LiFePo vs PB (Lead acid) ......

[Pete7]

Problem is one cock up with a lithium battery and you are down four figures. A lead acid battery? well £80. There is also the need to change the charging systems to match LFP. I don't do beta testing, so happy to let others lead the way and wait for the price to come down substantially.

 

[Refueler]

Wouldn't you also take into account expected life?

If your £80 110 Ah L/A battery is likely to last for 200, (or even 500) cycles, and a 110Ah Lithium is likely to last for 2000 cycles, how much could it be worth paying for the Lithium?

You forget some fundamentals .....

The Lead Acid is far more tolerant of over discharge than any Lithium based cells. Even with BMS cutting out at low voltage.

Second - that quoting 200 - 500 cycles for a Lead Acid is simply just regurgitating tech stats - not actual living working experience. Imagine your car or your boat - how many actual cycles do you really think they do ? How long would it take to do say 200 full cycles ? Being a serious regular user of Lithium based batterys - I cannot justify the cost of LiFe batterys instead of common Lead Acid ... the time factor to recover the cost vs Lead Acid is just too great.
Lets say the Lead Acid lasts you 3 years on board before replacement. With your example - you claim the Lithium will last ~12 years. (500 vs 2000 cycles). OK ... so the 80 quid LA will be replaced 3x ... making total outlay of 4 x 80 = 320 quid ... that's a fraction of the cost of the Lithium battery ...
Even at 10 LA batterys ... you are still under the price of the Lithium ... and who keeps a boat that long ? Most people change boats after a number of years ... so where's the saving now ?

Its not like the swap petrol engine for diesel .. where the cost recovery is relatively short and viable.

 

[Kelpie]

Problem is one cock up with a lithium battery and you are down four figures. A lead acid battery? well £80. There is also the need to change the charging systems to match LFP. I don't do beta testing, so happy to let others lead the way and wait for the price to come down substantially.

That's the conclusion I've come to as well. Looking at total life cycle costs LiFePO4 batteries can now almost match deep cycle 6v batteries, until you throw in the BMS and charging system. Both beat leisure batteries comfortably on life cycle cost, at least based on manufacturers figures.
But which type is best depends upon usage, really. For a weekend sailor leisure batteries make sense because of the low initial cost, and they might well die through old age or accidental total discharge before reaching their quoted number of cycles anyway.

 

[Poey50]

Problem is one cock up with a lithium battery and you are down four figures. A lead acid battery? well £80. There is also the need to change the charging systems to match LFP. I don't do beta testing, so happy to let others lead the way and wait for the price to come down substantially.

That's my approach, too. I think the weekend-and-holidays sailor (me at the moment) has less to gain than the longer term cruisers (me, eventually) and I would imagine the latter to be the main early adopters. The greater usable capacity compared to lead acid (even conservatively moving between 20% and 80% state of charge on LFP compared to moving between 50% and 85% state of charge on SLA) and the end of requirement to bring lead acid back to full charge to extend life will I think win out when price, reliability and more idiot-proof DIY solutions emerge. The other gain is to be able to increase usable capacity especially on smaller boats where adding another lead acid battery is tricky. In the moulded battery box of my Sadler 32 I could fit 200ah of which 120ah is usable even very conservatively. This compares to 70ah of usable capacity on 2 x 100ah SLAs assuming 50 to 85% state of charge. Of course, the charge still has to be replaced but LFP will charge quickly and, as said, there are no sulfation or storage worries if only partially charged.

 

[Richard10002]

You forget some fundamentals .....

The Lead Acid is far more tolerant of over discharge than any Lithium based cells. Even with BMS cutting out at low voltage.

