Tesla Batteries in Marine Use

[Cajunwolf]

First, some necessary exposition, the background information needed to understand the full scope of my question correctly. I've previously posted significantly more information in great detail in the marine forum section, but so far no one seems to have an answer. Since a marine environment can be a considered a harsh environment I thought I might try here too, and if you want to read the full description of what I'm doing here's the link to that thread.

http://www.diysolarforum.com/index.php?threads/eb-questions.135/#post-1285

The short version. I'm building a diesel-electric sailboat, a hybrid of a sort. The main auxiliary drive will be a 20kw 48VDC motor mounted in the back of the diesel, and above the shaft driving it via a cog belt. The Perkins 4-108 diesel now becomes the secondary auxiliary drive, or emergency drive and AC generator in addition to its alternator. I want to use something like Battleborn 12v 100ah LiFePO4 batteries, 12 of them in three banks of four with a total output of 300ah at 48VDC. This bank will be the primary storage bank what runs the electric auxiliary drive and ships power via inverter when not under sail. When under sail, and with the push of a button, the motor goes into regeneration mode utilizing the previously wasted drag of the spinning propeller because of the forward motion of the boat through the water supplied by the wind alone to generate free power to charge the batteries assisting the solar panels and wind turbine. Now your sailing and living on free energy being stored into your battery bank while sailing the seven seas seeking adventure.

I recently watched the video from back in July of 2018 on the Tesla comparison and was amazed; It was cheaper and better than Battleborn which was going to be $12,000 with shipping, damn! My question is, and since this is a harsh environment thread, and the saltwater and the damp environment of the seas is a harsh environment, will the Tesla battery work? Inquiring minds are eager to know.

 

[svetz]

... utilizing the previously wasted drag of the spinning propeller...

I'm fairly sure you're aware... Once the propeller is powering the regenerative system it will cause more drag just as lowering a hydrogenerator causes drag. It'll work, but there will be drag.

 

[Getyourbone]

This doesn’t relate to the harsh environment does relate to Tesla modules...

I asked this over yonder as well but would like your take on it. This all revolves around how modules match up with inverter specs so may not be applicable for dedicated propulsion banks.

Does a 12s for “48v” or 6s for 24v work or do you really need 14s / 7s configuration to have it make sense in similar system?...it has always be my take that 14s is the config that makes most of the repurposed modules work(hence why Nissan works so well in a 48v but not in a 7s) ...any deviation from that and one really needs to reevaluate as the value of the concept “degrades” rapidly..

Love to hear your opinion...

 

[PHoganDive]

The short version. I'm building a diesel-electric sailboat, a hybrid of a sort. The main auxiliary drive will be a 20kw 48VDC motor mounted in the back of the diesel, and above the shaft driving it via a cog belt. The Perkins 4-108 diesel now becomes the secondary auxiliary drive, or emergency drive and AC generator in addition to its alternator. I want to use something like Battleborn 12v 100ah LiFePO4 batteries, 12 of them in three banks of four with a total output of 300ah at 48VDC.

300amp/hours @ 48 volts gives you 14,400 watt/hours of total battery power. If you use 80% discharge, that gives you 11,520 watt/hours of useable power from a full charge. A 20Kw motor will use 20,000 watt/hours of power each hour of use at full power. That gives you 34.5 minutes of full power use of the motor from a full battery charge. It also doesn't include any power allotted for other electric use on the boat, which would further shorten that runtime. I don't know that I'd want to make that my primary mode of propulsion.

 

[BoloMKXXVIII]

How many cycles can the Tesla battery handle compared to the BattleBorn batteries? How difficult is it to fit the Tesla packs to your system voltage wise? Tesla batteries are not as forgiving as LiFePo4 batteries. I personally would not want to be on a boat in the middle of the ocean when the battery becomes a thermal runaway.

 

[Cajunwolf]

I'm fairly sure you're aware... Once the propeller is powering the regenerative system it will cause more drag just as lowering a hydrogenerator causes drag. It'll work, but there will be drag.

I'm fairly sure you're aware... Once the propeller is powering the regenerative system it will cause more drag just as lowering a hydrogenerator causes drag. It'll work, but there will be drag.

Excellent point requiring an execellent answer.

