Propulsion & house LFP bank

[aybabtme]

extracted from https://www.cruisersforum.com/forums/f166/merged-lifeypo4-1000ah-winston-prismatic-cells-and-all-electric-galley-201795-new-post.html

Alright I know just a few weeks ago I was lambasting the unecessity of using raw cells in our modern times with the abundance of high quality and cheap commercial packs. But alas, reality struck me and the odd shape of the locker where I can store the batteries is forcing me down the path of a custom pack made with raw cells.

* * *

Here's the requirement brief:

• 35ft lightweight catamaran (Seawind 1000 XL2)
• Rated for max 2x10kW engines, so design for 20kW continuous discharge (although will be less than that in reality).
• Aim for 1h range at full power (20kWh).
• Obviously 48V nominal for this power requirement. I don't want to go higher than 60V.
• Price is a lesser concern, since it's overall not a big differentiator in the overall project.
• Delivery to California (SF or LA).
• Available volume is two compartments of dimensions 890mm (length) 250mm (width) 41mm (height).
• Weight is a concern, so aluminum encased cells it is.

Right now the contenders are:

• CATL 302Ah in 2P16S: 185Wh/kg, 167kg, 30.9kWh
• CALB L173F230B in 2P16S: 175Wh/kg, 134.4kg, 23.6kWh
• Fortune 205Ah in 2P16S: 156Wh/kg, 134.4kg, 20.9kWh

The Fortune could seem a clear loser here, but they gain extra point in my book for being so easy to assemble and work with.

Here's my notes so far (see "Mothership: LFP cells"). The BMS is a Rec Q 16S. Busbars and distribution is Victron's Lynx setup with Cerbo GX and Multiplus II for main charge source.

Actual engines will probably be ePropulsion Navy 6.0, although their long shaft variant is a bit too short. Current engines are gas Yamaha 9.9 outboards with extra-long shafts (25"). I'll figure out some story for "range extension" later. We have gasoline tanks onboard so the easy way is to used Honda EU2200... but I don't like the smell of gasoline. And yes, it's unclear whether this is all a good idea or not, but I want to try it out so
* * *

I guess there should be a question: do you know of any cell I should evaluate here that's not in my spreadsheet?

[newhaul]

Ok something to seriously consider is the yamahas are 87 pounds each and gasoline is 7.5 ( apporx) per gallon .

Now you are replacing. X gallons of gas per engine with 295 pounds of battery per motor .

The navy 6.0 is 80 pounds so that's a wash .
$3600 each plus the cost of the battery and the controls for the motor.
Now will the battery also be available for house use or will you have a separate house bank?

$ 7200 just the motors well that's a lot of gas for the outboards and even enough left for a Honda generator and a lifetime of fuel for it to .

I'm a west coast sailor we live by the it ain't broke don't fix it.

Are you having issues with the operation of the yamahas? They are considered a reliable engine .

[CaptainRivet]

Originally Posted by newhaul

Ok something to seriously consider is the yamahas are 87 pounds each and gasoline is 7.5 ( apporx) per gallon .

Now you are replacing. X gallons of gas per engine with 295 pounds of battery per motor .

The navy 6.0 is 80 pounds so that's a wash .
$3600 each plus the cost of the battery and the controls for the motor.
Now will the battery also be available for house use or will you have a separate house bank?

$ 7200 just the motors well that's a lot of gas for the outboards and even enough left for a Honda generator and a lifetime of fuel for it to .

I'm a west coast sailor we live by the it ain't broke don't fix it.

Are you having issues with the operation of the yamahas? They are considered a reliable engine .

