Replacing diesel with electric

[StuM]

Originally Posted by StuM

With a 15HP engine, 1/2 to 2/3 of Max RPM would actually be around 2 to 6 HP (1.5 - 4.5 kW)

Oops, fumble fingers! That should read 1/2 to 3/4 of Max RPM.

[ranger58sb]

Originally Posted by ranger42c

Yes, fuel, lube, etc. are additional expenses... In my mind I guess I'd probably just mentally equate all that to the actual batteries in an all-electric set-up... but then that doesn't take into account recharging mechanisms, etc...

Guess it'd come down to a miles-per-battery-and-charging-system-$$$ vs. miles per diesel-$$$ to be able to compare very well?

I've thought of maybe a better way to equate fuel to fuel. Amps-in/amps-out would be more conceptually similar to diesel fuel, oil, etc.

So that means the batteries are part of the infrastructure ("plant"), similar to the diesel engine (block, etc.). With most electric, one maybe replaces parts of "plant" periodically, whereas with diesel, "plant" replacement would be much less common.

Not sure that gets me anywhere better, though, on how to do that the miles per electric or miles per diesel $$$ comparison.

-Chris

[double u]

sure, a new engineblock every 5-7 years...

[StuM]

Originally Posted by ranger42c

So that means the batteries are part of the infrastructure ("plant"), similar to the diesel engine (block, etc.). With most electric, one maybe replaces parts of "plant" periodically, whereas with diesel, "plant" replacement would be much less common.
-Chris

Batteries are actually the equivalent of the fuel tank.
But they:
are far more expensive to install,
don't store nearly as much energy,
take much longer to fill up,
lose capacity and need regular replacement.

[ranger58sb]

Originally Posted by StuM

Batteries are actually the equivalent of the fuel tank.

Hah! Even better parallel.

-Chris

[Maine Sail]

Originally Posted by StuM

Batteries are actually the equivalent of the fuel tank.
But they:
are far more expensive to install,
don't store nearly as much energy,
take much longer to fill up,
lose capacity and need regular replacement.

You forgot the most important one, that far too many folks including many e-propulsion re-sellers completely ignore, and that is Peukert.. The rate of discharge on the lead acid battery determines it's usable capacity. The "sticker" on the battery is NOT the Ah capacity you will get with e-propulsion and high discharge rates....

For example a 200Ah lead acid battery will only deliver its 200Ah rating at 77F and at a 10A fixed load. If the load goes higher than 10A, as it will with e-propulsion, you no longer have a 200Ah bank , you will have a smaller bank than 200 Ah.

I have done far to many "consults" for e-propulsion folks, who already have the system, and can't figure out why they can't get the range they were told they could. Getting the MATH right is something the e-propulsion community falls flat on far too often. Either that or they are just not being entirely honest.

If sticking with lead acid the battery with the lowest Peukert eg; Odyssey, Lifeline, Northstar etc. will yield the lowest Peukert related capacity losses at higher loads, and deliver most usable capacity when the discharge rate is above the 20 hour rate. The 20 hour discharge rate is easy to figure out;

Battery Capacity / 20 = Discharge Rate For Rated Capacity

or

100Ah / 20 = 5A

or

200Ah / 20 = 10A

or

225Ah / 20 = 11.25A

This means that in order to not get less than the rated Ah capacity of say a 225 Ah GC-2 golf car battery bank, you can not discharge it at any more than 11.25A or the banks usable capacity shrinks...

In other words at any discharge rate above 11.25A a 225 Ah 48V battery will not deliver 225 usable Ah's. Of course using face value ratings assumes you are using 100% of the capacity, which you should rarely if ever do except in an emergency.

When we take into consideration a nominal discharge floor of 50% DOD our 48V 225Ah bank is now really 112.5Ah's of usable caapcity at an 11.25A load & 77F. If we now apply a 30A load at 77F our usable capacity to 50% DOD now becomes somewhere in the vicinity of 86 usable Ah's not 112.5 Ah......

Also at any temperature lower than about 72 - 80F the battery will also deliver less usable capacity and this on top of Peukert, for those who sail in colder waters, can be a massive whack off of the capacity they assume they have.

Typical deep-cycle flooded batteries range from a Peukert of about 1.20 to as high as 1.50+....... The lower the Peukert the more usable capacity you can realize at high rate discharge. Conversely, for low rate discharges, such as a house bank, a high Peukert battery will deliver more usable capacity.

This chart does a very good job at summing up the Peukert effect on a deep cycle L-16 flooded battery.... When sizing and discussing usable capacity Peukert, average temp & design discharge floor (50% DOD etc.) should always be taken into account, but it rarely is ....

[valhalla360]

Originally Posted by StuM

A common misunderstanding.

