eBikes are growing in popularity and so is the battery technology associated with these exciting bicycles. Some problems that can occur with eBikes are familiar to electrical engineers/technicians in a number of sectors; electrical connector oxidation, water ingress, contact wear and even the infamous fretting corrosion phenomena. A private customer of our online shop recently emailed us with some great feedback; the dielectric connector grease called Nyogel 760G fixed a problem associated with the battery contacts mounted on a Shimano Steps E6000 series motor.
The customer reported that the e-bike electrical drive would cut out during a ride. The customer noted that the problem would appear to be random but sometimes corrected after the battery was removed/unmated and mated again. The battery/system is 250W, 36V with gold plated spade connectors/contacts. Gold is often used as a stable contact surface for electrical connections, it is a way to reduce fretting corrosion risk and gold will not react with environmental contaminants to form electrical insulating films. Pure gold can have relatively poor sliding wear performance and since gold is soft, it can be scratched or scared easily. One option to make gold harder it so add a hardener such as nickel but the process can negatively effect the otherwise inertness of gold. The solution is to make sure the gold coating applied is of a sufficient thickness. What thickness? There are theories and white papers on the web giving advice on gold plating/coating thicknesses but when gold is applied on a contact surface, much depends on the variables involved such as contact design, contact forces, temperature, expected functional life (number of cycles) etc. Because of the stability of gold, it is the material of choice for contact plating/coating in high performance electrical contact applications.
Gold is often the material of choice for electrical contact coatings but it is softer than other coatings, which means the surface can be scratched away after or during multiple mating and un-mating cycles.
The primary goal is to prevent the eBike from cutting out, so effective lubrication of the battery contacts to prevent further contact surface wear during battery changes is the first challenge. An additional challenge for any connector grease is the working environment for any e-bike; moisture ingress can of course be expected so this is a complicating factor. Plastic compatibility of the contact grease is also an important consideration so that the battery plastics do not swell or crack.
- A specialist connector grease based on a polyalphaolefin oil is ideal for this application as there are no extreme temperatures involved, just normal Summer and Winter temperatures.
- A dielectric connector grease is necessary so there is no short circuiting of pins when a grease is applied.
- The connector grease must seal the contact area and resist environmental contamination with water ingress being the most likely problem, so a formulation containing a hydrophobic silica thickener to will make the grease water repellant. Note Silica is completely different to Silicone, we DO NOT recommend using silicone on electrical connections.
- The chosen grease should NOT be conductive in an attempt to fix the problem, we DO NOT recommend using a conductive grease on electrical connectors.
- There must be no increase in contact resistance across terminations as a result of using a connector grease.
Nyogel 760G is our ‘go to’ dielectric connector grease and can be purchased at our online shop. It has a superb pedigree in a number of industry sectors, most notably the automotive sector. Nyogel 760G does not cause any increased resistance across the contact surfaces but is NOT conductive and does not contain silicone. Find out about some common myths and a few facts about the grease.
Applying The Grease
In terms of contact surface lubrication, only a thin coating of the electrical connector grease Nyogel 760G is required for the product to be effective. Quite often, the female side of a connector is the easiest option when wishing to grease connector contact surface but the male spade terminals on this Shimano device are easily accessible, quite large and also it is likely that any squirting of the grease into the female side would not reach the contact surface. So in this instance, the customer applied the 760G very diligently by squeezing a blob of 760G from a tube, on to the spade terminals, then redistributing the grease evenly over both sides of the spade contact surface.
Nyogel 760G looks like a clear gel, as a consequence it can be hard to inspect the presence of the gel/grease when applied in thin layers, so a UV dye was included in the formula to aid inspection:
The problem stopped occurring after the Nyogel 760G was applied. The customer was extremely pleased, now the customer could take care free rides without worrying about the electric drive cutting out/ceasing to work. Considering e-Bikes are a big ticket item/device to purchase, it’s amazing how just a few pennies of grease can make all the difference to the ownership experience of a eBike user.
THE NYOGEL 760G prevented the electric motor/battery cutting out and made all the difference to the e-bike owner.
It should be noted that periodic cleaning and re-greasing of the terminals would be considered best practice. The 760G will not dry up or evaporate and the grease does not migrate; however it should be considered that all grease can be mechanically pushed, so multiple battery changes will most likely mean that small amounts of grease will be lost or transferred to the the battery charger as time goes by. Also, although grease does not attract dirt, it could be that debris does slowly accumulate on the battery contact surfaces. A simple wiping away of the grease with a clean rag and the re-application of 760G is a sensible precaution/maintenance task. How often should the 760G be wiped away and re-applied? Hard to say as it depends on levels of bike use and number of battery changes per month/year, but changing the grease once or twice per year would seem sensible.
So what was the problem? What did the use of Nyogel 760G fix? Impossible for the author to be sure as we did not get to see the contact surfaces in person, but most likely a combination of oxidation and contact wear. The Nyogel 760G will prevent oxidation from occurring on the contact surfaces so an open circuit cannot be created. Fretting corrosion cannot be ruled out either, if the owner/rider experienced the ‘cut out’ mid-ride, it could be that there was microscopic debris building up between the contact surfaces as the ride progressed, building up to a point where one or more contact surfaces were affected enough to cause a failure. Why not find out more about fretting corrosion to understand what could be happening.
A Preventative Maintenance Solution, Not A Magical Repair Product
Very important that the reader notes the Nyogel 760G is not a magical repair gel/grease. The battery contacts were already damaged prior to Nyogel 760G being applied but were obviously not too badly damaged to prevent further use. The best use of a connector grease is to apply to your eBike immediately after purchase and prevent the problem starting. The connector grease will prevent further contact wear and any oxidation problems, but a connector grease is dielectric, not conductive….we never recommend using a conductive grease as it most likely lead to further problems.