[Review] Cheap 12v 20Ah Lifepo4 from Aliexpress (with low temp protection)

meetyg

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[Update] It seems to have low temp charging protection! See my update on this:

I have recently recieved the 12v 20Ah battery ordered from AliExpress.
I got it for $93, and free shipping. I was expecting it to take a few months to arrive, but I got it about a month and a half since ordering.

I am going to use it for a small project of mine, which you can read about here:

Anyways, I had the chance to test it during the weekend and so I'm writing a little review.

Unboxing:
It came fairly well packaged.
photo_2021-11-28_13-34-31.jpg photo_2021-11-28_13-34-36.jpgphoto_2021-11-28_13-34-40.jpg
Its a bit larger than I imagined, but the dimensions are correct as advertised.
I was impressed with the build: it seems solid and the ABS plastic felt like good quality.
I was hoping to be able to open it and peek inside, but the top part is fairly well glued on. Since I plan on using this battery, I wasn't in for a full tear-down.
I suppose they are using some form of cylindrical Lifepo4 cells for this size.

The terminals are fairly small though, with short screws. I guess that for a 1C discharge rating, they are enough.
photo_2021-11-28_13-34-46.jpg

Charging:
The voltage was at 13.17v when unboxed, so I assumed around 40% SOC.
I started charging using my PSU set to 14.6v connected directly to the screws. I noticed that when I increased the amperage to 10A, the screws got pretty hot and the voltage reading on the PSU was incorrect. So I just added some bus bars to get a better contact. That fixed the heating and inaccurate voltage reading.
I am using the original "crocodile" wires that came with my PSU, so they might not be ideal for such amperage, but I just wanted to get along with the testing.
So after fully charging (took a few hours) the PSU showed no current flowing at 14.6v.
Even at 10A charging (0.5C) the battery was still cool to the touch, with only the terminals and bus bars being a bit warm. Nice :)
photo_2021-11-28_13-34-52.jpgphoto_2021-11-28_10-22-21.jpg

Capacity Test (the interesting part...):
I let the battery sit for about half an hour. I checked the voltage and it was around 13.9-14.0v. Then I started capacity testing at 0.2C (4A) with my battery capacity meter. I disabled the under-voltage protection of the battery tester, so that I would get as much capacity as possible until the battery's BMS would cut-off.
After a few hours the BMS cut-off at about 10.8v.
The results were disappointing: only 17.4Ah :(
I was expecting at least 18Ah...
photo_2021-11-28_10-15-12.jpg
Anyways, I thought that maybe my testing wasn't accurate enough, or maybe I didn't charge it up all the way.

So I did another charge-discharge cycle. This time I connected a simple shunt, and charged the battery up again. After the PSU showed no current, I connected a small 3A Lifepo4 charger I had, just to make sure. When the small charger showed a green light (not much after connecting), I let the battery sit for around 20 minutes.
The shunt showed 17.3Ah went in during this charging session.
photo_2021-11-28_10-15-20.jpg

Then I reset the shunt and the capacity meter/tester and ran the test again at 0.2C / 4A.
The results were almost the same: 17.5Ah as both the shunt and capacity tester showed.
photo_2021-11-28_10-15-15.jpg


Summary:
This battery is under the advertised capacity, unfortunately. Even if the BMS cuts off at around 10.8v I should have gotten at least 95% capacity, but in reality I got 87% capacity. I am guessing that maybe the real capacity of this battery is 18Ah, not 20Ah as advertised.
But... For the price and nice build quality I am somewhat still pleased with this buy!
There are a few similar batteries of this type on AliExpress, branded under different names. You can get one for around $88 now with Black Friday sales, and sometime free shipping depending on your location.

I am opening a dispute on AliExpress, requesting a partial refund because of the lower capacity.
If someone here thinks that I didn't test correctly, I will be happy to hear and try again. From my knowledge, usually Lifepo4's outperform their rated capacity for the first few cycles, but this one under-performed.
I haven't had a chance to do a 1C discharge test, or over/under temp. testing either.
If someone is interested, I could do some more testing... just let me know. For my use its enough (not worried about under-temp).

Hope you enjoyed!
 
Last edited:

meetyg

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Jun 4, 2021
Messages
256
Just a little update:
After watching Andy's video:
about getting less Amp hours when charging Lifepo4 batteries faster (with more amps), I decided to give the battery a second (actually third) chance. I charged it up slowly (3amps, instead of 10amps initially) and now I'm doing another capacity test to see if it helped.
I will update when the test is finished.

BTW that video is really important. I had a feeling that the higher amps charging was getting the voltage too high too quickly but now Andy has officially stated this.
 

meetyg

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Joined
Jun 4, 2021
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256
Unfortunately slower charging didn't help :(
I still got 17.5Ah capacity.

I think that either this an 18Ah battery, or maybe the BMS settings are very restrictive in order to prolong battery life/cycles.
20211130_203913.jpg
 

meetyg

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Jun 4, 2021
Messages
256
As requested by a fellow forum member here:

I just did a low temp charging test. I put the battery in a deep freezer for a few hours.
Then I tried to connect my PSU to charge it.
Well, what do you know... it's not charging!
Either it has low temp charging protection, or I killed that battery entirely :oops:

I started out with my PSU set to 1 amp at 14.6v but no current is flowing (the battery wasn't full before being frozen).
Then I tried with 3 amps, same thing.

20211130_232022.jpg

As you can see its pretty frosty
20211130_232028.jpg
But it's able to discharge...

The specs state that charge temp is up to -2°C and discharge it up to -30° C.
So at least for low temp it seems to be according to spec (although they don't mention any low temp protection):
SmartSelect_20211201-000131_Chrome.jpg
That was a surprise!

Anyways, without a proper teardown you can't really tell if the temp sensor is placed on the cells or in/on the BMS. This would make a difference if the cells were too cold to be charged, but the BMS/MOSFETS are warm.
But to summarize, yes this battery has low temp charging protection!
 
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meetyg

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Joined
Jun 4, 2021
Messages
256
After letting the battery sit at room temperature for the night, it's charging again. So it seems that I didn't kill the battery with this low temp test :)
 
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