Realistic non-bs comparison of lithium to lead

[Taipe]

Originally Posted by Adelie

I'm not at all a fan of AGM, the downsides are too high and ultimately too expensive. If money weren't an issue for me I would go for Firefly AGMs which can go to 80%DoD regularly. I wouldn't believe it except MaineSail supports them.

As I am money constrained I have gone with Trojan T-1275 golfcart batteries.

AGM batteries receive and deliver the amps faster than the lead acid deep cycle and can be depleted to lower levels of remaining capacity more often before it is time to replace. Also, they can be installed in any physical orientation. In the long run, an AGM battery bank outlives the plain lead acid and therefore the cost outlay is similar. From the point of view of replacement cost in the case of a slim battery budget, or in the event of a prolonged and complete discharge, such as someone unplugging your dockside power while you are away from your boat and forgetting to plug you back in after finishing their project (it happens!), or a prolonged overcharge from regulator failure, then obviously hindsite would tell us that the choice of golf cart batteries was the best decision, the AGM was not so good, and the lithium was the worst decision. So, in view of how often undetected battery problems occur in saltwater conditions, I would automatically cross lithium batteries off of my list.

[KTP]

Originally Posted by Taipe

AGM batteries receive and deliver the amps faster than the lead acid deep cycle and can be depleted to lower levels of remaining capacity more often before it is time to replace.

I think when AGM first hit the market they claimed that was true but now it has been shown real world that AGM (which are also lead acid btw) are no better than flooded lead acid *true deep cycle* batteries at recovering from heavy discharge. For me flooded doesn't work because of where I want to keep the batteries plus I want a non-spillable battery. I also may need to mount them on their side, which doesn't work so well with flooded batteries.

[CatNewBee]

I would go with the 6V, just series, no parallel batteries, less issues.

Seria/parallel installations need more efforts to make them safe in case of a cell failure. you would either end up with a Bms, balancing cells, or two independent disconnected banks for safety, if you connect first parallel and then in series, you will need additional fuses per battery to protect from cell shorts / reverse currents.

[john61ct]

Originally Posted by Taipe

AGM batteries receive and deliver the amps faster than the lead acid deep cycle

True

> and can be depleted to lower levels of remaining capacity more often before it is time to replace.

False

> Also, they can be installed in any physical orientation.

True

> In the long run, an AGM battery bank outlives the plain lead acid

False

> and therefore the cost outlay is similar.

False

And FLA are much more robust, stand up to all kinds of abuse better, do not require such stringent charging requirements.

[KTP]

Originally Posted by CatNewBee

I would go with the 6V, just series, no parallel batteries, less issues.

Seria/parallel installations need more efforts to make them safe in case of a cell failure. you would either end up with a Bms, balancing cells, or two independent disconnected banks for safety, if you connect first parallel and then in series, you will need additional fuses per battery to protect from cell shorts / reverse currents.

It is just a mounting problem. I am not at the boat right now so I don't know if the 90 pound taller 6V batteries will actually fit in the compartments under the bench seats in the main cabin of the Pacific Seacraft 34. I measured it for the 12V GPL-31XT and it had plenty of room for that. I was going to make a little 7 inch wide wood shelf all along the bottom of those lockers and have four batteries on each side of the boat, long dimension parallel with the keel.

The 6V I would have to put four on each side, probably somehow situated on their side (they would be too tall and would poke up out of the sofa cushions if stood vertical). I would also need to run a cable across the beam of the boat to the other sofa compartment to connect the four + four 6V batteries together to get 48V. While not a huge issue, this cable would be rather long and probably have to run down into the bilge. Also the cable would carry all the amps for the bank where the parallel 12V cables would each carry half the amps.

How often do Lifeline AGM short a cell?

[john61ct]

Originally Posted by KTP

I have been thinking about the 6CT 6V Lifeline but have a few questions/issues.

Are the 6V batteries built any better than the 12V for Lifeline? They don't mention any difference in cycle life in the literature.

In theory the target cycles at 50% DoD are the same. IMO the larger AH lower voltage units will last longer IRL.

> Is there a big advantage in having one series string of eight 6V batteries to get to 48V vs two series strings of four 12V batteries (each fused) which is then paralleled?

I believe in a single pair paralleled for redundancy's sake, maintain target voltage even if a single battery fails catastrophically.

However the fewer strings paralleled the better for balancing issues, certainly four is at the upper limit.

The lighter weight per unit should make installation easier.

_____
You want - for best longevity, as frequently as possible - a charge source of .3C to .4C, .2C is a minimum.

It would be very unusual to split the bank for charging purposes, best to always have all of it treated as a single bank, except in emergency as outlined above.

[john61ct]

Fusing within the bank should only be required for longer connections, e.g. crossing port to starboard.

[Mike Banks]

Almost all of the electric drive systems I have seen for sailing vessels include a diesel engine driving a generator. This is a much smaller engine than would be required for the standard diesel engine as removed--but it still needs to be there for the days when the wind does not blow and the sun does not shine and for long windless night passages.

