Belt CP-X losing power mid flight

[ccole]

Hey guys, my heli started losing power about 3min in to a flight, was hovering with about half stick on the throttle and the heli decended to the ground. Its happened now on the last 3 flights. Still a bit of a noob and not too sure what the problem could be? Battery? ESC? Only have 1 battery so not able to test on another one to see if that's the problem.

[copterboy]

Ok, a nice mystery to try and solve!! I just happen to find myself waiting to go to a friends funeral, so I'll have first dibs.

I would say it sounds like a battery problem, but with the lack of a voltage reader, you also need to rule out that the machine is good working order.

I'm assuming the heli was brand new, that everything is stock - 1800mah battery, stock ESC and stock charger.

So first to check the pack is being charged properly. If using the stock charger - are you waiting for the light to stop flashing, or waiting about 3 hrs?

If recently re-built or tinkered with, I suspect part of the drive train maybe binding, thus increasing friction and wearing your battery out much sooner than it should. If you spin the rotor head with your fingers - how many times does the rotor head continue spinning?

Do you have a voltage reader/multimeter to check the pack voltage before and after charging flying?

I'm also thinking about the ESC, if it were programmable (I can't remember if the stock one is), can you check the LVC (Low Voltage Cut Off) settings?

[jperkosk]

+1 for the battery being a main suspect here. Critical to measure the voltage of the battery pack, both when fully charged and discharged.

Assuming the descent that you're observing is of the forced but controlled landing rather that crash-like sudden drop type?

[ccole]

Everything on the heli is stock and the battery does take 3 hours to charge. It seems that the problem occurs at about 3 min into flight everytime, if I leave the heli for a minute or so and try again it gets stuck at a very low head speed at half throttle.Very strange. The landing is controlled as im just hovering, but the head speed changes and the heli comes down.

I dont have a multimeter so cant read the voltage. The sales peron at a hobby shop says its the ESC as the standard one is not great but I'll rather take expert advance from my fellow Helifreak memebers

[Luke Warmwater]

Well, that sounds to me as if the Low Voltage Cut out on the ESC is kicking in. This basically assesses the voltage being put out and when it drops to a certain level, it slowly reduces power and forces you to land - assuming it is set to cut in slowly....if it was set to simply cut out, your heli would just drop like a stone...lol.

As mentioned, I am not sure how programmable the stock ESC is. ESCs can be programmed to for the LVC to cut it at different points (usually something like low, medium and high). If the stock ESC is programmable AND the LVC is set to high, it could be that it is too high and is kicking in early, in which case you need to lower it.

The other reason the LVC would cut in is that of course it needs to, because the battery voltage is actually too low. Again, as mentioned, you need to be able to check the voltage before and after flying.....although if the LiPo is damaged this may not always show up. I have a couple of worn batteries that show a good charge when charged, but I put them on the heli and they can't get it flying for more than a minute. I check the voltage then, but they still show a good charge. The problem is that although they are charged, they can't deliver the power quick enough anymore...

First things first; check your battery for the obvious and if possible, try a diffrerent battery....if you want to learn to fly, you will want a couple of extras anyway. Have you at any point before this run your battery flat? LiPos need to have AT LEAST 3V per cell left in them at the end of a flight, preferably about 3.6V as a minimum. If the voltage drops below this, it can and will damage the battery beyond repair.

Next up, get a decent charger. This will show you the end voltage as well as the voltage after you have flown and come to charge again. If you can't do this, at least get a voltmeter.....but a decent charger will be of more use to you as it will also reduce your charge time to about 1 hour.

[copterboy]

If the hobby shop you bought it from say it's the ESC, then I would let them take a look at it, if they are willing to cover the investigation and repair under warranty.

I assume the heli is not crashed then, or it's 2nd hand but you haven't crashed it.

From experience, I wouldn't be so quick to blame the Stock ESC. Most here have found it works, or it doesn't and goes up in smoke. I can't recall of reading about any other units doing this. If the LVC setting is programmable, check it has not been changed accidentally. I don't recall it being a programmable feature of the stock ESC, so please correct me if I'm wrong after checking the manual.

Most likely culprit is the battery voltage dropping, but you need to find out why it is dropping so soon. First you need to confirm the battery is getting a full charge. I recall the manual stating it should take 3 hrs, but have heard many reports of the stock charger still blinking after 5-6hrs. So, when you have finished charging after 3 hrs - can you confirm the light on the stock charger has stopped blinking?

Next to rule out if it is an old pack that has built up internal resistance, and won't hold a full charge. Again, you need a voltage reader to properly measure what mah's are going back into the pack. So we could get stuck here without some voltage readings, if you have bought a 2nd hand heli wih an old pack.

To confirm the drive train is not binding and reducing flight time. By this, I mean motor/main gear mesh, check all bearings are running smooth, from motor to tail output shaft, nothing to tight, nothing loose and sloppy. Like the main shaft collar clamping down on the main shaft top bearing. All happened to me before.

With that said, there is still the possibility that this is an old 2nd hand pack that has been sold on, or it has been overdischarged by yourself. So, how many packs/flights have you had out of it before the last 3 flights, and have you ever flown it till the headspeed dropped before this incident?

