Power rails

Hi all,
I was wondering if anyone had any good systems for featherweight power rails? With drive escs, weapon esc, the battery and power light all needing to be connected in parallel a set of power rails seems like a good idea, I'm just not sure what to use.

I had thought about using something like a screw earth terminal block (http://uk.rs-online.com/web/p/earth-blocks/0425544/) but not convinced the wires wouldn't work loose

Wire loom with all connections that don't need regular disconnections soldered. The rest with good connectors.

And no, Anderson connectors ain't that good.

Those uninsulated screw connectors you show are just asking for trouble.

Like Mario said, that terminal block is going to cause problems - expensive, smoky problems. The most reliable connectors for a power bus style wiring loom are crimped ring terminals (as long as you use a high quality crimper) and insulated binding posts. You need to cover the posts with tape after everything is assembled but they will never fail in normal use.

I now prefer point to point wiring using XT connectors; I'll have a larger XT90 for the battery connector and XT60 connectors for the individual motors. The wiring gets lighter as it fans out - 8 or 10 gauge at the battery, 10 or 12 gauge for the weapon motor and 14 gauge for the drive motors. That scheme makes for a light and compact wiring loom that is reliable and takes plenty of current where its needed.

I've moved from connector blocks (they were 4 way blocks that accepted ring terminals, got them off ebay) to pretty much what Nick said. [except for a Brit using metric cable ;) ]

I've just been using EC3s for the most part, with 10 and 12 AWG wire. Just bought a 100W soldering iron and gobbed them together, then wrapped the joints up in tape. 10AWG won't fit nicely in the EC3s though - what connectors do people usually use for that (and larger)?

Team RCC used EC5 for main connections, EC3 for motors (up to Bosch 750) and EC2 for solenoids, LED's and other low power applications.
But we're transitioning to XT60 and 90, as HK delivers most of their stuff with those presoldered on.

XT90 connectors work well up to 10AWG wire. They have a 'no spark' version that is ideal for battery connections.

Just another question about fuses - the rules say you need to have a fuse rated below your battery's maximum discharge current. For me, I have a battery which lists 65C as its continuous discharge, and 130C as its burst discharge rating. As far as I know, that means the max burst discharge current is 130*3.3Ah (or 3300 mAh) = 429A is my max burst discharge. So I bought a 400A fuse, but now it's here, it looks enormous. Am I going crazy, or is this what people normally use?
Attachment 6565

The 400A fuse is according the rules.

Team RCC didn't use a 400A fuse in any of our machines.
The "heaviest" was a 200A car-audio fuse in our spinners Caliope and Valkirie.

Currently, Hannibalito is using a 30A fuse (on the IBF ESC) and Kashei a 100A.(this is part of the link)

A few questions.

What are you powering?
How thick are the wires in the machine? (Battery leads to start with)

I have four 18V drill motors and a brushless RC car motor all powered by three TZ85s, so it's clearly drawing nothing like 400A. I just thought going for the max fuse size I could would be the best, since I can always reuse it anyway. Battery leads are 10AWG, as are the leads going to the removable link and fuse. 12AWG wires branch out from those to the three ESCs, which also use 12AWG wire for output to the motors.

Should I use a much smaller fuse? I have no real way to measure the current drawn - my multimeter only goes up to 10A.
This is the brushless I'm using - it powers my linear actuator: http://www.componentshop.co.uk/lbh36...or-2-pole.html

you certainly arent going to get close to 400A with 3 TZ85A. Heck when I've smoked a TZ85 with a stalled brushless it didnt pop the 80A fuse :)

10AWG is about 2.5mm2. A Maxi fuse is fine for feathers generally, a mega fuse on your setup will look big.
I run 2 x TZ85 with 50-60 brushless on 80A fuse. its fine. I have popped a 80A fuse with 2 DeWuts but thats another story...

Hi,

REC Team is using the LITTELFUSE 150A since 2014, never had problems.
http://pt.farnell.com/littelfuse/029...lay/dp/1354634

But you need to take in consideration the delay characteristics of all fuses, in our case the 150A (nominal) fuse will break after 100 seconds at 150A, ~500A for 1sec and instantly (0.01sec) break with 4000A!!

Thanks for your answers guys, I've ordered a 100A maxi fuse and holder, should be fine to replace my removable link too, and should end up being more well-protected. I doubt I'm ever going to be pushing more than 100A. Worst comes to the worst, I always have the stupidly big 400A to fall back on.

Guess I might as well ask while I'm here - will my lifter need any kind of safety retention bar? I'm expecting not because it's quite a slow electric lifter, but I suppose it could trap your fingers if you weren't careful. There's no pneumatics or anything.

For a more general rule on fuses, it's not just the source of power you're protecting, it's preventing the destruction of everything downstream to the fault and causing a fire from burning off the insulation.

In my previous job we considered about 4-5 A per sq mm of copper cable as the sensible limit, but these were very high reliability, continuous use items with a 20-30 yr service life. You could double that comfortably for short bursts. It does get a bit crazy above about 500A due to the volume vs surface area problem but I don't think many featherweights are pushing anything like that for more than a couple of seconds.

So if you wanted to protect some 10 sq mm cable you'd aim for a fuse rating between 60A and 100A, depending on how fast a blow fuse it is, and how hot it gets in your robot. Obviously still protect the battery, but you should aim to protect the lowest rated item.

Take a look at some tables like these below to see what I mean about current capacity:
https://www.cse-distributors.co.uk/c...fo/table-4e1a/

Note that although those are conservative figures for continuous use, they're also assuming a pretty big temperature rise (60deg C), I would imagine you could easily be 60deg C inside a hard working robot. Your mileage may vary.

I would take those charts with a pinch of salt for our applications, since we are normally using silicone cables and only running for very short lengths of time. Best bet is to try running at full tilt for a realistic amount of time and check how hot everything gets.

For example Triforce runs 6AWG silicone cable at about 400A (2x 150cc rotomax), but since it only pulls that for less than 10s it is fine, we use 2x 200A Mega fuses in parallel to protect from battery shorts.

Yes I completely agree take them with a pinch of salt! With silicone insulation you've just moved the tolerable cable temperatures from about 80deg C to about 160deg C. Temperature of all components is as you say the important aspect.

My point was that you're protecting more than just the battery and the fuse should match the lowest performing thing, unless it's expendable :mrgreen: