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kris
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Cheap lifepo4 Nov 4, 2023 18:32:35 GMT via mobile

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Post by kris on Nov 4, 2023 18:32:35 GMT

If these are real then they could be a good deal
selianenergy.com/collections/hakadi/products/hakadi-12v-200ah-lifepo4-lithium-battery-pack-2560-with-build-in-bms-and-14-6v-20a-charger?fbclid=IwAR3lSkMe9NmAC8sKa9trEdmT4V4txFNtXL7ps1F0CGxkGEhOO7TdTWUOpQE

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Cheap lifepo4 Nov 4, 2023 19:55:53 GMT via mobile

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Post by ‎ on Nov 4, 2023 19:55:53 GMT

For a 200Ah nominal 12v battery (4S LFP) these figures don't look great

Standard charging method: Constant Current 0.2C，Constant Voltage 14.6V，0.01C cut-off
Max. charge current: 50A

I think I would want to be able to charge faster than that if using rotating electrics. Maybe ok for a fairly small pv array.

You can call me admirable.

kris Super Member Posts: 22,559	Cheap lifepo4 Nov 4, 2023 20:00:41 GMT via mobile Quote Select Post Deselect Post Link to Post Back to Top Post by kris on Nov 4, 2023 20:00:41 GMT Yes it does seem that the quality might be questionable.

Telemachus Super Member Posts: 13,590	Cheap lifepo4 Nov 4, 2023 20:11:27 GMT Quote Select Post Deselect Post Link to Post Back to Top Post by Telemachus on Nov 4, 2023 20:11:27 GMT Obviously a cheap low spec BMS. But depending on the application, that might not be a deal breaker.

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Cheap lifepo4 Nov 4, 2023 21:00:02 GMT via mobile

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Post by ‎ on Nov 4, 2023 21:00:02 GMT

I was chatting to a friend (!) about this and he reckons it is not always to do with the BMS. His theory was that factory seconds, or thirds, are packaged into lower cost modules for onward sale with inferior specifications.

The modules we were talking about at the time were 'TN Power'.

Of course the ad for these ones says 'Grade A cells' but this seems like a throwaway phrase and I can't really see how it could be proved.

You can call me admirable.

Telemachus
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Cheap lifepo4 Nov 4, 2023 21:43:02 GMT

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Post by Telemachus on Nov 4, 2023 21:43:02 GMT

Nov 4, 2023 21:00:02 GMT ‎ said:

I was chatting to a friend (!) about this and he reckons it is not always to do with the BMS. His theory was that factory seconds, or thirds, are packaged into lower cost modules for onward sale with inferior specifications.

The modules we were talking about at the time were 'TN Power'.

Of course the ad for these ones says 'Grade A cells' but this seems like a throwaway phrase and I can't really see how it could be proved.

It is true that one of the attributes of grade A cells vs lower grade cells, is the internal resistance and hence the ability to charge and discharge at fast rates. However we are talking about very fast rates, much faster than 1C, such as might be needed for an electric vehicle. I think it is highly unlikely that the cell performance is anywhere near the limiting factor here. It is just about the MOSFETS used in the BMS switching, which have to pass all the charge and discharge current when in the "on" condition.

Post by kris on Nov 4, 2023 18:32:35 GMT

Post by ‎ on Nov 4, 2023 19:55:53 GMT

Post by kris on Nov 4, 2023 20:00:41 GMT

Post by Telemachus on Nov 4, 2023 20:11:27 GMT

Post by ‎ on Nov 4, 2023 21:00:02 GMT

Post by Telemachus on Nov 4, 2023 21:43:02 GMT

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