Lithium batteries for J/109 class

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Dan Corcoran
Posts: 220
Joined: Sun Jan 29, 2017 4:32 pm

Lithium batteries for J/109 class

Post by Dan Corcoran »

Hi. I am Dan Corcoran, a fellow J/109 owner, and a part-time marine electronics writer for practical sailor magazine. In addition, I own a software startup, focused on helping hospitals achieve the highest level of safety and quality (

Shortly after the J/109 Class Annual meeting the Class Measurer, Bengt Johansson, contacted me to discuss the most recent developments of lithium-ion battery technology, asking if this technology is suitable and ready for future use in the J/109.

He suggested I post a summary of what we are watching for, and the effort to develop new class rules for Lithium. I hear that such a new rule would be no sooner than 11 ½ months from now (e.g. Annual October 2022 meeting).

Are you excited about using lithium for weight savings? Don’t be! If you are thinking of replacing your lead-acid batteries with lithium only to save weight, don’t rejoice just yet. Our 2002 designed boats are not great candidates for these batteries if you are already configured at the class minimum of 150Ahr. With just 150Ahr, the weight savings when safely replacing lead acid with lithium could be negligible.

Instead, you can gain a lot more capacity for the same weight, useful for running your engine less frequently like in a distance race, but I am not writing here to promote this technology, rather share safety issues that concern me if shortcuts are taken in the conversion process.

I recently answered the question, “if lithium batteries are ⅓ the weight of lead-acid, how can you say no weight savings on a J/109.”. Can't we save 50 lbs?

This is the short version of the answer ...

Our boats are not designed for these batteries, neither I suspect are the latest J-boats. If they were so designed, they would have separate 12-volt charging vs. load buses (for safety reasons). Not only don’t our boats do this, but they also share the same red battery cable for (i) starting the boat, (ii) charging the batteries from the alternator, and (iii) providing a battery voltage sense lead to our Balmar regulators, a clear wiring shortcut. (Hint: Fix (iii) with a dedicated 10 gauge wire, and your batteries will charge from the engine faster)

Retrofitting our boats for lithium involves many wiring changes and the incorporation of circuitry to protect the batteries, alternators, and other electronics.

“Drop-In” lithium batteries are advertised as eliminating the need for extensive retrofits, enabling the owner to directly swap out lead-acid batteries one for one. I strongly don't recommend this.

To accomplish this feat the safety mechanisms that would be part of a standard Lithium retrofit, such as battery monitoring, high interrupt capacity fuses, and remote-controlled battery disconnects, are built into the batteries themselves so that the red and black cables to your lead-acid batteries simply connect instead to the drop-in lithium battery.

Lithium batteries don't like many things. They don't like to be discharged fully, they like even less to be charged when they are already very low, they don't like to be charged when they are cold, etc. Like sealed lead-acid batteries, they don't like to be overcharged or short-circuited either. Internal lithium battery monitors also don't like electrical storms that produce EMP pulses, something that lead-acid batteries tolerate very well.

The safety mechanisms in the battery will disconnect the internal lithium batteries from your electrical system if they sense any of the conditions that could cause damage to the batteries. And that’s the rub. That disconnection at best will leave you or your delivery crew without house power until a reset button is pressed. If the reset does not work you have only a starter battery that has silently deteriorated if your charging system isn't wired for two chemistries. If your engine was running at the time of disconnect, your boat's electronics and alternator can be destroyed as the power from your alternator, having nowhere to go, turns into a high voltage spike. In addition to the familiar alternator diode frying issue that happens if someone operates the battery switch while the alternator is running, boat system electronics are fried as well. Then your starter battery is useless, having nothing to power. No ship VHF, nav lights, smartphone chargers, etc. All gone.

At least we have sails. I can't imagine what a clueless powerboater would do. Hopefully, they at least have a towboat contact so it doesn’t become a salvage dispute when they fire off their flares.

In addition to the key challenge of drop-in batteries suddenly disconnecting power to protect the batteries, they are also less idiot-proof, placing demands on you and your crew to know more about your electrical system. For example, assuming the disconnect happened while the engine is off, does the delivery crew know this is the scenario to select the "both" position on the battery switch, the position you possibly labeled "NO".