I would strongly recommend a cheap voltage reader for now, which I'll have to ask someone else to provide you with a link. Well worth investing the money for helping to prolong your li-po life.

If you can get a voltage reader and a new li-po, it will help you sort out what's what for now, and keep you flying if this pack is duff.

However, you'll find using the stock charger takes too long for charging 2 packs, so have a look at new charger too (200W+). Seems the trend these days is to charge upto 6 packs in parrallel, so I would work towards that kind of setup. Less time waiting for your packs to charge up = more opportunity to fly, before the weather or something else changes

[sutty]

The guys have basically covered it, but if a further opinion helps, I agree, it is probably the battery, though if the mechanics aren't free to move then you can cause the battery to discharge more quickly, and also causing a bigger voltage drop as it gets tired, due to the higher load, causing the LVC to kick in even earlier. Incidentally I don't believe the stock ESC is programmable, it certainly didn't used to be, but maybe they are now, not sure. A decent charger is a must if you are going to stay in the hobby, and a few more battery packs should be high on your list too as real life flight time is what pushes your learning along at pace.

As for a voltmeter to check your packs, if you get a good charger you will be able to see the voltage, so this might not be needed. Even if you don't get a new charger, a simple lipo voltage checker is really cheap and is what I use as opposed to a voltmeter, even though I have got both a voltmeter and a good charger. Literally only a few pounds for one that can measure up to 6S packs. One thing is for sure, whichever way you decide to go, you have to be able to measure the pack voltage, as has also been mentioned, over discharged packs will be permanently damaged. Over charged packs will also be permanently damaged, but this shouldn't happen even with the very ordinary stock charger, as even that cheap one has the ability to stop at the correct voltage.

Just to throw in something a little contrary to what we have all been saying, my stock battery is one of the best lasting batteries I ever had. I knew nothing of not over discharging them, and would happily scoot around on the ground, practicing gentle nose in stick inputs, etc, whilst it could no longer get off the ground, with the LVC supplying only limited power to the motor. This should have killed it off much more quickly, but it just kept going and going, and I wouldn't be surprised if it still worked. Many other people will tell you the same that two things that seemed to be very reliable in the Belt was the stock motor and the stock battery. The only problem was that it was a little short of capacity, but it still seemed to be good for about 8 minutes or so with the relatively low power requirements of the stock motor, and at the quite low headspeeds that the Belt normally runs. I cannot get anywhere near that now with my 450 class heli, with the way it is set-up, headspeed and motor etc. Maybe 4.5 minutes, but that's what happens as you progress.

The stock ESC isn't that great, and lots of people swap it out to prevent an issue before it occurs. They have a tendency to catch fire, but if you are lucky enough to have one that doesn't, then it should do well enough to suit your needs for a while yet. Mine never did catch fire, but I read plenty of reports of those that did. Maybe they are better now?

My suggestion would be to start off with a cheap lipo monitor like this one. Can't say if this link is a reliable place to get it, I just include it to show you that they don't have to be expensive, and so you can see what they look like. Very simple and easy to use.

Lipo Checker

Just to add to the complexity a little though, just because it starts off at 4.2V per cell, when it comes off your charger, and reads 3.5V per cell, or similar, when you stop flying, it still doesn't tell you for sure if the battery is faulty. The reason is that you really could have used that much capacity just by having the heli set-up incorrectly, massively increasing the load on the pack during the flight.

This is one of the benefits of a decent charger. It can give you a better idea of what is going on, because it will be able to tell you how much charge you have to put back in the battery to get it back to 4.2V per cell.

For example, if your stock pack is 1800 mAh, and is still okay, when you get it down to hitting the LVC, which is the absolute limit of where you should discharge it to, recharging it should take about 14 or 1500 mAh. If it takes significanlty less than this to go from discharged voltage levels, to fully charged voltage levels, then the pack is damaged. If it takes the right amount, like say 1500 mAh, then you know that the discharge rate must have been very high, as they should be able to last for about 7 or 8 minutes, and this would point to a fault on your heli, over loading the power system, rather than the battery.

God I go on, but once you get started there is so much to say. There is a sticky at the top of the forum that has a lot of info about batteries. A nice read written by one of our fellow Belt-CP pals, redbird300.

Battery and charger stuff.

Cheers

Sutty
EDIT: We were at it at the same time Denis, lol.

[jperkosk]

And they say English is supposed to be a very concise language compared to most others

[sutty]

[jperkosk]

Originally Posted by sutty

Properly concise answer, IMHO

[wulfrun]

Originally Posted by ccole

The sales peron at a hobby shop says its the ESC as the standard one is not great but I'll rather take expert advance from my fellow Helifreak memebers

They're right, it's not a great ESC. As said elsewhere though, it tends either to work or blow up. Unless they've changed it since I had mine (mine was one of the sef-destruct variety) it's not programmable and it's set to reduce power at 3V per cell and cut power at 2.9V per cell. I agree that the battery is the most likely culprit and you'll need a meter or LiPo-checker to get a basic indication, as a minimum - and either is a good addition to your toolkit anyway. Despite sutty's experience, my stock battery did not last very well at all. If it's not the battery, the other posts cover your prime suspects.