LiFePO4 vs FLA - The Real Deal

[44'cruisingcat]

Originally Posted by john61ct

There really is little point trying to show some people the errors in their thinking, just a waste of time and mental bandwidth.

Yeah you're probably right. But it'sdifficult to say nothing when something as completely ridiculous as the OP is presented as fact.

Because a battery CAN be charged in one hour you MUST buy a genset big enough to do so.

Really?

[senormechanico]

[john61ct]

Yes if a statement may cause noobs to make mistakes it should be corrected.

But no long supporting argument is required.

Just quote a short bit and state this is false.

Others who also know the truth chime in.

Make it clear who is ignorantly wrong-headed to those who might not yet understand to ignore that poster.

But don't bother with long detailed back and forth with someone who has demonstrated hundreds of times they never admit they have something to learn, just dig in harder and ramble on.

[thinwater]

Originally Posted by newhaul

here is what I got for t105's
https://www.google.com/url?sa=t&sour...Voynp7Jbl-LjmG
Its not much of a difference so it seems it wouldn't make a difference in the real world.

0.0028 x 45 x 6 = 0.92 V at 22F. That is quite a bit in mid-winter. Almost 1 volt.

[thinwater]

From Battery University. I have read similar things other places. Please explain if this is wrong. Otherwise, this is a serious problem in some applications.


These are not my words. I have not worked with Li batteries much and make no claims of knowledge. Please guide me to a place that discusses sub-freezing charging.



Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a sub-freezing charge. This is permanent and cannot be removed with cycling. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers (Cadex) prevent charging Li-ion below freezing.
Advancements are being made to charge Li-ion below freezing temperatures. Charging is indeed possible with most lithium-ion cells but only at very low currents. According to research papers, the allowable charge rate at –30°C (–22°F) is 0.02C. At this low current, the charge time would stretch to over 50 hours, a time that is deemed impractical. There are, however, specialty Li-ions that can charge down to –10°C (14°F) at a reduced rate.

[a64pilot]

Reference the lead / Lithium hybrid.
I supposed the idea is use the Lithium’s better charge abilities and then discharge them into the lead so as to maintain a safety buffer if you will?
So do you charge them both when charging? If so then you only need enough lithium to cover both house loads and 15% of the leads capacity so that when discharged to a comfortable level the lead is 100%?
Run off of the lead until 50%, then crank the generator and charge both lead and Lithium?
I don’t see what that won’t work?

[newhaul]

Originally Posted by thinwater

0.0028 x 45 x 6 = 0.92 V at 22F. That is quite a bit in mid-winter. Almost 1 volt.

so you are saying that your batteries are at 22℉ ?
That temperature measure is supposed to be taken at the battery.

[newhaul]

Originally Posted by thinwater

From Battery University. I have read similar things other places. Please explain if this is wrong. Otherwise, this is a serious problem in some applications.


These are not my words. I have not worked with Li batteries much and make no claims of knowledge. Please guide me to a place that discusses sub-freezing charging.



Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a sub-freezing charge. This is permanent and cannot be removed with cycling. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers (Cadex) prevent charging Li-ion below freezing.
Advancements are being made to charge Li-ion below freezing temperatures. Charging is indeed possible with most lithium-ion cells but only at very low currents. According to research papers, the allowable charge rate at –30°C (–22°F) is 0.02C. At this low current, the charge time would stretch to over 50 hours, a time that is deemed impractical. There are, however, specialty Li-ions that can charge down to –10°C (14°F) at a reduced rate.

for Lfp that is actual battery temperature. I.e. In a car sitting in the carport. I rather doubt the battery compartment on your boat would be below freezing when you are onboard and using the batteries thereby needing to charge them.

[thinwater]

Originally Posted by newhaul

so you are saying that your batteries are at 22℉ ?
That temperature measure is supposed to be taken at the battery.

Obviously. It gets far colder than that.

a. The batteries do charge when no one is there.
b. The battery compartment is on the bridge deck, separated from the cabin by fully ventilated space (above and below and all 4 sides--outboard engine wells surrounded by non-heated lockers surrounding the cockpit--distilled water for refills freezes hard). The batteries are at ambient temperature, which is well below freezing at night most of the winter.

Sometimes I have to de-ice the decks in the morning, or at least chase the frost. It can be quite treacherous.


---


Does anyone have experience (at least a few years) with Li batteries charged with solar through the winter in a boat that is used for at least some cold weather cruising? I'm sure the RTW guys use them, but that would be just above freezing at worst, where the voltage would be considerably better than LA. This is a prime reason for them to use them, even better more important than weight or charging. I would also bet they understand the temp/voltage relationship and adapt. I'm sure they watch batteries like a hawk.

[newhaul]

Originally Posted by thinwater

Obviously. It gets far colder than that.

a. The batteries do charge when no one is there.
b. The battery compartment is on the bridge deck, separated from the cabin by fully ventilated space (above and below and all 4 sides--outboard engine wells surrounded by non-heated lockers surounding the cockpit--distilled water for refills freezes hard). The batteries are at ambient temperature, which is well below freezing at night most of the winter.


Sometimes I have to de-ice the decks in the morning, or at least chase the frost. It can be quite treacherous.

ok so Fla well then I would suggest you adjust your charging source to reflect the increased need

[hzcruiser]

That's a good one, love it!

Originally Posted by senormechanico

[hzcruiser]

Originally Posted by thinwater

[...]
Does anyone have experience (at least a few years) with Li batteries charged with solar through the winter in a boat that is used for at least some cold weather cruising? [...]

Just check any manufacturer's datasheet, they usually stress that you shouldn't charge LFPs below freezing, but you can discharge them if the temp is down to -10C:


E.g.: https://www.powerstream.com/LLLF.htm


Now it's good that you can start your engine from LFP even at -10C but then you somehow need to make sure to warm them up _before_ recharging them. Therefore you might need a resistor close to the batts that turns the alternator output into heat until you (or some electronics) switch it over.

[senormechanico]

Originally, we had LiFePo4.
Now, they're LifeYpo4.
The Y is Yttrium.
I read somewhere that it's been added to the mix for the ability to charge at sub freezing temps, but a quick search has not found corroboration.

[Paul L]

What is magic about the temperature water freezes at for LiPo batteries. I assume there is very little if any pure water in them. So does the charging at cold temperature problem start at around 0C and continue to get worse as it gets colder or is it some hard transition point?

[thinwater]

Originally Posted by senormechanico

I'm going to print that out and post it next to my PC!