Chinese wattmeter / power analyser fix

I bought a little wattmeter / power analyser with SB50 style plugs on it on eBay for about $20.

These devices have been common in the RC market for many years, and I have found them useful for a number of things but note that the input -ve lead is NOT directly connected to the output -ve lead, you cannot use them where the input -ve and output -ve are common.

 

The problems

Above is the promo pic. Of course they are not Anderson plugs, but clones.

The ‘Anderson plugs’ are SB50, rated for 50A

The wires are #12 silicone, and a reasonable current rating is 56A, way short of 150A (which would require about four times the cross section area, #4).

So, at this point, the 150A meter is good for no more than 50A continuous (if that).

But… on test, the connection is intermittent and traced to two loose terminals.

Above are the terminals and attachment. The terminals are for #8 conductors (3.3mm dia) and the wires are #12 (2.1mm dia), about one third of the size. The crimps should be either properly fitting hex crimps or indent crimps using correctly sized terminals.

But on extraction of the pins and examination of the terminals, two pulled off easily. Half of the crimp area on one was over the silicone insulation.

Above is the way these things are supplied without connectors, about 4mm of insulation is stripped and the ends solder dipped. This is fine if you want to solder them into connectors like XT-60, but you must not crimp solder loaded conductors as the solder will cold flow under crimp pressure and in no time there is no crimp pressure as happened in this case.

The fix

Both plug shells were removed, and the cables trimmed back to where there was no solder. Fortunately the Chinese cheats don’t let the wires soak up too much solder and removal of 6mm was sufficient (there is not a lot of wire to ply with).

Then four new genuine Anderson #10-12 terminals (which do not have the flared end) were fitted with a suitable indent crimper. These terminals have a thicker barrel and require a serious indent crimper, a hex crimper is not suitable for #12 wires in these terminals.

All done, it now connects reliably and works properly at 50A.