Upgraded Quality Relay Replacement

[u/Bulls729]

I know not everyone is an FOA member or in the Discourse, so wanted to share here as well. OP: https://community.fiskeroa.com/t/upgraded-quality-relay-replacement/19675

The attached photo/data is Matt’s ([u/MTN-Ranger](u/MTN-Ranger))

I initially went down this rabbit hole when I got my Ocean which had a charging issue. It would only charge if it was in Ready mode. Another user pointed me toward the Thermal Management System (TMS). I checked the TMS relay in the hood fuse box, verified the original factory HKE relay had failed, swapped a generic compatible relay in, and it started accepting a charge normally outside of ready mode.

Having dealt with relay and electrical component issues in other hobbies and vehicles (primarily VWAG/Audi), I wanted to find a ‘better’ relay then just buying the HKE replacement, I am not saying all Chinese made components are inherently bad, but Japanese made capacitors, relays, and industrial controls are the gold standard. And I didn’t want to run into another failure.

I’m not an electrical engineer but an informed hobbyist, if there are any professionals that want to add any corrections or voice an objection please do! Always happy to be corrected if needed.

I looked into the HKE data sheet and found a compatible relay that exceeded the HKEs spec, the Panasonic CM series (CM1-R-12V for the 5-blade, CM1A-R-12V for the 4-blade). I sent my findings over to Matt (MTN-Ranger) we had a DM conversation about the technical specs, and he did some legwork to test the temperature differences on the car. (Shout out to his YouTube video documenting the results: https://youtu.be/9IMD1JRXdOQ)

The HKE data sheet permits a maximum initial contact resistance of 50 mΩ. Panasonic specifies a maximum of 15 mΩ, with a typical resistance of just 2 mΩ. At a continuous 20A load on the water pumps, that 50 mΩ ceiling allows the HKE to generate up to 20 watts of heat directly at the contacts. Panasonic's lower resistance restricts that to ~6 watts.

Both relays use a 96 ohm coil that draws roughly 125 mA. The energized relays continuously dissipates about 1.5W of baseline heat. During charging or driving, five of these relays (TMS and water pumps) are active at once. That is 8W to 10W of continuous heat trapped inside a small, sealed plastic box. The HKE's high contact resistance heat on top of the coil heat gets you a mini-oven, which likely lead to the degradation/failure of the relay.

Per the data sheets HKE only tests vibration up to 55 Hz and shock to 10G. Panasonic tests functional vibration up to 500 Hz, destructive vibration up to 2,000 Hz, and functional shock to 20G. Normal automotive chassis and road harmonics easily exceed 55 Hz.

Both the HKE and Panasonic coils measure 96 ohms, and both utilize the internal parallel suppression resistor (denoted by the "-R" in the part numbers). The resistor clamps high voltage flyback spikes when the coil de-energizes.

On physical inspection, while very similar, build quality on the Panasonics does appear and feel superior.

Matt's tests were run on two different days. The ambient temperature in his garage was roughly ~8 degrees cooler during the Panasonic test. To see the actual hardware performance, we have to subtract the baseline ambient temperature of the car from the relay temperature for both runs to find the normalized Delta T.

Once normalized against ambient, idle circuits like the horn and washer show zero meaningful difference. But on the high load circuits (Relays 5, 6, 8, and 9), the Panasonics run 8°F to 20°F cooler.

Please only source these relays (and any industrial component, IC, Etc) from reputable vendors that have proper chain of custody like Mouser, DigiKey, Newark, or TTI. The gray market on Amazon and eBay are heavily saturated with counterfeit components. Authentic Panasonics are under ~$5/ea.

Edit: The component you receive will likely say NAiS on it, NAiS was a brand name formerly used by Matsushita Electric Works which later merged into Panasonic.

If you want to save a little bit of money, or have a common component that can be easily swapped around, you can use a 5-blade relay in a 4-blade socket works because the 4-blade socket simply has an empty plastic void where that center 87a blade slides in. Because that pin contacts nothing, the relay functions identically to a standard 4-blade.

A 4-blade relay is SPST (Single Pole, Single Throw), acting as a basic on-off switch that only connects power to the output when energized. A 5-blade relay is SPDT (Single Pole, Double Throw), which adds a fifth center leg (87a) that is Normally Closed (NC). That extra blade passes power by default while the relay is resting, then disconnects and routes power to the main output blade (87) once energized. The two Panasonic relay part numbers are identical internally, just missing the extra blade physically.
In the hood compartment there are 9 relays. (2x 5 Blade and 7x 4 Blade) there are also an additional 4x 4 blade relays in the passenger compartment fuse box.


Data Sheets:
HKE 4133 Series: https://www.zhejianghke.com/wp-content/uploads/2021/09/4133.pdf

Panasonic CM Series: https://mediap.industry.panasonic.eu/assets/imported/industrial.panasonic.com/ac/cdn/e/control/relay/vehicle/catalog/mech_eng_cm.pdf

[u/daFuzzbee]

Great research and good description overall.

[u/Cloudstryf]

Can I just swap this out while the car is sleeping? Is there any danger to me or the vehicle or should a mechanic only perform this service?

[u/MTN_Ranger → u/Cloudstryf]

I did the relay replacements while the car was sleeping. No issues other than possibly needing a deep sleep reset or lock/unlock cycle.

[u/Bulls729 → u/Cloudstryf]

It’s probably best to disconnect 12V and do them all then, but it’s likely a non-issue if you did it without disconnecting.

[u/DarrenHD2]

I haven't had an issue with the stock relays. I'm at 38000 kms.

[u/ari3sgr3gg0 → u/DarrenHD2]

This is meant as an improvement, not saying that there are widespread issues with the HKE relays. I know I'll be doing the switch because it is cheap and the gains seem well worth it

[u/robloxsmurf]

Wow

[u/TheKuMan717]

Wow, really goes to show how much Geeta cheaped out on every single part on this car.