Second - that quoting 200 - 500 cycles for a Lead Acid is simply just regurgitating tech stats - not actual living working experience. Imagine your car or your boat - how many actual cycles do you really think they do ? How long would it take to do say 200 full cycles ? Being a serious regular user of Lithium based batterys - I cannot justify the cost of LiFe batterys instead of common Lead Acid ... the time factor to recover the cost vs Lead Acid is just too great.
Lets say the Lead Acid lasts you 3 years on board before replacement. With your example - you claim the Lithium will last ~12 years. (500 vs 2000 cycles). OK ... so the 80 quid LA will be replaced 3x ... making total outlay of 4 x 80 = 320 quid ... that's a fraction of the cost of the Lithium battery ...
Even at 10 LA batterys ... you are still under the price of the Lithium ... and who keeps a boat that long ? Most people change boats after a number of years ... so where's the saving now ?

Its not like the swap petrol engine for diesel .. where the cost recovery is relatively short and viable.

OK.... just throwing something into the pot

How about the reduction in charging time and cost if off grid, using a petrol genny?

I bought my boat in 2011, and don't foresee it being sold any time soon. If I did, I would take the lithiums and system with me, and leave the LA bank in situ.

There is some talk that Lithiums can last 5000 cycles, particularly with the "gentle use" that boaters make of them?

Surely if the voltage is cut off well before it gets anywhere near "over" discharge, how do they over discharge - genuinely interested, it doesnt seem logical

 

[Refueler]

When it comes to Leisure / Deep Cycle batterys - the biggest killer is using them as starter batterys. They just cannot handle the load and the soft plates buckle.

Its as bad a factor as discharging too low.

If you have a 'Deep Cycle' battery on board rated to start engines - then that is NOT a true deep cycle - but a compromise battery developed for the RV industry to try and bridge the gap.

 

[Refueler]

Low Voltage Cutoff is a failsafe ... not an item to make regular use of. You have that cut in too often and your expensive LiFe battery is now an anchor weight.

Back to RC world .... ask any RC'r about LVC for Lithium batterys and even though we have user settable options in our battery systems - we do all possible to avoid LVC ... we value our batterys and wallets too much !

 

[Richard10002]

Low Voltage Cutoff is a failsafe ... not an item to make regular use of. You have that cut in too often and your expensive LiFe battery is now an anchor weight.

Back to RC world .... ask any RC'r about LVC for Lithium batterys and even though we have user settable options in our battery systems - we do all possible to avoid LVC ... we value our batterys and wallets too much !

Presumably, in the boating world, we would also do all possible to avoid LVC?

When you say "cut in too often", is it the cutting in that does the damage, i.e. the sudden stop of flow?

or is it due to the voltage falling to the LVC level. If the LVC was set to a high enough level, could this be avoided.... e.g. if the LVC were set at say 3.0V per cell, (3.2V?), or 12V, (12.8V?), for a nominal 12V drop in, would that be non fatal?

 

[Poey50]

When it comes to Leisure / Deep Cycle batterys - the biggest killer is using them as starter batterys. They just cannot handle the load and the soft plates buckle.

There is no need to use them as starting batteries. As previously said, one emerging promising solution is to connect the alternator to a lead acid start battery and charge the LFP house bank with a battery to battery charger. This one is fully customisable and a couple of us have snapped one up at this second hand price for future LFP systems. This also protects the alternator against a high voltage disconnect and, with a three-switch system which many of use have already, would enable the start battery to be used to power some essential house circuits for a short period if the LFP ever isolated itself. Battery to Battery Charger (used) 6 months warranty- several remaining

 

[lw395]

For me it simply comes down to cost. I can get a 110 a/h lead acid battery for £80. So let’s call that, for arguments sake, 50 or so useable amp/hours for £80. How much can you buy 50 or so amp/hours of lithium/whatever power for? I’m guessing substantially more than £80. Not all yotties are wealthy. I’m not, and until lithium power gets cheaper I’ll stick with lead/acid.

