LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[john61ct]

Originally Posted by mike_kelly

2. There are inexpensive high amp balancers on the market with no displays or apparent data ports so there appears that there is no way to determine if they are doing anything at all?

You mean like the Deligreen / QNBBM units @6A?

I think they'd be great to experiment with, let you balance quickly at **your** definition of "top" bottom or wherever.

IMO best as above, connect as needed for maintenance, not sitting there live full-time.

Start with quality new cells well-matched, avoiding the voltage shoulders for longevity, gentle C-rates, many people flying without any balancing BMS, go years without seeing any significant imbalances.

When that is the case, the protective-BMS functionality can be at the top-voltage pack level, perhaps using a bank midpoint-balance checker to guard against any major unforeseen events internal to the bank.

[nebster]

Originally Posted by mike_kelly

I am certainly not going to baby-sit my battery banks. So I am not going to be doing any manual balancing. That seems like dark-ages to me. So time to go to work.

Another option is to buy good cells, don't insist on running them up to 100% or down to 0%, and never balance them after the first time when you set up the pack. Plenty of folks have batteries running for a year (or years) and staying sufficiently in balance.

When you have the luxury of running a large storage pack, the need to squeeze every last drop of energy into the cells is reduced. Take advantage of that, and you can avoid having to fool with an active management scheme.

[john61ct]

Originally Posted by mike_kelly

That is what I was afraid of... Lack of clear standards is typical of the wild west stage or I suppose the other end of the lifecycle where corporations all have their own proprietary implementations and have put allt he garage operations out of business.



CANbus is not standard either and would lead to traps of proprietary protocols.


I was hoping to find some good open source or other DIY projects but it looks like even though the batteries have been around for a while they still have not been used much in real life.


It does make it quite difficult to jump in.

Yes, if you want easy and straightforward without educating yourself and taking responsibility as a system designer,

the only non-controversial approach is plonking thousands down for a packaged proprietary engineered system.

Victron, Mastervolt, Lithionics, some Aussie and S.A. specific vendors.

Then you get the propulsion-level vendors lots of kWh tens of thousands of dollars before you even get to the motor and hybrid genset required.

And Them that Know don't necessarily spill all their secrets in detailed "How to DIY on the cheap" build threads.

Catnewbee did a great one, but not so DIY and def not cheap.

[mike_kelly]

I am used to using li-po and li-ion that are both unforgiving and can be damaged easily if not used and stored properly.



I am glad that LiFEPo4 are apparently less likely to burn your house or your boat down.


I am not familar with the term "prismatic" and don't find a definition on the net. I see they do not have balance leads available.

[mike_kelly]

Originally Posted by john61ct

Yes, if you want easy and straightforward without educating yourself and taking responsibility as a system designer,

the only non-controversial approach is plonking thousands down for a packaged proprietary engineered system.

Victron, Mastervolt, Lithionics, some Aussie and S.A. specific vendors.

Then you get the propulsion-level vendors lots of kWh tens of thousands of dollars before you even get to the motor and hybrid genset required.

And Them that Know don't necessarily spill all their secrets in detailed "How to DIY on the cheap" build threads.

Catnewbee did a great one, but not so DIY and def not cheap.

No I am not paying anyone else to do it for me. I build everything myself and know how it works and how to repair it. It is not rocket science.

[john61ct]

Originally Posted by nebster

Another option is to buy good cells, don't insist on running them up to 100% or down to 0%, and never balance them after the first time when you set up the pack. Plenty of folks have batteries running for a year (or years) and staying sufficiently in balance.

When you have the luxury of running a large storage pack, the need to squeeze every last drop of energy into the cells is reduced. Take advantage of that, and you can avoid having to fool with an active management scheme.

++1 to all that.

So many run with no BMS at all by the standard definition, maybe just monitoring with alarms and bank level cutoffs,

but with a big bank costing thousands I know I'd be babysitting, at least until I had a lot of confidence in the automated bits.

Some BMS broadcast their detailed data and expose logs and custom variables to a smartphone or PC app.

[john61ct]

Originally Posted by mike_kelly

I am used to using li-po and li-ion that are both unforgiving and can be damaged easily if not used and stored properly.



I am glad that LiFEPo4 are apparently less likely to burn your house or your boat down.


I am not familar with the term "prismatic" and don't find a definition on the net. I see they do not have balance leads available.

Cell types - 1 hobby LiPo, 2 cylinders.

Pouches with tabs are 3A, prismatic 3B has come to mean enclosed in a hard rectangular shell, plastic or metal to help protect & contain the swelling, easy hookup with bolts or posts.

Google CALB 180Ah for example

[john61ct]

Originally Posted by mike_kelly

No I am not paying anyone else to do it for me. I build everything myself and know how it works and how to repair it. It is not rocket science.

I wholeheartedly agree, and hope you share your buildout, with diagrams, pics, BoM including prices & links, would be worth its own thread.

[mike_kelly]

Originally Posted by nebster

Another option is to buy good cells, don't insist on running them up to 100% or down to 0%, and never balance them after the first time when you set up the pack. Plenty of folks have batteries running for a year (or years) and staying sufficiently in balance.