Yes, I'm very aware of that but what you might be missing is that you're getting a return in power that far outweighs the additional drag when properly utilized. I've discussed this feature with Electric Yacht and Elco so far, and they have designed the motors to be as efficient in this mode as possible if you use the lightweight propellers intended for this purpose. If you've ever tried slowing or backing up a boat under power with a standard propeller you quickly learn it's not as good as when going forward. A conventional propeller is designed to give thrust, well actually "screw" itself into one direction efficiently. You already have built-in drag doing nothing from the propeller as is, even a feathering one. The amount of additional drag from regeneration is a product of how much power you're generating at a given speed through the water, the efficiency of the propeller for this purpose, and any build-in friction from the cutlass bearing, the rotational mass of the shaft, and frictional resistance of spinning the gearbox in neutral. It takes 1.7 HP to produce 1 kW under Ideal conditions; nothing is free.

To properly use this feature one must understand the mechanics of sailing, and I don't know, svetz, if your a sailor or not, but for the benefit of those who are not I'll add a bit of the technical background so they can follow what I'm trying to explain. You wouldn't use the regeneration mode in light wind because you will most likely have the mainsail fully deployed along with your 150% foresail to catch any breath mother nature blows your way to get enough headway to maintain heading. The last thing you need in this situation is more drag. Even in an 8 to 12-knot wind, depending on the boat and rig, your still under hull speed. Now, when you start getting above 15 to 20-knot winds and are fixing to have to take a reef in the mainsail because it's beginning to overpower the boat with the jib deployed at 80% that you are ready for regeneration. A reef reduces the size of the sail. You have more sail than you need for the wind available to drive the boat at hull speed being wasted in the excess heel. You're getting more hull drag with the additional heel. As the additional drag from regeneration slows the boat, add more sail to compensate until you find the perfect balance. This is why I love to sail; it requires skill and thought. With a powerboat, you basically point and hit the throttle.

 

[Cajunwolf]

This doesn’t relate to the harsh environment does relate to Tesla modules...

I asked this over yonder as well but would like your take on it. This all revolves around how modules match up with inverter specs so may not be applicable for dedicated propulsion banks.

Does a 12s for “48v” or 6s for 24v work or do you really need 14s / 7s configuration to have it make sense in similar system?...it has always be my take that 14s is the config that makes most of the repurposed modules work(hence why Nissan works so well in a 48v but not in a 7s) ...any deviation from that and one really needs to reevaluate as the value of the concept “degrades” rapidly..

Love to hear your opinion...

Now that's an interesting question, and could even be its own thread. What we did on John's boat, we're still getting ready for mine, was have 12 LiFePO4 100ah batteries wired in a 4s3p series and parallel configuration to produce 48VDC at 300ah. That is 3 banks of 4 batteries each bank (pack) wired in series to up the voltage to 48DC and then these three banks (packs) in parallel to up the current to 300ah. Correct me if I'm wrong. Now, I'm sure you could use different numbers of cells packaged in different quantities in series to achieve the same output voltages required by the various motor manufacturers of marine electric motors, but these will be in 12v, 24v, 48v and 72v for your big boats. If you take 14 3.2v cells in series, you get 44.8v, but 15 gets you 48v. I think the voltage of the motors available on the market dictates your series numbers more than anything else if I understand your question correctly. More detail on this can be found looking into the RC airplane genre. Those boys and girls get deep into this topic when replacing their old, inefficient, and heavy NiCad or NiMH batteries with Lithium batteries. Now, they are working in mah, not ah, but it's the same thing on a smaller scale. The math is the same, 1000mah = 1 ah.

 

[Cajunwolf]

300amp/hours @ 48 volts gives you 14,400 watt/hours of total battery power. If you use 80% discharge, that gives you 11,520 watt/hours of useable power from a full charge. A 20Kw motor will use 20,000 watt/hours of power each hour of use at full power. That gives you 34.5 minutes of full power use of the motor from a full battery charge. It also doesn't include any power allotted for other electric use on the boat, which would further shorten that runtime. I don't know that I'd want to make that my primary mode of propulsion.

True, but run your car with your foot to the floor and your gas mileage goes to shit in a handbasket real fast too; point-counterpoint. First, let's review what I said. The 20kw motor, at half throttle, will more than drive my boat at hull speed and in good sun my solar will keep up of even feed the batteries. The same motor in John's boat will do hull speed at about one-third throttle. At one-third throttle, he's usually making more in solar than he's using.
On the other hand, a 10kw on the same boat will push it at hull speed at full throttle, but it would be giving all it has to do so while eating up current like a hog at the trough. A 10 kW would strain to push my boat, which is longer with more displacement, and at half throttle still be using more than the solar can replace. The 20kw is a bit of overkill for my boat, a 15kw will work, but their usually a 10kw beefed up to where it has to be water-cooled, and that's but another thing to go wrong besides pushing a motor to its limit to save a buck, to me that's a motor that will fail sooner or later. Besides, John got a sweet deal on the two 20kw motors, so I got mine for a ridiculously low price. You also need to realize the auxiliary diesel or electric motor is just that, auxiliary power. A sailboats main propulsion is the sails. You use the auxiliary to get in and out of the marina and out to sea to where you can deploy your sails and turn off the auxiliary. Once the wind reaches specific velocities for a given boat with a given sail plan, you start to overpower your boat, and you have to reduce sail or reef as is the term. This is the time to put the electric motor in regeneration mode and reef-trim sails appropriately. Now my friend, your sailing the seven seas generating all of your energy needs from solar, wind, and regeneration. Is it perfect, no, but neither is anything else.

