Upgrading to Lithium Batteries, Battle Born vs. Renogy

Electric motors are great, they have few moving parts to maintain or fail, and they can run effortlessly forever…or until the power runs out!

The heart of an electric setup is not the motor, but actually the batteries. These boxes of energy house the electricity that the electric motor needs to propel your yacht. The more power you can carry in your batteries, the more power you can use with your motor.

When we did our conversion to electric propulsion back in 2014, we chose AGM batteries, simply because they were the most cost effective at the time. They provided us with a lot of power in a large space and required little maintenance.

Fast forward to the present, and our AGMs are old and outdated. Better battery technology has come down in price and the “better batteries” of 2014 are no longer prohibitively expensive.

At the moment, there are two companies that seem to be reigning as king over the “direct replacement” lithium batteries. These companies sell lithium batteries that are the same size as the more popular lead acid and AGM batteries, but at a fraction of the weight.

The first company is Battle Born

Source: https://amzn.to/2TfdpoP

These batteries are the same size as a Group 27, but contain the power of a Group 31. Moreover, they only weigh 31 pounds! Our current AGMs are Group 31 and weigh 67 pounds each, meaning these batteries weigh less than half of what our batteries weigh.

The next battery company that we will look at is Renogy.

Source: https://amzn.to/2TgtLO3

Renogy Batteries are also direct replacements for lead acid and AGM batteries, but these are even lighter in weight! Their 100ah battery weighs in at only 28 pounds!

Now that we know the major players in “direct replacement” batteries, lets look at why they are more sought after than a regular lithium battery. The first thing is familiarity. For our entire lives, batteries have been this rectangular box that sits in our boat or car and has two terminals on it. Lithium batteries can come in a huge variety of shapes and sizes, which sadly leads to people wondering “which side is the top?” Direct replacement batteries do away with this metal block to lithium by packing it into a familiar shape and size.

The second advantage comes with the voltage. Lithium batteries are made up of cells, and the entire battery pack can have any voltage value you want! This once again becomes a problem since people are used to a battery being 12 volt. In our case where we run a 48v motor, we simply have four 12 volt batteries hooked up in series to create the 48 volts we need to operate. Instead of Battle Born and Renogy offering their batteries in “custom voltages” they packaged them as 12 volt batteries.

You might be wondering, why switch to lithium at all if they take up practically the same space and give you the same amount of power? There are two answers to this question. The first is weight, and the second is usable power.

Lithium batteries weigh less than half of a regular battery. The best way to visualize this is to look at the Amps per Pound at 12 volts.

AGM batteries hold 105 amp hours and weigh 67 pounds
This is to say 1.567 amps per pound

If you want to have a 800 amp hour battery bank, it will weigh (800/1.567) 510.5 pounds.

Battle Born batteries hold 100 amps and weigh 31 pounds.
This is to say 3.225 amps per pound

That same 800 amp hour battery bank would now only weigh (800/3.225) 248 pounds

Renogy batteries, being the lightest, hold 100 amps and weigh 28 pounds
This is to say 3.571 amps per pound

The same 800 amp hour battery bank would weigh just a smidge less at (800/3.571) 224.0 pounds.

So, you might be wondering now, aside from weighing half as much, why bother with expensive batteries? They take up about the same space, and if the boat isn’t overloaded, why bother? Well the truth is, all batteries hold power, but they don’t all let go of the power the same.

Think of batteries as a jar of jelly. They all hold the same amount of jelly, but they differ in how the jar opens.
Lead Acid and AGM batteries have a small opening at the top of the jar, so you can get your spoon straight in, but you can’t get to the sides of the jar. When you have gotten all the jelly you can reach, you notice that there is still a lot of jelly left on the sides, but you just can’t seem to get to it!
Lithium batteries have a much larger opening at the top, so you can get to the sides of the jar much more easily. This lets you get to more jelly and leave the jar more empty when you are finished.

Lead Acid and AGMs can safely discharge down to 40%, while Lithium batteries can safely discharge down to 10%. This means that in a 100 amp hour battery, an AGM can give up 60 amps while a Lithium can give up 90 amps.

So, back to our hypothetical 800 amp hour battery bank, made up of eight 12 volt batteries. The batteries sitting in their box hold 800 amps hours. If these batteries are AGM or Lead acid, they could only give out about 480 amp hours. This identical battery bank made of Lithium batteries could now give out 720 amp hours. That’s an additional 50%, from half the weight!

