Charging a 12V Lifepo4 battery. Who has the key to this mystical ...

I have bought a lifepo4 12.8V 40Ah battery from an unknown but experienced manufacturer for a small project, that was not too expensive to wake the kraken and dragon of my spouse.

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It came at 13,33V and looked very tame.

I charged it with a blue smart ip65 12/15 charger on lithium configuration and low current (4A) instead of 15A to wake it up softly.

The manufacturer prescribes a CCCV load profile with cut off voltages of 14,6v high to 10V low. But Victron thinks that 10V is too low. They told me to cut off at 12,5V. And load with 14,2V.

I think Victron uses a more conservative load profile. Maybe to protect the battery from unballanced cells in these high limits? Is that right? Or does that have another reason? Lifepo4 is lifepo4 right?

The first charging got to 14,2V for a little while, but then very quickly started ballancing at 13.5V. Is that normal?

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So now the battery is 13,5V... Which is good I guess for storing the battery? When I look at a voltage chart of 12V Lifepo4, that is about 90%SOC? I have enough capacity to do what I want, so that's ok.

But I need to calibrate an Aili battery monitor (I know it might be rubbish but I want a little experiment). So when the battery is 100%, I have to tell the monitor by pushing a button that it's 100%SOC. But how do I know whether the battery is completely charged at 100%? On the voltage charts of lifepo4 I see that 13,5V is not 100%, but the smart charger brings the voltage automatically to 13.5V, and I don't want to start messing with the configurated values...

I also have a smart battery sense, a smart battery protect on load side, a battery protect on charge side, and an mppt 75/15 for a solar module when I install everything. Some are new, some were of a previous AGM project (that's why the chargers are 15A, instead of 10A which would be preferable for a 40Ah battery). But without a shunt, these victron appliances can't determine the SOC, so they can't help me either, although they all blink very willingly.

Any suggestions to educate me on this and protect my precious investment from my erratic ignorance, and help me to set this battery monitor please?

Would it calibrate itself when the battery reaches full capacity again? Even when the voltage drops again to 13,5 V?

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I know from a cost perspective that it's cheaper to put together your own LiFePO4 battery than buy one ready made, but I'm wonering which is more reliable? Assuming that I purchase Grade a cells and good quality BMS.

I've looked at Battle Born, SOK, LiTime, Lion Energy and others. All of which have some sort warranty, some have 10 year, some 5 year, some less. I haven't read all of the warranty documents, but I have read a few. So far everyone I've read says that they will fix or replace the battery at their descretion. Which means that they get to decide if they want to honor their warranty or not. I guess this makes sense because a perfectly good battery can be ruined if connected wrong or treated improperly. What surprised me however was that none of the warrantees covered shipping costs or any of thee damage done in shipping. So it is possible that you could spend more on shipping than the battery is worth, except possibly with a Battle Born. They are still crazy expensive and frankly not in consideration, even though they come with a 10 year warranty. For instance a 12V LiTime 100AH with low temp protection is now selling for $279.99. I can't imagine with it would cost to ship it back and forth to China for repair, but its got to more than $279.99. So in my opinion, the LiTime warranty is basically worthless.

So how reliable are these batteries? Is a DIY LiFePO4 (using grade A cells and good BMS) more reliable than store bought? I'd say it depends on the amount of storage you are looking at. For 5kWh it would not be much more cost effective by the time you've added all the bits (BMS, housing, fuses etc). But if you are looking at 15kWh+, then yes, still cost-effective. I have a DIY 280Ah (14.3kWh) system, which worked out about 2/3 of the price of buying 3 x 5kWh racks. That's with buying everything locally, apart from the BMS that came direct from Florida.

And for me having better control over the system is more important, so I'd go DIY even if it cost a bit more ?‍?

As for reliability - time will tell... but apart from the cells themselves (which I have a spare) and the BMS (easily replaceable) then the rest is all my own work which I trust more than any commercial offering.

