Easy to say....
As at that time EVE were the "real A grade" ....
Even now seem by most forum members as "the best"
Availability has also a lot to do with being able to buy, not so much with the price.
My BYD I now purchased..
42500 THB S16 260Ah including Jikong 2A / 350A BMS ..
Roughly $ 1300,-
To get at my doorstep all tax paid
The 280Ah Eve cells..
Roughly $1750...
Actually...
Even 25% less to get real A grade...
View attachment 57405
One pack of 8* 260Ah cells.
About 60kg.
Automotive grade.
View attachment 57406View attachment 57407View attachment 57408
This is how terminal contact should be.
Why the #)_+@?!!
Are we still risking?
Cheaper and way, way better quality then we ever can do...
If it was only available 18 months ago.......
fhorst,
first, I want yo thank you for sharing your experience and your persistence in being an evangelist for these safety concerns despite the widespread denial / defensiveness you’re unfortunately forced to put up with here on the Forum.
And second, I chose this post of yours to respond to because it made the biggest impression on me and most everyone else just seems to have glossed over it.
These large LiFePO4 cells we DIYers are all messing around with we’re designed for use in EVs, and since early-on I’ve had concerns with the weakness of the threads tapped into the aluminum terminals and even the welded studs that some vendors are now offering.
These pics you’ve posted above bring into focus how these cells were intended to be assembled and the risks we are taking by purchasing at the cell level and connecting using these various Mickey Mouse alternatives.
So I’m interested in the finished battery supplier you’ve identified and any finished battery manufacturers that are using EV-like assembly methods to build finished batteries from these LiFePO4 cells.
Now that I’ve got my system up and running, I’ve got many friends and family interested to ‘copy’ my system and I independently became concerned with many of the same safety issues your unfortunate experience and this thread highlight when realizing I would never want anyone I know putting one of these homebrew DIY LiFePO4 batteries in their basements.
So paying more for a battery assembled using intended EV-like methods and reducing risks of mishaps or fires to the absolute minimum is my top priority now and I’d like to learn more about any battery suppliers you believe meet that standard.
In terms of the DIY LiFePO4 batteries like the 560Ah 24V battery I’ve got in my basement, of course I’d prefer to keep it if I can be comfortable I’ve reduced risks down to EV-style preassembled battery levels, but as you very correctly point out, ‘what is the opportunity value of not spending $6000 on a safer battery but losing your home?’
So I’d appreciate your thoughts on what risks you’d perceive if you went to the trouble of building another LiFePO4 battery ‘the right way’ from scratch.
I have the advantage of having built my battery later than many of you early pioneers so I believe I’ve got it out together using close to current state-of-the-art practices but would appreciate your perspective. Here is a summary of what I’ve built:
16 280Ah cells in a single row clamped to 12psi
Stainless M6 grubscrews Red Loctited into all terminals
All cell connections made with custom 2/0 battery cables sized to connect every other cell (so ~6” long)
All connections properly torqued with a calibrated torque wrench
Standard 300A 8S Heltec BMS (for now, upgrading BNS and adding a contactor is one of the safety upgrades I’m contemplating)
If I summarize what I’ve understood from your various posts, here is a list of the risks I’m aware of and plan to address:
-mice or rats chewing through cables - I was already planning on building a rodent-proof enclosure for the battery and all critical cables, and your experience has assured that I’ll follow through
-a BMS failure or a cable connection failure resulting in overcharge of a cell. I believe you suspect this as your leading suspect in terms of what caused your fire. There is no way to be 100% certain that overcharging and bloating can never occur, and so I’m now thinking about adding a pressure sensor to my clamping fixture. If bloating cell = excessive pressure and a pressure sensor can detect that and open a contactor before a runaway event goes too far, that seems like it might be a viable path to increasing safety against an overcharge/overbloat event.
-after those two risks, the only other risk I can see is cell failure, and primarily internal short / self-discharge resulting in heat, heating and bloating of neighboring cels, and possibly fire from still-being-debated causes. First, if a cell can fail in that way in one of our DIY batteries , it can fail in that way in a preassembled battery or even an EV (so risk should be low unless associated with the cheap ‘grade-A’ factory-reject cells many of us are purchasing through Alibaba). If any such cell failure will result in pack bloat before it can result in a fire, the same pressure sensor safety solution sketched above should reduce risk of fire in the event of cell failure.
I’m interested in whether you can think of risks I’ve overlooked. My battery is stationary and will be enclosed / protected like your finished battery, so there should be little/no risk of a spontaneous cable failure or short.
If a pressure sensor on the clamping fixture is a good way to address any risk associated with runaway/bloat which encompasses 99.9% of the risk if fire developing, that same signal could be used to trigger whichever fire extinguishing solution the board settles on as best for LiFePO4 (which can also be triggered by a heat sensor).
So I’m thinking a stationary DIY build which has been done carefully enough can be made as safe as the EV-class finished battery you have adopted with enough expense and effort (which would probably not be worth the trouble if starting from scratch, as you point out), but I’d be very interested in your opinion.
And as for the rest of the board, please don’t waste any effort on posts telling me I’m being over-conservative or blowing these safety concerns out of proportion.
In a boat or an RV, fine, but I’ve been concerned about the safety of having one of these powerful LiFePO4 batteries in my basement since day 1.
Unless I can have confidence that I’ve got a safety solution which is at least as good as what’s going into the batteries being put into EVs (amd let’s not even bring up the Chevy Bolt, and yes, I understand it’s not LiFePO4), I’ll be ditching my DIY battery for an EV-class preassembled battery like the one fhorst has discovered.
Any constructive comments/opinions as to whether increased pressure/bloat is a necessary precondition to any failure that can result in fire from LiFePO4 cells appreciated, but please don’t waste your time or breath trying to convince me I’m crying wolf (as many of you are disappointingly expressing to fhorst).