I flew my new T-33 today, and discovered a problem. The first flight went nicely, and lasted around four minutes. After letting the battery pack cool for a while I charged it up and flew again. After 45 seconds or so, the ESC cut the motor out. Thinking I had a bad charge, I charged up the battery again, with the same results.

What could be causing this to happen? I am using a 7-cell pack with an ESC designed for 6-12 cells, and I have the standard cooling holes in the front of the nose cut out. It may be possible that the ESC is going to overheat protection mode, but it didn't seem to have any problems on the first flight. The charger showed about 9.6 volts at the end of the charge, and when I plugged the battery back in after the short flights it was reading 8.38 or so.

I am thinking I may have a cooling problem but I am open to any possibilities.

Here are the equipment particulars:
ESC: Jeti 350
Battery: 7 cell Ultra-Sport 2000 (car pack), Deans plugs
Stock motor (AP-29L I believe)
Charger: MRC 959, set to 4.5 amps

Any help would be appreciated. Thanks!

Did you remove the pack for charging?

This sounds like the ESC is overheating. How old it the ESC? Does it have a sucessful history of use?

Have you tried switching the ESC with another?

With a 7 cell pack the motor might be drawing 30 amps. I use the same ESC with 8 cells, no problems.

The pack would be suspect to me since the Ultra "Sport" packs are not Sanyo cells.

Most RC Cars don't get anywhere near 30 amps, so the Ultra packs can last a long time for them.

I've got several (5) Duratrak car packs that clear show the Sanyo cells. Two of my car packs are from SMC and state that they are Sanyo; probably European cells, but perform just like the Duratrak.

I'd suggest getting or borrowing another pack.

Problem solved

What looks to be the case is I was not allowing the pack to cool off quite enough after the flights before putting it back on the charger. After cooling off the pack really well with a fan, the battery would peak at 10 volts, rather than 9.5 or so on a partial charge. That .5 volts meant the difference between 45 seconds and 4.5 minutes of flying! I am now a true T-33 believer - what a great plane!

HMMM? I had the same problem one timewith one of my packs. I found a bad solder joint on the Deans plug.

Ted