Lead Acid, AGM vs Lithium Ion batteries

[macd]

I agree, more or less. At the moment, 12V lead-acid costs about £1 per Ah while Li-ion costs about £10 per Ah. However, since you can fully discharge Li-ion but shouldn't really make a habit of taking lead-acid below 50%, that's £2 vs £10 per usable Ah. Too much of a difference for me, but when Li-ion is effectively only twice as much - ie when I can buy 100Ah for £400, I'll go for it like a shot.

I expect that point in about five from now. Here's a useful chart from Bloomberg, showing the last few years' prices:

Interesting graphic, thanks, Jumble. I would though, take some issue with your simple Ah cost comparison (the one allowing for relative depth of charge). To my mind it's not very meaningful without a 'life cycles' factor, or some comparable measure. Bloomberg's chart, with it's kWh figure, may be more representative, although its scope is limited.

There's another comparison (clearly highly partial, but nonetheless interesting), near the foot of this page: https://www.powertechsystems.eu/home/tech-corner/lithium-ion-vs-lead-acid-cost-analysis/

Despite the conventional wisdom that lead-acid batteries shouldn't be cycled below 50%, there's another side to that coin, too. Graphs published by Trojan for their T105 show very little difference in gross lifetime Ah, whether routinely discharged to -50% or -90%. I've no way of assessing the accuracy of their claim, but neither have I specific reason to doubt it. (Our T105s very rarely get below -40%.)

Clearly to anyone strapped for cash, up-front cost is paramount, in which case I suspect that lead-acid will rule for many years yet.

 

[GHA]

Just to add more to the mix, for cruisers not having the constant battle to get back to 100% state of charge would be a plus for LifePo4, as would high charge acceptance nearly all the way up and not degrading if it's really hot. Needing a sophisticated charging management system and not being able to get some new ones off the beaten track would be negatives, which will keep me with the near bullet proof T105's for the foreseeable.

 

[Strolls]

In a thread on one of the mailing lists I subscribe to (Amel owners Yahoo Group, I think) there was a post by someone who seemed very knowledgable, and who claimed to work in the industry, that convinced me that lithium (LiFePO4, I think) now has a lower total cost of ownership than lead acid batteries.

He was adamant that, if you expect to own the boat long enough to pay off the initial investment, it's a "no brainer" to choose lithium.

It seems to me that the cost of newer battery technology is still falling, however, and you may get an even better deal in 5 years' time. I think I'd still prefer to buy lead-acid (Trojan T-105's), which remains a known quantity and requires no disruption to the existing wiring and charging systems, and review things next time.

I like new technology and the advances it can bring, but it still feels a bit too early for me, on this one.

 

[GregOddity]

Who would have thought that making sense of a battery bank would turn into a discussion bordering the lines of the sex of angels? I had to take a break from trying to design a battery bank … inclined to go AGM over wet cell or steal a power pack from a Prius at night in some badly lit Pub parking.

 

[JumbleDuck]

Interesting graphic, thanks, Jumble. I would though, take some issue with your simple Ah cost comparison (the one allowing for relative depth of charge). To my mind it's not very meaningful without a 'life cycles' factor, or some comparable measure.

That's a good point. Lifetimes for Li-ion seem to be increasing as well - not because of better chemistry, it seems, but because user experience is showing that they last better than expected. Tesla Roadster batteries were initially expected to last 5 years, but I gather that this keeps getting extended as the ones in service are holding up fine. From memory, the Tesla Powerwall was originally sold as capable of 500 full cycles, but now comes with a 10-year warranty.

I also take your point about depth of discharge. Some people are very nervous about lead-acid and stick to 20% discharge, but 50% seems fine and, as you say, some will do more. I think Trojans cost more too, don't they?

Finally, another useful aspect of Li-ion is that they are light and so don't have to live in low spaces, so installation is more flexible. No hydrogen to worry about either!

As I said, they are still way too expensive for me, but I don't think it will be long before they are worth it for at least some sailors.

 

[pvb]

Who would have thought that making sense of a battery bank would turn into a discussion bordering the lines of the sex of angels? I had to take a break from trying to design a battery bank … inclined to go AGM over wet cell or steal a power pack from a Prius at night in some badly lit Pub parking.