Exactly
You can also replace the Yamaha with the Tohatsu M9.8hp 2 Stroke, it's the lightest 9.8hp engine with 26kg and millions of fisherman using it for centuries,extremely reliable and simple. You can find them online as they are still allowed for commercial use in eg UK or Netherlands.
Your setup with light weight cat, short length=small payload and light 10hp outboards has the worst preconditions to be converted to electric propulsion.
Additionally
20kW in 48V means you have constant 470A floating, startup/exceleration surge for aprox 20ms will be 3-8x times this so 3200A.
1)add another big chunk of weight for thick and expensive copper cables. They got freaking expensive...
2)what's the peak C-rate rating of your suggested cells... Expect 2C, so 2x304Ax2 parallel =1218A due to a 2p16S config for the 304AH cells... You need 3200A so much more capacity...

[aybabtme]

This isn't an endeavour in saving money, it's an experiment to see how it's like. The goal is to have electric propulsion with fossil fuel for range extension. If it doesn't work, I'll scrap it, sell the parts at a loss and put back the Yamahas. "If it works don't fix it" doesn't apply since we got the boat in large part for the purpose of doing this test. I'm not trying to be pragmatic and boring here, I'm trying to have some fun and test something out.

Now you are replacing. X gallons of gas per engine with 295 pounds of battery per motor .

295 pounds is the overall bank for BOTH motors.

The navy 6.0 is 80 pounds so that's a wash .

Each Navy 6.0 is 26kg, the Yamahas are 45kg each.

Now will the battery also be available for house use or will you have a separate house bank?

For house load too (via B2B). 12V will keep a battery to support the windlass.

As for the peak load, I'm not actually concerned with the peak satrtup current you're mentionning. The motors and the controllers are designed to work with the E175 batteries, which have worse C rating properties than the pack I'm designing here. The controller is most likely not a dumb inductive load like an AC motor; it can regulate the power requested. But there's some cells in this short list that peak a lot higher than the C rating I put in the spreadsheet. The C rating there is for _continuous_ max discharge rate.

In term of cable gauge, since we're talking of 2 motors, and 6kW for the immediate outboards I'm looking at (Navy 6.0) it's a max continuous current of 125A. Gauge 2 works for the ampacity. At 10kW it'd be 3/0, not small and a few kilos but not the end of the world either. Nothing that'll tip the overall mass equation.



With regard to weight and balance. I've got more math on the weight & balance going on in this spreadsheet (incomplete). Electric and hybrid combinations are of course trending higher than the current setup, but it's on the order of "one less fat person aboard" type of weight. The spreadsheet uses E175 batteries for simplicity and those have poor Wh/kg. https://docs.google.com/spreadsheets...it?usp=sharing

[Adelie]

I have several comments:
A. The Navy-6.0 draws 5500W. So for 1hr at full thrust using 2 motors you need 11kWhr. 11kWhr / 90% = 12.2kWhr plus reserve for house demands.
B. The Navy-6.0 uses a podded motor which will entail regular maintenance of the motor seals with the possibility of seal failure leading to motor failure despite the maintenance. I believe Torqueedo is the same.
C. Have you considered Elco 9.9 which use top mounted motors? They cost about $800 less at the cost of about 700W of output each.

[aybabtme]

Originally Posted by Adelie

I have several comments:
A. The Navy-6.0 draws 5500W. So for 1hr at full thrust using 2 motors you need 11kWhr. 11kWhr / 90% = 12.2kWhr plus reserve for house demands.
B. The Navy-6.0 uses a podded motor which will entail regular maintenance of the motor seals with the possibility of seal failure leading to motor failure despite the maintenance. I believe Torqueedo is the same.
C. Have you considered Elco 9.9 which use top mounted motors? They cost about $800 less at the cost of about 700W of output each.

I didn't look seriously since the Navy 6.0 has regen, something I'm interested in. I'll look more!

[CaptainRivet]

Hi Antoine,

That's a great approach.
Really testing out stuff and prepared to loose some money is the right start.

