310 Ahr 3.2V Li batteries; too good to be true?

[marchem]

I came across somebody talking about combining four of these 310 Ahr, 3.2V Li cells into a 12V package. The size ends up being about the same as a Group31, but with, apparently, 310 Ahr, compared to 100 Ahr for just about any G31 Li (or Pb-acid) battery I've ever seen.

Am I missing something here? Seems too good to be true. I know you have to add a BMS, and they probably wouldn't work for starting an engine, but as a deep cycle house battery that's a lot of juice.

BYD-310Ah-LiFePO4-Battery-Cells (batteryfinds.com)

 

[Maine Sail]

I came across somebody talking about combining four of these 310 Ahr, 3.2V Li cells into a 12V package. The size ends up being about the same as a Group31, but with, apparently, 310 Ahr, compared to 100 Ahr for just about any G31 Li (or Pb-acid) battery I've ever seen.

Am I missing something here? Seems too good to be true. I know you have to add a BMS, and they probably wouldn't work for starting an engine, but as a deep cycle house battery that's a lot of juice.

BYD-310Ah-LiFePO4-Battery-Cells (batteryfinds.com)

yes, you are Missing some details.

here’s a start.. LiFePO4 Batteries On Boats - Marine How To

 

[DArcy]

That's just 4 cells, you also need a BMS to properly charge the battery. If you just hook it up with jumpers between the cells it will not charge evenly and you will destroy cells, possibly dangerously. If you aren't sure about any of this, don't do it. Or at the very least research lithium battery charging. It does seem like a good price, but it is only part of the system.

 

[marchem]

That's just 4 cells, you also need a BMS to properly charge the battery. If you just hook it up with jumpers between the cells it will not charge evenly and you will destroy cells, possibly dangerously. If you aren't sure about any of this, don't do it. Or at the very least research lithium battery charging. It does seem like a good price, but it is only part of the system.

I understand the need for the BMS. This is not something I am interested in doing, but is part of a conversation I’m having with someone. The usage is actually in an RV; in some ways very similar to marine, in some different, I think. Maximum current output required may be less, although that may depend on the existence of an inverter, and it’s size.

The biggest question I have is how this could have 310 Ahr capacity, in the same size that most others have only 100. Even if an integrated system has a BMS and thicker casing does that account for a factor of three?

I have read Maine Sail’s article in the past, and just reread it. I’ll admit there’s a lot I don’t fully understand in there, but I think I get the main points. But I don’t remember reading anything about the difference in capacity.

 

[marchem]

yes, you are Missing some details.

here’s a start.. LiFePO4 Batteries On Boats - Marine How To

Thanks for the quick reply. It’s great to see you posting! Hope you are feeling and doing better.

My reply to Darcy above has more details, and questions.

 

[DArcy]

The biggest question I have is how this could have 310 Ahr capacity, in the same size that most others have only 100. Even if an integrated system has a BMS and thicker casing does that account for a factor of three?

Marketing. I've bought lithium cells off eBay and Amazon, most have ludicrous capacity claims. They work ok but don't have 5 times the capacity of the big brand names that actually measure the capacity properly.

 

[marchem]

Marketing. I've bought lithium cells off eBay and Amazon, most have ludicrous capacity claims. They work ok but don't have 5 times the capacity of the big brand names that actually measure the capacity properly.

That makes a lot of sense. And the price didn’t seem that great to me, especially since you need to add additional pieces to make it usable and hopefully safe.

 

[Johnb]

You do know that price is per cell so 4 of them are pushing $3500?

 

[marchem]

You do know that price is per cell so 4 of them are pushing $3500?

I think the price is for 4 cells. Even so, it’s still not impressively inexpensive.

 

[jviss]

You do know that price is per cell so 4 of them are pushing $3500?

No, that is incorrect, the price is for four cells. How do I know? I put it into my shopping cart, and then viewed the cart.

 

[Maine Sail]

#1 You are buying from an unknown Chinese vendor(BE CAREFUL)

#2 With the rate of LFP cell production happening in China right now this means thousands of "reject grade cells are produced every day. None of these cells go unsold they all go to unsuspecting buyers who don't know what they don't know.

