Our NEW GO-TO LiFePO4 vendor...09.20.21

[Henderson]

On the charging issues - JRed and I recently got my batteries in and top balanced them. He got them a few days before I got there and put them in sets of 4 on a 12V Victron charger without a BMS. 2 of the cells went up to 3.8V before he caught it and shut them down.

I ordered an iCharger S6 which arrived the same day I got there. We hooked up each set of 4 in parallel and charged at 3.65V. The iCharger is awesome, by the way. 40A at any voltage you want up to around 14.6V. (maybe higher, I haven't checked) Most of the sets were full in 10-20 minutes, but 2 of the groups ran much longer. I forget the exact amount of time but it was around 10 hours. From 0 it would have taken 28 hours at 40A, and was nowhere near that.

The 2 cells that went high settled right back down once we put them in parallel. They are now working in the full 16s banks, and are all balanced to within 10mV. There was no swelling at all. So a bit of over-voltage is fine, nothing to worry about. Along the way I did some research and found that people used to charge these above 4V and discovered that battery life suffered, so they gradually eased it back and 3.65 as a max is now a de-facto standard. But that does not mean they can't ever go over that and will immediately die. It's more like many cycles at higher voltages will begin to do damage and shorten life.

I recommend the iCharger. S6 is 40A, X6, X8, and X12 are 30A. All are fairly similar, just have different numbers of balance leads. Their price/performance/precision/flexibility is better than any other charger I've seen for the 0-15V range.

Are there iChargers for 16S configurations? Or, if I get the 8S, can I break up my 16 cells into 2P8S and top balance that way and then break it down and place it in 16S?

 

[upnorthandpersonal]

What would 10% and 20% SOC voltage values be?

Voltage with LiFePO4 isn't a good SoC indicator. You need a Coulomb counter to really know this - many BMS have this integrated, or use a stand alone shunt such as a Victron SmartShunt.

If you want to use voltage, you can only put some limits: for example 3V lower and 3.45V upper limit per cell. These won't correlate to SoC exactly, but are pretty decent safety margins for a long life time. Keep in mind that calendar aging will most likely have more impact than cell use on typical solar applications since we don't have high C rates and don't usually have full cycles very often.

 

[Don B. Cilly]

Are you aware of the fact that "In 2019, four of the seven SI base units specified in the International System of Quantities were redefined in terms of natural physical constants", including the Ampere - and therefore the Coulomb?

Which could explain why my Victron shunt is mainly good for guessing lottery numbers?

But what worries me, they redefined the Mole. So, supposedly, any game of Whack-a-Mole is now all out-of-whack. Like my shunt, basically.


Sorry, sorry, couldn't help it :·)
-

 

[Henderson]

Voltage with LiFePO4 isn't a good SoC indicator. You need a Coulomb counter to really know this - many BMS have this integrated, or use a stand alone shunt such as a Victron SmartShunt.

If you want to use voltage, you can only put some limits: for example 3V lower and 3.45V upper limit per cell. These won't correlate to SoC exactly, but are pretty decent safety margins for a long life time. Keep in mind that calendar aging will most likely have more impact than cell use on typical solar applications since we don't have high C rates and don't usually have full cycles very often.

Ok, I see your point. Makes sense. Thanks.

 

[Rossman]

Are there iChargers for 16S configurations?

No - you don't use the balancing leads of the icharger. people just use them to top balance cells in parallel because they can deliver up to 40A instead of the usual 10A benchtop supply.

 

[Henderson]

No - you don't use the balancing leads of the icharger. people just use them to top balance cells in parallel because they can deliver up to 40A instead of the usual 10A benchtop supply.

Hi Rossman. Just to make sure I understand, so we're putting the 3.2v cells all in parallel and connecting them to the icharger and top balance that way? And once completed, build the 48v battery?

 

[Rossman]

Hi Rossman. Just to make sure I understand, so we're putting the 3.2v cells all in parallel and connecting them to the icharger and top balance that way? And once completed, build the 48v battery?

That is correct!
If you need more information on top balancing then you can refer to this document: https://diysolarforum.com/resources...ls-using-a-low-cost-benchtop-power-supply.65/

 

[Henderson]

That is correct!
If you need more information on top balancing then you can refer to this document: https://diysolarforum.com/resources...ls-using-a-low-cost-benchtop-power-supply.65/

Nice...thanks.

 

[Pendrak]

I just receive my eve cells (LF280K) from Docan, i use the QR code to check then, it say that was manufacture 1 year ago (april/may 2021), this is a problem?

All cells looks good, they arrive at perfect condition, i test the voltage on all cells and show 3.29 volts, i need do discharge test but i don't have the equipment right now.

EDIT: Volts wrong thanks to Mastech multimeter

 

[Just John]

I just receive my eve cells (LF280K) from Docan, i use the QR code to check then, it say that was manufacture 1 year ago (april/may 2021), this is a problem?

All cells looks good, they arrive at perfect condition, i test the voltage on all cells and show 3.406 volts, i need do discharge test but i don't have the equipment right now.

One year is not a problem. The 3.4v is not good, they were shipped fully charged. They should not be stored fully charged. It is actually against the law to ship them fully charged.

 

[740GLE]

Do you have another meter to check your reading against? Don’t think I’ve ever heard them shipping anything but 3.29v cells.

 

[Pendrak]

Do you have another meter to check your reading against? Don’t think I’ve ever heard them shipping anything but 3.29v cells.

Thank you, now i know that i have to send to trash CAN my MASTECH multimeter, see this:

 

[Rossman]

Thank you, now i know that i have to send to trash CAN my MASTECH multimeter, see this:

damn!

 

[740GLE]

Elekcity for the win, lol.

Bummer about the other DMM, I’ve never had one go bad.

 

[Bud Martin]

BTW, low meter battery can make the reading show higher than it should be.

 

[smdl]

Hi, folks. Just thought I would put up another endorsement of Jenny Wu. I ordered 16 LF280K cells from Jenny back in January, and they finally arrived yesterday in very good condition. I'm in Canada, so was not able to order through the US warehouse, and had to wait for shipping from China. Initially, there was a delay for Chinese New Year, followed by extensive delays for shipping backlog and especially COVID lockdown. Through all of this, Jenny kept me well-informed, and was very patient with my repeated requests for updates as time passed. She was always completely honest and forthright, despite the fact that I was sometimes frustrated by delays that were beyond get control. She is a true professional, and I wouldn't hesitate to order from her again. Find her on Facebook!

 

[Rossman]

I'm adding a conditional endorsement of Amy @ Docan - received 3 out of 16 boxes of batteries today and the batteries all appeared to be in good shape on initial inspection. One of the boxes looked like it had taken quite the fall but the packing foam seems to have done its job and I noticed nothing unusual about any of the batteries in that box.

I will post an update when the remaining batteries are delivered and I get a chance to test them.

 

[740GLE]

You order 280k?

 

[Rossman]

You order 280k?

Yeah! 64 in total :D

 

[Pendrak]

Price?