There is a need for a LIFEPO4 Best Practices Tab

[FredDaniel]

As a new user, I find it odd there is no "Best Practices" tab for new and old users to compile what is generally considered the best methods to build or install LIFEPO4 battery cells, modules, banks or powerwalls, and related products such as BMS. This could start with simple issues such as safe mounting positions, or unsafe like mounting prismatic cells on their side. Other issues such as the need for fuses [or lack of] at the individual cell level, with photos and anecdotes. This should include some trade-offs considered along the way. Some obvious additions like why no one should use a PWM solar regulator/charger on LIFEPO4 cells should be added.

In addition, there are numerous individuals and small companies who salvage near new and used battery modules assembled by some of the best and brightest engineers. Many of these modules contain unique or brilliant methods to protect or improve the life or safety of the cells. When these Best Practices are observed, they should be photographed and shared with the DIY world to add to our common knowledge and improve product safety. This DIY Forum is as good as place as any to get started.

I have been a Telecommunications Engineer specializing in radio & microwave for more than 50 years and am still learning. I just wish it were easier for everyone to learn more thoughtful information, faster.

Fred Daniel

 

[toms]

Some obvious additions like why no one should use a PWM solar regulator/charger on LIFEPO4 cells should be added.

Right there is the problem- what is obvious to you isn’t agreed upon by all.

I can see no obvious reason not to use PWM on LiFePO4. In fact i have seen many long term installs (5 years +) that have used PWM regulators.

There are people arguing in another thread that it’s best practice to hold cells at high knee voltage and low current- as even though it causes cell damage they can’t find written studies on how much damage- so it must be OK.

Good luck getting people to agree on “best practice”

My suggestion is to find someone that has had a system with the same requirements as yourself in operation for the longest time you can - and see what they have done.

Over time you if you follow enough installs you get a pattern of what decreases the lifespan of these cells.

Of course not everyone wants maximum lifespan or maximum kwh/dollar - so “best practice” will be what suits them the best.

 

[FredDaniel]

As you know, most inexpensive PWM controllers from China do not allow the user to select the battery profile to be used. A unit set up for lead acid with either steady or a three stage charge and a float requirement, will not properly charge a LiFePO4 battery with a two stage CC/CV constant current, constant voltage charge profile requirement. In fact, this lead acid battery profile will cause over time a LIFEPO4 battery to gas and swell the housing, often times cracking the housing and leaking.

Reportedly, as the cells reach a fully charged state, they draw less current and no longer limit the peak voltage to the critical point of less than 4.2 volts per cell. This is because with Pulse Width Modulation, the charge voltage is not reduced but the duty-cycle is simply switched on & off to reduce the charge current. This issue is covered in greater depth, with photos, in the fine article at

Charging Marine Lithium Battery Banks | Nordkyn Design

However, there are exceptions in life, as quality PWM controllers that are designed for several battery types, including LIFEPO4 are available. One is made by Renogy, but I have not used it. The point is to advise everyone and let them decide if their selected controller is right for their application.

 

[toms]

As you know, most inexpensive PWM controllers from China do not allow the user to select the battery profile to be used. A unit set up for lead acid with either steady or a three stage charge and a float requirement, will not properly charge a LiFePO4 battery with a two stage CC/CV constant current, constant voltage charge profile requirement. In fact, this lead acid battery profile will cause over time a LIFEPO4 battery to gas and swell the housing, often times cracking the housing and leaking.

Reportedly, as the cells reach a fully charged state, they draw less current and no longer limit the peak voltage to the critical point of less than 4.2 volts per cell. This is because with Pulse Width Modulation, the charge voltage is not reduced but the duty-cycle is simply switched on & off to reduce the charge current. This issue is covered in greater depth, with photos, in the fine article at

Charging Marine Lithium Battery Banks | Nordkyn Design

However, there are exceptions in life, as quality PWM controllers that are designed for several battery types, including LIFEPO4 are available. One is made by Renogy, but I have not used it. The point is to advise everyone and let them decide if their selected controller is right for their application.

MPPT controllers also use PWM to regulate voltage. Every PWM regulator i’ve used is filtered to ensure constant output voltage (in the same way MPPT regulators are)

Perhaps you should have just said it’s best practice not to use lead acid charge regimes on lithium batteries..

 

[HighTechLab]

And I present to you, this thread, as validation of Tom's point,

what is obvious to you isn’t agreed upon by all.

which I do agree with, however not everyone will.

I see things as well from time to time where I think to myself "Glad that is working for you but I'd never do it in a million years", but it's not always wrong or bad practice, just a unique aspect of that user's install.