#3 Right now AliExpress and othersleazy companies claiming to be the manufacturer are a huge dumping ground for these cells.I call these "back-door cells or cells that get sold out of the factory back door to the sleaziest of re-sellers. The front door is reserved for EVgrade cells.

#4 We have lost count of how many direct from China cells we've tested that were horribly matched/completely unusable. Hint : You cannot build a pack from mismatched cells(cell to cell Ah capacity sould be within1% max if you want good life/servivce from them !

#5Always buy from a reputable US based cell importer (electric car parts co. etc.)in-case the cells don't match/perform. It will cost you more than you paid for the cells to sip them back to China.

#6When building your own pack you are liable for, cell discharge capacity matching, Top balancing,Cell internal resistance matching, Building adequate cell compression/fixture case. Choosing& installing the right BMS. Hint : Large capacity cells cannot be adequately balanced with typical 10mA to 30mA BMS's..

Here is an example of the level of scammers going on...

here's another

 

[DArcy]

That makes a lot of sense. And the price didn’t seem that great to me, especially since you need to add additional pieces to make it usable and hopefully safe.

I just realized, the 310 AHr rating is probably wired in parallel, not series. The listing does say this:

Operational voltage: 2.5 V – 3.65 V​

Nominal capacity: 310Ah​

That's only around 77 AHr if you wired them in series for 12V. They may well meet that since the first video in @Maine Sail link measured 80 AHr although these are a bit smaller (5.3kg vs. 6kg for 4 cells).

 

[Maine Sail]

I just realized, the 310 AHr rating is probably wired in parallel, not series. The listing does say this:

Operational voltage: 2.5 V – 3.65 V​

Nominal capacity: 310Ah​

That's only around 77 AHr if you wired them in series for 12V. They may well meet that since the first video in @Maine Sail link measured 80 AHr although these are a bit smaller (5.3kg vs. 6kg for 4 cells).

each3.2V cell is 310Ah.wire four in series and you have a 310Ah. 12.8v bank..

 

[DArcy]

each3.2V cell is 310Ah.wire four in series and you have a 310Ah. 12.8v bank..

Normally yes but the listing for these cells is different, could be considered misleading because it is not the norm. The total for the 4 cells is 3.2V, 310AHr (992 W-Hr) Not 12V, 310AHr (3720 W-Hr)

 

[heritage]

https://www.amazon.com/CNEEL-CATL-310Ah-Lifepo4-Battery/dp/B096LLH1R6?th=1

These appear to be the cells that you are talking about and similar to the ones in the videos that Maine Sail linked to. The Amazon reviews are both good and really bad. The You Tube videos had similar results. You might get lucky, but for a little more money you should get cells from a reputable Chinese manufacturer and sold by a USA company after being quality checked.

 

[Garbonzo]

I just realized, the 310 AHr rating is probably wired in parallel, not series. The listing does say this:

Operational voltage: 2.5 V – 3.65 V​

Nominal capacity: 310Ah​

That's only around 77 AHr if you wired them in series for 12V. They may well meet that since the first video in @Maine Sail link measured 80 AHr although these are a bit smaller (5.3kg vs. 6kg for 4 cells).

You are overthinking this... ALL LiFePO4 cells are 3.2volts... so four, which this is clearly for, is 12ish. No other way, and yes very cheap, and yes very not a good idea unless you want issues. There are some 310 AH batteries coming on the market probably using this same form factor cells with better quality control and for more money. No free lunch and as least it is good to support SOMETHING in the USA rather than direct to China, so at least some assembly and marketing and QA gets done here, but that is my opinion.

 

[Garbonzo]

70 pounds of battery here so that is about right, little light 7.5in by 8.14 by 12 seems prepostourously small tho.

 

[marchem]

So these cells may actually have a capacity of close to 310 Ah, but their quality and lifetime are probably low. No free lunch here. Thanks to all for their comments.

 

[cagreen75]

After looking at their website I noticed so many RED FLAGS that I would never buy these. The warranty and about us page are particularly telling.