LiFePo4 Batteries

[Cosmo]

I am eager to get a Lithium. For me the show stopper has been charging in below freezing temps.

Are you in warmer temps or have you solved this?

This article below outlines the concern. Apparently this applies to all Lithium batteries from the cell phone to the RV. No issue discharging but charging can be a concern in the cold.

I called Battle Born and they said they had a heating pad that draws power from the battery to heat the battery to allow it to charge. I am not sure I have that kind of power to spare in my small setup. The article below sounds like the heater was placed in the battery. There is a lot of decision making technology in the battery.

https://relionbattery.com/blog/lithium- ... ld-weather

[MtnDon]

I am eager to get a Lithium. For me the show stopper has been charging in below freezing temps.

Are you in warmer temps or have you solved this?

With the cabin installation, the lead-acid batteries were stored in an add-on compartment outside at the service panel end. That was enclosed and roofed but not airtight and not insulated, heated or cooled. The lithium cells take up less space than the lead-acid, but as you point out Cosmo, they cannot be charged when the battery is below freezing.

One solution would be to do like Tesla and the Chevy Volt. They have water passages running through the battery and they can heat or cool depending on the need. My solution was to move the lithium cells indoors. I built a cabinet on the inside of the wall where the lead-acid batteries were stored. The LiFeMnPO4 cell packs are located in that. Cabinet sides have screens on two sides as well as a door. There is a fan I can use to circulate air within the cabinet. I have several temperature sensors inside the packs with a readout on the cabinet end. When we arrive there if the pack temperature is less than zero C, I do not charge them. It only takes a couple, maybe three hours to get the interior warm. I did not package my cells together in a big battery pack but made groups of two cells. That leaves more cell surface area open and the cells warm more quickly. We don't have a problem with overheating the cells. The cells we have can be discharged down to -20 C (-4 F) but need to be above freezing to charge.

FWIW, lithium batteries can be used in motorcycles, ATV's and the like in freezing weather with no cold temperature concerns, IF one does something that seems a little weird at first thought. Before starting (electric start) you need to turn on the headlight and draw off some power. That causes the battery to self warm. Then the Li battery puts out enough voltage / power to easily crank the engine. The warmed battery can also then accept charge input from the alternator. If you don't turn on the headlight for a few minutes first the battery is cold and cannot supply enough power to crank the engine.

FYI, the prismatic cells like I used have some sort of plastic cases. Under some operating conditions they may swell. That is not good for them. The cells are usually assembled into packs of four or more cells. Aluminum or steel plates are used along with straps of some kind or threaded rods to make a unit that will not swell.

[John61CT]

Or just isolate the LFP bank and get the vehicle going and warmed up for a while before using it.

A Reserve lead bank can be a good idea anyway if off-grid in freezing weather.

Can also be used as a Starter batt rather than carrying "dead lead" dedicated to that one usage.

Note there is a long time lag if your large LFP mass is in an insulated compartment, so just because it got below zero for a few hours doesn't mean you can't safely use the bank.

Drawing from is much safer / lower than charging.

A good BMS will include temp sensor / cutoff.

Winston / Thundersky claims their Yttrium doping allows for charging at much lower temps.

And finally, a silicon heating pad will not use up many Ah, set on a timer a while before needed, and are not expensive even custom made.

[MtnDon]

Note there is a long time lag if your large LFP mass is in an insulated compartment, so just because it got below zero for a few hours doesn't mean you can't safely use the bank.

Of course, but our bank sits for 2 to 3 weeks minimum in between winter uses so it is very much at ambient indoor temperatures. Most often that is lower than the average daytime outdoor temperature. With the old lead-acid batteries insulating made things slower to warm up, but of course they did stay warm longer.

[KTM_Guy]

I looked real hard at LiFePo4 for my build. Talked to a few people about LiFePo4 and AGM, crunched some numbers and couldn't make the numbers work for me. I didn't want to put the weight of AGM on the tongue but couldn't justify the money for LiFePo4.

I looked at how many charges the AGM battery I was looking at could take at certain discharges. If I go from 100% to 20% for every discharge the battery is rated for 350 charges like that. If I camp two weekends a month thats 24 trips a year. I can abuse the battery every other weekend for 14 years. The life on the battery is 8-10 years. Why spend $800-1000 for LiFePo4 over $220 for AGM? If I get 8 years out of it I can the look at LiFePo4 or what ever is the newest then. If I was 20-30 yers old I might rethink the LiFePo4, but at my age I'll just buy AGM's when I need them and be money ahead.

Todd

[bdosborn]

Charging the batteries won't be an issue for me, the batteries are inside the camper so they'll be in a heated space. The trailer is a garage queen so I don't have to worry about the batteries getting cold during the winter. I'm most interested in the reduced voltage drop when loaded, i.e. virtually no Peukert's law effect. The voltage drop on my current golf cart batteries is so bad when they are cold that my heater will lock-out on low voltage.

Bruce

[bdosborn]

I looked real hard at LiFePo4 for my build. Talked to a few people about LiFePo4 and AGM, crunched some numbers and couldn't make the numbers work for me. I didn't want to put the weight of AGM on the tongue but couldn't justify the money for LiFePo4.

I think you're right; unless you have a specific niche that a LiFePO4 battery fills, it's pretty hard to justify the cost on an $/amp-hr basis. It's especially true if you a a casual camper, only going out every couple of weeks or so during the summer. I think the scales tip towards LiFePO4 if you're a full timer that cycles your battery heavily. For me, there are a lot of characteristics of lead-acid batteries that have always annoyed me and I'll probably pull the trigger on LiFePO4 because they seem to have mitigated those issues, not because they make more sense from a cost perspective.

Bruce

[John61CT]

Yes, if you aren't fulltiming the ROI does not work

Now if you're wealthy, and weight space are worth it, like racing yachts, that's different.

2000 cycles is barely breaking in, zero capacity decline if you've been coddling, pass them on to grankids

[bdosborn]

Woohoo! There's a new battery on the block!




Bruce

[John61CT]

Das de good stuff right der

[MtnDon]

Quality cells!!

[tony.latham]

Woohoo! There's a new battery on the block!

Bruce:

I'm thinking they are just lead-acid bats with gold plates surrounded by heavy water.

They do look sweeter than a leaky DieHard that's fer damn sure.

Tony

[aggie79]

Source?

[John61CT]

cared for properly, I bet lasts many times longer than you could with a basic drop-in like BB

[kennyf]

I put in two BB 100 amp hr in series for a 24 volt system with 600 watts of solar and 3000 watt inverter. I did more research after than before to figure them out. What I found was that the bms in the battery will shut them down at 14.6 and your charge controller needs to be able to shut down before that to be able to avoid possible damage to it. It is hard to determine state of charge based on voltage and a shunt may be needed if that is important to you. It may also be a bad idea to have them charged by your vehicle alternator considering their fast charge capacity could overheat your alternator (don't know much about that). It may be better if you don't fully charge or discharge them or store fully charged to extend the already long life. I set my charge controller at 14.3 (not the BB recommended 14.4). The terms absorption and float don't apply so I set absorption for 40 minutes (20 per battery per BB) and float voltage at 13.2 (BB recommends 13.4 I think). There seems to be various opinions including using HVD as low as 13.88 and no absorption or float and LVR at 13.29 but that seems to be old information. Storing them at freezing is ok but you can't charge them, however, storing in high temp is bad for them. While I could not really justify them I just wanted them thinking I would not have to think about them and getting to the point that I don't. I run a 120 volt frig that will use 1 killawatt hour a day or a little more (plus the interter on all the time), an induction cook top and microwave some and I am back to full charge (14.3) by noon. I have not used it enough to know how I will do in cloudy and winter weather. I was considering AC when I put in the system and may add a little more solar and do that with a 5000btu window unit.- (or just try it with this set up)