New ESC or not

[Dennis Ainsworth]

Hi, I have an Ikarus Eco 8 Heli fitted with an Ikarus Sport motor and I am running on Ni-Cads and the ESC is a Jeti Jes 350 Eco, I am changing from Ni-cads to NiMH and can anyone tell me if I need to change the ESC because on the one at the moment it says Ni-Cads and I have seen some that will work on both.
Any help will be gratefully received.
Dennis

[GrumpyGnome]

No need to change the ESC as the lvc is fine for NiCad and NiMhs. Should work fine - all my Jeti's have.

Don't use with LiPos though, unless you have a separate BEC as the lvc is too low and will ruin the cells.

GG

[Dennis Ainsworth]

Hi GG, many thanks for the answer and nice to know that I dont have to spend again and I can leave the setup as it is. On my ESC I have two small pins on which a small plugs fits to cut out the braking, trouble is the plug was left out of the packing when I had it and cant think of what to use and dont feel like soldering them in case the heat does damage, have you ever had that problem and what did you use.Wish I could get rid of the BEC as well but dont think thats possible, or is it.
Dennis.

[Tim Mackey]

A seperate BEC on its own will not stop you running the pack down to a low level....that is the job of the LVC function of the ESC.

[Dennis Ainsworth]

Sorry Timbo, you are losing me a bit here, I know they did or do a version of ESC without the BEC because when the BEC cuts in in a heli and you are several feet up its the proverbial like a stone job, not so bad if you have enough height to do an autorotation but if lower things get bent a bit, I was just wondering if on the one I have it can be disabled but on second thoughts its probably too old.
Dennis.

[Tim Mackey]

You do NOT want to disable the BEC. Seperate BECS combined with LiPos, or independant nickel based battery units are ususally found on larger models where the built in BEC on the ESC board is not really man enough for the job, and a seperate power supply is used to feed the radio and servos.
You are confusing the BEC with the LVC. This is a common mis-understanding, and even respected magazine journalists have been known to get this wrong :)
The BEC has NO EFFECT on the operation of the motor, it merely supplies 5V to power the radio receiver and servos. It is the LVC ( low voltage cutoff ) which is a seperate device built into the ESC which cuts off power to the motor when the supplying battery voltage drops to a pre-determined level NOT THE BEC !!
As for your 2 x pins - this is ususally bridged by what is called a "jumper" - they were very common on older PC motherboards, and you can get them from maplins and the like. However I am sure if you pop into a PC shop, they will readily give you one for nowt :-)
I have zillions here...but you are not here.... LOL

[Dennis Ainsworth]

Hi Timbo, thanks for that, more or less got it the right way round now in my noddle and wont worry any more about it, wouldnt have known about the LVC if you hadnt have said, learn something new every day, much appreciated, will try to get a jumper, never thought of a PC one as I thought the Jeti one was special to them, thanks again.
Cheers Dennis.

[GrumpyGnome]

Perhaps my terminology is wrong. You can buy inline devices to allow you to use ESC's designed for Ni* use with LiPos that have a higher lvc thus 'cutting' power to the motor before damaging the LiPos. No need to disable any BEC at the ESC.

Possibly irrelevant anyway as none of my electric helis get anywhere near the lvc level before power noticably drops so much that landing is he only sensible option. Never reached a complete cut in power to the rotors..............

Denis - you may find that those jumpers are the same size as those used on computer motherboards and peripherals. Pop along to a proper computer shop and you can get some for just a few pennies. Or less.

GG

[Dennis Ainsworth]

Thanks GG,not thinking of going to LiPos yet the cost of them are a bit out of my reach really, OAP and all that, it was just the change to NiMH that was concerning me.
The reason my heli was cutting I suppose I can put it down to to small a capacity Ni-Cad as I only got a few minutes before a recharge, what I did then was put a 12v motor in and use an umbilical cord running from a car battery, trouble is I have now got to the stage where I cant hump a decent car battery about so the next thing is to up the battery capacity but they all seem to be NiMH, back to the start now as you can now see why the original question about the ESC.
Anyway, thanks all for all the advice and its very much appreciated, there may be something sometime I can help with, say in model engineering on steam locos etc.
Dennis

[Tim Mackey]

Well on that original point about whether you can use nimh instead of nicad YES the ESC will see no discernable difference.
LiPo batteries are now available that are actually cheaper than nimh,
have just changed all my transmitter packs for LiPos and each 2500 m/a tr pack cost me just around £14 shipped to my door.

