Are Lithium batteries becoming realistic?

[charles_reed]

Andy, I've spent years researching, sometimes attempting electric propulsion...the worst thing about it isn't inadequate power, it's how terrifying it becomes when there's a fault!

I too concluded that something like a sail-converted MFV (or other heavy hull, more easily driven), with tonnes of concreted scrap metal ballast in her bilges, could instead house a huge weight of batteries that might allow reasonable range at moderate speed. I still think the idea of silent auxiliary power is among the most exciting prospects in sailing today.

I had a look lately at the ups and downs of lithium batteries, and I wasn't very impressed. They don't seem that much lighter than lead-acid, and their cost is jaw-dropping.

Still, I recognise that having far more usable power per kilo in Li-ion cells is a huge plus.

The OP will laugh at my craziness...but I'd still been looking at the Heavenly Twins, not as a prospective purchase but as a bit of design I find very interesting...and I'd wondered about an electric auxiliary on her, too. Excess weight & overloading being really bad for the HT's limited performance, conventional battery-weight would be catastrophic...

...but solar cells & sound-proofed generator charging Li-ion batteries, powering Agni motors turning folding propellers...well, it mayn't be practical, but I'm excited by the concept.

I've seen a couple of PV powered catamarans around in the Ionian - I believe using banks of common lead-acid cells as reserve rather than exotic Li batteries.
Whilst Li batteries appear to be fairly easily obtainable and economically prices in the States, neither are commonplace in Europe.
6 years ago I had to import a decent MPPT controller direct from the US as nothing comparable was then available over here.
EU tariff barriers would have increased the price considerably if we hadn't taken steps to treat it as a sample.

 

[Greenheart]

The HT is perfect for electric propulsion - light displacement - put a 6HP pod under each hull, 300AH batteries to get you in and out of the marina or tick over to motor sail and a diesel genny to run a diesel electric system for long runs and all the power you'd want on board for cooking, lighting, heating, air con

I'm grateful for the encouragement of my ideas! But, I wonder if it wouldn't first be necessary to resign oneself entirely to the HT's pedestrian performance when overladen...

...diesel generators, packaged inside effective sound-proofing, and grunty enough to provide power equivalent to a pair of I/C auxiliaries for when the batteries are flat, seem very heavy and expensive. The wonderfully quiet (49db) 1500rpm Paguro 6500w caught my eye...though perhaps two x 4hp pods would be the biggest motors it could drive...

...but it's 170kg and costs about £8000...so by the time even little batteries were added, an HT would be as low in the water as her owner's wallet would be on cash.

Not that any such reflection will discourage my dreaming.

 

[charles_reed]

Replacing every light with LED's has transformed our power use, especially with three children, three sleeping cabins, two heads, a saloon, galley and wheelhouse - how often were lights left on? Now I don't care! The fridge is a pain, draws an average of 1.7 amps - that's 40amps a day - which is an hour's motoring.

We put 200watts of solar on last year and that has been brilliant, so much so that I'm thinking of dropping the bank down to 330AH and saving a battery. It's irritating to think that 330AH, weighing about 140kg and costing about £330 only gives me 120AH or realistic usable power, a bit pathetic really.

If you move S you'll get more sun (but need more reserve for the fridge) @ 40N my 328 watts give me complete power independence May - August, My fridge also uses about 40AH/day, which is about the same as the laptop - lighting is less than 6% of the daily budget, but then, single-handed, sailboat and I use the mobile and headphones for audio-books, music etc.

 

[Seajet]

Dan,

well 4hp isn't going to have her going like something out of Thunderbirds is it ?!

Even if everything else, like prices, could be made to work I can't help thinking that if I had a diesel / electric setup I'd try hard to have an emergency Plan B with the generator in direct drive, as long as it didn't introduce friction the rest of the time; no doubt could be done, but even more cost, complexity and weight...

 

[ffiill]

water. Lithium doesn't like it.


I spent a merry day on the M5 some time ago managing the emergency services response to a lithium battery fire in a batch of ex helicopter batteries from Yeovilton. It took a lot of persuading to stop the FB using hose reels.


They are a serious, very serious, fire hazard unless managed in a very technical way. I'd stick with familiar lead-acid, or AGM technology, and look at options for maximising your present battery-charging regime. You are unlikely to have the storage space or electrical capacity constraints which can justify lithium.

Having had a rc heli one of about 500 mili ah! short out in my bedroom and burst into flames producing nasty acrid smoke before throwing it out of the window!

 

[noelex]

There are a number of lithium battery technologies. Lithium boat batteries are LIFEPO4 cells. These are reasonably safe, probably as safe, or safer, than flooded lead acid batteries. They are new technology and the safety in boat systems needs to fully proven, but the evidence suggests there is no need to be concerned. The bad reputation is mostly from other types of Lithium batteries.

Unfortunately lithium batteries need quite different management to lead acid. Commercial systems that manage this automatically are very expensive. So those using the technology at reasonable prices need considerable understanding of the technology.

The advantages are significant, but lithium batteries are not for the mainstream yet.
Eventually I think they prove to be the superior system.

For boats with generators, or boats where weight is critical they are certainly worth a serious look if you are reasonably technically savvy.

 

[Greenheart]

My apologies to the O.P., Mr Kipper, for subjecting the Li-ion theme to such leeway...but since he had a Heavenly Twins, I'm interested by his approval of the diesel-electric idea.

Clearly, it wouldn't be a sporty solution - but nor would a couple of 5.7-litre petrol V8s, in the Heavenly Twins - the hulls just aren't shaped for speed. My hope was that there could be a tenable alternative to a centrally-mounted outboard, or putting headache-generating single-cylinder diesels in each of her hulls...and nothing's quieter than electric thrust.

Assuming Li-ion batteries (sufficient in number to drive one hull for up to about an hour) could be fitted without plunging the Plimsoll line beneath the surface...

...and assuming, for those periods when sustained power is critical to safety, something like a Yanmar 1GM was put in the other hull...

...I wonder if the best of both worlds might be possible? Solar panels aside, it would seem smart to fit some high-output charger to the diesel, for reviving the batteries after use. I don't understand why alternators on marine diesels seem usually to be fairly small - wouldn't all that diesel power be able to generate many kilowatts at high ampage, given a big enough alternator, when the unit isn't simultaneously being used to propel the yacht?

Anyway, regarding the Heavenly Twins and other cats, I suppose it rather depends whether running an engine in only one hull, causes dreadful trouble with the steering.

 

[maxi77]

I've seen a couple of PV powered catamarans around in the Ionian - I believe using banks of common lead-acid cells as reserve rather than exotic Li batteries.
Whilst Li batteries appear to be fairly easily obtainable and economically prices in the States, neither are commonplace in Europe.
6 years ago I had to import a decent MPPT controller direct from the US as nothing comparable was then available over here.
EU tariff barriers would have increased the price considerably if we hadn't taken steps to treat it as a sample.

Li batteries usable in traction applications are readily available in the UK. All elecri bikes sold now have li batteries and they work well. Our preeent bikes have a similar capacity to our old one but in a box that is much lighter though 3 times the price to replace.