Those are designed to keep a constant clamping force and unless you are using a torque wrench to tighten the bolts, which you should be but almost nobody, including me, actually dose, the point is almost moot. I would recommend replacing them with either BZP equipment's or better still shakeproof star washers, also BZP. The latter are less springy so if you over tighten them they will be flat when you remove the connection, clearly indicating that they have been crushed beyond what is required. Ideally you still want to fit a new one every time you reconnect but in the real world these will teach you to get the torque more or less correct.by feel, and at the same time lock the nut in place without the need to over tighten it.

I will probably get called out for saying this, as not using a torque wrench is demonstrably incorrect, but given the real world, I personally feel that... Lug - Flat washer - Shakeproof washer - Nut, is a secure and safe alternative to not buying a £150 torque wrench to use once every couple of years.

Thanks for the reply, Alistair. I was thinking I'd just buy the copper spring washers below off of amazon to try to match the originals as much as possible. You are right about the torque. The specified torque values are not even to the initial stopping point using a ~standard size torque wrench. It's hard not to want to tighten them just a little bit further. It would probably help if Victron explained the reasoning behind their torque values, i.e. people wouldn't just crank down on the nuts until they couldn't turn them any further.

"uxcell M8 Copper Split Lock Sealing Ring Spring Washer Fastener 8pcs)"

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Agree with @Alistair Warburton on all points.

Lock washers serve several purposes

• Provide compliance and stored energy to maintain contact pressure over long service life
• Have anti-rotation feature to resist vibration
• Their compliance gives a more gradual tightening curve so it is less easy to over-tighten

Starlock washers are IMO better for antivibration as they have multiple edges but perhaps slightly less good on the other two.

If you use a ring-spanner or open-ended spanner rather than a socket set their length varies with the nut size so making it less likely you will over-torque the nut. IME torque wrenches produce pre-load which is heavily dependent on friction conditions (old, new, dirty, oiled) so less useful than having a good sense of how the force is varying as you get to the end point. As @marksmartt says he has found.

To the newbies like myself, it seems counter-intuitive that a tighter nut would be less secure against vibration, etc. than a looser one. But I guess logic says stop (~just) before completely flattening the lock washer. I was initially thinking that Victron using the copper washer had something to do with better conductivity even though its placement/order on the screw didn't suggest that. Sounds like the lock washer being copper (apparently) was just to limit how much torque was applied vs, say, a stainless steel lock washer. Thanks to all for your info!

It gets way more complex than that... Nothing springy in the system means that even the slightest movement results in a loose connection. In reality everything is a bit compliant but in general too tight risk damage and may actually be less secure over time.

Material science comes into it too, SS is horrible stuff for electrical and thermal connections and there would be significant galvanic potential between the mating faces risking corrosion, pitting and even mechanical damage due to oxide growth. It is surprising how much design go's into an electrical fastening/terminal spec.

Has anyone at Victron confirmed exactly what material the original split spring washers are made from? If these are indeed intended to be single use then it should be possible to buy replacements either through Victron distributors or, if a spec is published, through the open market.

It’s easy to assume they are just “copper” but could just as easily be Phosphor Bronze or even Beryllium Copper. The latter in particular is used to make springs and electrical contacts for example which sounds ideal for this application. Would be good to confirm what they actually are.

Edit: Just stumbled on this interesting and relevant thread.

https://www.electriciantalk.com/threads/belleville-spring-washers-for-electrical-connections.293780/