I have a home-built launch controller that previously used 6 AA batteries, and has worked flawlessly for several years. I recently upgraded it to a LiPo (2200 mAh 3s 50c) rechargeable battery. It seemed to work fine in testing, so I took it out to the field.
First launch attempt, igniter burned but motor did not start. No big deal, it happens (though not often in my BAR life - either the igniters are better now or I'm better at installing them). So I replaced the igniter and tried again. Same result.
Okay, let's try a different rocket. I put rocket number two on the pad, try to launch, and... same result. Obviously something isn't working with this battery, so I swap back in the 6 AAs instead and try to launch again and... same result again! Now I'm really scratching my head and getting a bit embarrassed because we're out at the field with my young son and one of his friends and nothing has worked yet.
Son insisted we try yet another different rocket, so I do and... it launches! We proceeded to launch a bunch more rockets, all worked fine. We did not try again with the two rockets that failed to fly in the first place.
In the end we had the failure three times with the LiPo battery and once with the AAs, followed by a bunch of successful launches on the AAs. The failures to launch were with Estes igniters and engines. One was a 1/2A6-2, the other was a C6-0.
I thought perhaps the battery's protection circuit was interfering, although this doesn't explain the failure with the AAs. Anyway, at home I did a bunch of tests with the launcher and both types of batteries. Both appeared to fire igniters equally well, and the LiPo protection circuit never kicked in. I also tried just using the steel wires from used Estes igniters, and the Lipo had no trouble burning them apart without tripping the protection circuit.
So what's going on here? Is there some reason the LiPo can burn igniters but not launch rockets? Did I badly install igniters four times in a row, even when I was very specifically trying hard to get them installed correctly because I'd just had a failure? Is it a manufacturing defect in the motors and I just happened to get two in a row of different types that had the same defect?
First launch attempt, igniter burned but motor did not start. No big deal, it happens (though not often in my BAR life - either the igniters are better now or I'm better at installing them). So I replaced the igniter and tried again. Same result.
Okay, let's try a different rocket. I put rocket number two on the pad, try to launch, and... same result. Obviously something isn't working with this battery, so I swap back in the 6 AAs instead and try to launch again and... same result again! Now I'm really scratching my head and getting a bit embarrassed because we're out at the field with my young son and one of his friends and nothing has worked yet.
Son insisted we try yet another different rocket, so I do and... it launches! We proceeded to launch a bunch more rockets, all worked fine. We did not try again with the two rockets that failed to fly in the first place.
In the end we had the failure three times with the LiPo battery and once with the AAs, followed by a bunch of successful launches on the AAs. The failures to launch were with Estes igniters and engines. One was a 1/2A6-2, the other was a C6-0.
I thought perhaps the battery's protection circuit was interfering, although this doesn't explain the failure with the AAs. Anyway, at home I did a bunch of tests with the launcher and both types of batteries. Both appeared to fire igniters equally well, and the LiPo protection circuit never kicked in. I also tried just using the steel wires from used Estes igniters, and the Lipo had no trouble burning them apart without tripping the protection circuit.
So what's going on here? Is there some reason the LiPo can burn igniters but not launch rockets? Did I badly install igniters four times in a row, even when I was very specifically trying hard to get them installed correctly because I'd just had a failure? Is it a manufacturing defect in the motors and I just happened to get two in a row of different types that had the same defect?