The opposite of idiot-proof, this is complicated stuff. For example, if you have a lead-acid battery and a lithium battery on your boat, you have to modify your charging to treat each battery differently and be careful not to use the BOTH setting on your battery switch. Using BOTH with the alternator running will silently cook and reduce the capacity of your starting battery, using your stock J/109 shore charger will damage one battery or the other.

Even with TPPL batteries, there are ways to wire your starter battery where the battery is drained by about 1+ Ahr every hour, while the engine is charging your house battery. After 18-hours of motoring, your starter battery may not be able to start your engine next time you need it.

The solution to these challenges lies in a mixture of having two drop-in lithium batteries, instead of one, some additional wiring and protection devices in case both lithiums fail at the same time, protecting your starter battery from mixed chemistries with a smart lead-acid trickle charger, having chosen lithium batteries with remote control panels, and supplemental alarming so you know if a lithium battery has disconnected, leaving you with just one.

Some wiring scenarios will require your lithium battery has 3 connections, a ground, +12v load, and +12v charging. Many lithium batteries come with only two.

Once done safely the weight savings compared to 105 Ahr house and 50 Ahr starter battery may be none, but you will have weight savings if today you race with 2 or 3 105 Ahr batteries. If done right, you could have more idiot-proofing then a stock J/109 electrical system, and a whole lot more usable battery capacity than 2x 105 Ahr, for activities like distance racing and cruising.

Until that day where we have class rules in support of lithium batteries, try to hold back your enthusiasm and avoid drop-in lithium. They are not class legal, not safe enough for you and your crew, and they place the alternator and electrical systems of your boat at risk of destruction.

The batteries may also not be compatible with our future class rules and may not be ABYC marine standards-compliant, an issue if you sell your boat.

It is my intent to design an upgrade to my boat, probably before I help the effort for the new class rule. When I do so, I will be sure to write again and share how to do it safely either to the class or in Practical Sailor magazine. Until then check out the latest December 2021 issue where I write about the Furuno SX200 compass.

Sail Safe, and if you are in the healthcare or investment industry, ask me about my startup SafeQual. I can be reached through Gmail at 516captain.

J/109 Class | Owner #332 Strider
practical sailor magazine | marine electronics contributor
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Vento Solare
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Joined: Wed Dec 31, 1969 8:00 pm
Location: Newport, RI

Re: Lithium batteries for J/109 class

Post by Vento Solare »

All I can say is wow Dan. This is one of the most comprehensive reviews I have ever seen about Lithium battery conversion issues. Excellent work!
Bengt J
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Re: Lithium batteries for J/109 class

Post by Bengt J »

Thanks Dan!

A very good summary of the issues we face approving Lithum Ion batteries. From a Class rule point of view the perceived weight savings may be the main issue, we do not want to get into an arms race spending three times as much to potentially save 80 - 90 # and on top of that have severe safety issues.

For all to know, the reason to start this discussion now is to collect enough information for the TC to make a decision if we want to propose a rule change in time for the annual meeting October 2022.

To be clear, Lithium Ion batteries are not approved for the 2022 season.
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Re: Lithium batteries for J/109 class

Post by carlbraden »

Great information Dan - many thanks for sharing - look forward to whether these idiot proof lithium drop in batteries in the future can improve and address the risks and issues you identified.
Dan Corcoran
Posts: 220
Joined: Sun Jan 29, 2017 4:32 pm

Re: Lithium batteries for J/109 class

Post by Dan Corcoran »

I am interested in knowing if we have any experienced electrical installers in the class, and if so:
- how would you alarm two lithium batteries, to indicate to the owner one in alarm?
- what drop-in lithium batteries are gaining popularity where you are located?