So, bringing the battery bank and electric motor out of the hypothetical realm and into reality:

Our electric motor draws from our battery bank composed of eight AGM Group 31 batteries, each with 105 amp hours. We can motor at a slow speed of 2 knots for about 20 hours, giving us a range of 40 miles. With a Lithium bank, we would be able to motor 60 miles! That might not sound like much, but that is a lot of miles from the same size of battery bank. Yes, more batteries would give more miles, but space is an issue on a sailboat.

The switch to Lithium will be coming, and we will then be able to compare lithium batteries to AGM in terms of usability and performance.

Electric Motor Regeneration

Electric motors have one key advantage over a diesel when it comes to blue water cruising: regeneration.

It is common practice to run your diesel motor once or twice a day to "charge up the batteries" while crossing an ocean. The winds are consistent offshore, so you don't need the motor for propulsion, but you do need the motor for power. 

Imagine being out on a gorgeous day of sailing and then have to crank on your motor for a few hours. All the peace and tranquility is ruined as your diesel clanks and clunks away, shaking the boat and your eardrums for hours!​

Electric motors can not be "run" to make power. Running them actually consumes power! The only way an electric motor will produce power is if you are sailing fast enough that the water passing over the propeller actually causes the propeller to spin. This in turn spins the electric motor and causes the motor to act more as a generator, producing power that is then fed back into your battery bank.​

There is no need to tarnish your perfect sailing day with a noisy diesel motor. The propeller is spinning all the time and producing power that keeps all your batteries topped off! In this particular moment, we were sailing along at around 7 to 8 knots and the motor was constantly producing between 6.0 amps and 6.9 amps. That might not sound like much until you recognize the fact that this in in 48V. When this is stepped down to 12V, the amps are multiplied by a factor of 4. This means that 6.0 amps @ 48V becomes 24 amps @ 12V and 6.9 amps @ 48V becomes 27.6 amps @ 12V!​

Imagine having a quiet source of power that cranks out 24 amps continuously, day and night! Needless to say, we had no issues with power demands while we crossed the Atlantic in the summer of 2018, all without the need for a noisy diesel motor.​

The Mysterious Case of the Electric Motor Controller Malfunction

Our electric motor had functioned flawlessly for years, until we added a new step in the system: the generator. While the manufacturer states that running the motor while charging is fine, I think it might have been the culprit!

See, the manufacturer claims that it is acceptable to do, but they have a nice and fully functioning charger. On Wisdom, we have a half dead hand-me-down that we got for free, and I suspect that it is the problem.

It all started when we were in Hatteras and decided that the North Atlantic during winter gales is not a place we wish to sail. We changed our plan from crossing the Atlantic in October to "Sail to the Bahamas and cross the ocean at the correct time of year." We bought a Honda 2000 generator to allow us the ability to charge the batteries while away from a pier. Before we left, I performed a test (which I feel was the first nail in the coffin for the charge controller). Wisdom was plugged into shore power and the charger was running. I hypothesized that if we ran the motor at 14 amps, we would be able to run indefinitely since our charger puts out 15 amps. We carried out the test for about 14 hours straight. The charger kept pace with the motor and when the test was concluded, everything was shut down to reveal that yes, the batteries were still full charge and the motor ran entirely off of the charger. Success!

Then we motor sailed away from Hatteras and into Oriental, NC. We were there for a week and decided it was time to move on, but the motor had a different plan. It was dead and completely unresponsive.

I called the manufacturer and spoke directly with the builder of the motors who walked me through the diagnostics which led to the discovery of the dead controller. The manufacturer then sent out a replacement controller and off we went!

We continued motoring down the state of North Carolina for a few months (we are slow) until we were nearing the NC/SC line when the motor began alternating between forward and reverse on its own! We were moving forward, and the shaft was being viciously tossed in alternating directions with the full strength of the motors. We contacted the manufacturer again, and the tests once again concluded that the controller died. They sent us a new one and also sent us a spare one since we had plans of cruising internationally.

I installed the new controller and everything seemed to be operating just fine, but we decided to make a rule after some thought. The motor needs to be off when the charger is on.

Yes, the manufacturer insists that you can charge and motor, but I think our charger may have a fault that is killing the controller over and over. We have replaced the controller twice (and still have the spare in a locker) and have had no problems since we implemented this rule.

Our future plans include a new, properly functioning controller that will grant us the luxury of motoring while charging, but in the mean time, our mysterious issue seems to be resolved.