Factory gate prices of Lithium batteries for cars are reportedly in the $150 to $200 region per kWh. And falling.
50 usable Ah is 600 or so Wh. £80 is $166 per kWh. OK, that's retail and inc VAT
So, it seems to me that we are not far away from commodity Li Batteries being very cost effective indeed. Once the price drops enough, a retail market will open up.
The downside is that early adopters will have paid a lot of money for something that's now a lot cheaper.

 

[Monique]

There is an interesting U-tube blogger at:

He seems to know what he is talking about.

I believe the Tesla batteries have a higher energy density but don't last as long as LiFeP04, but could be wrong

Hello Lucy,

I fully agree with you. Will Prowse is extremely well informed and his videos are very informative. He might be the BEST expert on LIPo.. batteries.

 

[Richard10002]

Hello Lucy,

I fully agree with you. Will Prowse is extremely well informed and his videos are very informative. He might be the BEST expert on LIPo.. batteries.

I think he was an RC fanatic in his earlier years, and maybe still is.

 

[ryanroberts]

Have replaced 6x lead acid batteries 4 times in 8 years with heavy off grid use. This is without running a fridge and having a KW of solar for the last 4 -5years, though admittedly the first time they blew was due to an electrician who miswired the adverc and ran 30V through the system above tickover, the ebersplutter wasn't happy about that either. This is not to mention other lead acid fun like having to get 200Kg of batteries down to the towpath. Was very tempted to early adopt for the last set.

 

[Refueler]

Presumably, in the boating world, we would also do all possible to avoid LVC?

Absolutely.

When you say "cut in too often", is it the cutting in that does the damage, i.e. the sudden stop of flow?

or is it due to the voltage falling to the LVC level. If the LVC was set to a high enough level, could this be avoided.... e.g. if the LVC were set at say 3.0V per cell, (3.2V?), or 12V, (12.8V?), for a nominal 12V drop in, would that be non fatal?

Its not the stopping of flow ... its the voltage its dropped to. With Lithium cells - the lower the level of charge you take them to under load - the more damage is done. Lithium cells damage is accumulative. There are no products or remedies for damage to them. Unlike LA where you can desulphate .... solve plate coated problems etc. - once a Lithium cell starts to go - its irreversible.

 

[Refueler]

He might be the BEST expert on LIPo.. batteries.

Do not mix up LiPo batterys with LiFe .... they are different batterys and have significant differences in use.

LiPo has a higher voltage per cell 4.2v instead of 3.6v ..., will be damaged by maintaining over 50% charge levels continuously .... are less 'safe' and can if mistreated / overcharged rupture and burst into flame..... the fire being self sustaining and no extinguisher you carry can put it out.

 

[Refueler]

Before people continue to think I am against Lithium based cells ... far from it. I am a daily user of both Lithium Ion Polymer (LiPo standard and High Voltage versions) as well as LiFePo and have been for many years as they progressively took over the NiXX market.
There are many different versions of the Lithium batterys - 6 at least are available to street users. Each has a different use and maintenance requirement.
Lithium based have a high power to form ratio, usually expressed as Energy Density than literally any other format. But they come at a price.

In the RC world - we are literally forced to pay high price for them if we want to have the performance levels general and competition flight demands. LiPo especially has revolutionised the model world giving us models capable of more than the wet fuel models they replace. But the problem of duration of power and the storage remains to be solved. I have models that the LiPo's are pushing out over 1Kw from cells the size of a cigarette packet. But flight is very short. I have other models using same cells but flying for 20 minutes because load is significantly less.

Whether you are looking at boat battery ... RC models .... car ..... - the Lithium format is same. The only differences are size and BMS systems. I have long thought about utilising Lithium on my boats - but until price drops to marketable level to compete with traditional - I will stay with Lead Acid.
Yes - I hate humping heavy batterys about ... but at 20 Euros a pop for an 80A/hr battery that came out of a perfectly good car before it had its accident ... I think its a no-brainer. Even if I only get 1 year out of it .... which given my experience using 2nd hand batterys is highly likely I will get far more than that ... I rest my case M'lord.

