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Anyone tried ordering LiFePo4 from China ?
#11
In terms of the test results the key element is if you believe the cycle life test results (test 6 - download 3)

The other chart, which is odd and unclear is in download 1, the Amp-Hours vs Volts (101# 102# series) as to why the voltage apparently increases part way through the discharge process / Ah.

The cells may well last 10yr and 2000 cycles at 0.2C, or not.


For ordering, is you don't mind paying a premium for shipping the use thier method (and pray that they turn up - who insures the shipping) This is ok for small value orders but larger values I would advise finding your own shipper. They tend to be able to export and do DAP at a cheap price for a reason...

DAP (delivered to destination port) is typical, leaving you to collect and arrange clearance. Beware if they turn up incorrectly listed as lithium cell and then try to clear them through via a different agent as the new shipper collecting the cells may refuse to handle them.

If you use your own shipper then collect Ex-Works (ExW) if your shipper can process the export license and get them out of the country and onto a ship. Typically Lithium cells are not exported with as lithium batteries due to the shipping conditions and this is part of the issue with shipping costs (premium).

No airline will legally fly a large volume of large format (>30Ah I think - check FAA and other airline shipping restrictions) lithium cells, which are notfully approved/tested/etc. so your cells will normally be on a slow boat.

This is from my experience and research of shipping half a ton of cells from China last year for my system.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#12
Document #1
(09-07-2019, 04:11 PM)completelycharged Wrote: The other chart, which is odd and unclear is in download 1, the Amp-Hours vs Volts (101# 102# series) as to why the voltage apparently increases part way through the discharge process / Ah.

So re the curves in docs linked in the post by donnib's: Volts vs Ahrs = note this graph does not have time (Hrs) across the bottom, it's not voltage vs time, it's AHrs ie capacity.
This graph just says battery voltage is lower with low current (eg left side) voltage rises with medium current (middle area) & voltage drops as expected with higher current (ie right side).
The rise like this might be from cell internal temp rise with medium currents. But yes, why volts are lower with low current discharge does seem unusual (my cells don't do that).

Factors in cycle life seem to be:
- DoD % (less DoD gives longer life), most gain in reducing from 100% to approx 80% or 90%.
- Cell voltage range (not charging to 3.65V & not discharging low either), stay on the voltage plateau is best (flatter middle part) from voltage graphs.
- charge & discharge currents (0.5C or less, eg 0.2C is better)
- not charging when cold (< 0 degC not good)
- not using in higher temps (> approx 35 degC not good)

Yeah - agree with your comments re shipping!
Running off solar, DIY & electronics fan :-)
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