Our batteries are reaching a stage where replacement will be needed shortly. Consequently we are thinking about LiFePO4 batteries which are lighter, smaller, don't require same capacity, can be discharged further and last longer but are a bit more costly.  Does anyone have any experience or advice re these batteries?

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Simon Currin - 10 Oct 2021

Forgive my ignorance but why is this such a big deal when plenty have made a smooth transition to lithium? We have carried a couple of 500 watt Torqeedo batteries for 10 years which we have charged on board at both 12 volts and 24 volts without incident. I do appreciate that lithium fires are a big deal but lead acid charging has destroyed plenty of boats too. Don’t these batteries have their own charge controllers built in that make disaster less likely (unless the cells are damaged)? I have limited knowledge of the issues but we are all using plenty of lithium powered devices every day without issue and yet there is still nervousness about scaling up to a marine system. Our car charges reliably and quickly with huge DC currents and the batteries are designed to survive crashes at speeds far greater than Shimshal will ever achieve. Surely the safety and reliability issues must be well mitigated by now on boats too?Sorry for the Devil’s advocacy but I am genuinely wondering why more haven’t made the move.Simon

Hm. Safety you are correct about in that Lithium Iron Phospate LiFePO4 is safer than Lithium-ion LiCoO2 and not likely to combust. However, from what I have gleaned so far it is not a simple case of dropping in LiFePO4 batteries to replace your lead acid/gel/AGM batteries, especially if you have multiple charging sources - alternators, solar, wind, aqua - and you have for example an AGM for engine starting.
Also, I read one article that says you cannot connect more than two LiFePO4 batteries in parallel, but that sounds a bit odd.
I know there are insurance issues in the USA as Dick has mentioned, and given the cost and complexity I have not followed up with our insurer Topsail. 
I have nevertheless come to the conclusion that since we need new batteries now, we will stick with the AGMs.  There is a very good article here about LiFePO4 batteries: https://marinehowto.com/lifepo4-batteries-on-boats/ 
If anyone has a straightforward what to do with your Battery Management System if you have  multiple charging sources and not all LiFePO4 batteries then we would all be extremely grateful.

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Philip Heaton - 10 Oct 2021

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Simon Currin - 10 Oct 2021

Forgive my ignorance but why is this such a big deal when plenty have made a smooth transition to lithium? We have carried a couple of 500 watt Torqeedo batteries for 10 years which we have charged on board at both 12 volts and 24 volts without incident. I do appreciate that lithium fires are a big deal but lead acid charging has destroyed plenty of boats too. Don’t these batteries have their own charge controllers built in that make disaster less likely (unless the cells are damaged)? I have limited knowledge of the issues but we are all using plenty of lithium powered devices every day without issue and yet there is still nervousness about scaling up to a marine system. Our car charges reliably and quickly with huge DC currents and the batteries are designed to survive crashes at speeds far greater than Shimshal will ever achieve. Surely the safety and reliability issues must be well mitigated by now on boats too?Sorry for the Devil’s advocacy but I am genuinely wondering why more haven’t made the move.Simon

Hm. Safety you are correct about in that Lithium Iron Phospate LiFePO4 is safer than Lithium-ion LiCoO2 and not likely to combust. However, from what I have gleaned so far it is not a simple case of dropping in LiFePO4 batteries to replace your lead acid/gel/AGM batteries, especially if you have multiple charging sources - alternators, solar, wind, aqua - and you have for example an AGM for engine starting.
Also, I read one article that says you cannot connect more than two LiFePO4 batteries in parallel, but that sounds a bit odd.
I know there are insurance issues in the USA as Dick has mentioned, and given the cost and complexity I have not followed up with our insurer Topsail. 
I have nevertheless come to the conclusion that since we need new batteries now, we will stick with the AGMs.  There is a very good article here about LiFePO4 batteries: https://marinehowto.com/lifepo4-batteries-on-boats/ 
If anyone has a straightforward what to do with your Battery Management System if you have  multiple charging sources and not all LiFePO4 batteries then we would all be extremely grateful.

Hi Simon,
Good question without a satisfying answer. A couple of thoughts, but in no way from an educated person in this area, just stuff I have picked up:
Insurance companies are inherently cautious and conservative. Over time they usually get things right, but often take time to get there.
Not all lithium chemistries are alike in performance and safety. LiFePo4 sounds like the safest, but it is, in many ways, still early days for marine house battery usage.
There have been serious fires and there continue to be. And there continues to be random, somewhat rare, but occasional fires. These occur with the proliferation not only of phones computers (charged on bedding for example), but now high voltage, hi amp lithium batteries for the power tools (drills, vacuums, saws etc.) that are now part of everyone’s tool kit. Poorly stowed on a bouncing around boat, they can short out and get damaged, not to mention the accumulated stress (not designed for) by being around salty air 24/7/265.
Lithium fires are particularly hard to fight, I think.
Lithium has to employ a sophisticated battery management system (BMS) to be charged safely.
Some lithium battery manufacturers (house batteries in a boat’s bank) are flogging their product in ways that have yet to be proven by the test of time.
It is one thing to have a fire in a car or home that you can walk away from: a boat is a different story. There is little that scares me more than a fire onboard.
All vessels should have as part of their regular safety habits a recognition that battery charging of the proliferation of devices deserves a attention. On Alchemy, this includes a review of chargers: probably best to always go with the manufacturer’s chargers (even if more expensive) than the much cheaper charger from a “super-huge” store. Also keep an eye on wiring, especially the joint from the wire to the connector into the device (I often augment the joint with some strain- relief tape on devices that are vulnerable to repeated ins-and-outs or wires that get tugged occasionally). All charging is also done on a hard surface and I have smoke detectors as part of Alchemy’s early fire detection.
All the above said, I think the area of lithium batteries is evolving quickly from a Wild-West free-for-all atmosphere to something much more predictable, safe and every-day. I suspect every year a greater percentage of boats will have lithium batteries.
My best, Dick Stevenson, s/v Alchemy