 

[Richard10002]

Its not the stopping of flow ... its the voltage its dropped to.

That's what I thought. So if the low voltage cut off is set above the damage causing voltage, presumably, the concern is mitigated?

Assuming I'm correct, how low could this be? or how high should this be?

 

[Refueler]

That's what I thought. So if the low voltage cut off is set above the damage causing voltage, presumably, the concern is mitigated?

Assuming I'm correct, how low could this be? or how high should this be?

Think you missed one part of that ....

Lithium batterys suffer damage as they discharge and this is exponential based on how low you go. The lower you go - the greater the rate of damage. This damage is accumulative and irreversible.
People go on about the amount of power can be used from Lithium vs Lead Acid ... yes its true that you can use up to 80% of a lithium's power vs a Lead Acid that you should not go more than 50%. But that extra 30% you use from that Lithium is actually damaging those cells.

LiFePo are much better at handling this than LiPo ... but it is still a factor.

LiFePo max voltage per cell is 3.6V. Nominal storage and shipping voltage is 3.2 ~ 3.3V. Maximum discharged state is often quoted at 2.5V - but I suggest that going below 3.0V is not advised if you wish to have long service life. If I was to use LiFePo - I would try to not go below 3.2V generally but with occasional drop to 3.0V acceptable.

Second that to get real advantage of Lithium based - you need to have balanced cells. Unlike Lead Acid and NiXX format that will generally balance as charged - Lithium's need a dedicated balancing format to achieve it. That is the second function of the BMS - to not only look after high and low values of the overall battery - but also to monitor individual cells to keep balanced. This is a specific requirement of Lithium based cells and cannot be catered for by non Lithium designed BMS systems.
Unfortunately - in the model world we have many examples of such BMS systems not performing as well as they should. That is why we have specially designed Programmable chargers to carry out this vital function. Is it then not a logical progression to consider that larger battery systems such as for RV use may suffer from similar poor BMS units ?
I would expect reputable brands to have good BMS systems fitted, you are paying a premium price. But it would be no surprise t hear that some budget systems are not as good.

It is relatively early days for boaters in this field. I think like with RC - it will take a while for it to develop and reach a steady level of standards at affordable pricing.

My boat is worth maybe 8000 - 9000 Euros on the market here ... probably more like 6000 in UK if lucky. Am I really going to hand out over half that value in LiFePo batterys ??

 

[Poey50]

That's what I thought. So if the low voltage cut off is set above the damage causing voltage, presumably, the concern is mitigated?

Assuming I'm correct, how low could this be? or how high should this be?

I'm still learning about LiFeP04 (LFP) batteries and there is a very great deal to learn. But my understanding is that the problem with low and high voltage, and temperature disconnects is that they depend on the battery management system (BMS) doing its job as an insurance policy against destroying the battery. From my reading, some early adopters used the BMS as a routine control system rather than a backstop. The problem there is that BMSs vary greatly in quality and may simply not work when needed. Many drop-in LFP batteries apparently are produced to be replacements for lead acid for off-grid static street signs or lighting so may be nowhere near robust enough for marine applications especially given the longer anticipated life. So the answer may lie in really robust DIY systems using an external BMS or in high quality drop-ins (like the Battle Born). At the moment, few - including me - seem to have the knowledge for the former, and even fewer - also including me - want to stump up for the latter.

 

[lw395]

....

My boat is worth maybe 8000 - 9000 Euros on the market here ... probably more like 6000 in UK if lucky. Am I really going to hand out over half that value in LiFePo batterys ??

A lot of people seem to shell out big sums of money for lots of Trojans and so forth, one could question the actual value they get from those too.
Back last century, we made do with quite modest battery capacity, despite using filament lightbulbs.
OK, these days we use a heater more often, and get value from that in terms of more sailing in a longer season.
But 20 years ago, most sailing boat owners would have questioned the 'need' for more than a couple of hundred quid's worth of batteries at today's prices.