I just wanted to post this and maybe help save a helicopter. Last week I was flying my Raptor 90, it has a Duralite 7.4v 4000Mah battery and a 5.1 Duralite regulator. On the 3rd flight all of a sudden it wouldn't go nose right, I went into a hover, went nose left fine, tried to go right and nothing. I started to get it down on the ground as quick as I could and 10 feet off the deck it whipped around a couple rotations and stopped. All most got the skids on the ground and it started whiping around again, not knowing the cause, I throttled up and got some altitude to do a auto. It straighten out and when I was coming in on the auto it started spinning again. I got lucky and still got it on it's skids (I'll admit it was luck). I figured if it did it on the auto it was probably electrical, after checking the servo, gyro and connectors everything seemed fine. Checked all the links and tail and that was all good. checked the battery and it seemed kinda low for only a few flights. I put a full charge on it and it checked out at 8.4v, put a 1 amp load on it and it dropped to 7.4, discharged it a little and put a 1 amp load on it and it went down to 6.7v. I know it was a long story but wanted to share it and load test your batteries. I replaced the pack and put some flights on it today and everything is perfect.

Too true, Sir! Not only check them for voltage, but be sure they're secure . I wouldn't have those marks on the side of my house if I had made sure my battery was secure

- Chaz

There is a Raptor 30 V1 in the bottom of Milford Lake, Kansas due to the same reason. The batteries were not properly strapped down. Well, I can't really confirm that statement as I have not found the helicopter yet.

[link]http://www.runryder.net/helicopter/t142562p1/?highlight=fortune[/link]

Rafael

badazzbusa:

How old were the batteries? What caused a set of batteries to drop voltage that fast?

Rafael

I asume it has a dead cell, since it's a 4 cell 7.4 pack. The pack is 2 years old. I found the date on it after taking it out the heli. I had just bought the heli used. It charged up fine but I didn't load test it. In the sellers defense, when I was programming it I forgot and left it on and went in the house for several hours and could have damaged the pack then. Luckly nothing was hurt so it was still a good deal.

Lithium packs have a shelf life that starts ticking when they are made, whether they sit in a drawer or fly every day. 2 to 3 years and they loose capacity.

Glad you didn't tear it up.

I watched a guy setting up a new EVO, tinkered too long and killed his reciever battery. Unfortunately it happened during a test hop. It was sitting on the ground at 50 percent throttle and maybe a degree or two of negative pitch holding it down on a VERY gusty day. I ran in the building and got a shovel, slid it across the skids and knelt on the handle to hold it to the ground till the motor finally leaned out and quit. He was at the field yesterday with a new loaded battery checker