LiFePo4 Batteries

[Tom&Shelly]

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




Bruce

Why do the characters say "Front, Toward Enemy"?

(Just kidding!)

Tom

[tony.latham]

Why do the characters say "Front, Toward Enemy"?

When in the process of setting up an L-shaped ambush... you should always read the directions. Because somebody somewhere got it wrong.

T

[rkanz]

https://youtu.be/RAO5qARz6FA

These LiFepo batteries need careful management. If you look at the cost of the Amazon batteries in the video, and the lack of warranty, they may not be a good deal compared to a built battery from Battleborn or another manufacturer.


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[MtnDon]

That type of LiFePO4 cell needs to be used with a BMS for worry free long life. They very well may be some off brands out there but if one sticks with one of the big names they are wonderfully reliable. You high quality equipment for charging along with the BMS. All that BB has done is prepackage in a box they sell as a battery. But we all can decide what we are most comfortable with.

[John61CT]

The quality internally is a total wildcard with a drop-in, no telling who the actual cell mfg is.

Plus in many contexts only BMS functionality is required, not a single device with that name.

Easy to upgrade / repair too, drop-ins can severely limit current rates.

I doubt you'll get the same decades' longevity out of BB

[Nodrog]

Don't listen to me.....

[rkanz]

The quality internally is a total wildcard with a drop-in, no telling who the actual cell mfg is.

Plus in many contexts only BMS functionality is required, not a single device with that name.

Easy to upgrade / repair too, drop-ins can severely limit current rates.

I doubt you'll get the same decades' longevity out of BB

Do these cells need a BMS and balancer? Who makes a good BMS?


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[John61CT]

Those are not settled issues, nor easily answered.

I see "BMS" as a collection of functionality, not a gadget you just buy.

At least not for under hundreds of dollars.

Many just act as the BMS themselves, manually check on health, balance rarely needed.

Lots depends on the quality of the cells themselves.

Others just freak out at that idea, but are OK with cheap-Chinese gear for $6.

If you want automated bulletproof reliability, spend lots and lots of money, or put in hundreds of hours researching, become your own expert.

[Esteban]

I've been considering using a 100 watt AGM battery in my teardrop. A VMAX MR-127-100 AGM battery would cost $247.49 or a (higher quality?) Lifeline GPL-31T 105 AH AGM battery would cost $339.99. A good approx.100 AH AGM battery would cost about $247.49 to $339.99. The 100 AH AGM battery should not be discharged below 50%, which means it would supply about 50 usable amp hours of power.

If instead I buy a Battle Born LiFePO battery I'd need to pay $949.00 for a 100Ah 12V LifePO4 or $575.00 for a 50Ah 12V LifePO4. The 100 AH Battle Born battery can be drawn down 100% safely so it can supply twice the safely usable power of a 100 AH AGM battery. Or I could buy the 50 AH Battle Born battery and have the same amount of usable power as a 100 AH AGM battery. A LiFePO battery may also be easier, and faster, to recharge with a solar panel.

For roughly $245 to $327.50 more than the cost of a 100 AH AGM battery I could use a 50 AH LiFePO battery with a similar useful capacity. It's (somewhat) tempting to buy a LifePO battery that would recharge more quickly, would be usable for many more years, over a longer term would save money instead of buying replacement batteries, and that would save weight.

The $649 to $701.50 cost premium for a 100 AH LiFePO battery is considerably less attractive. It would be wonderful to have one, if not for the cost.



Excellent explanations of the pros and cons of AGM and LiFePO batteries for a RV

[bdosborn]

:applause:

Source?

https://www.electriccarpartscompany.com/

They have cells in stock, shipping is still higher than I would have liked.

Bruce

[bdosborn]

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




Bruce

Why do the characters say "Front, Toward Enemy"?

(Just kidding!)

Tom

[bdosborn]

The quality internally is a total wildcard with a drop-in, no telling who the actual cell mfg is.

Plus in many contexts only BMS functionality is required, not a single device with that name.

Easy to upgrade / repair too, drop-ins can severely limit current rates.

I doubt you'll get the same decades' longevity out of BB

Do these cells need a BMS and balancer? Who makes a good BMS?


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I did get a BMS from Electric Car Parts and it was DOA. I've added 6 Amp cell balancers that seem to be keeping the cells within .005V of each other. I'm still looking for a BMS and disappointed with what is out there, they're either super expensive or Chinese junk. I have an Iota charger with the LiFePO4 smart module. It's a little more aggressive than I 'd like as it takes one of the cells up 3.667V but it's only charging at less than 1 amp when it gets there. Most of the time while charging the cells are at 3.50V, only rising up to 3.3667V at the very end. Lots to learn about these, the voltages are just out of wack from what I'm used to. I have a low voltage disconnect set to disconnect the battery at 12V, just need a BMS that works for over charge. The good news is I can load the battery with 30A DC and the voltage only drops by 0.05V. Voltage drop was locking out my heater with the LA battery. More to follow after I experiment some more.

I do wonder how accurate the Iota battery charger is at reading the battery voltage, I'm not sure its fair to expect Fluke class accuracy from it.

I charged at 45A for 3 hours for the initial topping off charge and the cells stayed cool as cucumbers. I connected the cells in parallel for several hours before charging so they were all at the same voltage. I need to upsize battery charging wires though, the #6 got a little warm.

I only blew one fuse getting the battery installed in the trailer.

Bruce

[John61CT]

The Iota is adjustable right?

Just tweak it until you see no cell goes over 3.5V or whatever your top is.

Don't hand balance low down, do it starting at say 3.4, be consistent.

Then set pack LVC so no cell drops below 3.2V.

Once you have all this setup, the BMS becomes redundant, can try different cheap ones if you like as another layer of protection, but not depending on them.

[MtnDon]

The Iota is adjustable right?

Just tweak it until you see no cell goes over 3.5V or whatever your top is.

There is usually an internal pot that may be adjusted to raise and lower voltage. I used to have one Iota that was adjusted upwards to put out equalization voltage on the lead-acid cabin system.

[bdosborn]

The Iota is adjustable right?

Just tweak it until you see no cell goes over 3.5V or whatever your top is.

Don't hand balance low down, do it starting at say 3.4, be consistent.

Then set pack LVC so no cell drops below 3.2V.

Once you have all this setup, the BMS becomes redundant, can try different cheap ones if you like as another layer of protection, but not depending on them.

I'll be looking at this but I don't know how it will work with the charge controller. Does the charge controller adjust all the voltages down proportionally with the internal pot or will it still expect to see 14.6V overall=charged? We'll see...

Bruce

P.S. Looking at a Victron battery Monitor as it has a high voltage disconnect relay as well as midpoint cell monitoring...

P.P.S. The Iota charge profile is real close to the recommended: Standard Charge Method:C/3 Constant Current to 3.65V Limit, then Constant 3.65V Voltage with Current Taper to C/20.