Regarding data sheets of these cells is a question how reliable are they. For cont C that might be ok for the popular once like EVE, Lishen, Basen...but for peak? Using 2x cont C as peak C is common practice and these cells don't differ that much internally.
Propulsion you need peak C-rate and should stay within range otherwise they won't last long.
Top of my list would be Winston, they have 2C cont and 4C peak plus they are underrated, you buy 400AH and get 480-500AH. Their datasheet is reliable and worst case, means that what you get even you got cells at the end of the tolerance spectrum.
That the bank does not get significant imbalance very quick, you need to stay for discharge below 50% of cont C rate. If you go above you need chunky active balancers, the 2A the Rec delivers won't be enough.
Cables I would use biggest you can fit, 4/0 to motor as to spec it will get warm and voltage drop rises, wise to go 2 sizes up here.

[aybabtme]

Originally Posted by CaptainRivet

Hi Antoine,

That's a great approach.
Really testing out stuff and prepared to loose some money is the right start.

Regarding data sheets of these cells is a question how reliable are they. For cont C that might be ok for the popular once like EVE, Lishen, Basen...but for peak? Using 2x cont C as peak C is common practice and these cells don't differ that much internally.
Propulsion you need peak C-rate and should stay within range otherwise they won't last long.
Top of my list would be Winston, they have 2C cont and 4C peak plus they are underrated, you buy 400AH and get 480-500AH. Their datasheet is reliable and worst case, means that what you get even you got cells at the end of the tolerance spectrum.
That the bank does not get significant imbalance very quick, you need to stay for discharge below 50% of cont C rate. If you go above you need chunky active balancers, the 2A the Rec delivers won't be enough.
Cables I would use biggest you can fit, 4/0 to motor as to spec it will get warm and voltage drop rises, wise to go 2 sizes up here.

The problem with Winston cells and other nylon cases is that they have really poor Wh/kg (less than 100), as opposed to 175+ for aluminum cases. Once way to get higher C ratings with aluminum cases is to use smaller cells and put more in parallel. The Wh/kg suffers again but remains in the >120 Wh/kg range (example using CALB's CAM72F). But smaller cells equals more parallel connections, which is a (minor) complication.

In addition, my experience and literature review suggests that there's a logarithmic relationship between the power provided and the speed obtained: you get almost as fast at 50% power as at 100% power applied, but with obviously much less power wasted. Thus I don't expect to run the motors at full power for any long duration of time. Case in point: running my Navy 3.0 at 700W drives our dinghy at 7km/h (tiller GPS), while running at 3000W drives us at 8.5km/h. So I obviously drive it at 700W.

All this to say, I hear you about the peak current idea but I'm not sure (1) it's actually a problem for these controller-managed motors and (2) my expected continuous load is nowhere near the peak applied load, along with (3) the cells I'm speccing here suggest ample power available to support the max applied load within the margins of their stated max continuous discharge rate.

Do let me know if you think I'm blind to something. One particular point is perhaps my belief that there's no big in-rush current happening here with these controllers. This is an assumption where my belief differs from your statements, and is material in my conclusions.

[Adelie]

Originally Posted by aybabtme

I didn't look seriously since the Navy 6.0 has regen, something I'm interested in. I'll look more!

I hadn’t considered that. Based on waterline length and SA/D ratio you might average 6.0kt while sailing.
The HydroGen graph indicates 240W at 6kt. Let’s assume half of that to compensate for marketing exaggeration and real world vs test conditions, but since you will be dragging 2 motors around that’s a wash.
So 24hr * 240W = 5,770Whr.
Assume 92% battery efficiency —> 5.36kWhr back to the motor for propulsion.

All this assume you can average 6kt. Let’s say the boat’s loaded for cruising and average speed drops to 5kt. That means 100W output average and 2.4kWhr daily.
That’s still significant energy but you need to be putting the mottoes into the water and pulling them out whenever speed drops to
4kt or you are just slowing the boat down without any electricity to show for it.

