December 30, 2022

Aren’t All Lithium-Ion Battery Management Systems (BMS) the Same?

This is the fourth in a six-part series on lithium batteries:

  1. What’s Inside a Lithium-Ion battery?
  2. How is a Lithium-Ion battery different than a Lead-Acid battery?
  3. Which is a better Lithium-Ion battery, NMC or LFP?
  4. Aren’t all Battery Management Systems (BMS) the same?
  5. What is the future of lithium batteries?
  6. Beyond Lithium Ion – what’s the future of energy storage and renewable energy generation?

No battery manufacturer will tell you their batteries are unsafe. However, we at Green Yachts believe less than 1% of lithium batteries are safe enough to put on a marine vessel. The difference between safe and unsafe batteries is not the chemistry as our last blog discussed (link), but due to the wide differences in how the BMS (Battery Management System) functions.

We experienced a thermal runaway event on a sailboat with a LiPO4 lithium battery that provided power to a bowthruster because the BMS did not properly regulate battery charging (fortunately we were at the dock). And yet that battery complies with all these safety standards:

  • 2006/66/EC on environmental EU compliance
  • 2004/108/EC on electromagnetic compatibility
  • IEC 62133, safety requirements for portable sealed secondary cells
  • IEC 62619, safety requirements for secondary lithium cells and batteries
  • 3, procedures, test methods and criteria relating to class 9 lithium-ion batteries
  • IEC 62281, safety of primary and secondary lithium cells and batteries during transport

Battery Safety Standards such as ASTM F3353-19, American Bureau of Shipping Guide for Use of Lithium Batteries in the Marine, or DNV Guidelines for Large Maritime Battery Systems and Offshore Industries are NOT effective and none of the safety provisions in place stopped incidents like this.

If the regulatory agencies around the world don’t have adequate safety guidelines for lithium batteries, what can a vessel operator do to ensure the safety of their vessel?

Click here to read more…

November 17, 2022

Which is a better Lithium-Ion battery, NMC or LFP?

The most common question we get at Green Yachts – which is a better lithium battery, NMC or LFP?

And the answer is……. Both!  They each have their advantages and disadvantages, but despite the ferocious and sometimes uninformed arguments one can find online, neither is better than the other.

Unfortunately, if you were looking for a decisive, expert advise to quash all the internet and blogger (czzzzzz)  debates about which is better, NMC (Nickle Manganese Cobalt, chemical equation: LiMn2O4) or (Lithium Iron Phosphate – chemical equation: LiFEPO4), you’re not going to get it here. It’s not that we are afraid of waging into a debate and offering an opinion. It’s that we believe everyone making an argument about NMC vs LFP is missing the point.

This is the third in a six-part series on lithium batteries:

  1. What’s Inside a Lithium-Ion battery?
  2. How is a Lithium-Ion battery different than a Lead-Acid battery?
  3. Which is a better Lithium-Ion battery, NMC or LFP?
  4. Aren’t all Battery Management Systems (BMS) the same?
  5. What is the future of lithium batteries?
  6. Beyond Lithium Ion – what’s the future of energy storage and renewable energy generation?

This blog explains the differences between NMC and LFP, the use cases for each and some examples of good NMC and LFP battery manufacturers.

Click to read more….

November 10, 2022

How Is A Lithium-Ion Battery Different Than A Lead-Acid Battery?

This is the second in a six-part series on lithium batteries:

  1. What’s Inside a Lithium-Ion battery? Read our earlier post here.
  2. How is a Lithium-Ion battery different than a Lead-Acid battery?
  3. Which is a better Lithium-Ion battery, NMC or LFP?
  4. Aren’t all Battery Management Systems (BMS) the same?
  5. What is the future of lithium batteries?
  6. Beyond Lithium Ion – what’s the future of energy storage and renewable energy generation?

First, although AGM (Absorbed Glass Mat) and flooded batteries are both considered lead-acid batteries, they are different. An AGM battery has a thin glass-mat separator that absorbs the electrolyte. Flooded batteries need to be topped off with water every six months to prevent sulfuric concentration increases in the electrolyte. AGM batteries provide better cycling performance and faster charging performance. AGM batteries demonstrate minimal gassing and acid leakage, last longer and are resistant to freezing.

For the purposes of this blog post, we are going to compare AGM batteries to an LFP Lithium-Ion available at West Marine that is needed to store one kWh (1080 watts or 90 Ah at 12V) of energy.

