After reading several threads about replacing the batteries in the Trend Airshield Pro I decided to give it a try.
I ordered 3 4/3A NiMH batteries and a Tenergy 01006 Universal Smart Charger for Nimh battery Pack (2.4V - 7.2V) from battery junction.
I removed the old batteries and installed the new ones. I plugged in my original Trend charger and all is well.
I then used the alligator clip adapter on the smart charger and touched the two contacts on the battery pack. The smart charger light turned red to indicate the battery is being charged.
I then wired the plug from the original Trend battery charger to the smart charger so I can charge the battery pack without removing it from the Airshield.
When I plug in the charger in the AC circuit the light flashes twice to indicate AC power is connected, but when I plug the Smart Charger into the the Airshield I get no lights to indicate the battery is being charged.

Has anyone else tried using a Smart Charger with a plug attached to charge the batteries in the Airshield?