Difference between revisions of "DIY E-Bike Battery"

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(Individual Cell Measurements: added out-of-the-box voltage measurements for Row 07. One more essentially-dead cell ☹️)
(Individual Cell Measurements: added out-of-the-box voltage measurements for Row 08)
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Revision as of 00:21, 28 July 2021

A project by User:Jpt4 and AVH to homebuild batteries their personal ebikes.


Contents

Cells

120 (total) LiFePO₄ 26650 cells purchased from Battery Hookup for the $228. Specifications:

  • Make/Model: K2 LFP26650E
  • Size: 26650
  • Voltage: 3.2
  • Capacity: 3.8 amp-hours (12.16 watt-hours)
  • Maximum Voltage: 3.65 (safe) 4.1 (maximum)
  • Minimum Voltage: 2.5 (safe) 2.0 (minimum)
  • Continuous Discharge Current: 12 amps
  • Maximum Discharge Current: 28 amps for 30 seconds
  • Recommended Charging Current: 3.8 amps

Packaging

The cells arrived in a tightly-fitting two-piece vacuum-formed plastic package that holds all the cells vertically in a 10x12 grid. The top of half of the package had some splits and cracks near one corner. The package, along with a desiccant pack, was in a thin plastic bag, zip-tied shut, in an exactly-fitting cardboard box.

Labels and Markings

Each cell is marked from the factory:

  Li-Ion IFpR27/65
+ K2 Energy LP26650E-3800-21 -
  3.2V 3.8AH(12.16Wh)

Also, each cell has a serial number in a QR code near the negative terminal, (usually, but not always) on the side opposite the label. The dot-matrix printer that made the codes wasn't perfectly aligned, so many cells have codes that are slightly distorted and difficult to scan. Using the Barcode Scanner app, I found the codes could be scanned more reliably sideways.

To make it easier for us to keep track of the cells, the first time each cell was removed from the packaging, we gave them a three-digit number corresponding to the row and column they were from in the box. 000 is from the top-left, 009 is from the top-right, 110 is from the bottom-left, and 119 is from the bottom-right. The labels are written in permanent marker on the ample blank, white space on the cell wrappers, and underlined so that there is no ambiguity which way the number is supposed to be read.

Individual Cell Measurements

K2 26650 Li-Ion Cells
Serial Number Label Out-Of-The-Box Voltage
PH190223-132431 000 3.29
PH190223-132415 001 3.29
PH190223-132362 002 3.29
PH190223-132351 003 3.29
PH190223-132270 004 3.29
PH190223-132286 005 3.29
PH190223-132393 006 3.29
PH190223-132397 007 3.29
PH190223-132328 008 3.29
PH190223-132317 009 3.29
PH190223-132458 010 3.29
PH190223-132442 011 3.29
PH190223-132426 012 3.29
PH190223-132378 013 3.29
PH190223-132265 014 3.29
PH190223-132281 015 3.29
PH190223-132457 016 3.29
PH190223-132424 017 3.29
PH190223-132392 018 3.29
PH190223-132344 019 3.29
PH190223-132367 020 0.00 😭
PH190223-132350 021 3.29
PH190223-132334 022 3.29
PH190223-132233 023 3.29
PH190223-132269 024 3.29
PH190223-132462 025 3.29
PH190223-132398 026 3.19 🙁
PH190223-132414 027 3.29
PH190223-132413 028 3.29
PH190223-132333 029 3.29
PH190223-132394 030 3.29
PH190223-132361 031 3.29
PH190223-132345 032 3.29
PH190223-132329 033 3.29
PH190223-132296 034 3.29
PH190223-132280 035 3.29
PH190223-132409 036 3.29
PH190223-132425 037 3.29
PH190223-132440 038 3.29
PH190223-132360 039 3.29
PH190223-134729 040 3.29
PH190223-134648 041 3.29
PH190223-134519 042 3.29
PH120223-134644 043 3.29
PH190223-134515 044 3.29
PH190223-134691 045 3.29
PH190223-134713 046 3.29
PH190223-134628 047 3.29
PH190223-134632 048 3.29
PH190223-134760 049 3.29
PH190223-134552 050 3.29
PH190223-134712 051 3.29
PH190223-134631 052 3.29
PH190223-134708 053 3.29
PH190223-134595 054 3.29
PH190223-134755 055 3.29
PH190223-134536 056 3.29
PH190223-134692 057 3.29
PH190223-134696 058 3.29
PH190223-134599 059 3.29
PH190223-134756 060 3.29
PH190223-134675 061 3.29
PH190223-134697 062 3.29
PH190223-134584 063 3.29
PH190223-134744 064 3.29
PH190223-134596 065 3.29
PH190223-134740 066 3.29
PH190223-134643 067 3.29
PH190223-134681 068 3.29
PH190223-134568 069 3.29
PH190223-134579 070 3.29
PH190223-134739 071 3.29
PH190223-134761 072 3.29
PH190223-134680 073 3.29
PH190223-134551 074 3.29
PH190223-134676 075 3.29
PH190223-134563 076 0.65 😢
PH190223-134723 077 3.29
PH190223-134745 078 3.29
PH190223-134664 079 3.29
PH190223-134728 080 3.29
PH190223-134564 081 3.29
PH190223-134724 082 3.29
PH190223-134627 083 3.29
PH190223-132318 084 3.29
PH190223-132446 085 3.29
PH190223-132365 086 3.29
PH190223-134709 087 3.29
PH190223-134693 088 3.29
PH190223-132399 089 3.29

Cell Testing

Out-Of-Box Voltage

When the package arrived, cell voltage was measured with the Ballantine 3028A bench multimeter.

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