Cheap Chinese LiFePo4?

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Peter

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May 27, 2021, 2:25:51 PMMay 27
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Hello guys,

does someone have some experience with these cheap Chinese LiFePo4 prismatic cells?
H3efb29e8c6d34b20af33136aeb60245aV.jpg


My mind is blown with the price which is around $128 per kWh including shipping to EU (and even without import taxes..).
Most buyers seems to be happy with the purchase, only very few report bad capacity and strange condition of cells.
I am considering 24 pieces for 23.8 kWh pack for my camper.
What do you think about such a purchase?


John Gibson

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May 28, 2021, 8:54:53 AMMay 28
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I have made 3 different buys to test a few out...mixed bag on results.  However what ever you do make sure you get grade A cells.  Others are junk.  Also check out this YouTube channel where he does a bunch of testing on various cells:   (165) DIY Solar Power with Will Prowse - YouTube

Peter

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May 28, 2021, 6:54:57 PMMay 28
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Hello John,
thank you for your recommendation of Will Prowse channel. I like that guy and already seen lots of his content.
Actually he tested same type of cells from the same seller on Aliexpress. And his cells were good.
I have do it. Just ordered 24x 310Ah LiFePo4 for $3051 (23,8 kWh). Wish me luck! :-)

Dne pátek 28. května 2021 v 14:54:53 UTC+2 uživatel john...@gmail.com napsal:

Dave McCampbell

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Jun 1, 2021, 12:20:42 AM (12 days ago) Jun 1
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Peter.  The price of about $115US for the 280 ahr cells is right in the middle of where most sellers of these prismatic cells are.  I have seen ungraded similar capacity cells as low as about $75US and Grade A with 5 year warrantee up to about $150US.  How can you be sure these are grade A and is there a warrantee?  EVE and Lishen Grade A cells are mostly well regarded by the UTube testers at a price point near these.  Both are big Chinese companies.  Google for more testing videos.  Good shopping!

Jhon

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Jun 1, 2021, 10:25:54 AM (11 days ago) Jun 1
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Hello Peter,

I am a bit late to answer, but after reading a lot on Will Prowse's forum. I ended up buying my cells from Shenshen Basen https://basen.en.alibaba.com/  They are a little cheaper than your vendor.  On my first order of 8 280Ah cells, one of the boxes was dropped and one of the cells was damaged despite being well packaged.  The cells look good, no bloating etc and the pack worked out fine at first, but after a couple of weeks, the cell started to drop in voltage a lot faster then the others.  After going back and forth with the vendor for a few weeks, they send a replacement, which should arrive in a few weeks I hope.  Right now I am only getting 50% of the capacity because of that single cell.   They seem to be one of the better vendors on Alibaba, although still not quite as good as what you would expect from a European store.  Shipping takes about 2 months to Canada.  I will be interested to see your experience with this vendor.

On the boating forums, they seem to recommend smaller cells, 100Ah max because the bigger ones 280Ah might sustain internal mechanical failures with the constant bouncing.  However, you will have to do some more research on that as I can't verify that claim, but you might consider some form of cushioning.

As for the SBMS0 and DSSR20's, I chose those because they produce almost no heat, heat is wasted energy most of the time and that heat has to be moved using even more energy.  The second part is the SBMS0 uses a signal to switch of the inverter charger, in my case a Victron Multiplus as I want to be able to use shore power/small generator to charge my battery.

All in all it has been a steep learning curve.  The short circuit current these cells are able to produce are frighting.  Be REALLY careful!!! Insulate your tools and cover the terminals when you do the install and use circuit breakers.

As for balancing it took me forever, wire them in parallel first for a day or so, then wire them in series, let the solar charge the battery and trust that the BMS0 (properly wired and configured for LiFePo4) cut of the charge.  After that, assuming they are not too far out of balance, (I do not know the exact figures, but you do not want high currents) wire them back in parallel and top balance using a bench top power supply.  A better option might be the EBC-A20 or if you don't want rewire from parallel to series twice  it's bigger brother, both available on Aliexpress.   After top balancing install the batteries in series (again) and do a partial discharge to 80% of capacity.  Top balancing takes patience and relying on the equipment to turn off when it is supposed to, helps.

Dacian Todea

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Jun 1, 2021, 1:00:54 PM (11 days ago) Jun 1
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I made an order from this same seller in my case the 240Ah cells but so far seller did not contacted me. I usually expect questions as my address is a PO Box and they do not like that but will see.
If they ship I will let you know what the quality is. I prefer the 240Ah cells as they have the laser welded bolt instead of drilling in to connectors.  I also seen that the 310Ah cells have laser welded aluminium cylinders so maybe they did not drilled in to connectors still the short aluminium tap is easier to strip if not careful.
The busbars provided are fairly useless so I will need to find or build something else. 


On Thursday, May 27, 2021 at 12:25:51 PM UTC-6 Peter wrote:

Peter

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Jun 1, 2021, 2:31:04 PM (11 days ago) Jun 1
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Guys, thank you for your responses!