Also interested in which owners have upgraded from their
1. Balmar Smart Regulator, MC-614. Which product did you choose?
2. Shore charger. Which product and model did you choose?
3. Link 20. Which product did you choose?
(I use the Balmar SG200)
4. Choose a small starter battery, how small did you go, what worked for you?
(I use the Odyssey TPPL PC925L, 28Ahr. Note because the charging voltages are different, my house battery is also an Odyssey TPPL, the PC2250)
Dan Corcoran
Posts: 220
Joined: Sun Jan 29, 2017 4:32 pm

Re: Lithium batteries for J/109 class

Post by Dan Corcoran »

Writing to update everyone on the first post in this article. Marine electrical ABYC Standards for Lithium Batteries on boats in the US won't be out until July 2022. It may be optimistic that I have something to offer up for the class rules this year. We may need to wait for new battery products that follow, as potentially none of the drop-in battery products will meet this requirement:

ABYC TE-13 13.5.6 If a shutdown condition is approaching, a BMS (battery management system) should notify the operator with a visual and/or audible alarm prior to disconnecting the battery from the DC system. (Note The ISO/European standard requires the visual/audible alarm is "Clearly perceptible from the main helm position, prior to disconnecting the battery from the DC system", and could potentially work its way into the ABYC requirements before they become final in July 2022.

Why is that a proposed standard for Lithium batteries and not lead-acid you might ask? That's because Lithium batteries have protection circuity built into them, that ultimately requires all the electric current to pass through a bank of semiconductor electronics that is programmed to shut off under various conditions like low voltage, high temperature, etc. They can also be prompted to shut off from a nearby electrical discharge, When this happens the boat operator may be surprised, better that they are alerted before or at least during the power outage as to the cause. Not an issue with lead-acid batteries, even if lightning strikes the boat directly, the battery will keep on going unless damaged.

Many drop-in lithium batteries have an alarm built into the battery to sound or light after they shut down the power. That will be hard to hear / muffled on a J/109. Some drop-ins don't have a provision for a remote alarm. As far as I know, none will alarm after a lightning strike nearby, but you could instead rig up a bilge alarm style circuit with a small battery if you have some skills.

Before I go on. REMINDER, LITHIUM BATTERIES ARE NOT CLASS LEGAL. When you are done reversing the change to be class legal, e.g. replacing the lithium batteries with lead-acid to be legal for any given race, you will have increased the weight of your boat with all the extra cabling, etc. while sailing with lead-acid.

Undoubtedly someone here isn't going to wait. If that will be you, I suggest you first take a peek at the articles below. Having this information will inform you of either converting your current installation into something safer or purchasing for a new install when you are not racing.

If you are interested in Lithium for weight savings, just stop now. As I wrote in the first article, a safe installation let alone an ABYC standards installation is achievable on a J/109 with weight savings vs. the weight of a 150 Ahr minimum class legal lead-acid install. The only reason to consider lithium is if you "need" to power your boat without starting the engine for much longer periods of time, or want to add conveniences like a microwave oven, air conditioner, or inverter capable of running a hairdryer or something.

If that is you, you need more power (not weight savings), great articles here about issues I will encounter helping to create a recommended install, that could inform your decisions as well:

Drop-in batteries: ... -consumer/
Make your own: (read above first)

When I do get to that recommended configuration, I will be looking for something along the lines of the drop-in batteries article as the make you own approach is just too much work, and the Mastervolt (not drop-in, Lithium Ion) won't fit in our 109's (batteries are too tall)

Dan Corcoran
Posts: 220
Joined: Sun Jan 29, 2017 4:32 pm

Re: Lithium batteries for J/109 class

Post by Dan Corcoran »

Another perspective, written with some humor, on things to consider in an install. Some of this adds more weight :-( ... oDkRkqUo3c
Dan Corcoran
Posts: 220
Joined: Sun Jan 29, 2017 4:32 pm

Re: Lithium batteries for J/109 class

Post by Dan Corcoran »

Making progress on this. Is there a J/109 owner, that does not do class racing, implimenting Lithium that would be interested in collaborating?

As I cannot make the changes to my own boat without causing a rule violation, and frankly don't see a weight benefit in a safe design even if I could, I would be interested in collaborating with someone who can.
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Re: Lithium batteries for J/109 class

Post by traci15Ren »

This is interesting information
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