Once in the ocean, with good wind, the dynamotor will charge the batteries by taking some of the power imparted by the sails. Solar will have a negligible impact--so it is only this wind that you have allowed for in the recharging of the batteries.

I think that is too much of a risk--a windless day and a strong current could see you on the rocks at worst. In the weight you propose to save I would also include in that weight the 12 horsepower diesel genset. Sooner or later you will be glad you installed it.

The idea of diesel electric was not so much to save weight, but to improve overall sailing efficiency and saving fuel. Pure electric seems to me to be a disaster awaiting its time.

Yiour question was Lithium versus lead.

Lithuim is lighter and lead is safer. Lithium is more efficient and more expensive. Lead can be replaced almost anywhere ion the planet. Lithium will be harder to find in remote places--but if you are only coastal hopping, I would probably go with Lithium--because furter improvements ciontinue to be made--and lead development reached its peak a long time ago.

Another option one might consider are alkaline batteries of the NiCad type. Used in aircraft, they used to be available from military disposals, and have huge advantages in terms of lifetime but take up a lot more space than lead. They can go complertely flat and be recharged without harm. Having said that--I have not seen any of them for years--so you may have to do some searching.

[KTP]

Originally Posted by Mike Banks

Once in the ocean, with good wind, the dynamotor will charge the batteries by taking some of the power imparted by the sails. Solar will have a negligible impact--so it is only this wind that you have allowed for in the recharging of the batteries.

I think that is too much of a risk--a windless day and a strong current could see you on the rocks at worst. In the weight you propose to save I would also include in that weight the 12 horsepower diesel genset. Sooner or later you will be glad you installed it.

Actually I have read that you get a lot more from solar than you do from regen but this will need to be proven in testing to me as I think regen with the right prop could be significant.

As for danger, if you have a windless day and somehow manage to have ignored tides and such, you hopefully at least reserved some of your battery bank to allow you to move away from the rocks, at least to the point where you can drop anchor. There are plenty of disaster scenarios one can come up with for sailing. What if you forget to check the tides and are motoring and tear off your keel on a submerged rock? What if you leave the boat to go ashore and forget to turn off the seacock to your engine and a hose bursts, sinking your boat? I can continue here with scenarios that actually do happen. There are people who now sail without any motor ability at all...and sail around the world...several times in some cases. There are also people who really should just take down their mast permanently so they have a better view.

That being said, when the PS34 was designed long long ago, people were a lot shorter and could actually fit behind to service things like steering/rudder/prop shaft. With modern man, the PS34 really does not have room for a diesel engine.

[GrowleyMonster]

Originally Posted by Mike Banks

Almost all of the electric drive systems I have seen for sailing vessels include a diesel engine driving a generator. This is a much smaller engine than would be required for the standard diesel engine as removed--but it still needs to be there for the days when the wind does not blow and the sun does not shine and for long windless night passages.

Once in the ocean, with good wind, the dynamotor will charge the batteries by taking some of the power imparted by the sails. Solar will have a negligible impact--so it is only this wind that you have allowed for in the recharging of the batteries.

I think that is too much of a risk--a windless day and a strong current could see you on the rocks at worst. In the weight you propose to save I would also include in that weight the 12 horsepower diesel genset. Sooner or later you will be glad you installed it.

The idea of diesel electric was not so much to save weight, but to improve overall sailing efficiency and saving fuel. Pure electric seems to me to be a disaster awaiting its time.

Yiour question was Lithium versus lead.

Lithuim is lighter and lead is safer. Lithium is more efficient and more expensive. Lead can be replaced almost anywhere ion the planet. Lithium will be harder to find in remote places--but if you are only coastal hopping, I would probably go with Lithium--because furter improvements ciontinue to be made--and lead development reached its peak a long time ago.

Another option one might consider are alkaline batteries of the NiCad type. Used in aircraft, they used to be available from military disposals, and have huge advantages in terms of lifetime but take up a lot more space than lead. They can go complertely flat and be recharged without harm. Having said that--I have not seen any of them for years--so you may have to do some searching.

Have you ever owned an electric boat? I do. I do wish everyone who doesn't, never has, and never will, would stop sharing this urban legend about regen. It is not magic. You are first of all not taking power from the wind and turning it into electricity. You are taking power from the wind and driving the hull at a certain speed, and then robbing some of that speed to convert to electricity in a very inefficient manner. Yes, it exists. No, for most owners or operators it is not going to save the day unless you ROUTINELY sail at double digit speeds. Or somehow find yourself in a situation where you are exceeding hull speed and the hull therefore has excess energy to burn instead of trying to climb its bow wave. Change props all you like. A higher pitch prop will be easier to start turning with the motor/generator under an electrical load but will not turn very fast. A lower pitch prop will harness more energy from the moving hull once it is turning, but create more drag. A bigger prop will also harness more energy (which of course, comes from the hull moving through the water, so the hull will be moving through less water, i.e. slower) but create more drag. You simply cannot have your cake and eat it too. You can have a twinkie and nibble a corner of it, while paying the price for gourmet cream puffs. To make an analogy. Regen is significant with big, fast boats where you don't mind not going quite so fast. That's it. You can't create energy out of nothing. You can only convert it from one form to another, with significant losses along the way. Sometimes enormous losses. In this case, it is the enormous ones.