[CaptainRivet]

Ohh you are right, the Winston are really heavy, somehow overlooked that.
I have Lishen 272AH AH which are very good for their price. The new gen EVE 280AH have 3C peak now which are a well known good performer, old gen only not so.
C-rates: discharge
Peak rate, stay inside range best below 80%
Cont discharge is best at 30% of C rate of the cell, above 50% of C-rate cell get imbalance quick and need a active balancer, the more cells in parallel the bigger the active balancer must be
Above 50% of C-rate continuous cells heat up, 70% you need cooling.

Maybe use tesla battery modules, they are made for that BUT then you have the fire risk as thy are Li On.

[newhaul]

Originally Posted by aybabtme

The problem with Winston cells and other nylon cases is that they have really poor Wh/kg (less than 100), as opposed to 175+ for aluminum cases. Once way to get higher C ratings with aluminum cases is to use smaller cells and put more in parallel. The Wh/kg suffers again but remains in the >120 Wh/kg range (example using CALB's CAM72F). But smaller cells equals more parallel connections, which is a (minor) complication.

In addition, my experience and literature review suggests that there's a logarithmic relationship between the power provided and the speed obtained: you get almost as fast at 50% power as at 100% power applied, but with obviously much less power wasted. Thus I don't expect to run the motors at full power for any long duration of time. Case in point: running my Navy 3.0 at 700W drives our dinghy at 7km/h (tiller GPS), while running at 3000W drives us at 8.5km/h. So I obviously drive it at 700W.

All this to say, I hear you about the peak current idea but I'm not sure (1) it's actually a problem for these controller-managed motors and (2) my expected continuous load is nowhere near the peak applied load, along with (3) the cells I'm speccing here suggest ample power available to support the max applied load within the margins of their stated max continuous discharge rate.

Do let me know if you think I'm blind to something. One particular point is perhaps my belief that there's no big in-rush current happening here with these controllers. This is an assumption where my belief differs from your statements, and is material in my conclusions.

One idea to try considering what you just posted . A cat has twin engines but 1 engine is sufficient to push at 80% of running both . Doma test run with your navy 3.0 to see what kind of performance you get it will give you a good idea without the expense. If it does good then go for it but if it can't even get out of its own way we'll then you know that to.
But I do understand your desire to go all electric. You also need more solar .

[Dirk01]

In My opinion – wrong aproach.

I’m doing in the same direction and thought about the whole thing since two years (and I’ve still two years left until I’ll have to make a bottom line).
1st: 10kW per hull is more than enough.
2nd: 2 x 300AH@48VDC equals to about 12kWh net, which is a bit more than one hour.
3rd: Install a little genset of about 5-6 KW. That would give you nearly another half hour per engine.
4th: Solar @2kW peak (or more if possible). 1kW underway and 2kW at anchor.
5th: Convert everything to electric (without the BBQ of course :-) ).

Think about the battery bank size. In my opinion too much for a seawind 1000.
I’m designing a retractable propulsion solution, using mil grade underwater engines from FMT Marinetechnik (fmt-kempen.de).

PM me if you are interested in my findings.

Cheers
Dirk
(Germany)

[Adelie]

Originally Posted by newhaul

One idea to try considering what you just posted . A cat has twin engines but 1 engine is sufficient to push at 80% of running both . Doma test run with your navy 3.0 to see what kind of performance you get it will give you a good idea without the expense. If it does good then go for it but if it can't even get out of its own way we'll then you know that to.

But I do understand your desire to go all electric. You also need more solar .

This is a good idea.

Another idea is to install a Navy-6.0 on one side and a gas 9.9 High thrust on the other.

This gives you the the ability to chose gas or battery or both.
For burst of high output, both.
For long range at moderate speed (5kt) or in extended periods of poor solar conditions, gas.
For short to medium range, electric.
For long range at slow speeds (3.0-3.5kt), electric.

[aybabtme]

The 1 electric 1 gas idea is interesting, but a major selling point of electric for me is the reliability when docking. And on a catamaran having two engines is a major component of maneuverability (differential thrust, drive it like a tank).

[Adelie]

You can still get differential thrust in a mixed system. The existing ICE system gave differential thrust.