anderson plug voltage loss.

Submitted: Thursday, Apr 21, 2005 at 23:19
ThreadID: 22274 Views:9200 Replies:4 FollowUps:3
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gday just a quickie.
i have a 50amp anderson plug on the back of the jack going to the second battery in the camper.
i have 13.9 volts at the plug on the car but only 13 on the other plug conected to the camper.
what have i did wrong lol.
cheers and thanks
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Reply By: rolande- Thursday, Apr 21, 2005 at 23:43

Thursday, Apr 21, 2005 at 23:43
G'Day Diamond,

Have you checked the anderson power company web site to ensure you have the plugs assembled correctly?

I thought mine were O.K. until I checked the graphic on the site, all good now.

AnswerID: 107747

Reply By: Mike Harding - Friday, Apr 22, 2005 at 07:02

Friday, Apr 22, 2005 at 07:02
You didn't say if there was any current flowing when you made that measurement.

If there was zero current flow then there is a problem either with the plug (unlikely because I would expect all voltage or no voltage at zero I) or with your measurement.

If there was (say) 10 amps flowing then as R = V/I: R = 0.9/10 = 0.09R or 90 milliohms and as that current has to flow through 2 pins (power and ground) then each pin is presenting a resistance of 45 milliohms which (from memory) sounds reasonable for a push fit connector to me.

Mike Harding
AnswerID: 107768

Reply By: Keith_A (Qld) - Friday, Apr 22, 2005 at 08:32

Friday, Apr 22, 2005 at 08:32
Hi Diamond - there are several possible reasons for a voltage drop.
The 2 most likely are - 1. gauge of wire and 2. assembly of anderson plug.

1. All wire has resistance when carrying a current, and hence a voltage drop.
My wire is 6mm diam of copper = 28mm2 area. Yes fairly thick (battery cable).
This has a resitance of 2.68mv per Amp per meter. So over a 8m length (from car to camper), carrying 20 amps, I would expect a drop of 430 mv or .43 volt.
The thinner your wire the greater the voltage drop, for a given current.
If you intend to charge the camper battery, this becomes critical.
The recommended wire is 32mm2 = heavy battery cable, and I think the copper core is too thick to fit a 50 amp anderson plug pin.

2. An Anderson plug can be ASSEMBLED in 2 ways.
One way causes massive resistance and over-heating when 2 plugs are clicked together. The other is the right way.
Both ways will seem to work correctly - until you feel the wires, or
smell the burning insulation.
As you probably guessed I managed to assemble them the wrong way first.
Put simply, the thick pins must be pushed up near the front of the
plug. Takes some effort, and you will hear 2 clicks during ASSEMBLY.
When two plugs come together, the thick pins must interlock.
These carry the current.
Now for the wong way : When you ASSEMBLE the plug, if you only push
the thick pins onto the sping clips (eg one click), when the two plugs
come together the SPRING clips will click and connect.
These are NOT supposed to carry current, and of cource will overheat and drop a huge voltage.
With my inverter plugged in, it worked OK then gave error beeps.
I felt the Anderson plugs & they were VERY hot - as were the wires.
Fortunately they were beside me, not out-of-sight in the trailer plug.
If you have never ASSEMBLED an anderson plug before in your life, it is
worth knowing it can be assembled incorrectly.
Hope this helps....regards......
AnswerID: 107775

Follow Up By: Moggs - Friday, Apr 22, 2005 at 10:48

Friday, Apr 22, 2005 at 10:48
Good post - Just one other thing to be aware of for those who have never wired up a 50amp Anderson Plug:

The thick pins have a lip on one side which is designed to slide over the flat spring and hold the terminal in place. This is the 2nd 'click' that you will hear when assembling.

Make sure you have the lip on the thick pin facing down to the spring side when assembling. If you put it in the other way you will not hear the 2nd 'click' and when you connect the Anderson plug to another Anderson plug (if you have also assembled this one incorrectly) the 2 lips will lock and the plug will not be able to be pulled apart.

In addition it is worthy to note that Narva now make a dust boot for the 50 Amp Anderson Plug that is a good tight fit and is attached to the plug via a rubber loop when not in use. A worthy addition for those who have Anderson Plugs installed which are exposed to the elements or for those who are concerned about getting dirty connectors or shorting the connection when it is not connected to another Anderson Plug. They are about $11, which is expensive with regard to the plug itself only costing about $13 - but a good addition nonetheless.
FollowupID: 364673

Follow Up By: Member - Beatit (QLD) - Friday, Apr 22, 2005 at 11:40

Friday, Apr 22, 2005 at 11:40
G'day Moggs,

Bought the dust cover but was unable to fit because the general mounting of these plugs (mine anyway) means that if you use the two holes in the plug to afix it to some part of the car (rear bumper in my case) leaves unsuffient plug showing to take the cover.

The covers are a little bulky so there needs to be anough plug showing to accomodate the cover, probably roughly the amount of the recessed bit. A good idea though all the same, just have to give it some thought when mounting the plug.

Kind regards
FollowupID: 364675

Follow Up By: Member - Rohan - Friday, Apr 22, 2005 at 11:50

Friday, Apr 22, 2005 at 11:50
Yep. Been there, done that Keith :(

Fortunately, before running any current through it I suspected something was wrong and contacted the very helpful folks at
Fridge and Solar who gave me step-by-step instructions on how to correctly assemble the plugs.

I haven't had any voltage drop or heating of the connection at all.
FollowupID: 364678

Reply By: phil - Friday, Apr 22, 2005 at 14:15

Friday, Apr 22, 2005 at 14:15
For those interested,
Jaycar Electronics have the 30A Anderson plug at $7.95 a pair and 120A at $19.95 a pair.

Phil I
AnswerID: 107818

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