JHon,

I was in direct contact with Basen, for 24x 310Ah LiFePo4 they wanted $5614 including shipping and taxes to Czech rep.
These sellers on Aliexpress offered me best price $3051 - $3100:


I have picked LiitokalaVariCoreFlagship Store for these reasons: almost best price, fast English communication, Will Prowse tested theirs 280 Ah cells and they look fine. I will let you guys here know if this pick was lucky.

Bouncing problem.
It came to my mind few times but in the end I was just going to risk it without cushioning.
Can you imagine cushioning real solution in the van of 135 kg block of cells? I will probably compress them just to have one single piece. But I guess primarily I need to mount it securely to the van. Would someone have a suggestion how to securely cushion such battery?

Yes, the short circuit current keeps also bothering me. Impedance of single cell is according to datasheet only 0.18 mΩ. That is crazy.
What is short circuit current of 8S3P pack? Over million amps? If I will be even able to get a fuse which will be able to break such current..
Does even exist circuit breakers what can stop such current?
I have sent a question to Basen what would be short circuit current of 8S3P battery, I am looking forward to their reply.


Dacian,

why do you think their bus bars are useless? I imagine they are quite thin.. but I will take only 150A, they could handle that. Maybe their lower quality bus bars would help me to lower short circuit current so fuses or breakers could be more successful. Does it make any sense?
Dne úterý 1. června 2021 v 19:00:54 UTC+2 uživatel electr...@gmail.com napsal:

Dacian Todea

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Jun 1, 2021, 8:19:27 PM (11 days ago) Jun 1
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Peter,

If cells are 0.18mOhm then 3 cells in parallel will ideally be 0.06mOhm but there is also some contact resistance and busbar resistance then 8 cells in series will be 0.06mOhm x 8 = 0.48mOhm but when you add the connectors contact resistance and busbars you will be lucky to have 1mOhm total battery resistance then there are the cables that will add some resistance.
So absolute worse case short on the battery terminals will be 26V / 0.001Ohm = 26kA so not as extreme as you think and there are many breakers capable of much more than that. The typical small breakers are usually capable of 10kA and those are usually connected to thinner wires that add resistance thus short circuit current will be much lower than at the battery terminals.

The busbars are thick enough but they are not flexible. They should be made from multiple much thinner sheets of copper that have a bend in the middle to allow for thermal expansion/contraction and also cell expansion contraction with SOC
Here is a photo from someone using the SBMS0 that has proper busbars but just  in one direction he still uses the bad busbars that comes with the cells even if is a bit less critical in that direction.

 4s2p-lifepo4-2.jpg




Peter

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Jun 2, 2021, 9:55:07 AM (10 days ago) Jun 2
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Dacian,

thank you very much for short circuit current estimation, now its all clear to me, nice.

Battery cell busbars..
Is thermal expansion of busbars a problem?
I guess if busbars get hot, they are undersized and should be bigger.

Is SOC cell expansion a problem?
With compression of cells there should be no stress on busbars and battery terminals.
Without compression I guess it should be fine to define 2mm gap between the cells. Also it seams these cells are already prepared for some SOC expansion:
cells.png

Those bended multi copper or braided busbars look awesome but they are also expensive as hell.
I tried to look for local thin copper sheet if I could create my own multi copper bended busbars but it seems its not realistic option.

I will probably compress the cells because in the van I will have only one block to mount to the floor.
Then I was going to use original busbars and missing pieces I would do from 18x1 mm copper pipe.
Do you think thats acceptable solution?



Dne středa 2. června 2021 v 2:19:27 UTC+2 uživatel electr...@gmail.com napsal:

Robert Slackware

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Jun 2, 2021, 11:01:23 AM (10 days ago) Jun 2
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lord mounts, and may seem strange, but the shocks on a small motorcycle or mini bike should be just about right for that weight.  Maybe look at the mono shocks to keep space down.
Woke up with one of those kid science shows on tv.  Rare earth magnets, and let them "float" on a magnetic cushion?  If nothing else would make a neat experiment on effects of magnetic fields next to a high amp wire.  Get an extra 0.002 amps when the van is a rockin?  I swear officer, we were just charging the batteries......

Dacian Todea

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Jun 2, 2021, 12:47:33 PM (10 days ago) Jun 2
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Peter,

You will normally have some compliant pads between the cells and those will deal with small bumps/uniformities but those two side bumps shown in that video will be reduced to almost nothing when cells will be compressed.
Any temperature difference even just +10C will produce expansion/contraction and not all materials will contract and expand at the same rate. You have copper, aluminium and steel all with different expansion coefficients.
Of course that expansion/contraction will be small and not visible with the naked eye but those cycles over time will degrade the connection point with will create more heat and so making things even worse.
You will probably compress the cells with some long steel screws and those will of course also be affected by thermal expansion/contraction.
Sellers should provide proper busbars with the cells but they just try to reduce cost. Below is my old GBS battery with the included busbars that are properly done (there are 4 thin silver plated aluminium busbars on each connection and they have a bend to help absorb any movement). And each group of 4 cells already have compression plates with steel straps installed from factory.

P1200263.JPG
 

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