Solar-wise, I've only ever had to have a Victron component replaced, which was done without question, but it still took 2 weeks to send it back for testing before a new one was sent out - had that been a critical component, it would have been an unacceptable delay. So I prefer to 'self-warranty' and fix things myself wherever possible - but obviously everyone's mileage may vary, depending on skills, tools and how critical the system is.

Most companies have a grace period for shipping damages and you just need to take pics and contact them within that grace period and they will replace it.

I have had many batteries shipped and all were well packed with no damage even with some of our stupid fed ex drivers here. UPS seems to be better at handling the packages.

You are more likely to get damaged cells and products ordering from overseas shippers like Ali Baba and I have gotten damaged products from them a few times. Those shipments are rough handled and may transfer between planes, ships and camels before it gets to you.

I've yet to find any of the warantees mention any grace period about free shipping due to defects. The only grace period I've seen mentioned is for returns. Most give you up to 30 days to return unwanted items, but they almost always include a restocking fee. Typically the warranty includes statements that clearly state shipping there and back isn't free. The statement below is from the SOK warranty.

What does this limited warranty cover?​

This Limited Warranty covers any defects in material or workmanship under normal use during the Warranty Period.

During the Warranty Period, SOK Battery will repair or replace, at no charge(but NOT including the round shipping fee during warranty time), products or parts of a product that proves defective because of improper material or workmanship, under normal use and maintenance.

I'm only looking to build a 12V 400AH-500AH LiFePO4 battery bank for my travel trailer. I can do a DIY or I can buy assembled batteries. I'm wondering which way is more reliable. Do you work on your own car? Do you enjoy maintaining most of the plumbing & electrical at home? If yes, you might be a good candidate for a DIY lifepo4 build.

In my opinion, purchasing from a reliable, proven source (typically US-based) is your best way to minimize major problems. That goes for pre-built or individual DIY purchases. Don't order until you're prepared to build and test thoroughly. On average, you may be good for 30 days of return/tech support, after that be prepared to be on your own. As for warrantees, if they deliver at all, consider that icing on the cake---placing upfront value on a warranty can easily disappoint.

When/if you DIY you may learn, whether you want to or not, everything you did or didn't want to learn about lifepo4 cells and BMS's. It's part of the territory. If this doesn't sound the least bit appealing---recommend a hard-pass on DIY.

Doing it DIY, you're in the best position to deal with issues---you built it, odds are high you can fix it. With pre-built you're at the mercy of the manufacturer or seller.

As for whether pre-built or DIY offers the best value, what's your time and knowledge gained worth to you?

Good luck!

I know from a cost perspective that it's cheaper to put together your own LiFePO4 battery than buy one ready made, but I'm wonering which is more reliable? Assuming that I purchase Grade a cells and good quality BMS.

I've looked at Battle Born, SOK, LiTime, Lion Energy and others. All of which have some sort warranty, some have 10 year, some 5 year, some less. I haven't read all of the warranty documents, but I have read a few. So far everyone I've read says that they will fix or replace the battery at their descretion. Which means that they get to decide if they want to honor their warranty or not. I guess this makes sense because a perfectly good battery can be ruined if connected wrong or treated improperly. What surprised me however was that none of the warrantees covered shipping costs or any of thee damage done in shipping. So it is possible that you could spend more on shipping than the battery is worth, except possibly with a Battle Born. They are still crazy expensive and frankly not in consideration, even though they come with a 10 year warranty. For instance a 12V LiTime 100AH with low temp protection is now selling for $279.99. I can't imagine with it would cost to ship it back and forth to China for repair, but its got to more than $279.99. So in my opinion, the LiTime warranty is basically worthless.

So how reliable are these batteries? Is a DIY LiFePO4 (using grade A cells and good BMS) more reliable than store bought?

