JMcRae

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Hi everyone. After contemplating jumping on the electric bandwagon for a year or so, I have finally done it. I scratch built a 40" ws Cub on floats from a set of reduced GP plans and powered it with a GWS EPS 350C-D and a 730 MA 11.1V Thunderpower lipo. I have three flights on it so far and it is a blast to fly and will hover at 3/4 throttle and take off at half throttle in ten feet. It flys around "Cub like" at 1/4 to 3/8 throttle. I have to admit that I am scared S%*@less of these Lipo's. I've heard a lot of horror stories and the last thing I want to do is have it explode on me. I am using a Hobbico MKII field charger at 0.4 amps to charge the pack and it takes about a hour and fifteen minutes to charge it. I usually charge it in my palm (just to be safe) and the pack doesn't even get warm. So here are my questions-

1- Is the MKII charger safe and will it cycle the pack to it's peak (I'm looking to keep this pack as long as possible)?

2- Do the GWS ESC's have the proper low voltage cutoff for a lipo?

3- I am running a GWS 5 amp ESC. Is this good enough for what I am doing or should I go up to a 10 amp (I have ran the motor at 3/4 throttle for 5 minutes and I can still keep my finger on it, but it is a little hot)?

4- I have a Wattage 30amp ESC. Should I run this instead?

5- I have cycled the pack 3 times now. When can I crank up the charger amps to around .7amps (I know you don't want to exceed what the pack has, i.e., for a 730 MA pack don't charge it faster than 730 MA)?

6- I have only been flying for 5-7 minutes at a time and so far and the pack doesn't even get warm. When can I fly the duration of the battery?

7- I have only hit full throttle once and I thought that I was going to rip the wings off so I am not going to be doing that again. Since then, I have never exceeded 3/4 thottle. Even so, is a 11.1 volt pack too much for this motor and ESC?

Thanks everyone!!! I appreciate the help. If you want to check out the build thread do a search for "Baby Cub on floats build" in the seaplane forum.

Proace

Hope someone answers I would like to know a little more about the LiPos.
BTW excellent job on the plane. Seems to be super sharp.

JMcRae

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Thanks!!! It took 4 days to build. I still have to add the sunburst pattern. I'm not sure if I'm going to paint it or just use some white covering.

Foamaholic

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The GWS esc is not lipo friendly. At cutoff it will have drained the battery too low. Try to land before it cuts off and it should be okay.
3 cell lipo is pushing it for this motor and esc. It it's working for you go ahead and use it.

WolfeWind

You have a recipe for disaster on your hands with the set up you described.

First of all, a 5 amp esc is not enough for the 350 motor - you need a 10 amp. Anything bigger than that will not come with the compatible JST connectors that are on your motor. The 30 amp Wattage esc will not work with a 3-cell lipo either because the pre-programmed voltage cut of will be too low.

Lipos should not be drained down to less than 3 volts per cell. So on the 3-cell you are using you need to use a programmable esc that you can set at a 9 volt cut off. The GWS esc you are using now is preset to cut off at 4.7V - less than 2 volts per cell on the 3-cell lipos. If you fly it that way, you will definitely ruin the lipo and it may vent and catch fire.

You could probably get a way with using a 2-cell Lipo with either of those esc's, though I would still not make a habit of running the motor all the way to cut off. The safest way to use lipo's is to get a progammable esc that is made for them,, The Castle Creations Pixie 20 was designed to use with lipo bateries and brushed motors - so it may well be your best bet. You will have to solder on your own conectors, though.

The charger you are using will only charge Lipo bateries to about 80% of their capacity. It was made for Lithium Ion bateries, not Lipoly's. The danger with that charger is that if you don't get the three push on the button code correct, you will charge the lipo at the wrong setting and you will at the very least ruin the battery. You don't need to hold the lipo in your hand. Just set it up outside on a cement when you charge it and watch it carefully. It you see any sign of swelling stop the charge immediately. Be aware that lipo's often swell, vent and catch fire well after they have been damaged.

If you are going Lipo's, you need to become very familiear with the safety proceedures required - or just don't use them. CAUTION and SAFETY are a must, or you will end up with a fire and who knows what kind of damage to yourself, your car, or your house