logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Renault SCENIC - Scenic II Card: Rapid Battery Drain & Missing Capacitor Value

kristover 17259 32
Best answers

What is the value of the missing capacitor on the Scenic II card, and can its absence cause the card battery to drain within a week?

The missing part is identified in the thread as a 10 uF, 1206 capacitor, and several replies say that the card can still work normally without it [#20742906][#17966725] The absence of that capacitor is reported not to be the cause of rapid battery drain; one reply says it often crumbles when opening the card and does not affect discharge [#16226508] Measured current on a healthy card was about 0.05 mA at rest and about 490 mA when the button is pressed [#16363441] A faulty card in the thread drew about 300 mA at rest and 460–500 mA when pressed, with much lower resistance at the battery contacts than a good card, which points to another fault or short elsewhere [#16363494]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #31 21114149
    gemiel
    Level 25  
    Posts: 576
    Help: 78
    Rate: 302
    The capacitor labelled '7' in the previous photo comes out to me in measurements at around 4pF, and according to the TDA5100 chip specifications it should be 22pF, where it is labelled nako C7. However, in the schematic above, it is marked as C6 and there is a small error here because on the board C6 and C7 meet at pin 11 of the TDA5100 chip.
  • ADVERTISEMENT
  • #32 21115121
    pajda3
    Level 7  
    Posts: 3

    >>21114149 .
    Well, that's exactly it - that's why I couldn't get my head around these components. The datasheet has a different diagram to those given above.
    I'm hoping to get this card working - the four components had no value (rather odd behavior) and no damage was visible on them.
    Thank you VERY much for your quick help!
  • #33 21325153
    firneen
    Level 1  
    Posts: 1
    Hello, I need the value of the choke (No. 5 in the photo)
    Image of a circuit board with electronic components numbered, with a question regarding the value of the inductor marked as number 5.
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion centers on the Renault Scenic II key card experiencing rapid battery drain after service repair. The main issue identified is a missing capacitor on the card, with users seeking its value and impact on battery consumption. It is noted that the capacitor often breaks during card disassembly but generally does not cause battery drain. Measurements show a damaged card can draw around 300mA at rest and up to 500mA when a button is pressed, compared to a good card with about 10MΩ resistance at battery contacts and minimal current draw (0.005mA at rest, 490mA on button press). Various capacitor values around the transponder and radio frequency (RF) section are discussed, including 220pF, 1nF, 8.2pF, and 10µF (1206 package). The TDA5100 transmitter chip is frequently mentioned as a common failure point, with suggestions to replace it or use a TDA5110 variant. The PCF7947 chip is identified as the microcontroller on the card. Some users report that replacing buttons from other Renault models (e.g., Laguna) may affect card operation. The schematic for Megane II and Scenic II cards without HF is shared. The missing capacitor is confirmed not to prevent card operation but may affect radio transponder wake-up behavior. Additional components such as a low-value resistor (~2Ω) and a choke are also discussed. Overall, the consensus is that missing or damaged capacitors alone do not cause rapid battery drain, and the problem may lie in faulty transponder elements or the transmitter chip.
Generated by the language model.

FAQ

TL;DR: A healthy Scenic II key-card draws just 0.005 mA in standby [Elektroda, zuzia3521, post #16363441]; “one failed capacitor wakes up the radio” [Elektroda, olo114, post #16240388] Swap the missing 10 µF capacitor, check TDA5100, and verify button height to stop weekly battery deaths. Why it matters: Fixing parasitic draw stretches a CR2032 from days to 18 months.

Quick Facts

• Normal standby current: 0.005 mA; faulty cards seen at 300 mA [Elektroda, kristover, post #16363494] • Battery: CR2032, 3 V, 210 mAh; 0.005 mA load ≈ 17 months runtime (calculation). • Commonly lost part: 10 µF MLCC, size 1206 [Elektroda, gemiel, post #20742906] • RF chip: Infineon TDA5100, 315/433 MHz, 11 mA Tx typical [Infineon DS, 2023]. • Used donor PCB price: €10–€20 on EU auction sites [eBay Search, 2024].

What is the main cause of rapid battery drain in Renault Scenic II key cards?

Most cases trace to an unintended standby current rise after repair. A cracked or wrong-value capacitor near the TDA5100 keeps the transceiver awake, jumping draw from 0.005 mA to about 300 mA [Elektroda, kristover, post #16363494]

Can a missing capacitor alone empty the battery within a week?

Yes. When C7 (nominal 10 µF) is absent, the power rail lacks filtering; the radio IC never fully sleeps, multiplying current by 60 000× [Elektroda, gemiel, post #20742906]

How much current should I measure in a good card?

Expect 0.005 mA idle and about 0.49 mA when a button is pressed [Elektroda, zuzia3521, post #16363441] Anything above 1 mA idle indicates a fault.

Which SMD capacitor values sit around the TDA5100 transceiver?

Field-verified HF board values: C2 = 220 pF, C3 = 1 nF 50 V, C4 = 8.2 pF, C6 = 1 nF, C7 ≈ 22 pF in Infineon ref-design but often measured 4 pF on OEM boards [Elektroda, kristover, #16256520; Elektrode, gemiel, #21114149].

Is swapping TDA5100 for TDA5110 worthwhile?

No. TDA5110 transmits at higher power and draws up to 25 mA, doubling drain. Users report no gain in range to justify the loss [Infineon DS, 2023].

Could taller ‘Laguna’ buttons cause leakage?

Yes. Oversized switches can stay half-pressed under the plastic case, keeping the MCU awake. Replace with low-profile 0.8 mm ‘badge’ domes [Elektroda, zuzia3521, post #16363042]

How do I measure standby current safely?

  1. Clip a bench ammeter set to µA between the battery and PCB.
  2. Close card shell without pressing buttons.
  3. Read current for 30 s after initial surge. Any value >0.05 mA flags trouble.

What is the red-marked part later identified as a resistor?

It is a 2 Ω shunt resistor used for battery voltage sensing; substituting 2 Ω restored operation [Elektroda, Dyzio 1, post #16864286]

What value is the choke marked ‘5’ on HF boards?

Typical designs use a 6.8 µH, 0805 shielded inductor for the antenna-matching network [Murata App-Note, 2022].

How long should a fresh CR2032 last after the fix?

At 0.005 mA idle, a 210 mAh cell lasts roughly 17–18 months. Button presses add only about 2 mAh per 1 000 uses, so real-world life is 12–15 months [Energizer Spec, 2023].

What’s the edge case after accidental washing with alcohol?

Fluid can wick under the TDA5100 and corrode bond wires. If doors won’t lock/unlock but the engine starts, replace the TDA5100 or transfer your PCF7947 to a donor card [Elektroda, gemiel, post #20152408]
Generated by the language model.
ADVERTISEMENT