I can't speak for the chins but my Redodo 12v 100Ah minis shipped from a US warehouse and were delivered in 2 days and would be returned to a US address if needed. I'm pretty sure if you have an issue they just ship you a replacement and don't worry about the return due to shipping requirements for lithium etc. I build batteries and have been doing so for a while and I feel I better Chime In here.
- It is not that hard to do but it is not a simple slap-it-together deal, unless you want troubles.
There are tools required ! That costs money and a few things that can't be skimped on either such as a good quality Digital Multimeter (at least 2 decimal point accurate) with DC Clamp. Wire cutters, crimpers (Lugs & Terminals) and more... Of course a DC Charging Powersource to top balance etc... This stuff adds up FAST... some of us have the gear because we are into electronics etc but there is always something we don't have.

The Question, if you have the tools & equipment, then DIY is a great option, but if you do not have the tools etc, will that "investment" have more life beyond building the batteries or not ? That can only be answered by YOU !

Cells, Cases, BMS' etc are all easily obtained and there are Known Good Vendors that have been supplying the membership here for quite some time. You can build Larger Capacity batteries than those on offer by most vendors.
! Take 48V Rackmounts, they are mostly 100AH, a few get to 200AH but not beyond that.
A 48V/100AH Pack weighs 47kg (103.6lb) +/- Where a 48V/280AH weighs 135Kg (297lb) +/- a bit. and can't be mounted into a rack for obvious reasons.

I build batteries and have been doing so for a while and I feel I better Chime In here.
- It is not that hard to do but it is not a simple slap-it-together deal, unless you want troubles.
There are tools required ! That costs money and a few things that can't be skimped on either such as a good quality Digital Multimeter (at least 2 decimal point accurate) with DC Clamp. Wire cutters, crimpers (Lugs & Terminals) and more... Of course a DC Charging Powersource to top balance etc... This stuff adds up FAST... some of us have the gear because we are into electronics etc but there is always something we don't have.

The Question, if you have the tools & equipment, then DIY is a great option, but if you do not have the tools etc, will that "investment" have more life beyond building the batteries or not ? That can only be answered by YOU !

Cells, Cases, BMS' etc are all easily obtained and there are Known Good Vendors that have been supplying the membership here for quite some time. You can build Larger Capacity batteries than those on offer by most vendors.
! Take 48V Rackmounts, they are mostly 100AH, a few get to 200AH but not beyond that.
A 48V/100AH Pack weighs 47kg (103.6lb) +/- Where a 48V/280AH weighs 135Kg (297lb) +/- a bit. and can't be mounted into a rack for obvious reasons.

That's 100% correct. If you add everything up, especially the tools, building yourself offers no large financial benefits.
The real benefit is that you know and understand the system and can decide what bms you want etc.

I am an engineer with a lot of experience with large 48V and 53V DC power plants. I am normally a DIY type of person. I do my own appliance repairs and I do the maintenance on my own vehicles. I've restored 5 "handy-man special" homes, inluding upgrading thier electrical panels. I also have an extensive collection of tools, meters, etc.. Having said that I would need to buy a variable DC power supply if I decide to put together my own LiFePO4 battery. So I'm sure that I have the skills and tools to build a battery. My quesquestion has more to do with reliability. Unfortunately I don't have any experience with LiFePO4 cells and I don't how reliable they are. So I'd like to hear your opinions on whether ready made 12V batteries more or less reliable than the DIY batteries. I am honestly leaning towards building my own battery, but I don't know how reliable those 3.2V cells are.

We purchased a DC power supply to top-balance our first build. Quickly transitioned to installing Heltec 5a active balancers (with an off/on switch) for subsequent builds. The Heltecs do a fine job of top-balancing. Only takes a few hours with large deltas---smaller deltas, less than an hour. Plus they can be easily switched on to top-balance, as needed, down the road. Rewiring a battery pack, after the fact, to top-balance with a DC power supply is a PITA. The DC power supply has come in very handy for various other electrical projects and testing, but we no longer use it for top-balancing.

Once you start doing DIY builds you'll find the very least of your worries is reliability. Cell failures are extremely rare. BMS's may occasionally fail, but they're very easy to replace. Your biggest concern, by far, is hoping the vendor sells you a well-balanced set of cells. Top-balancing can't fix cells that have inherently different ah capabilities. This is why purchasing from a reputable source is important.