Batteries. Temperature vs. Voltage

[john61ct]

Originally Posted by thinwater

Boats are not heated through the winter.

which boats where? whose boats?

[thinwater]

Originally Posted by john61ct

which boats where? whose boats?

John, where do you sail? Do you sail in the winter? My questions are very simple; "Does anyone have practical experience using Li in a cold climate where the boat is either stored in the water or cruised?" So far there have been zero experience-based responses, only speculation. That's fine. It is honest. I am very weight conscious and am interested if Li if it will work year-round. At the moment, the information is not encouraging, it is only "maybe."

Running a heater in may marinas in the winter, unattended, is expressly forbidden. It is in my contract and is locally common. Another case would be boats left on moorings, which is common.


The water temperature is obviously very near 0C and sometimes below. The dull stuff without waves is ice.

If Li cannot be charged ~0C it is not a robust answer for some northern sailors. Frankly, I'm a little disappointed, but that is where all of the data points. It's not like LA is not working for me.

I also feel strongly that the right answer depends on the boat and the use pattern. It might have fit my last boat well.

[hellosailor]

Thinwater-
When you say you are specifically looking for someone with experience using Li batteries on a boat year round, I would suggest that you are ignoring the forest for the trees.
Boats don't matter here. The focal point is "How to lithium batteries respond to freezing temperatures?" and every manufacturer will tell you the same thing: Good way to kill the batteries, sometimes in an explosive manner.
Heck, even CAMERA makers will tell you that when a camera has a lithium battery, it may be dangerous to charge it or run it down in freezing temperatures. Either it is a conspiracy to sell Jonesee Hand Warmers, or you're missing the fact that the entire choir is singing the same song.

The only question that is relevant for a boater using lithium batteries is "How can I keep these at or above maybe 40F all year round?"

If you get them out of the bridge deck and down in the hulls, they'll stay warmer because they are "warmed" by the cold water against the hull, instead of colder air. If you add thermal mass and insulation, that may be enough to passively keep them warm, i.e. from the warmth of daytime charging.

Or you can do what Tesla and other carmakers do. That's right, even Tesla uses active liquid thermal management. Their batteries are HEATED in the winter and cooled during operation. This is all old hat, routine, mandatory stuff among the commercial users.

Boaters? Really? A DIY crowd who each have implemented custom power solutions? Not a very scientific sample, not a real meaningful measurement, even if it might seem tightly focused on what you need. If you're going to spend $2000? on batteries, and that's not disposable income, you might want to manage them the way the makers say is necessary.

Or not. Just one man's opinion.

[john61ct]

Originally Posted by thinwater

"Does anyone have practical experience using Li in a cold climate

And I answered yes, nothing to do with sailing though, these issues are much more common with off-grid stationary and land vehicles usage.

And nothing I have stated is speculative.

The detailed specs have been linked to and posted as to what such banks require.

**How you decide** to ensure your LFP bank is not destroyed by extreme cold conditions is up to you.

An insulated box with a thermostat and a set of silicon heating pads at the bottom is far from rocket science.

Personally I would not leave such a setup unattended for long, but many do, and there are dozens of other solutions, including making your packs portable and storing them inside.

If you decide all such measures are too much trouble or too risky, whatever, then simple, don't go LFP just stick to lead.

I really don't know what other information you might be looking for.

Maybe contact Bruce at Ocean Planet or Maine Sail directly, it gets pretty cold in Maine.

[thinwater]

I was asking for actual experience in boats that winter over in the water. I am well aware of the chemistry.

• Warming by placing below the WL. Note that the image I posted showed ice. The water is insignificantly different from 0C. This is quite common on the east coast of the US. It will be below 40F for several months minimum. The air will be far colder than that, creating freezing conditions for any water not actually in contact with the hull. I've had water bottles and cans burst in the bilge. Not unusual at all.
• Heat. Obvious and not a route most would chose for long-term unattended operation. I might choose that strategy for long-term cruising in cold areas. But those areas tend to be remote, so I would probably opt for the more robust LA.

Obviously I can stay with LA. I'm not asking anyone to create new facts to suit me. I was not asking for theory, which I understand very well (chemical engineer). I'm not trying to bash LiFePO4.

Just experience from winter sailors. Like long term cruisers, it's a small sub-set.

(FYI, Mainesail hauls out and wisely does not try to charge if is cold--That's on a thread here somewhere. I asked. I contacted 2 manufacturers. They mumbled a lot, not wanting to simply say "they don't work in that application.")

My conclusion, thus far, is that it isn't done. Just not worth it. Works for me. I started the thread in case someone had a clever solution.

[john61ct]

Originally Posted by thinwater

Note that the image I posted showed ice. The water is insignificantly different from 0C. This is quite common on the east coast of the US. It will be below 40F for several months minimum.

And recall those temps are no problem for storage, only for charging.

And in fact much better for longevity than indoors room temperature.

Down the east coast south of Providence, as long as I was nearby, or someone reliable was checking on the boat say weekly, storing LFP isolated down below the waterline should be NP.

Mains power, backed by a cheap lead bank for always-on security needs.

Or whatever you personally feel comfortable with, your boat.

[guyrj33]

Originally Posted by john61ct

I have no idea what you mean by "drawing through".

Yes, if they are warm enough to draw from, doing so at a high rate does increase temperature.

So using them to power their own warming pads will warm them faster than using a different source.

But in long-term arctic storage conditions, that IF condition above may not be reliably true.

"drawing current from" some people believe that turning on your headlights before starting a cold car will help by warming up the battery first.

[guyrj33]

I think this discussion explains why it was necessary for our lithium battery electric car to have temperature conditioned batteries.

[john61ct]

Yes, aka thermal management strategies

but remember "lithium" can be any of dozens of very different chemistries.

I don't know of mainstream EVs using LFP.

Which is why keeping the cells **cool** at high amp rates is even more important. Boom bad.