ElectroDynamics Inc
ElectroDynamics Inc
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    EDR-103 Glow Drivers
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Ultra Switch II

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ED-Nano Store

A123 Rx Battery going unbalanced while "just sitting"?

It has come to our attention that some modelers have been having issues with A123 Rx batteries from different manufacturers (including ElectroDynamics' EDN-2S1P) going unbalanced just "sitting idle" for an extended period of time. 

These batteries were installed in existing models already equipped with a 3-wire Rx switch, e.g.

... and plugged into the 3-wire NODE/BALANCE cable of the A123 battery, for the convenience of being able to balance-charge thru the switch's charge port, not realizing that the "signal" wire on these switches are not disconnected when the switch is off,  since they were originally designed for the "DSC" (Direct Servo Control) function.


ED-Nano Rx batteries feature a 3-wire “JR” NODE/BALANCE cable and a 2-wire POWER cable.

The “signal” (orange) lead on the NODE/BALANCE connector is “hot”!  It is internally connected to the “center tap” of the battery, and carries approx. 3.3V. 

The 3-wire NODE/BALANCE connector should never be plugged directly into the Rx  nor routed to the Rx via a standard 3-wire switch.  The battery's 3.3V tap will being permanently connected to the Rx and can cause unpredictable operation. This will also drain one cell on the ED-Nano battery, causing a severe cell imbalance.

This drain is normally quite low, so during the regular flying season, as the pack is being used and recharged often, the issue may not surface, but over a period of sitting idle, the pack can become so imbalanced that A123-compatible chargers go into "Safety Charge Mode" which takes a long time to charge the pack, or worse, abort with an error.

The solution?  DO NOT plug the Node/Balance cable from the A123 battery into a standard 3-wire switch!  Use the 2-wire POWER cable instead.

But, I want to be able to charge my A123 Rx battery without having to dig around my model for the NODE/BALANCE connector. 

Is there a way of doing that without having to replace the existing switch in the model?
Yes, with a bit of work:

Carefully SNIP OFF and INSULATE the exposed end of the “signal” wire (Orange or White) at the connector from the switch to the Rx.

Better yet, simply replace your switch with our
Ultra Switch ED-Nano!

ElectroDynamics stocks all the necessary chargers, cables, adapters and complete packages
for E-Z, no-brainer charging and installation!


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31091 Schoolcraft Road; GAZ Commercial Center; Livonia, MI 48150