I am aware that per proper experimental models, I need to reintroduce the charger while motoring and see if it kills our controller. The truth is, the controller is annoying to change and I would rather not have to do that again, so I have yet to properly reintroduce the variable.

If you are considering electric propulsion, or have electric propulsion and are considering adding a generator, I would suggest contacting the manufacturer of your electric motor and buying a new charger per their recommendations.

Electric Motor 4 Year Review

Wisdom was converted from Diesel to Electric in 2014 and it is about time we look at how electric propulsion has been for us.

We started off with the electric motor and no means of charging other than the regenerative feature of the motor. This worked well for daysailing or weekend trips where you never venture very far from a marina that you can plug in to. The little power that was burned up in getting out of the slip and marina was quickly recuperated when the sails filled and the boat started moving through the water with speed. When we approach 5 knots through the water, the force of the water pushing on our dragging propeller will cause it to spin and this will in turn spin your motor. Since the motor is being turned by the propeller, the motor will actually produce electricity and send it back to the batteries!

We then did a month long cruise, planning on generating all of our power needs with this handy feature of the electric motor. That was a mistake! Our fridge consumed so much power that the short and slow daysails we were doing were not able to feed it the amps it consumed!

When we got back from that trip, we quickly added solar panels to Wisdom, giving us the ability to produce electricity while at anchor. This was a major game changer, and with only 100W of panels, we were able to become free from the dock!

We now had the ability to motor a short distance, anchor for the weekend, and leave with a full charge. Due to space limitations, we were only able to squeeze 300W of panels into our array, but if we were able to carry more solar panels, we would be granted even more freedom.

In 2017, we released ourselves from the constraints of land and set off as full time cruisers with the electric motor. At this point, we only had a small solar array to feed our amp hungry fridge and the electric motor, and this was enough for us. We only used the motor for short bursts of power when anchoring or getting out of the way of another boat. While the solar panels did provide the bulk of the power we produced, some did come from the electric motor regenerating power on especially windy days when we zipped through the waves.

All was well until we got beat up in a storm off of Cape Hatteras and decided to head south for the winter inside the protection (pronounced "no wind") of the ICW. We knew we would never be able to motor the next 1000 miles to Florida with only a small solar array giving us charge, so we added a Honda 2000 generator. By running the generator, we could then run the battery charger and technically motor for as long as we had gasoline to burn!

Two things happened in this situation: 1. Our battery charger was very small and old. 2. Our charge controller started to die on us.

Lets start with the first part: Our battery charger was a gift from a friend who took it out of another boat because the owner wanted it replaced. The LEDs in the display had died, but otherwise it was still producing power, so we installed it and went cruising. The charger produces 15amps at 48vDC. 15 amps does make a fair amount of prop wash and will make all your docklines become taught if you try putting the motor in gear in the slip, but when you are out in the water, 15 amps is barely moving. We could do around 1 knot, but the current in the ICW is fierce, meaning we could go with the current or backwards (and still with the current). We then began running the generator all the time and only motoring when the tide and current were in our favor. When the current switched, we had to anchor to prevent moving backwards over ground.

This system was slow but it worked. We moved around 10 to 15 miles each day towards Florida from North Carolina by motoring along at around 20 to 30 amps, and then running the generator for the entire day to replenish everything that had been consumed. Then the problems started happening.

We were anchored in Oriental when the first controller died. We had been there for a week and decided it was time to raise anchor and move on, but the motor would not work. You would push or pull the throttle and there was no response from the motor. Since it is an electric motor, parts are not found at your local chandlery, so we had to wait two more weeks for the part to come in. With the new controller installed, the motor ran beautifully again and off we went!

Not too long later, the motor began switching between forward and reverse, and then not working at all! It turns out that the controller had died again!

Since the motor was new (I accidentally submerged our first electric motor in fresh water; the moral here is always disconnect your boat from the dock hose) the controller was covered under the warranty. The manufacturer was exceedingly helpful in trouble shooting, diagnosing over the phone, and mailing out the appropriate parts both times! This is really important because you probably won't find a skilled mechanic/electrician in some of the ports you wish to visit.

Maddie and I started analyzing what was going on here and what was killing the controllers. The manufacturer firmly believes that running the generator while motoring is fine to do because they are designed to be operated in this manner, but we wondered if something else might be wrong with our charger aside from dead LEDs! We decided to stop motoring with the generator on and see if the controller survives for longer than a few months.

This thought came to us because we had experienced many years of trouble free operation before the generator. We charged with the funky old charger when we were tied up in a marina, but the motor was never on at the same time! We started a new rule: The motor bank switch has to be off when the generator is turned on.

