New link design

I have a new link design on my robot Cayenne. Due to space problems I cant fit the normal 175A connectors in, so Ive come up with my own solution which is shown on my profile.
The link is a piece of flat copper bar which clips into place between the battery terminals. The links are removed by pulling the cord. They are easier to pull out than a 175A connector.

To fit with the rules on battery terminal insulation, the link will be covered by tough fabric (seatbelt material) which is held on by velcro. The cord will protrude from under the battery insulation, so the insulation and link can be removed in one action.

There are two links - Cayenne has always had two - which the rules allow, but they do have to be adjacent. Theyre about 50cm apart on Cayenne - do you think this counts as adjacent? Also, any other comments you have on the design would be useful - better to find out now than at Magna.

There are some bigger pictures at :
http://mode7.srimech.com/gallery/newlinks/http://mode7.srimech.com/gallery/newlinks/

Its a link like any other kind of links I have seen. So if it does what the rules ask, you can use it.According to me.

But do you need to pull the 2 links to shut down completely?

Hi Jim.

2 things. First, it looks a bugger to arm. I dont fancy putting that lot together, lidding it up and then fighting it. It doesnt look simple nor easy to arm.

Second, not sure about having to have 2 links in a machine before it will disarm and be deemed to be safe.

Other than that, nice work.

Mike.

Only one pointer to make and that is contact resistance. You will find a temperature rise at the wiping connections which will be transferred into the Hawkers which will complain! I remember using a solid copper link between two Hawkers once which very slightly worked loose - the M5 bolts still were too tight to undo with your fingers. This contact resistance caused the copper to heat up, the Hawker case to melt and one cell to fail.

So unless you can guarantee a very low contact resistance (remembering greasy fingers on the key causing tarnishing etc.) that does not worsen in service, I would look for another solution.

Paul

Cant you put a 175A connector flat, and have the access from the side/back? How do you access the link if the robot is inverted?

How about using a 50A connector? These are much smaller than a 175A one.

We use 1 with no problems, although it did burn out the contacts after a years worth of use (caused by initial charging of the capacitors rather than current loading). We run upto a peak current of 300A and its never been a problem.

Thanks for your responses, all good points...

Mike: The links just push in, like a normal link. The bolts you can see in the picture are static, you dont need to tighten them or anything when arming.

Paul - a good point which I will need to think about. I use a PCB cleaning block to shine up the link before using it, which may be enough, I havent noticed it getting warm yet. However, dangers of heating up batteries notwithstanding, performance and damage to components are secondary to safety.

Alan and Mario have perhaps the most important points. It does require both links to be pulled to make the robot safe, and I think this is where most disagreement will occur. The reason there are two links is because its very nearly a clusterbot . The front and the back are just bolted together at the moment, theres no or mechanical or electrical connection between them and both can run independently. Once I sort out a mechanism to disconnect them, it will be a true clusterbot, but I would still like to run it as a joined up unit if possible. Id really like to keep the two sides independent and that means not running cables between them.

RE inversion - yes, its going to be difficult to remove the links if it gets flipped over, but I think this is true of quite a few robots.

Jim.

We have an example in history. Stinger.

In theory you must be able to disarm the whole machine with 1 link.On the other side, I believe that the rules are not put into cast iron.
Not that I will accept a multiple parallel link in machines that could be builded with 1.
Multiple series mounted links for added safety is no problem.

Also, we have run Tough As Nails with the Anderson minipowerpoles. Normaly accepted to 45A, but more than capable to survive 5 minute uses over a 100.
So, if this alternative link doesnt satisfy, the miniandersons are an option.

Weve replaced those with normal 50A andersons ages ago, suspecting them of problems. Weve never used minipowerpoles as a link.

We also use the small Anderson connectors but now use 2 in parallel, but bolted together. Dont forget the the current rating is for the connect/disconnect rating only and will handle far more. Think of them like Relays where they have 2 current ratings, Swithcing current and max on current.