When you have the luxury of running a large storage pack, the need to squeeze every last drop of energy into the cells is reduced. Take advantage of that, and you can avoid having to fool with an active management scheme.

I will always use the technology within design limits but I also have no such luxury to be sloppy. Using the tech properly includes maximizing functionality to me by knowing how it works and using it properly. In my world sufficiently balanced is a constant requirement maybe it will not be in LiFePo4 but I'll find out and I will squeeze every last drop out.

[mike_kelly]

Originally Posted by john61ct

I wholeheartedly agree, and hope you share your buildout, with diagrams, pics, BoM including prices & links, would be worth its own thread.

I'll do that once I get it down.

[mike_kelly]

Originally Posted by john61ct

Cell types - 1 hobby LiPo, 2 cylinders.

Pouches with tabs are 3A, prismatic 3B has come to mean enclosed in a hard rectangular shell, plastic or metal to help protect & contain the swelling, easy hookup with bolts or posts.

Google CALB 180Ah for example

So by one you mean typical square flat vacuum packed Lithium Polymer

two you mean Li-ion cells like the 18650's etc?
three a you mean LiFePo4 cells, are they vaccum bags essentially? Are the plastic cases just protection or do they have a habit of "puffing" and the plastic is to prevent them damaging each other.?


Do LiFePO4's need to be stored at a mid-point charge level? What are their operational
voltage limits? They are apparently 3.2v nominal cells.


Thanks

[john61ct]

Originally Posted by mike_kelly

I will always use the technology within design limits but I also have no such luxury to be sloppy. Using the tech properly includes maximizing functionality to me by knowing how it works and using it properly. In my world sufficiently balanced is a constant requirement maybe it will not be in LiFePo4 but I'll find out and I will squeeze every last drop out.

As you know from the hobby world, there are always trade offs.

If you're happy with 3-5000 cycles and get a rigorous protective and live-balancing system working that is also KISS reliable, no worries, cycle from 5% to 100% and Bob's your uncle.

But if you'd rather not have to balance live, maybe just once a year or never, and

would like to be able to pass the bank onto your grandkids maybe many decades later, then cycle from say 12% to 92%.

Up to you!

[john61ct]

Originally Posted by mike_kelly

So by one you mean typical square flat vacuum packed Lithium Polymer

two you mean Li-ion cells like the 18650's etc?
three a you mean LiFePo4 cells

Yes

Many makers package LFP in soft pouches and cylinders too.

But when 100s of Ah are wanted, too many connections increases complexity thus reduces reliability, at least without Tesla-level protective systems engineering.

> they vaccum bags essentially? Are the plastic cases just protection or do they have a habit of "puffing" and the plastic is to prevent them damaging each other.?

Dunno never heard of vacuum anything. Both protection and easy connections.

Puffing a bit is normal, as are compression plates and strapping. Just google for images and you'll see!

Major puffing, past a few % is from "unexpected events" a good BMS should prevent, especially over-high current rates. Normal in House banks is 0.2 - 0.3C max charging, normal usage same, maybe occasionally get to 0.4 - 0.5C rates, say for a windlass, best to support the bank with ICE charge sources.


> Do LiFePO4's need to be stored at a mid-point charge level?

Don't sit at Full for long periods, just before loads come online is best. Never need to get to Full at all as far as cells are concerned, but stupid slow-balancing BMS that only start when V is too high make people think that's normal.

So for actual storage, not as critical as other LI, but yes for longevity ~40-50% SoC or even lower, long as you're fully isolating and sure not to drop voltage too low from self-discharge.

And cool temps are a huge longevity factor, heat in general is the enemy.

But can't charge below freezing, can be instant scrap just like allowing dead flat.

> What are their operational voltage limits? They are apparently 3.2v nominal cells.

3.45Vpc is where I stop at low charge rates. High amps OK to go a bit higher, say 3.5Vpc, it will sag at rest after charger cuts out. If holding Absorb CV time, no need to go higher, I'd stop at a 0.02C taper or sooner.

Vendor max is usually 3.6 or 3.65V I think? Only adds a few % to "range", IMO shortens life if you make a habit of it.

Best to not Float if possible, if you do then low V say 3.2 or 3.3Vpc.

LVC at 3.15V for longevity, but at high current that may sacrifice too much range. 3.0Vpc would be my "never go lower", but silly vendors might say 2.5V.

Note these are my opinions, many find them controversial, or do not prioritize longevity over range or conformity as much as I do.

[ruixulifepo4]

I am Rachel from RUIXU battery.

All the Sinopoly 12V kits are made of Sinopoly brand new cells
The 12V drop-in series are made by the brand cell in China. we have specification for the 12V series,if anyone need,pls message me.

Yes,we do not sell cells,we are LiFePO4 battery solutions factory in China.

[newhaul]

Originally Posted by ruixulifepo4

I am Rachel from RUIXU battery.

All the Sinopoly 12V kits are made of Sinopoly brand new cells
The 12V drop-in series are made by the brand cell in China. we have specification for the 12V series,if anyone need,pls message me.

Yes,we do not sell cells,we are LiFePO4 battery solutions factory in China.

links to your company website please