It has been around 7 months and an ocean crossing since we started that rule, and everything is working perfectly. I know that to really test out this theory, I need to reintroduce the variable and see if the problem replicates itself; but I don't want to kill our controller again, so I have never performed this part of a proper scientific examination.

Having the generator did give us the ability to navigate the ICW, but a generator is far from necessary for an electric propulsion yacht, as long as you plan to remain in open waters where you can sail.

In my personal opinion, if you plan on cruising the ICW and want to make bridge openings on a set schedule, a Diesel engine will be your friend and an electric motor will be a nightmare. Since we had no hurry and were willing to put up with the slow pace of progress, we trudged along the ICW from Hatteras, NC to Georgetown, SC. This little distance took us about 4 months, so very slow! Once we made it to Georgetown, we began coastal hopping down the East Coast and were free from the ICW. Here the electric motor shined like a star!

We would typically burn up about 20-30% of our battery bank in getting out of the harbor we were anchored, but all of this was regenerated by the time we made it to our next inlet. We had plenty of power to motor in (with the tide) and anchor. We would then crank on the generator to charge back what we consumed in getting there.

Having a generator was really handy for coastal hopping and mandatory for the ICW, but that is about where it's uses end for us.

We left Florida and sailed to the Bahamas where we were able to sail in and out of anchorages, as well as between the islands with ease. We used the motor for short spurts of power in some tricky areas, but the intense sun was able to charge the batteries back in about a week. The generator helped give us more power and sooner than a week; but it was not mandatory, only helpful.

When we left the Bahamas for the Azores, we carried 10 gallons of gasoline for the generator to help power us along the way. We had no wind and this voyage took 21 days to get to Bermuda, but we only ran the generator twice in our time at sea.

Foolishly, we purchased a third gas can and carried with us 15 gallons of gasoline when we left Bermuda for the Azores.

The winds were much more favorable and present, giving us the ability to sail the whole way across the ocean with considerable speed. On this voyage, we discovered that all of our solar panels had died of corrosion, meaning that our only two power sources were the generator and the motors regeneration to keep our fridge running.

The reason I say we foolishly carried 15 gallons of fuel is because we never needed to run the generator. The propeller spinning 24 hours a day provided us with so much power that we spent most of the journey at full charge!

In the open ocean, an electric motor is far superior to a Diesel engine. It will silently produce electricity all the time with no limitations of fuel capacities. When the winds are good, you will be sailing, and when the winds are not blowing, grab a book and wait for them to return! We crossed from Bermuda to the Azores in 24 days, with 4 days in a row where we were totally becalmed. The other 20 days had great winds that carried us over 100 miles per day and kept all the batteries charged.

An electric motor is not ideal for every situation, and not ideal for every sailor. If you have a tight schedule or want to move at a set minimum speed, you will be better off with a diesel motor. If you actually sail, and/or sail long distances, then an electric motor will be your new best friend.

We personally view our electric motor as a hydrogenerator that helps with docking and have never been happier with it!

How Do We Power Our Yacht While Crossing an Ocean?

Having an electric motor means that we can't fire up the old diesel to charge up the batteries. When we crossed the Atlantic Ocean in July of 2018, we carried with us three methods of charging. The first is our solar panels. We have 200W on the deck and 100W on the stern as fold out wings. We also have a Honda Generator (EU2000i) and lastly we have the electric motor that functions as a hydro generator.

The solar panels started out as a great method of charging when we were anchored, but failed us on the ocean. The deck panels get stepped on accidentally, or things fall on them, or the salt finally kills them. Either way, both 100W flexible panels are dead and not producing any power.

The 100W on the stern is composed of two 50W rigid panels. One works fine, the other panel corroded away at its terminals, literally corroding away to the panel itself with no way of reworking it!

So, our 300W solar system is limping along at 50W.

Thankfully we have the generator! Right?

Actually, the electric motor functioning as a hydro generator has produced all the power we need and fully met our demands. We have yet to turn on the generator and are nearing land after 22 days at sea.

Right now, as I write this, the motor is producing 4.8amps @48vDC. When this is converted to 12vDC with a step down converter, it becomes 19.2amps @12vDC; silently!

Yes, the electric motor that has a very limited range of motoring offers unlimited and quiet electrical production for us as we sail across the vastness of the Atlantic.

We left Bermuda with 15 gallons of gasoline, and it appears that we will arrive with the same amount in the Azores.