400A and don't expect to get that problem again.

In theory you could get a bad cell or dead BMS but in a well built system using decent quality components, that's really not very likely, and I wouldn't worry about it any more than I'd worry about a lead acid system going bad though e.g. a corroded component. Incidentally that's happened to me when my 1-2-both switch had a bit of corrosion on the contacts.

We were talking about failure not about going offline for a BMS safety cut out which of course can be immediately reset but otherwise I take your point

My 7 batteries can flow 700 amps as each has a 100a BMS and of course my maximum draw is 300 ish and I’m fused at 350 with wiring good to 500 so they’re unlikely to have the issue you did as I build the system specifically for high load usage like cooking

Next upgrade is going in shortly- 1200 ah home built bank and a 5kw 24v Victron inverter as my wife now wants a full domestic electric oven to bake in and that’s 3500w

 

[geem]

We were talking about failure not about going offline for a BMS safety cut out which of course can be immediately reset but otherwise I take your point

My 7 batteries can flow 700 amps as each has a 100a BMS and of course my maximum draw is 300 ish and I’m fused at 350 with wiring good to 500 so they’re unlikely to have the issue you did as I build the system specifically for high load usage like cooking

Next upgrade is going in shortly- 1200 ah home built bank and a 5kw 24v Victron inverter as my wife now wants a full domestic electric oven to bake in and that’s 3500w

24v is definitely the way to go for high loads. We don't have enough solar panel capacity to run an all electric galley. We do use the induction hob all the time though. We have a standard 2kw unit. With 24v we have a pair of 200A bms batteries so we can theoretically run at 400 A but I sized cables for 200A and fused accordingly. The3kw inverter actually limits us to about 125A anyway and that is by far our largest load we generally don't run more than 2.4kw. All easy with much reduced cable sizes at 24v

 

[Trident]

24v is definitely the way to go for high loads. We don't have enough solar panel capacity to run an all electric galley. We do use the induction hob all the time though. We have a standard 2kw unit. With 24v we have a pair of 200A bms batteries so we can theoretically run at 400 A but I sized cables for 200A and fused accordingly. The3kw inverter actually limits us to about 125A anyway and that is by far our largest load we generally don't run more than 2.4kw. All easy with much reduced cable sizes at 24v

Indeed - I wired with 120mm cable for high loads at 12v but to run to 5kw I need either to go even bigger on the cable or change to 24v and the latter makes far more sense - all my switches and fuses can remain the same too and 24v is 1% more efficient on the inverter. I just need to decide whether to run step down transformers for 12v or a separate system between 12v for DC and 24v just for the AC Inverter.

 

[geem]

Indeed - I wired with 120mm cable for high loads at 12v but to run to 5kw I need either to go even bigger on the cable or change to 24v and the latter makes far more sense - all my switches and fuses can remain the same too and 24v is 1% more efficient on the inverter. I just need to decide whether to run step down transformers for 12v or a separate system between 12v for DC and 24v just for the AC Inverter.

We use multiple step down transformers. It gives some redundancy. I carry a couple of spares but only had one failure in 12 years

 

[Trident]

We use multiple step down transformers. It gives some redundancy. I carry a couple of spares but only had one failure in 12 years

I think I will go Victron 24/12 70 or as you suggest do two in parallel of the 30 or 50 amp models for redundancy and then for DCDC alternator to battery charge a couple of Orion 12/24 - I've only ever used my current 12v DCDC chargers to test as solar does the job but it would be foolish not to have the option and a pair of 30 amp DCDC at 24v will not over stress the 125a 12v alternators

Obviously with the OPs worries in mind, with the EVE cells and JK BMS its easy to go 24v for me but in an emergency I can also within minutes reconfigure it all to 12v and add my spare JK in to run the 24v pack as two 12v packs - not sure when I might need to but imagine a cascade of failures and a need to run boat systems and its really the work of a few minutes to set it up. Ok, I lose my inverter for house loads but again, I'm hypothetically in some unknown deep trouble..

It's not something I'd suggest those who are not very familiar with this stuff do but my point is hopefully illustrated that LifePo batteries are not scary or super high tech - so long as you learn what you need to do and use the right fuses and cables etc to do a safe install - or pay an expert to do so BUT teach you how everything works as he does it - it can be game changing. You not only get more power for less space and weight and much better results from solar but also a really flexible system that you can configure to your own needs.

 

[B27]

You can sail and navigate without power. If you need a plotter to navigate then a low cost tablet with solar charger deals with that issue. If you need a water maker you maintain and emergency stock of water. If. You cook on electric, you keep a low cost camping style gas cooker for an emergency. Buy a battery powered night vision monocular and that takes care of failed navigation lights.

The point is, it’s not an issue, you should be able to deal with power outages mid ocean in order not to be a victim.

Mid ocean might actually be less of an issue than coastal.

One thing I would not be without is a well sorted back up for the engine start battery.
That might need thought, if the rest of the system is 24V and/or lithium?

 

[mattonthesea]

So - the chances are minimal and you have 12V backup for systems. Seems good to me. Even if they did all go you have your eyes and the barometer

I did have a Garmin 72 but I practised (practiced?) noting north star and our sun and time which gave me a decent idea of which part of the ocean I was in. And a simpleton's guide to astronav usually got me within 30 miles accuracy!

And I found that looking at the clouds and barometer clearly indicated approach of bad weather.

Sorry for the thread drift but it's the next stage of pre-departure, free floating anxiety!

I'm envious; go and have a fantastic time.

M