Type

VoltageAhDepth of DischargeNumberPrice (Total)Weight (lbs)Avg Life (yrs)10 Year Life Cost
AGM12V9050%2$799.981243.33$2,399.94
Lithium12V10090%1$1,159.9929.810$1,159

 

Source: https://www.westmarine.com/relion-group-31-rb100-hp-lithium-deep-cycle-battery-12v-100ah-20482964.html

Source: https://www.westmarine.com/mastervolt-agm-12-90-group-31-sealed-marine-battery-10976389.html

It is recommended that one not discharge lead-acid batteries below 50% and lithium-ion batteries more than 90% discharged.  Given these depth of discharge percentages, one needs two AGM batteries and one lithium-ion battery. Initially, a lithium battery costs more, $1,160 vs $800. But, over ten years, AGM batteries have to be replaced twice bringing the total cost to more than double that of a lithium battery. Additionally, the weight of the AGM batteries is four times higher.

It seems like lithium is the obvious answer as it is cheaper over the long run and weighs less. Why then are so many boaters still using lead-acid batteries?

There are two reasons. First, lithium batteries are perceived as being unsafe. Second, many boaters have experienced problems swapping out a lead-acid battery for a lithium battery on their boat. In regards to the first problem, please see the fourth blog in this series about the BMS (Battery Management System). The short answer is that a BMS specifically designed for a lithium battery provides very strong levels of safety whereas a legacy lead-acid BMS adapted to lithium, which the majority of battery manufacturers do, creates a safety risk.

To answer the second question, it is important to never use a battery charger designed for a lead-acid battery with a lithium battery. This is important. And yet, we see companies that make batteries and chargers saying it is “recommended to use a lithium battery charger to charge lithium batteries, but not required.”  NO!!!   Having been on a boat in which a lead-acid battery charge regulator caused a thermal runaway event in a lithium battery, we strongly disagree.

The challenge lies in the discharge profile of a lead-acid vs lithium-ion battery. Take a look at the graph below. The lead-acid has a fairly constant relationship between the voltage level and SOC (state of charge). Therefore, the charger can read the voltage level of the battery and slow and then end charging based on voltage readings. A lead-acid charger has a 3-stage charge algorithm. For initial charging below 80% SOC or ~12.6V, the charger is in bulk state normally charging battery at full current. At 80% SOC, the charger will transition to the absorption stage until reaching 100% SOC and goes into a float stage.

As the voltage reading in a lead-acid battery get higher, the charger knows to slow down the charge. If this fails, the battery will heat up and destroy the battery, but won’t become hot enough to damage anything nearby nor create significant offgassing.

However, a lithium-ion battery has a sinusoidal discharge profile with a relatively flat voltage profile for most of the discharge spectrum. A lithium battery holds a higher voltage charge per cell, cannot handle voltage imbalances across cells, and if is overcharged has much more significant consequences than a lead-acid battery. Therefore, a lithium-ion battery needs a charger specific to a lithium battery. Not doing so has resulted in lost generators, lost engines, and lost bow thrusters with many a boater saying lithium is dangerous when what they should have said is that the dangerous situation was created by using a lead-acid battery charger to charge a lithium battery because they did not know that battery chargers are not battery chargers, that they are different for lead-acid and lithium-ion.

And now you know. Unfortunately, the information in this blog post is not widely available on the internet, but it would have saved many a boater if they could have read this. Now you know and I doubt anyone who has read this will ever use a lithium battery without making sure they have a battery charger specifically designed for lithium-ion batteries.  And please take a second to send a link to this blog to your boating friends. Even if they aren’t ready to go electric, this post is useful for all boaters who are considering putting a lithium battery on their boat whether it be as the starter battery of a diesel engine or the battery bank of an electric boat.

November 03, 2022

What’s Inside a Lithium-Ion Battery?

Lithium batteries are the best form of energy storage available today for use on electric boats.

Most boaters who are interested in electric boats don’t know enough about lithium-ion batteries. But we can understand why as it is a confusing subject and making it harder is that there is a lot of misinformation said by everyone from ‘experts’ to bloggers.  Our hope is that this series of blogs about lithium batteries helps boaters have a better understanding of them.

This is the first in a six-part series on lithium batteries:

  1. What’s Inside a Lithium-Ion battery?
  2. How is a Lithium-Ion battery different than a Lead-Acid battery?
  3. Which is a better Lithium-Ion battery, NMC or LFP?
  4. Aren’t all Battery Management Systems (BMS) the same?
  5. What is the future of lithium batteries?
  6. Beyond Lithium Ion – what’s the future of energy storage and renewable energy generation?

