Robustness, repairability, and reusability of the NFCP3628B

These batteries are replacing the familiar NEE1009-W batteries. The NEE1009-W batteries are in use with various scooter rental companies in Norway and around the world.

Battkomp has repaired some  NEE1009-W batteries with connector issues, but the repair process was too time consuming and therefore expensive to scale. We could not do anything about the water damaged batteries.

The photo shows the connector issue on the NEE1009-W: the power socket plating would damage rendering the battery unusable. The only solution to that is to replace the connector.

Battkomp has also completed teardowns of the NEE1009-W with the goal of reusing the cells. That has proved to be not commercially attractive due to the potting material used in the battery.

This teardown has taken place at Battkomp's workshop in Oslo, between 18th and 20th December 2022.  The battery we worked on carried the serial number 19BEQ22DDC0760. The goal is to provide an independent evaluation of the new generation NFCP3628B battery from a robustness, repairability, and reusability perspective.

Characteristics and appearance

28700 mAh / 1033 Wh

10INR22/71-6

• 10 means there are 10 cells groups in series, thereby giving a nominal voltage of 36V
• INR = lithium iron phosphate cylindrical cell
  • I = lithium ion
  • N =nickel/manganese oxide cathode
  • R = round cell type
  • INRs are also sometimes called “LiNiMnCoO2” or “NMC”
• 22/71 means it has 21700 cells (Samsung-50E)
• 6 means that there is 6 in parallel - this is a 10S6P configuration

Similarities with previous generation

• Produced by the same company
• Compatible with the same scooters
• Same outer dimensions
• Approximately the same capacity
• Uses the same chargers
• IP rating IPX7
• Potted for better water- and vibration-resistance

Differences from previous generation

	NFCP3628B (new)	NEE1009-W (old)
Cells	60x 21700 format	90x 18650 format
Capacity	1033 Wh	1009 Wh
Housing material	Aluminium	Plastic
Housing structure	Extruded tube with two cast end pieces, held together by 12 screws	Two plastic tubs held together by clips and 13 bolts

The difference in the housing structure has significant implications when it comes to repairability, as we will explain later.

Tests before teardown

• The discharge connector does not show the full voltage unless it is enabled through communication
• Therefore, we did not do a discharge test
• Charging is possible without communication, and that way we could learn the pack voltage before opening

Teardown

This document refers to the end cap with the connectors as the 'connector end', and the other one as the 'far end'.

Bolts

• T15S bolts torqued to 1NM only, M4 thread w/ Loctite (blue), 6 on each end.
• On the far end, there are 4 more T15S bolts that bolt into the battery pack spacers. Their heads are covered under gel.
• Discharge connector has 4 T10S bolts, but even with those out, it is impossible to remove due to excess use of glue.

Connectors

Couldn't press the pack out of the aluminium tube due to the potting material holding it in place too strong. With a purpose built press, it would be possible to press it out safely.

It seems the potting material was poured in from the far end, which has two openings for seemingly that purpose.

BMS

Design highlights

Robustness

Pros:

• Extruded aluminium frame with cast aluminium end pieces, as opposed to the plastic halves design
  • Much stronger, much less likely to crack
  • Better conductor of heat
  • Does not burn or melt easily - more likely to contain a malfunction
• Shorter seals - less opportunity for failure!
• Filled with silicone again - good for durability!

Cons:

• The seal on this battery runs around the longest axis, and therefore touches the ground when stored. This is not great when stored on ground where there might be water puddles.

Repairability

Pros:

• Easy to open
• The connectors are no longer soldered directly to the BMS - they are connected through connectors!
• All the problematic pieces on one end - easy to replace!

Cons:

• Filled with silicone again - no good for repairability.
• Not possible to easily remove the discharge connector itself: the connector end needs to be replaced as a module

Reusability

Pros:

•  21700 cells are more attractive for reuse than 18650 cells, because they are easier to harvest
• Convenient shape and large size ideal for reuse as is

Cons:

• Cell harvesting would only be possible with purpose built press setup
• Module level reuse would require the communication to be opened (doable)

It is important to declare that the best reuse is the one that needs not happen. With these batteries being so robust and more repairable than the previous generation, as well as compatible with a large fleet of future-proof scooters used by a large number of companies, it is unlikely that they would become available for repurposing - they will be worn out in their originally intended application!