I've just bought a 2 cell 7.2v 1400mah lithium ion battery for my Aerohawk but it doesn't lift the heli off the ground[]

Midland Helicopters state that it is suitable for the Fixed pitch Piccolo so I took a chance thinking the Aerohawk is a similar size but it didn't pay off.

Is the Piccolo a much lighter heli or is there something else I need to do to use li-ion baterries? Do I need the 3-cell 10.8v (don't want to cook the board) or is there a suitable upgrade battery anyone can suggest?

It flies well on the stock batteries but I want longer than the 6-7 mins flight I'm currently getting.

I use a Ripmax Mercury EX charger that has 7.2v 2 cell 1400mah setting so I dont think its a charging problem.

Any info appreciated [8D]

I used a 2 cell li/ion and got the same results,not enough head speed. So i tried a 3 cell on the standard motor and it goes like a bomb. i put a heatsink on the fet`s on the board just in case.

So far no problems with the board,gets a little bit warm but the motor does get a bit hot to touch.

I think your right quaker1. I've e-mailed Midland Helicopters to see if they will exchange it for a 10.8v 3 cell 700mah.

The motor gets pretty hot when using the standard battery so I'll probably just put some extra thermal paste under the heatsink and fit some extra heatsinks on the board.

I wonder how it manages to lift the Piccolo then?

In my opinion, don't fly lipo and you have less to worry about: no overburning your motors, not overheating your electronics, no power cutoff in flight. If you have more money than that to pour in, that's another story.

BTW, can you fly 15 min in one go? Or do you really want to burn you heli that long?

15 min or more flight time is easily achieved with two Nimh packs. Take a break, it's good for the wellbeing of your heli and your own health.

You're using a Lithium-Ion battery on the Aerohawk? That sounds a bit scary with the currents required. You should get Li-po instead

Hold On Guys! I used a KOKAM Lipoly Battery pack on my Aerohawk. It was a 7.4V 1200 mAh 2 cell battery that I borrowed from my MS Hornet and my aerohawk flew twice as long. It worked for me. something else is wrong somewhere.

Well the 2 cell Li-ion I bought lifts the heli about 6 inches off the ground. Its 7.2v though not 7.4v but thats not much difference is it.

I think it is because the current draw is too much for the LI-ion but the original 8.4v Nimh batteries cope ok. I checked my flight duration and I'm only getting 3-4 mins of good hovering before the heli loses power then it takes an hour to safely charge them up again so I was looking for a bit longer flight time than that.

Quaker1 seems to be getting good results from 3 cell so Im going to try it- with extra heatsinks in place of course

Just to add when measuring with a meter:

Nimh 8.4v = 8.9v when flat ( heli won't lift off ground/tail motor erratic)

Li-ion 2 cell 7.2v = 7.9v when fully charged ( heli wont lift off ground/tail motor erratic)

The 8,4V ni-mh isn't 8,9V under load when flat. It's probably closer to 6V under load when it's flat. When it's fully charged I estimate it's between 7 and 8V under load.

tahustvedt - good point, those measurements are off load but you can see what I'm getting at

The LI-ion are probably 2 volts down on those readings you gave which Is why I think they aren't performing so well.

That is strange, I have been using Li-ion for a while without any problem. In fact, I have the heli lift off higher and longer than the stock NiMh battery. I am using 2 cells Li-ion weight in at 78 g (or 2.8 oz). I tie it to the frame right under the receiver and the CG is right on - No more adjusting the CG everytime I change the battery as in the stock LiMh battery. If you search the article on battery on the internet, you will find Li-ion has LESS internal resistance than Li-Ploymer - ie. higher current output. Li-ion has most of the advantage over Li-polymer except the little bit heavier than Li-polymer (due to the metal casing of the Li-ion). Internally, they build differently but it doesn't affect the way I use it. They both use the same charging method.