Lithium Ion Battery Explained: First, let’s take a look at what’s in a lithium ion battery. A lithium-ion battery is comprised of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative) attached to terminals that extrude from the battery. The following components are common to both NMC and LFP batteries:

  • Electrolyte – a lithium salt, most commonly LiPF6
  • Separator – a polymer, most commonly, polyolefin, which is produced from olefin by polymerizing olefin ethylene
  • Anode –What is commonly called the negative side of the battery (more on that in just a bit). It is typically made of graphite in lithium-ion batteries.
  • Current collectors – Conduct electrons from inside the battery from electrochemical processes to the external terminal. Copper Foil is commonly used for the negative current collector and aluminum for the positive current collector
  • Terminals – the external attachment point of a battery that is labeled positive and negative. For marine lithium-ion batteries, these are available in lead, epoxy coated lead, and brass with plated fasteners
  • Cathode – there is a reason we put this apart from the Anode in the list. All the components above are the same for different chemistry types of lithium-Ion batteries. It is the cathode material that differs and gives them their respective names. The NMC cathode is made out of Nickle, Manganese and Cobalt (chemical equation: LiMn2O4). The LFP cathode, is made of Lithium Iron Phosphate and Oxygen (chemical equation: LiFePO4)

A lithium-ion battery functions based on creating stored energy potential through charging and releasing that energy potential when discharging. To achieve this, the electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector.  The electrical current then flows from the current collector through a device being powered (cell phone, electric motor, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery in order to create the electron gradient in the circuit. When the battery is charged, the flow of electrical current is reversed and it is the movement of lithium ions back over to the anode from the cathode that creates the energy potential of stored electrons.

We realize that’s a lot of detailed information and probably our most boring blog post in our company’s history. But, it sets the state for the next blog posts in this series on Lithium-Ion batteries. Take a look back at the image and the terms and then continue on to the next blog in the series that looks at the differences between Lithium-Ion and Lead-Acid batteries.

 

October 11, 2022

All Hybrids are NOT Equal

There is a lot of variation of what is called a hybrid propulsion system in the marine industry. This blog looks at the different system that various folks call a hybrid. And, we’ll share our opinion on Green Yachts on what the definition of hybrid SHOULD be in the marine industry.

ICE – To be comprehensive, we’ll start with the ICE, internal combustion engine, usually a diesel engine, it’s what most recreational boaters and commercial vessel operators are familiar with. We will refer to the ICE a fair bit in this blog.  Click to read more…

November 08, 2021

Kika’s Reminder

For the past few years, Sailing Uma, Green Yachts, Oceanvolt, Electric Yachts and others have been showing boaters that electric propulsion technology is real, it is here and it is better.

In a recent Tedx talk, Kika from Sailing Uma reminded us why. This blog is a reflection of listening to Kika’s Tedx talk, which you can skip to 3:41:34 on this recording and listen to yourself.

Kika’s spot-on comparison of climate change to credit cards reminds us all of what is at stake. Credit cards allow one to buy something now and pay later. Using oil is similar and the irony of a plastic credit card being made of oil is not lost upon us.

Click to read more…

October 06, 2021

Trouble at Sea Survived

Green Yachts is known for selling boats with electric propulsion. But what most sailors may not know is Green Yachts traveled the planet researching well-built performance sailboats that perform well to put Oceanvolt electric propulsion systems on because we believe sailboats should be electric, sail well and be safe.

The importance of our focus on safety got put to the test on September 21, 2021.

An experienced delivery captain and good sailor was delivering the Salona S46 from Newport to Annapolis for the Annapolis Sailboat Show. At 2318 hours, just over 50 miles into the trip, the rudder pulled out. At the end of this blog, we’ll explain why this happened, but first let’s get back to the rudderless Salona S46 17nm offshore from Long Island.

Click to read more…

September 20, 2021

Green Yachts at Newport International Boat Show

Newport International Boat Show was exhilarating for the Green Yachts team. Not only was the Salona S46 selected out of the largest number of entrants ever as the best green boat of the show, but the interest and enthusiasm in the Salona S46 and electric sailing was amazing! Hundreds of boaters who visited Green Yachts were excited and enthralled by the Salona S46 and electric propulsion.

We would estimate that 1/3rd of our visitors had seen the Sailing Uma video about the Salona S46 and came to the Newport Boat Show to see the Salona S46. 1/3rd of our visitors were open to electric propulsion, but didn’t know much about it.  1/3rd of our visitors had never heard about boats being electric and it was all new to them.

Click to read more….

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