Connection to battery - is a stainless nut OK?

  1. My model of MX-5 is: __ ND2 (RF)
  2. I’m based near: __ London
  3. I’m looking for technical help or recommendations on: __ Battery connection for Ctek charger.

Hi,

I want to connect the permanent wiring that comes with my Ctek charger, to the battery terminals.

I need to buy some nuts for this (I think I need M6 - confirmation would be great!) but I am not sure if I should be using stainless steel.

The existing battery connections (to which this would be secured) don’t look like stainless and I am concerned about using different steel, in case I can’t get them off in the future.

Your thoughts would be much appreciated.

Thank you!

Hmm, those nuts on the newer Mazda battery terminals are captive, they undo but don’t come off because the bolt has been staked to spread its end. Not a problem with the older ones like on my NC.

So when I fitted a captive socket for a charger to my Mazda3 I needed to slot/spread the M6 rings on the ends of the captive lead to make them a U-shape instead, loosened the nuts on the terminals and slipped the U-shaped lugs into the gaps.

With the charge counting system it is useful to put the negative connection to chassis side of the measurement plate, as pointed to in this pic. This is recommended because the self discharge with these types of batteries is less than the dark current taken by the car.

Take great care not to stress the thin coppery sensor plate between post terminal and cable terminal!

EDIT. Here’s the picture showing the (expensive) sensor system a bit more clearly. This was from before I added my lead.

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Stainless nuts should be fine, even steel nuts are plated typically, Brass would probably be even better for connection resistence but I would use stainless without doubt.

Roy

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Thanks Richard and Roy - That’s really helpful.

I shall order some M6 nuts and fit them as suggested.

All the best,

Chris.

I used a plastic number plate fastener nut.
:heart:

Always assuming you can remove the original ones. :grinning:
You might also need new bolts.

It should be OK, Richard. I think there is probably enough thread available to accommodate both the connector and a nut, without removing anything.

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There is so you will be able to piggyback as I did.
:heart:

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Unfortunately, my experience has been the same as Richard’s; the end of the threads has been staked, so I am unable to attach a new bolt.

I guess I shall have to stick with the crocodile clips.

Oh well … thank you for your suggestions!

I have seen small holes drilled in the top of battery posts and self tapping screws used for connections, maybe worth a go but I don’t know how much of the post is lead these days.

Roy

Hi Roy,

I don’t really want to drill holes in the battery posts, so I think I shall just live with the clips instead. The battery is now fully charged again.

Chris.

Ok, without knowing how the post is made up it may cause issues I guess.

I can’t see why you can’t use the post mounting bolt, even with a connection tag and a washer ontop of that it will still tighten the post the same as normal??? Maybe Richard could explain the issue he sees here.

Also if there is enough thread protruding another nut on top of the origianal would be fine on the post mount bolt.

I would solve this connection issue for the pure ease long term when connecting your charger.

Roy

The problem is that the end of the thread is such that another nut cannot be fitted, even though there is enough thread available to permit this.

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Good quality spanners, keep unscrewing … something will give! The bolt/nut will either strip or if lucky shear off, it may even unscrew so you can simply replace the bolt.

You will be able to get a junior hacksaw blade between the clamp to cut the bolt if you remove the clamp from the battery in the normal way, i.e. the clamps normally spring open. Holding the clamp/bolt with mole grips or similar and using a fine hacksaw blade will make it easier; it’s just a nut and bolt after all.

If you have I assume a current sensor (resistor) i.e. that copper plate connector I recon I would sort/use the main clamp bolt anyway.

I’ll take a photo of my CTEK connector in a bit to see how I did my one, all I recall is that it was simple to fit.

Roy

No need for any of that destructive palaver. Just read my reply to X100, second post in the thread.

I modified the charger lead’s ring tags to U tags by slotting them. Slacken the clamp nut enough to allow this U tag to be slipped in under the nut (or bolt head or washer as appropriate) and tighten the nut again.

Simples.

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Aha, Richard, read that properly now, agreed then the nut just needs loosening to slide the tag in, good idea!!

Here is my NC version, but the clamps are different on mine so it was very easy.

Also note I wrapped my wires with Spiro Wrap for added protection. I didn’t like just the single insulated CTEK cables in case they scuffed on any metal parts.

Roy

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You can also buy these, just make sure you get the correct size and crimp it properly on the CTEK cable.

Roy