Most cruising boats typically run at 1/2 to 3/4 RPM

Given the typical power curve of a diesel engine, that is a lot less that 1/2 to 3/4 power. (1/2 power would typically be around 80% RPM and 3/4 power around 90% RPM)
With a 15HP engine, 1/2 to 2/3 of Max RPM would actually be around 2 to 6 HP (1.5 - 4.5 kW)

You can certainly run at lower power but assuming a 3600rpm peak, 1800rpm is well below what I typically hear people suggesting they run at. Usually I hear people reporting the 2400-2800rpm range....2400 is around 2/3 of max RPM and 2800 is higher. Peak HP is often below peak RPM as you lose torque at peak RPM. So yes, I was talking about portion of peak power not RPM.

Even at 4.5kw, he's going to have a real tough time feeding the electric motor sustained power and this is just normal cruising not fighting a current or headwind where you need substantially more.

[StuM]

Originally Posted by valhalla360

You can certainly run at lower power but assuming a 3600rpm peak, 1800rpm is well below what I typically hear people suggesting they run at. Usually I hear people reporting the 2400-2800rpm range....2400 is around 2/3 of max RPM and 2800 is higher. Peak HP is often below peak RPM as you lose torque at peak RPM. So yes, I was talking about portion of peak power not RPM.

Even at 4.5kw, he's going to have a real tough time feeding the electric motor sustained power and this is just normal cruising not fighting a current or headwind where you need substantially more.

Dunno about your experience, but all the Perkins and Yanmars that I have used have max HP at max RPM/WOT according to the manufacturers power curves.

My Yanmars have a max RPM of 3800.
I generally run them at 1800-2400 RPM (lower end of that when motor sailing in very light conditions or when manouvering). If I have to go to 2800 on one engine, I will switch to 2 engines at 2200 for the same speed and lower fuel consumption. I would very rarely need 2800 on both engines.

[DeepFrz]

I don't see any mention of LFP batteries. I think they are a game changer in the electric propulsion question.

[iGrf]

Just to add to the mix ...

These guys are halfway on their sustainable circumnavigation !

Duurzaam Jacht - Sustainable Yacht Ya, traveling the world without a drop of fuel!

[Kenomac]

Originally Posted by iGrf

Just to add to the mix ...

These guys are halfway on their sustainable circumnavigation !

Duurzaam Jacht - Sustainable Yacht Ya, traveling the world without a drop of fuel!

I read their website, and I hate to break it to those guys, but......

Ferdinand Magellan beat them to it by 500 years... they won't be the first.

And he didn't have "electric engines, an induction cooker, a freezer, a microwave, Wi-Fi, GPS, radar and anything [we] could possibly need," including LED lighting as their website describes.

[witzgall]

Originally Posted by GrowleyMonster

Lithium batteries can pose a serious fire risk on a boat. More so than FLA, anyway. With a BMS failure, things can go north pretty quickly. Just sayin. Lithium has a lot of advantages, but cost, and safety, are not among them. Yes you can routinely discharge them to near zero. Yes they weigh less and with a proper BMS, will last longer. But that is not always the best solution. Depends on the useage and user. Don't throw the lead battery under the bus. It is perfect for some of us.

I will take exception to the above opinions. Lithium, if installed properly, is in my opinion safer than Lead acid. This means LIFEPO4 or LTO batteries, and possibly others. I know there are exponentially more lead acid equipped boats out there, there they can, and do cause fires as well. Ever hear of hydrogen gas?

Chris

[GrowleyMonster]

Originally Posted by Kenomac

I read their website, and I hate to break it to those guys, but......

Ferdinand Magellan beat them to it by 500 years... they won't be the first.

And he didn't have "electric engines, an induction cooker, a freezer, a microwave, Wi-Fi, GPS, radar and anything [we] could possibly need," including LED lighting as their website describes.

True. But it wasn't a "pleasure yacht". At least, I suspect his crew didn't think it was, anyway.

BUT, there was another electric yacht that circumnavigated a couple years ago, as I recall. So they are STILL not the first "pleasure yacht" to circunabigate without burning any fossil fuel.

EDIT: And it didn't have sails, either.

[Kenomac]

Originally Posted by GrowleyMonster

True. But it wasn't a "pleasure yacht". At least, I suspect his crew didn't think it was, anyway.

BUT, there was another electric yacht that circumnavigated a couple years ago, as I recall. So they are STILL not the first "pleasure yacht" to circunabigate without burning any fossil fuel.

EDIT: And it didn't have sails, either.

And not the oldest either because there's Jeanne Socrates at 70yrs who did it solo and non-stop.

Apparently they didn't do any research homework before leaving.

[Lantau]

Originally Posted by keith4001r

...

I also know that with electric I can eliminate raw water strainers, impellers, exhaust manifolds, heat exchangers and all sort of other stuff that I don't understand.

...

I wouldn't be surprised if we all were going over to electric with 15 years at most. A big shift could be coming sooner than we think.

That said, it's possible to avoid most of what you seem not to like (water strainers, exhaust manifolds, heat exchangers) and still have a diesel engine by having dry exhaust and keel cooling.