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Dick - 10 Oct 2021

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Philip Heaton - 10 Oct 2021

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Simon Currin - 10 Oct 2021

Forgive my ignorance but why is this such a big deal when plenty have made a smooth transition to lithium? We have carried a couple of 500 watt Torqeedo batteries for 10 years which we have charged on board at both 12 volts and 24 volts without incident. I do appreciate that lithium fires are a big deal but lead acid charging has destroyed plenty of boats too. Don’t these batteries have their own charge controllers built in that make disaster less likely (unless the cells are damaged)? I have limited knowledge of the issues but we are all using plenty of lithium powered devices every day without issue and yet there is still nervousness about scaling up to a marine system. Our car charges reliably and quickly with huge DC currents and the batteries are designed to survive crashes at speeds far greater than Shimshal will ever achieve. Surely the safety and reliability issues must be well mitigated by now on boats too?Sorry for the Devil’s advocacy but I am genuinely wondering why more haven’t made the move.Simon

Hm. Safety you are correct about in that Lithium Iron Phospate LiFePO4 is safer than Lithium-ion LiCoO2 and not likely to combust. However, from what I have gleaned so far it is not a simple case of dropping in LiFePO4 batteries to replace your lead acid/gel/AGM batteries, especially if you have multiple charging sources - alternators, solar, wind, aqua - and you have for example an AGM for engine starting.
Also, I read one article that says you cannot connect more than two LiFePO4 batteries in parallel, but that sounds a bit odd.
I know there are insurance issues in the USA as Dick has mentioned, and given the cost and complexity I have not followed up with our insurer Topsail. 
I have nevertheless come to the conclusion that since we need new batteries now, we will stick with the AGMs.  There is a very good article here about LiFePO4 batteries: https://marinehowto.com/lifepo4-batteries-on-boats/ 
If anyone has a straightforward what to do with your Battery Management System if you have  multiple charging sources and not all LiFePO4 batteries then we would all be extremely grateful.

Hi Simon,
Good question without a satisfying answer. A couple of thoughts, but in no way from an educated person in this area, just stuff I have picked up:
Insurance companies are inherently cautious and conservative. Over time they usually get things right, but often take time to get there.
Not all lithium chemistries are alike in performance and safety. LiFePo4 sounds like the safest, but it is, in many ways, still early days for marine house battery usage.
There have been serious fires and there continue to be. And there continues to be random, somewhat rare, but occasional fires. These occur with the proliferation not only of phones computers (charged on bedding for example), but now high voltage, hi amp lithium batteries for the power tools (drills, vacuums, saws etc.) that are now part of everyone’s tool kit. Poorly stowed on a bouncing around boat, they can short out and get damaged, not to mention the accumulated stress (not designed for) by being around salty air 24/7/265.
Lithium fires are particularly hard to fight, I think.
Lithium has to employ a sophisticated battery management system (BMS) to be charged safely.
Some lithium battery manufacturers (house batteries in a boat’s bank) are flogging their product in ways that have yet to be proven by the test of time.
It is one thing to have a fire in a car or home that you can walk away from: a boat is a different story. There is little that scares me more than a fire onboard.
All vessels should have as part of their regular safety habits a recognition that battery charging of the proliferation of devices deserves a attention. On Alchemy, this includes a review of chargers: probably best to always go with the manufacturer’s chargers (even if more expensive) than the much cheaper charger from a “super-huge” store. Also keep an eye on wiring, especially the joint from the wire to the connector into the device (I often augment the joint with some strain- relief tape on devices that are vulnerable to repeated ins-and-outs or wires that get tugged occasionally). All charging is also done on a hard surface and I have smoke detectors as part of Alchemy’s early fire detection.
All the above said, I think the area of lithium batteries is evolving quickly from a Wild-West free-for-all atmosphere to something much more predictable, safe and every-day. I suspect every year a greater percentage of boats will have lithium batteries.
My best, Dick Stevenson, s/v Alchemy

Hi Philip,
AGM batteries seems to have dominated the marine battery landscape of late. A couple of cautions/thoughts:
AGMs are not all made alike. They vary dramatically in quality and construction.
The better ones (Lifeline) are able to be equalized, but many AGM manufacturers do not recommend this or do not give instructions on how to do this.
Equalization is (can be) an impressively complicated process, usually demanding shore power to do properly.
According to manufacturers (and cruiser experience), all AGM batteries “need” (or benefit greatly) from being fully charged regularly (every couple of weeks) or else they lose capacity. This is an especially potent complication for those boats who spend a lot of their cruising time at anchor (as I do).
Earlier this season, I was angling toward AGM batteries to replace my gel cells (7 years old, and some abuse from long and weird storage), which I had been using for decades. The above considerations (along with impressively differing recommendations and field reports) lead me to buy again, good quality gel cells, which have no maintenance demands, are quite forgiving, give me 6-8 year service, and I am quite familiar with.
My best, Dick Stevenson, s/v Alchemy