30 Seconds. That's What a Lithium Fire Gives You.

[dlandersson]

30 Seconds. That's What a Lithium Fire Gives You.

[Strange]

Just because you CAN put something on a boat doesn’t mean you should.

[pitchpolehobie]

It seems to be a very rare but catestrophic event. I have thought about switching but my use case of mostly inland day sailing and weekly excursions with mostly marina overnights means I dont need the energy density and weight improvement of Li batteries. Id be open to the tech in the future if there are further improvements. Currently I use 2 deep cycle lead acid batteries from 2020 that I top off twice a year and run maintainers in the offseason. Each has a dedicsted voltmeter too. Iwas thinking of replacing this year and considering AGM.

[rsvpasap]

It's important to remember that the term "lithium battery" has a variety of meanings. And just for clarity I'm going to point out that the video link above concerns a YouTuber's speculation about a cruising sailboat that installed an electric car battery (such as a Tesla) to power their large inboard electric motor, also referred to as a saildrive.

Meanwhile, lifepo4 batteries, which are the type of lithium batteries widely adopted in the marine industry and now common on boats, are actually safer and less likely to experience thermal runaway or other fire producing events than are any other type of battery, including traditional lead acid batteries.

https://www.google.com/search?q=what+is ... a+sailboat

[pitchpolehobie]

Very good to know. Currently I have 2x lead acid hooked up to a perko battery selector and charge straight thru to terminals without a battery management system. Thst is how the boat came to me and seems to have worked great with 2 batteries of the same age and health. I have pretty sparse electrical needs with basically my garmin sonar as the main power draw. I have all LED lights inside and rarely use my exterior lights. If i switched to a lifepo4 system - would it be a drop in replacement for each of my lead acid batteries? Do i need batteried with built in BMS and a new charge selector?

[Be Free]

It seems to be a very rare but catastrophic event. I have thought about switching but my use case of mostly inland day sailing and weekly excursions with mostly marina overnights means I don't need the energy density and weight improvement of Li batteries. I'd be open to the tech in the future if there are further improvements. Currently I use 2 deep cycle lead acid batteries from 2020 that I top off twice a year and run maintainers in the off-season. Each has a dedicated voltmeter too. I was thinking of replacing this year and considering AGM.

Yes, thermal runaway is very rare in lithium (LiFePO4) batteries. Early forms of other lithium chemistries had serious problems. While I would not consider them appropriate for use as a house bank on a boat, they are much safer and better understood now.

Car batteries are usually Lithium Nickel Manganese Cobalt Oxide (NMC). In my opinion, they have no place on a boat. They are more likely to experience thermal runaway and while they weigh less than an equivalent LiFePO4 battery, I don't feel the weight savings are worth the decrease in thermal stability. I would never put a used battery in my boat and that goes double for a used automotive lithium battery.

If what you are have now is working for you and you don't foresee any significant change in your sailing habits then I don't see any reason to change your battery chemistry. If you are not staying off-grid for days at a time anything built around healthy lead acid batteries will likely work just fine.

Based on your use case, I wouldn't even switch to AGM. Eliminating the regular maintenance would not be worth the extra cost to me. They have a slightly better energy density, don't require regular maintenance, and can be charged a little bit faster but there are no actual deep cycle AGM batteries regardless of what the label says. If the battery is rated to start an engine (it will have a CCA or MCA rating) it is unlikely to be a true deep cycle battery.

[Be Free]

It's important to remember that the term "lithium battery" has a variety of meanings. And just for clarity I'm going to point out that the video link above concerns a YouTuber's speculation about a cruising sailboat that installed an electric car battery (such as a Tesla) to power their large inboard electric motor, also referred to as a saildrive.

Meanwhile, lifepo4 batteries, which are the type of lithium batteries widely adopted in the marine industry and now common on boats, are actually safer and less likely to experience thermal runaway or other fire producing events than are any other type of battery, including traditional lead acid batteries.

https://www.google.com/search?q=what+is ... a+sailboat

Exactly!

While he suspected that the fire started from the inappropriate battery (a very high probability) his main points were related to changing our "ditch" procedures and relatively inexpensive tools that can help rescuers find us easier. I know from experience that my VHS and my AIS can communicate with the Coast Guard anywhere I've ever chosen to sail but he's almost got me convinced to add a PLB to my ditch bag. I know the boat is unlikely to sink (I still have all of my flotation) but it could burn. Even in my prime (and I'm way past my "best by" date) 20 miles would be a long swim to shore.

[Be Free]

Very good to know. Currently I have 2x lead acid hooked up to a perko battery selector and charge straight thru to terminals without a battery management system. Thst is how the boat came to me and seems to have worked great with 2 batteries of the same age and health. I have pretty sparse electrical needs with basically my garmin sonar as the main power draw. I have all LED lights inside and rarely use my exterior lights. If i switched to a lifepo4 system - would it be a drop in replacement for each of my lead acid batteries? Do i need batteried with built in BMS and a new charge selector?

Lots to unpack here...

Lead acid batteries don't have or need a battery management system. Their internal chemistry and internal resistance work with the alternator/voltage regulator/battery charger to keep the battery from charging too quickly.

You are correct when you mention having batteries of the same age and health if you are going to connect them together with your Perko switch (both position). To simplify a whole lot of stuff, when you connect them together they will only work as well as the worst of the two. A bad battery will degrade (possibly damage) a good battery when you hook them together. Keep them as "matched" as you can.

On the supply side, your Garmin and lights won't notice if you switch to a Li battery. The charging side is much more complicated and has been covered in other threads. I don't want to add drift to this one by going down that path here. Given your electrical needs, you don't need Li unless you want to be off-grid for a week or more without recharging. Switching to Li is more complicated than just swapping out the batteries.

A lead acid bank is fine for the use case you've mentioned. If you do change to Li your existing Perko switch will work fine.

"Drop in" is about as varied as "lithium" in this context. It really only means that the battery case meets the size requirements (eg: group 24 or group 27). The important part is what is actually inside the case and how it is constructed. I'd recommend checking out Will Prowse's YouTube channel where he deconstructs a lot of lithium batteries. Some batteries are surprisingly good and some are scarily bad. A lot of the cases are surprisingly empty.

I don't know of any "drop in" batteries that have no BMS but there are differences. A good system will monitor battery temperature and voltage (both high and low), individual cell voltages, charge cycles, and will initiate balancing between the cells if they vary too much. In a lithium battery, individual cells need to be kept balanced for the same reason your lead acid batteries need to be as similar as possible.

[dlandersson]

Nice observation.

It seems to be a very rare but catestrophic event

[dlandersson]

Ditto

but he's almost got me convinced to add a PLB to my ditch bag.

[pitchpolehobie]

Nice observation.

It seems to be a very rare but catestrophic event

[Strange]

Clearly a personal opinion, but …

I get the increased power capacity. But in a SMALL boat with only 2 exits, that rare, catastrophic event will result in serious injuries if not death. And the total loss of the boat is a given.

It is a chemical fire that cannot be fought. ANYTHING you do to try to extinguish it will only spread it.

And I get that marine rated systems have almost everything in place to prevent such failures. But, the best laid plans always have a weak point.

Do you keep gas (a fire you CAN fight), propane or other explosive chemicals in your cabin? (An obvious exception here is BOOZE!). I doubt that you do.

For me, a portable gas powered generator (and a couple extra gas cans lashed to the deck) keeps me powered (and the A/C running all night). Many would be bothered by the noise. I find it comforting for 2 reasons. First, if I can hear it, the A/C will be working. That is really important ‘round here! Second, if I can hear it, no one has stolen it from where I sat it up on shore!