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Old Sep 16, 2011, 10:00 AM
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Lipo lesson learned.

Built my own battery pack for my new Beast. I used two Hyperion 240mAh batts, and followed the videos and info I found here. Everything worked out fine during the build, and I left the batteries in the garage in a fireproof area just in case my soldering/liquid electrical tape/rolled electrical tape precautions failed. After a couple of days of the battery just sitting there quietly, I decided it was time to charge it.

I bought a new AC680 Thunder Charger, watched the how to videos, and set out to charge my new pack. Everything worked great. Per Allerc's website, I did the first charge at 3C. I used a balancing plug as well. When it came time to disconnect the harnesses, it was obvious it would take some doing. these connectors are small and delicate. I brought the pack with the plugs still attached into the house to get out of the cold, and have better light. While I was trying to get everything unplugged, I noticed the wire harnesses, and the battery were getting warm to the touch! Not a good sign. After watching all of youtube lipo fire videos online, I thought I was about to have one of my own in my kitchen. I grabbed the battery, and ran outside with it.

It turns out, when I was trying to unplug everything, the banana plugs breifly made contact with each other. Needless to say, my new procedure will be to immediately cap one of the banana plugs when they are removed from the charger.

Tim
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Old Sep 16, 2011, 10:23 AM
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If I read correctly, you unplugged the leads from the charger first. If this is the case, that's a huge no no for the exact reason you're writing about. Always unplug the leads from the lipo first, always. You don't want exposed leads to the lipo, which is what you had.
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Old Sep 16, 2011, 10:55 AM
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Yup, you read it right. I had to pull the banana plugs because I couldn't unplug the battery from the harness while it was still hooked up to the charger. I do plan on making a cover for one of the banana plugs in case this happens again. Fortunately, it was a small lipo pack, it didn't heat up beyond what I have felt with my UM 1S packs after flying them, and nothing came of it.

I have a healthy amount of respect for these batteries, along with a small dose of fear. Just enough fear of a fire to maintain that respect, and keep vigilant when handling them.

Tim
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Old Sep 16, 2011, 01:44 PM
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Why cant you disconnect from the harness?

Seems like a pair of banna plugs dangling around is asking for trouble.
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Old Sep 16, 2011, 01:57 PM
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Yeah, uncovered banana clips is asking for trouble. I found that out for sure.

This was the first time I was using this charger, as well as the balancing board, and the battery. All of the connectors were virgin, and had never been plugged in before. Combine that with the little retention nubs that hold them together, and they are then pretty tough to separate. Not to mention, they are very small, and made with light gauge wire that is delicate.
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Old Sep 16, 2011, 04:49 PM
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Maybe put a switch in the main harness.

I forgot this was only a 1S.
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Old Sep 16, 2011, 08:18 PM
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I think I'm just going to carefully take a little plastic off of the charging harnesses to make plugging and unplugging easier. This way, I won't have to struggle with it.

Tim
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Old Sep 16, 2011, 11:27 PM
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A least with only one cell @ 200mah the fireworks would have been much easier to deal with.
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