Amp rating for Andersons, key switches and cable

[Stalkingcat]

Hi all, I'm trying to get my head around having my bike set up with the least power resistance possible and cant seem to find any 'bike specific' correlating answers?

Here's a low-down of what I think I understand so far and some questions that I have...

Firstly, It's a bit silly to splash out on a mega motor, battery and controller set up, without thinking about the most efficient power flow through various connectors and cables etc. Quite a bit of power can be lost through using the wrong components for this
I'll prob end up using XT150 connectors anyhow but would like to get to the bottom of this conundrum.

The above picture shows an Anderson connector rated for 50amps, A smaller Anderson rated for 45amps and a key switch connection rated for 10amps.
As you can see, there is a huge difference in size between the large and small Anderson which have pretty much the same rating. The 45amp Anderson and the 10amp rated keyswitch are about the same size.

I think I understand that the rating is not to do so much with the metal connection but more so to do with the cable size that each connector can take. Both these Andersons can take 10awg wire and so they are rated about the same.

10awg cable is rated for a max of 52amps, hence a connector rating of around the same figure.

I think however that this cable rating, is for use on longer runs, household electric etc and for short runs, as on an electric bike, they can actually take a lot more current.
Please correct me on this if anyone knows better?

So, down to my specific query!
I've been using a key switch, purchased from Crystalyte, which connects and disconnects the main battery supply (full voltage) to and from the rest of the bike, as below.



I though that I'd try to make up my own keyswitch and purchased a cheap £3 10amp rated ignition switch, took it apart and it has exactly the same switching internals as the Crystalyte one which is being used on high power builds all over the world.

So my very long winded question, is
Does anyone actually know how much power is lost through these small copper connectors and also how much is actually lost through small runs of cable compared to the longer runs that cable is usually rated for?

I could start taking reading but thought I may as well ask here first

btw, Ive been running around 80amps through this Crystalyte keyswitch with no problems, which is a bit strange considering that it is basically the same as a 10amp ignition switch.

I put on a 10amp ignition switch today, connected directly to the pack and again had no problems running it. Not sure how much, if any power was being lost through the connection though?

 

[Deleted member 4366]

If you were losing power through it, it would heat up and melt. The power has to go somewhere.

Do you know where to buy those key switches? I need one for my old Oxygen Emate.

 

[Stalkingcat]

Thanks, that makes sense, ,maybe i'll keep a track on how warm the connectors are getting? If getting too hot, I may have to install one of those big and ugly 100a red kill switches, as cant find a nice key equivalent?

The 10a key switch that I'm soldering thicker exiting wires onto, is available here.

The already assembled ones with the Andersons, are available direct from Crystalyte or Crystalyte stockists.
Ill be putting an air mail order in soon for a few bit and bobs so PM me if you want a pre-assemble one, they're around £12 I think?

 

[Deleted member 4366]

You can make electronic switches using MOSFETs, which is how a BMS works. You can then use any small switch to switch your battery on and off. You can also add inrush control. If you look on Endless Sphere, there's a current thread

http://endless-sphere.com/forums/viewtopic.php?f=3&t=40142&p=1011316&hilit=inrush#p1011316

I made mine like Jeremy's original design and they worked fine, though I did hear of people blowing them at higher voltages, so the final design might be better because it controls the voltage on the gates better.

 

[trex]

for the kind of power you have in mind (up to 11kw), I reckon you'd need a relay that can handle 100A without melting, something like this one:

http://www.aliexpress.com/item/1pcs-DC-12V-500A-AMP-High-Current-Relay-Contactor-Power-Motor-Control-On-Off-E4027/1734108571.htm

or a solid state relay like this one:
http://www.jaycarelectronics.co.uk/productView.asp?ID=sy4086

 

[Stalkingcat]

Yep, a relay was the original plan for my more powerful build but then got sidetracked into taking apart a key switch and wondering if it would actually take those sort of power levels.
Then i started to question my knowledge of power loss through connections and cables. I was going to use 10awg throughout but then wondered if 45a rated connections would loose energy at 10kw, or if it was worth beefing the whole lot up and going to 8awg with different connections ??

Liking the solid state Mosfet Relays.

Just having a good read of the E/S thread trying to get my head around it all....

 

[trex]

I'd go for a straightforward 12V mechanical relay and normal lock switch. SSRs are dodgy if you don't fit a big heatsink.

 

[Stalkingcat]

Thanks Trex, trying to stay away from any more cooling problems, so mechanical it will be.