 

[Getyourbone]

Now that's an interesting question, and could even be its own thread...

I realize I’m looking for a simple slam dunk all size fits one answer and it really comes down to the specific components and situation is being used in.

I’m also traditionally used to thinking ~3.7 which I believe most re-purposed EV modules are but I’m sure there’s some 3.2’rs out there and then that begins to complicate the simple answer of determining what configuration makes sense.

And there’s no set answer on voltage cut off‘s… Everybody has their own opinion on it! With my Chevy volt modules I had no problem with 2.9 to 3.0 on the low and 4.2 on the high but I was looking more for capacity than longevity.

I can say that you shouldn’t charge a Chevy volt module to 5.2v and run it down to 2.3v... It appeared to lose about 15% of its capacity after that. A “typo“ on my part setting up the cut off voltage on one of my modules.

 

[Cajunwolf]

How many cycles can the Tesla battery handle compared to the BattleBorn batteries? How difficult is it to fit the Tesla packs to your system voltage wise? Tesla batteries are not as forgiving as LiFePo4 batteries. I personally would not want to be on a boat in the middle of the ocean when the battery becomes a thermal runaway.

Well, "How difficult is it to fit the Tesla packs to your system voltage wise?" is one of my questions to start with, but as far as cycle life the Tesla kick Battleborn in the butt walking down the road, and one of the reasons for my interest. If you would watch the video I linked to in my original post here, most of your questions would be answered. Here's a taste.

Battleborn Lithium iron phosphate: (Most expensive battery)
$3600 for 4.8 kWh for 3000-5000 cycles which comes to $150-$250 per kWh they weigh (4) 116 pounds.

Tesla Model S Battery:
$1300 for 5.3 kWh for 5k cycles for $49 per kWh for 5k cycles. They weigh 55 pounds

Here is the link, watch the video, you will enjoy and learn from it.
Off-grid Solar Battery Price Comparison: Tesla vs. FLA vs. SLA vs. LiFePO4 vs. Tesla

 

[Cajunwolf]

I realize I’m looking for a simple slam dunk all size fits one answer and it really comes down to the specific components and situation is being used in.

I’m also traditionally used to thinking ~3.7 which I believe most re-purposed EV modules are but I’m sure there’s some 3.2’rs out there and then that begins to complicate the simple answer of determining what configuration makes sense.

And there’s no set answer on voltage cut off‘s… Everybody has their own opinion on it! With my Chevy volt modules I had no problem with 2.9 to 3.0 on the low and 4.2 on the high but I was looking more for capacity than longevity.

I can say that you shouldn’t charge a Chevy volt module to 5.2v and run it down to 2.3v... It appeared to lose about 15% of its capacity after that. A “typo“ on my part setting up the cut off voltage on one of my modules.

I see what you're getting at now, and my 3.7 volts might have been wrong, I could have been 3.2, I'll have to go back and look. There seem to be different voltages for cells from manufacturer to manufacturer though. The end game though is to get the right voltage at the right current to handle the required load or discharge rate/C rating for your individual application, right? I'm not that up on electric cars yet, I don't have one, but very interested; I'd give a testicle or two, I no longer have use for them, for a P85D. I have two Jeeps, who are my spoiled babies: A 94 Cherokee two-door with a stroker 4.0 to 4,7, and a 2k Grand Cherokee with SelectTrac 4x4 and the 4.0.

Edit, oh dear, now you've sent me down another rabbit hole. I'm suffering from, no wrong, I enjoy my adult ADD, and interesting stuff like this can send me into a hyperfocus state of research that's hard to crawl back out of.

 

[Cajunwolf]

I realize I’m looking for a simple slam dunk all size fits one answer and it really comes down to the specific components and situation is being used in.

I’m also traditionally used to thinking ~3.7 which I believe most re-purposed EV modules are but I’m sure there’s some 3.2’rs out there and then that begins to complicate the simple answer of determining what configuration makes sense.

And there’s no set answer on voltage cut off‘s… Everybody has their own opinion on it! With my Chevy volt modules I had no problem with 2.9 to 3.0 on the low and 4.2 on the high but I was looking more for capacity than longevity.

I can say that you shouldn’t charge a Chevy volt module to 5.2v and run it down to 2.3v... It appeared to lose about 15% of its capacity after that. A “typo“ on my part setting up the cut off voltage on one of my modules.

Here's something found with interesting facts on cutoff voltages you might find interesting. It's from an RC Airplane site that a friend of mine, who is really into this, sent me a link to just now. And yes, I know it's about model airplanes, but it's the battery information that's relevant and might be applicable to your research. One never knows until, right?

3. Voltage and Cell Count:
LiPolys act differently than NiCad or NiMH batteries do when charging and discharging. Lithium batteries are fully charged when each cell has a voltage of 4.2 volts. They are fully discharged when each cell has a voltage of 3.0 volts. It is important not to exceed both the high voltage of 4.2 volts and the low voltage of 3.0 volts. Exceeding these limits can harm the battery.
The way to ensure that you do not go below 3.0 volts while flying is to set the low voltage cutoff (LVC) of your electronic speed control (ESC). It important to use a programmable ESC since the correct voltage cutoff is critical to the life of your batteries. Use the ESC's programming mode to set the LVC to 3.0 volts per cell with a hard cutoff, or 3.3 volts per cell with a soft cutoff. If your ESC does not have hard or soft cutoff, use 3.0 volts per cell. You will know when flying that it is time to land when you experience a sudden drop in power caused by the LVC.
If your ESC has an automatic lithium mode. Use it, it will correctly sense the number of cells and set the auto cutoff appropriately.
If you have previously been flying with NiCad or NiMH batteries, switching over to lithium polymer will result in a different number of cells being used. If you had 6 to 7 round cells then 2 lithium polymer cells will correctly duplicate the voltage of those cells. If you had 10-11 cells then 3 lithium polymer cells would be right for you. There are a lot of 8 cell flyer's out there that are stuck between 2 and 3 cells. In my experience the best option is to determine how many watts you were using before and duplicate that with your LiPos, Motor, and Prop. For example. If you were running 8 cells (9.6volts) at 10 amps on a speed 400 airplane, then you have 9.6 x10, 96 watts. So if you went with 2 lithium polymer cells (7.2 volts nominal) then you'd need to change your prop such that you used 13 amps. If you went to 3 LiPoly's (10.8 volts nominal) then you'd need to reduce the amperage to 8.9 amps. These estimates are approximate, and some experimentation is required for best results but conserving Watts is a good way to start.

Here's the link to the site if interested.

RCGroups: Remote Control, Radio Control Planes, Drones, Cars and Boats

RC Groups - the most active Radio Control model community: electric and fuel rc airplanes,rc helis,rc boats and rc cars. Features discussion forums, blogs, videos and classifieds.

www.rcgroups.com

 

[captainrivet]

Hi Cajunwolf,

did you go with the tesla modules?
Your problem for propulsion use is that over 1C discharge rate the Tesla modules need active cooling and cell balancing.
Kitting my bluewater 42ft sailboat with 12t displayment for a world cruise and updated already on power generation and looking into Tesla modules as house bank. Will stay with the diesel as this boat has not enough room for EV and the heavy displacement is contra productive too.
I have a permanent magnet shaft generator approx 1000W, build for a huge wind generator (low RPM) to generate my power when under way, which generates 15A/24V at 5kn sailing (reduces speed by 0.2kn) and nearly 35A/24V at 7kn (reduces speed by 0.3-0.5kn depending on wind speed).
At anker approx 1400W solar + wind gen charge the batteries.
Curious which reduction you see with a 20kw motor in regen mode. Ok you have a 1++ Perkins, means your boat is 50ft+ so more room and hull speed.

To Tesla modules marine use:
I want to use 2 of them as my house bank and never exceed 0.5C with 2 of them as a 5000W victron inverter is the biggest load.
What I figured so far:
To make them ready for marine environment you need to put the modules in an water tight box together with a BMS with low temp cutoff, so the agressive salt air is not penetrating into the battery.
best is each module seperatly with its own BMS in a box. I will mount both modules easy accessible in the Pilot house in one of the lockers.
That "tesla" box is then wrapped in a Fire-Resistent blanket for welding with two holding points. Due to a fire brigade captain this gives me approx 3 min time to toss it overboard (just cut the two cables and rip it out) when a thermal runaway tesla module catches fire. That 3 min it will need to burn through that blanket. Just as last borderline/plan D is everything else goes wrong.
A 200A fuse at each module to ensure you don't run it above 1C and get thermal problems.

Cheers
Chris aka CaptainRivet