How to Quickly Identify Fake LFP Battery Cells Part 1 – Weight & Volume


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Tim Lee

New member
Joined
Jul 28, 2021
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10
Seeing that many people have the experience of buying fake LFP battery cells.

Like this real example:
A LiFePO4 battery cell is sold and labeled A brand 3.2V 310Ah, weighs 5.3kg, size is 210mm x 170mm x 70mm. Buyer received and tested only 240Ah.

How to quickly identity its capacity is real or fake before purchasing?

Here is a simple way.

Roughly calculating the energy density according the weight

The production process of LFP battery cells has fully entered the era of energy density of 160Wh/kg-170Wh/kg from 2020(Only CATL‘s large capacity LFP cell can achieve 170Wh/kg~180Wh/kg).

Although Gotion announced in January 2021 that it had achieved an energy density of 210Wh/kg by using silicon as the negative electrode. However, This type cells are not available in the market so far (August 2021).

You can calculate the capacity to weight ratio.

If the result is greater than 180Wh/kg, please stay away from these cells.

Let’s calculate the energy density of this A brand 3.2V 310Ah cell(weights 5.3kg).

Energy density = (3.2V x 310Ah)/ 5.3kg = 187.16 Wh/kg.

It is significantly higher than 170Wh/kg. It is not achievable with the current process.

It is very likely misrepresented with real capacity.

Actually according buyer’s test result, the actual capacity is 240Ah. The energy density is1 44Wh/kg.

So it’s a 3.2V 240Ah cell and sold as 3.2V 310Ah.

You can also use the volume to aid in identification.​

For comparison purposes, we use the EVE 3.2V 280Ah LF280N A-Grade cell as a reference, which weighs 5.3kg and measures 204mm x 173mm x 71.5mm.

So the energy density of EVE LF280N is (3.2V x 280Ah)/5.3kg = 169Wh/kg.

Calculate the volume ratio of the two cells.

Ratio = (210x170x70)/(204x173x71.5) = 0.99

Well, the volume is slightly smaller than the EVE 3.2v 280Ah cell, but the capacity is 10% larger? That’s not very easy to do.

It can also be a another reason for you to stay away from deal.
 

slimf

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Joined
Sep 26, 2017
Messages
219
Good post - thanks, the only issue is, with so many suppliers offering deals, how can you believe a thing they say. If they lie about capacity then misrepresenting weight won’t be a problem for them either. I’ve got 800ah 48v wall of Nissan Leaf modules, but contemplated replacing with a huge Lifepo4 pack but with thousands on the line picking a Chinese supplier is a gamble at best.
 

Oberfail

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Jun 22, 2021
Messages
247
Find a place with solid Return Policy, i personally like Alibaba, since their Return Policy worked well for me so far and in case they refuse it, I'd still have 180 days in total to revoke my payment via PayPal.
 

Tim Lee

New member
Joined
Jul 28, 2021
Messages
10
Good post - thanks, the only issue is, with so many suppliers offering deals, how can you believe a thing they say. If they lie about capacity then misrepresenting weight won’t be a problem for them either. I’ve got 800ah 48v wall of Nissan Leaf modules, but contemplated replacing with a huge Lifepo4 pack but with thousands on the line picking a Chinese supplier is a gamble at best.
@slimf

Yes, this does not 100% avoid buying a fake battery.

Especially for first time buyers, it is very difficult to identify whether the battery is real or fake from the limited information available.

But there are still ways we can get as close to the truth as possible.

So I am working on some ways based on my experience to try to let people know some more things about LFP battery cells before buying. I am trying to come up with more details and need to take the time to write them down.

My experience comes from my knowledge of the industry as a battery cell seller and I hope this will not be construed as advertising or against community policy.

I totally agree with you that it's hard for buyers to find a trustworthy deal among the many sellers.

In fact these fake batteries are not only a disservice to buyers, but also to those sellers of A-grade cells. You know, bad money drives out good money.
 

Overmind

Member
Joined
Jan 16, 2019
Messages
457
Useful info, now we need the experience with them.
For Li-ion cells I kind of know the proper weight for any 18650-21700-26650 so that's one of the 1st basic filters I use when dealing with an unknown cell.

For LiFePo4s I did not had fakes to see how they behave compared to originals. Hopefully we won't see mass-fakes any time soon.
 

100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
801
Useful info, now we need the experience with them.
I took the gamble and i ordered 96 cells from 3 different sellers.
As per your calculation methode it seems plausibel but as @slimf stated:
If they lie about capacity then misrepresenting weight won’t be a problem for them either

After buying of course 🤪 i read this topic

With some digging on the net to compare different sizes, two sellers have 90% SOH and one seller would be 65% to 70% SOH.
When they arrive i will test them immediately on weight and there story.
After that I will apply my trusted testing method.
Charge them full to 3.65v, 16 in one go(top balancing?) leave them (due time) just 24 hours
Test for IR (yr1035)
Discharge to 2.5v with 3Ah (or 6?)
And see what will come out of it.

One seller was 80Ah (95ish%soh according to your calculation)
one was 105 (90ish%soh according to your calculation)
and one stated 135, now this one is now in my doubt, according to your calculation just 65 to 70% SOH

The first rubber boat will appear around 18 April.
Sellers where from Ali express and all are refundable if the product does not meet the standards.
With best regards Igor
 
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