Hello from Italy

asato

New member
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Jan 1, 2021
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3
I'm Alex (alessandro) from Rome, Italy. Happy New Year to all;)
thanks to your work on this forum, you are a mine of knowledge.
in this "look down" period. thanks to this forum i'm learning to build my first power wall. for now I am testing 700 cells. I already have a photovoltaic system with lead batteries, when they are exhausted I will change them with recycleds li-ions.:)
 

OffGridInTheCity

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Dec 15, 2018
Messages
1,242
Welcome. 700cells could be turned into a respectable 7s100p (24v) or 14s50p (48v) powerwall - have you decided how you plan to configure them?
 

asato

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Jan 1, 2021
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thanks offgrid, happy to be here. from what I understood reading on the forum, I would like to get 14s80p or 15s80p to not stress the cells, my inverter is 48v. so I need, 1120/1200 cells. I have to find 500 more cells !!! and use them 3,5v-4v (49v-56v) or 3,3v-4v (49,5v-60v). for the test of the cells I have 2 liitokala lii-500 the resistance (ir) measured is acceptable? or better to buy a separate ir-tester?
 

OffGridInTheCity

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Dec 15, 2018
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1,242
>use them 3,5v-4v (49v-56v) or 3,3v-4v (49,5v-60v).
Very reasonable. You'll find that 3.4v-3.5v is pretty much the low as this is where the discharge curve 'knee' drops sharply with 18650. 3.3v is not unreasonable but in daily practice for extra long life @ 14s I cut-off at 49.5v(3.54) - 49v(3.5v).

> I have 2 liitokala lii-500 the resistance (ir) measured is acceptable? or better to buy a separate ir-tester?
I'm on the 'lax side' of IR testing and just use my OPUSs (similar to litokala) which report IR pretty imprecisely/wildly. I might get 60mOhms or 80mOhms and say OK knowing this is likely off 50%. I typically toss if over 100mOhms per my OPUSs but this is just a guess over 3 years of using my OPUSs. However, my powerwall is large enough that the 'per cell' charge/discharge is quite small (e.g. 150ma-300ma/cell) and so IR doesn't hurt me as much as if I were doing 1a/cell.

Here's a recent thread on a RC3563 IR tester - https://secondlifestorage.com/index.php?threads/rc3563-ir-tester.8380/#post-68178

Maybe @Wolf (IR expert) will weigh in :)
 
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asato

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Jan 1, 2021
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3
ok, thanks offgrid for the explanations, go for 14s. and for now (ir) <80mOhms, now I will try to decide for the bms (there are many topics to read). thank you again! :)
 
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