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October 20, 2019, 12:14:45 12:14


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Author Topic: Experience with chinese LiFePo4 batteries?  (Read 1329 times)
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zac
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« on: June 14, 2019, 08:21:49 20:21 »

I'm trying to set up an offgrid solar system and came across these LiFePo4 batteries that are much cheaper than the typical ones designed for telecom.  A [email protected] pack with battery management electronics is only US$0.56/watt-hour and the bare [email protected] cells are  US$0.44/watt-hour (including shipping).    

Any thoughts about these chinese made batteries and battery management systems?

https://www.amazon.com/dp/B07QCS2WDH

https://www.amazon.com/LiFePO4-Lithium-Phosphate-Off-Grid-Applications/dp/B07SCZ7PBF

http://www.ruixulithiumbattery.com/

I've used these telecel batteries before, but they are too expensive (US$2.50/watt-hour) for my budget.  (I still have a couple [email protected] leftover ones I attached to a UPS.)

http://www.pbtelecom.net/PBT-204%20Telecel%20Range%20Product%20Spec.pdf
« Last Edit: June 15, 2019, 11:26:07 11:26 by zac » Logged
PICker
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« Reply #1 on: June 15, 2019, 03:02:53 03:02 »

I don not have direct experience with LiFePo4 but only with Lead Acid batteries.
It seems that LiFePo4 technology is much better than LA.
I've found some online comparison/discussions that can support your choice:
https://www.youtube.com/watch?v=ZkMk8djVUQk
https://www.arkportablepower.com/blogs/news/54925381-deep-cycle-lifepo4-vs-lead-acid-pros-and-cons
https://www.eng-tips.com/viewthread.cfm?qid=448676
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pickit2
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« Reply #2 on: June 15, 2019, 06:25:20 06:25 »

in a project in my last place of work there was a question as to use LiFePo4 or Li-on batteries.
Li-on won on cost, both in useage and battery management.

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zac
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« Reply #3 on: June 15, 2019, 11:48:35 11:48 »

Sorry, I meant to ask if anyone had any experience with chinese made unknown brand LiFePo4 batteries and BMS.  

Here's some useful comparison info about various rechargeable lithium chemistry batteries:

https://batteryuniversity.com/learn/article/types_of_lithium_ion

I prefer LiFePo4 for applications without space/weight constraints as in the case of stationary offgrid solar.  But, LiFePo4 is reputedly more sensitive to manufacturing process (like contamination) than others so there is higher chance of low quality cells.  Cycle life is much higher than conventional lithium ion so is better suited for solar daily cyclic use.    





Info on lithium battery aging:

https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Tesla uses conventional lithium ion 18650 cells in their automotive and power wall packs with supposedly 10 year warranty.   Solar duty means daily cycle so 3650 cycles of varying depth-of-discharge in 10 years.  It's surprising that they could warranty their powerwall to maintain 70% of its rated capacity over 10 years unless the actual capacity when new is substantially higher than their rated capacity.  

https://www.energysage.com/solar/solar-energy-storage/tesla-powerwall-home-battery/

This thesis about LiFePo4 aging may be of interest:

https://uwspace.uwaterloo.ca/bitstream/handle/10012/12177/Catton_John.pdf?
« Last Edit: June 15, 2019, 12:20:33 12:20 by zac » Logged
maurer
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« Reply #4 on: June 16, 2019, 06:50:40 06:50 »

Form my experience LiFePo suffer from unbalancing problem more than the classical good 18650 (panasonic, samsung). You will probably need some active balancing circuit.
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zac
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« Reply #5 on: June 16, 2019, 09:45:51 21:45 »

This is the board from one of the Telecel batteries.  These were designed as drop in replacements for lead acid AGM batteries for telecom applications.  The documentation received with these batteries was very limited.  They include what appears to be a 4 wire interface, but it is undocumented beyond labels (LOW-C, ALL-UP, FFULL, DGND) and was not used in our application.  I'm not sure what everything on that board does, but there is a resistor array and mosfet associated with each of the 7 cells which presumably balances while charging by shunting current across the cell to the resistor array (seven 470 ohms resistors in parallel) when the voltage exceeds the desired threshold.  

Each cell has these parts associated with it:

The 8 pin soic is a low dropout LP2951 voltage regulator
The 14 pin soic is a MCP6544 quad analog comparator
The 16 pin soic is a TLP291-4 quad optocoupler

There is what appears to be an unidentified ST microcontroller in the white box:
(I'm assuming it isn't an LM339 since there is a reset button associated with it.)




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vern
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« Reply #6 on: June 17, 2019, 06:34:22 06:34 »

it is a LM339, they don't have controllers with "339" and also nothing with 14 Pins SO housing.
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bigtoy
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« Reply #7 on: June 18, 2019, 11:52:00 23:52 »

I've used some small LiFePO4 batteries from the Chinese company "Soshine" in a couple of projects. These have been single-cell nominal 3.2V cells. I've been pleased with them. Capacity has been approximately what's claimed, and lifetime has been good. I'm certainly a fan of LiFePO4; I much prefer them to LiPo (which I've also used).
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