No need to steal Prius batteries, just do what Tesla did - use torch batteries. Each Tesla S has 7000-8000 torch batteries built into the floorpan. The battery type is 18650, lithium-ion rechargeables, freely available for purchase from loads of sources.

 

[GregOddity]

No need to steal Prius batteries, just do what Tesla did - use torch batteries. Each Tesla S has 7000-8000 torch batteries built into the floorpan. The battery type is 18650, lithium-ion rechargeables, freely available for purchase from loads of sources.

Out of curiosity I actually asked a price for retail on an order of 300 of them. The problem is not the batteries themselves but controlling the charge and discharge of small but obvious chemical differences on the batteries themselves which lead to different charge levels on quite a few if not all at some stage. Building a set up for charge and temperature control is a bit out of my league to say the least. So that’s where the bulk of the money will go.. sadly..

Pity no company offers a readymade solution where we could just plug 18650's / 26650 to our heart contempt. ( HINT HINT ! ! ! )

 

[JumbleDuck]

The problem is not the batteries themselves but controlling the charge and discharge ...

That's partly why the car-battery sized ones from Mastervolt and the like are expensive - they include sophisticated control and monitoring circuitry.

 

[prv]

That's partly why the car-battery sized ones from Mastervolt and the like are expensive - they include sophisticated control and monitoring circuitry.

Indeed, I’ve programmed a system using something similar at work. The batteries had RS485 ports that connected to the management system so that it knew exactly what was going on inside each individual cell.

That system (necessarily including the management unit) would probably work quite well on a yacht, come to think of it, though I have no idea how much it cost.

Pete

 

[William_H]

Out of curiosity I actually asked a price for retail on an order of 300 of them. The problem is not the batteries themselves but controlling the charge and discharge of small but obvious chemical differences on the batteries themselves which lead to different charge levels on quite a few if not all at some stage. Building a set up for charge and temperature control is a bit out of my league to say the least. So that’s where the bulk of the money will go.. sadly..

Pity no company offers a readymade solution where we could just plug 18650's / 26650 to our heart contempt. ( HINT HINT ! ! ! )

Well beware of Chinese 18650 batteries as I have bought quite a few. Great for flashlight but seem to struggle to deliver 10% of claimed AH rating. Cheap though.

To Coopec with his new build boat. I think if I were you I would fit an ordinary car/truck battery for engine using the engine supplied charging equipment. You could think about an a to b (alternator to battery) charger then for lithium if you wanted for services. You would need as said a proper lithium charge controller with discharge cut off.
For a 12v system you need to decide if you want 3 cells or 4 cells.
3 cells gives an operating voltage of between 10v and 12.3v with a charge voltage needed of about 14volts. So operating volts are a bit low but mostly acceptable for 12v devices. Charging supply is easy from a VSR from engine system.
4 cells gives an operating voltage between 11v and 16.4v but you need about 18v to push charge in (need a voltage booster in some form) which can be too high for devices on line while charging. (might need to arrange switching to use engine Lead acid battery or a lithium not being charged for supply to services when lithium is being charged.)
Any way I can hardly claim to know much about these batteries having only fiddled with smaller 18650 lithium.
So I think I would go lead acid for services battery as well.
I don't know how big your engine is but this might be a good time to go 24v system. Much better for a big engine with less voltage drop in wiring especially for anchor winch and starter. You could go 24v for engine (and anchor winch) with a converter to charge a 12v bank for service. (need a VSR to ensure only 12v charge when engine running.) This would be a cheap simple system but having only partial alternative jump start capability if 24v battery fails. (ie use the 12v battery to jump start bottom half of 24v or rewire 2x12v batteries in to series to jump start engine battery.)
Lots of options for you at this stage but as I said I would stick with lead acid and I don't think I would go for expensive calcium etc olewill

 

[GHA]

Well beware of Chinese 18650 batteries as I have bought quite a few. Great for flashlight but seem to struggle to deliver 10% of claimed AH rating. Cheap though.

There are actually a number of websites with test data on 18650's to check before ordering . Buy cheap rubbish you get rubbish, same in every country , China does very good as well as cheap rubbish but you have to pay more for good.