I did not get this from a sales or anti-sales brochure or drunken chatter at the bar or off an internet message board. I got it from my electric boat.


Regen capability is fine to have. Mostly, because if you don't use it, it costs you nothing whatsoever. If you are surfing and sliding down some big ol waves, seeing crazy speed in your small boat, and desiring to slow down a bit anyway because pitchpoling probably sucks, (I wouldn't know first hand but it sure seems like it would suck) you are in the one in a thousand situation where regen charging is a win/win thing. I lost about a half knot to make 140 watts. 140 watts. I know you wish I meant 14kw, but no, not even 1400 watts. 140 watts. Significant? Less significant than the drop in speed IYAM.



Want to charge a propulsion bank at sea without running a generator? Have a solar array rated for at least 10% of your bank's capacity in kwhrs. And keep the house loads modest. No radar, no chatter on the HF at 500w, no dolby surround sound movie watching on the 102 inch flat screen, no jaccuzzi, no sauna, no prime rib roast in the electric oven, no washer/dryer use, and no running the motor when you don't need it. How to keep from killing your solar output with shade from the sails and rigging will be for you to figure out, but it can be done, at least to some degree.


Yes, you will most likely be able to generate (convert!) power with the trailing prop, depending on motor and controller. No, it will not save the day. It will just be a weak dribble of pee in the energy bucket and a huge energy loss, actually, when you look at (1) the energy harvested, and (2) the energy required to increase your speed by the amount that the trailing prop in regen mode slows the boat, and compare them, you can do the math in seconds and see how inefficient and wasteful it is. Simple arithmetic. I won't touch wind charging just now and you don't want me to start, trust me. The way to always be able to charge your bank no matter what, is to have a generator. The way to keep from having to use the generator as much, POSSIBLY eliminate its use under nearly all circumstances, is to have plenty of solar charging capability. And I don't mean one or two 200 watt panels hanging over the stern, either.


Okay, </rant> I feel better now.

[a64pilot]

I don’t have nor do I see an electric boat in my future, but I know a little about aerodynamics that may help.
One reason you see such inefficient regen numbers is the prop is being driven backwards, it’s inefficient that way, if possible it needs to be turned around, I think or maybe pitch 180 out? I know that’s an Azipod or whatever and not realistic for us poor people, but trying to explain to some of the non believers why you get so little power from regen when there is all this sales literature that says you should be getting KW, not Watts. Your driving a thing that is designed to drive.
Ideally also you want a very lightweight stupid big, slow turning prop likely composite, but that would kill sailing ability.

[KTP]

I read in that famous boat motor prop book (forget the author) that the most efficient prop would have a diameter of 1/3 of the LWL (so about 10 feet diameter) and spin at 12 rpm. It would be nearly 100% efficient for propulsion and probably regen, but kind of suck for sailing.

Our boat has a 18 inch 3 blade prop, which is likely going to be a lot more efficient than the typical 6 inch or so prop on a 5hp outboard kicker. Not sure where the realistic but ideal point would be...maybe 18 to 20 inches is about the max you would ever want on a 34 foot boat.

[BigBeakie]

Or you could design it and engineer it properly so you DO get kW's instead of watts. Or you could use a prop that gives you 140 watts. Your choice.




Sent from my iPad using Cruisers Sailing Forum

[KTP]

Growl, what do you use for grounding once you pulled your motor? Do you bond the negative battery lead to the prop shaft and use a galvanic isolator to shore power? I need to read up on this a bit more...

[GrowleyMonster]

Originally Posted by a64pilot

I don’t have nor do I see an electric boat in my future, but I know a little about aerodynamics that may help.
One reason you see such inefficient regen numbers is the prop is being driven backwards, it’s inefficient that way, if possible it needs to be turned around, I think or maybe pitch 180 out? I know that’s an Azipod or whatever and not realistic for us poor people, but trying to explain to some of the non believers why you get so little power from regen when there is all this sales literature that says you should be getting KW, not Watts. Your driving a thing that is designed to drive.
Ideally also you want a very lightweight stupid big, slow turning prop likely composite, but that would kill sailing ability.

You have a point there. A prop makes a poor turbine for the same reason that a turbine makes a poor prop. Neither one is made to do the other thing. BUT... consider a drogue generator. Certainly, that is a machine optimized for dragging through the water and producing electricity. But if they were really great, everyone would have one. I dont have one and have never had one, so I suppose I should take my own medicine and not comment, but the concept would seem to be a poor one, anyhow. The idea is to make the boat go. Converting some of the go even with reasonable efficiency into electricity just doesn't seem like a good idea under most circumstances, when solar is available. And nothing is as utterly dependable as a backup generator.