European non dissipative Bypass

Status date

The bypass switch should allow, after qualification, to:

  • Avoid US export licenses (ITAR regulation for actual switches), Limit inspection cost and Shorten the procurement lead time by having an European manufacturer,
  • Get a second source for bypass switch dedicated to Li-ion batteries for space application,
  • Be compatible in term of current rating with high performance Li-ion cell and battery power range linked to serial/parallel cells arrangement,
  • Be “plug and play” with the least possible design modifications to existing batteries,
  • Keep low thermal dissipation and no open-circuit on battery serial connecting per existing technology.

200A bypass model (source: Souriau)

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  • Design as far as possible “plug and play” with inventive design for all functions.
  • Get the right design compliant for motorization and electrical resistance compromise (generic RFD to ECSS Q30 11A standard is submitted for static motorization margin).
  • Guaranty stable resistance and mechanical integrity whatever the severe environment applicable to this component (shock, vibe).
  • Ensure right operating of actuator (fuse blowing/latching).
  • Take care of right representative but not corrupting test set-up.
  • Supplier is French which simplifies purchasing activities. Their core business is connecting which leads to heritage/reactivity on the subject.
  • Rating range is shifted up which gives an advantage for more powerful batteries when comparing, especially to existing batteries using competitor 100A bypass.
  • Interface fitting with regular batteries manufactured to date (by Saft).
  • Original competitive design still aligned on A/g ratio compared to competitor’s concept involving typical compact contacts.
  • Bypass product line can be easily extended due to 100% common materials and processes on the actual design. This leads also to easier personnel and subcontractor training, Understanding of key parameter to insure right resistance and motorization, Similarity of parts and architecture.

And also:

  • Limitation of arcing effect at T2 contact opening.
  • Bypass status by visual inspection even with opaque housing material.
  • Secured fuse leads to avoid rotation and impact on actuator operating.

External interface is composed of:

  • Electrical power circuit : T1/T2/T3 terminals,
  • Electrical command circuit: T4/T5 circuit,
  • Mechanical assembly: 4 feet in housing.

Component is the assembly of:

  • An actuator whose T4T5 lead wires are the terminals (fuse wire technology as trigger of the next part),
  • A release mechanism (spool winding technology as latch of next part) combined with a compression spring for motorization purpose,
  • A power circuit including T1/T2/T3 terminals, internal contacts, mobile driver.


Bypass connecting to a battery:

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nominal mode prior activation (T1T2 bypass terminals in series with battery composed of 3 cells in parallel)

Prior activation:
T1 & T2: contact
T1 & T3: open
T4 & T5: fuse intact

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During activation:
T1 & T2 & T3: contact contact motion & «make before break»
T4 & T5: fuse blown

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After activation:
T1 & T2: open
T1 & T3: contact

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Bypass characteristics:


Rating: 200 & 480A (for 40°C ambient, vacuum)
Activation/fuse blowing energy: 3A square signal/516A² ms max
Typical heating at 75% of rating: 48°C max in vacuum,   (75% rating = application current per ESA derating; compatible with 50°C connecting heating at application current in vacuum)
Max. resistance (100% screening): 120/90µOhm (resp. 200/480A bypass)
Pulse (250ms): 600/1440A (resp. 200/480A bypass)


Sine vibe (5/100Hz): 10mm 0/peak / 20g; excursion to 25g max
Random vibe (typ. 20/2000Hz): 0,3g²/Hz max/22,5g rms (out of plane), 0,1g²/Hz max/16,4g rms (in plane)
Shock: 30g/100Hz, 1300g/2000 to 10000Hz
Assembly: Refer user manual for screws type, dimensions and torque.
Motorization: Static > 2 (min. at end of motion mitigated by dynamic)
Dynamic > 3
Mass: 115/315g max  


 Max. temperature:  143°C
 Max. operating temperature:  122°C
  Max. radiation:  300Mrad
Note: for typical electrical, thermal, mechanical or other condition out of standards, contact manufacturer for assistance.

Plan has been established in accordance with ESA quality standards.

  • Evaluation/validation of early sub-functions on prototypes (actuator, power contacts),
  • Manufacturing and testing of engineering models,
  • Manufacturing and testing of qualification models,
  • All associated documentation released per statement of work. Any non conformance, deviation or waiver identified.
Current status

Qualification was successfully completed in Dec 2006. A motorization characterization test (out of qualification) in vacuum at extreme temperature is pending.