 

[macd]

Buy cheap rubbish you get rubbish.

Er...buy expensive rubbish and you get rubbish, too, GHA. It's just dearer :ambivalence:

 

[GHA]

Er...buy expensive rubbish and you get rubbish, too, GHA. It's just dearer :ambivalence:

Don't buy rubbish then

No real excuse anymore with the colossal amount of crowd sourced data on the web, just spend a few minutes sifting through it.

https://lygte-info.dk/review/batteries2012/Common18650Summary UK.html

 

[coopec]

Thanks guys! I've yet to go through all your comments but you've certainly given me something to think about.

I like all the attributes of L-ion but I think cost will be the biggest factor as one price I saw was absolutely hideous

Clive Cooper.

 

[GregOddity]

Indeed, I’ve programmed a system using something similar at work. The batteries had RS485 ports that connected to the management system so that it knew exactly what was going on inside each individual cell.

That system (necessarily including the management unit) would probably work quite well on a yacht, come to think of it, though I have no idea how much it cost.

Pete

RS485 ports can cost a mint, I was using some at £52 a pop for RTS GPS systems. I'm sure there's a way of getting around the 485's as the port. It would be interesting to discuss that further. PM me if you want.

'pologies to the OP for a slight hijack of the thread. it's distracting from his needs.

 

[GregOddity]

Thanks guys! I've yet to go through all your comments but you've certainly given me something to think about.

I like all the attributes of L-ion but I think cost will be the biggest factor as one price I saw was absolutely hideous

Clive Cooper.

you managed to describe my problem in an elegant way!

 

[prv]

RS485 ports can cost a mint, I was using some at £52 a pop for RTS GPS systems. I'm sure there's a way of getting around the 485's as the port.

Bit puzzled here. Are you talking about some particular connector? RS485 is a serial interface standard like RS232, and as far as I know doesn't specify a connector. The batteries happened to use an AMP Superseal or something similar to it, but we also have drive systems that use a round connector similar to a plastic NMEA2000 plug, and some things inside enclosures using a small Molex.

Pete

 

[Daydream believer]

Are these Li-on batteries the same as one gets in model RC aeroplanes?
If they are then i would not touch them with a barge pole.
I have seen one burst into flames when slightly over charged & it burnt through a wooden table & fell to the floor.
I have heard of a number of similar accidents.

 

[coopec]

.
I don't know how big your engine is but this might be a good time to go 24v system. Much better for a big engine with less voltage drop in wiring especially for anchor winch and starter. You could go 24v for engine (and anchor winch) with a converter to charge a 12v bank for service. (need a VSR to ensure only 12v charge when engine running.) This would be a cheap simple system but having only partial alternative jump start capability if 24v battery fails. (ie use the 12v battery to jump start bottom half of 24v or rewire 2x12v batteries in to series to jump start engine battery.)
olewill

William

I have a Perkins 4 108 engine and I intend replacing the 12V 40A(?) alternator with a 24V 60A alternator. I am using 24V for anchor winch, fridge/freezer, bilge pumps (X3) and macerator.

I worry when I see that the L-ion batteries have to be charged in a certain way and you mustn't flatten them: I really don't understand the technology. I've yet to do more reading of these comments but I think I'll go for AGM but because of the weight I'll mount them fairly close to amid-ships. (I've seen some of the Roberts Mauritius 43 ft yachts just about dragging the transom in the water because people have installed oversize motors). I think an auto pilot is a high priority so I'll spend the money on that.

I don't know where I read you couldn't start the motor with the L-ion battery. Maybe it was because the batteries couldn't withstand a large current draw because they were storage batteries?

Thanks everyone for your opinions, I've got a bit more reading to do though

Clive Cooper

 

[GregOddity]

Bit puzzled here. Are you talking about some particular connector? RS485 is a serial interface standard like RS232, and as far as I know doesn't specify a connector. The batteries happened to use an AMP Superseal or something similar to it, but we also have drive systems that use a round connector similar to a plastic NMEA2000 plug, and some things inside enclosures using a small Molex.

Pete

I meant this one.. but a bit of a brain freeze to be honest. Had some coffee and that helped. This is not what I would use for what we were discussing off course.