Check your BECs!

Jan 22, 2014 2 Comments by

I recently had the pleasure of reviewing the Blade 600X, and I have found it to be the best-engineered 600-class heli I personally have flown.  The quality of construction is outstanding, the drivetrain is extremely stout, and handling is silky-smooth.  I look forward to getting a lot more flying time on this bird.  (See my full review in the May issue of Model Airplane News!)

The only issue I encountered with my 600X build was with the wiring harness.  Like many 12-cell helis, the 600X uses two 6S packs connected in series by a harness that’s included in the kit.  On the early kits the arrangement of the external BEC power lead would cause a failure in many high-voltage speed controls like my Edge HV 120.

As supplied, the BEC output was soldered to the second battery connector.  While this looks fine when measured on the bench with a DVM, when the BEC is connected this results in a “floating voltage” condition which will damage some high-voltage speed controls.  While some opto-isolated ESCs can tolerate this arrangement, it’s not the ideal approach.  For all helis with an external BEC, the ground leg for the BEC output should always be soldered to the “most negative” contact.

Blade quickly corrected this on all kits, but by all means check that yours has the correct layout.  And if you have any other helis with series harnesses and external BECs, check them as well.

This diagram shows how easy it is to overlook an incorrectly wired BEC:


Helicopters, Jim Ryan

About the author

A longtime contributor and the current "Heli Talk" columnist for Electric Flight, Jim has been heavily into aeromodeling for nearly 25 years. Electric warbirds are his main love, although in recent years helicopters have taken much of his attention. He is focused on scale helis and his favorite part of the hobby remains designing and scratch building.

2 Responses to “Check your BECs!”

  1. John says:

    Am I crazy ? What would happen if 3 batteries were to be connected ?

  2. Don says:

    If you connect the connector with the BEC output to the first battery, wouldn’t that solve the problem?

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