[Dennis Ainsworth]

At this stage I dont want to get into LiPo batts, for one thing as yet dont fully understand them (to be truthfull not much really) and I would have to rekit myself with chargers etc so for the time being will give them a miss and stick to the NiMh, but I did think the LiPo packs for motors were a good bit dearer.
About half an hour ago I was reading a leaflet that came with an ESC and the penny dropped as to what you have been telling me Timbo about the BEC, got it now, if you dont use a seperate r/x batt then you must have a BEC circuit and all that does is supply the r/c r/x gear with the correct supply and only that.
GG, wish you would tell me the secret how you manage to fly your helis without getting to the cut off point. Just had mine out and with a fully charged pack (7.2 x 1900mah) it lasted a bare 5 min before it cut completely off, perhaps the bigger battery will give me more, gets frustrating because just as I am starting to get the trims right and before I can lift off it goes on me. Next thing that goes is me legs!!! Tempus Fugit.
Dennis.

[Tim Mackey]

A bigger CAPACITY battery will give you proportionaly longer flights yes, but there is no secret as such to not reaching the cut off point, you simply observe the behaviour closely, and land when it starts to slow a bit.

[GrumpyGnome]

Yep, on all of them (Eolo, Dolphin, Twister 3D, HoneyBee, Piccolo) power drops off noticeably and quite rapidly but I've not had one reach the cut off point yet. Eolo on Nicads gets closest.

But I don't do 3D or anything fancy .........................

GG

[Dennis Ainsworth]

On mine same as this afternoon there is no slowing down, it gets so that I am in the middle of trimming and getting set up for the hover and I dont get any warning at all, it just stops or switches off and I havnt even got the throttle full open. Wondering if I have a faulty ESC with a high cut off voltage, that or a bad batt pack. I shall have to see if I can find the destructions for it and see what the cut off voltage is for it. I have got another new one that came this week and the voltage for that one is 4.2v, I wouldnt have thought that 5 min or a bit less of running at much less than full throttle would get me down to 4.2 so quick. Like I said before, I cant even get into the hover before it goes, its always been like that really.
Dennis.

[Tim Mackey]

On a 6 cell nickel pack, you should be stopping when the pack approaches 6V not 4.2. Nickels should be classed as completely empty at 1.0V full at 1.5V and nominal of 1.2V
4.2V is a strange cut off figure.

[Myron Beaumont]

Timbo
Must admit I'm impressed by your know- how(& I'm NOT joking for once ).I'm reading the threads about 'lectric flight & your contributions & am sort of beginning to think it's the way forward.BUT like a lot of folks I'm a bit worried as to where to start 'cos the parameters seem to change day by day (due to folk's experience & problems).Of course it's the cost as well with the feeling that something is going to self destruct & have to be re-placed at more cost Whereas with IC's I know where I am .Understand & yes I've been reading the articles in RCM&E BUT am not yet sure what to do. By the way I am fully conversant with the terms associated witn 'lectricity having been edificated about such things at a very early age (I was born so young that my Mum had to choose a name for me 'cos I couldn't speak !)By the way I check voltages with my equipment Tx's & Rx's under load as I ve said before & keep graphical records of their performance before & after charging (quite enlightening )

[Dennis Ainsworth]

Do know that the maximum discharge level per cell is 1v but from all the specs I have read the majority do quote for their ESCs the cut off voltage as 4.2, never looked at it your way as of course the level per cell is far below the reccommended level and from what I know about NiCads in the past to intentionally discharge them to a very low level can reverse the polarity.
Think the best thing I can do is keep to 8.4v NiMH packs and not 7.2.
Have been reading up a bit on LiPos and more or less got the hang of them except for the C bit, cant quite get that, but if I was to eventually go to those packs it would entail quite a bit of work to be correct such as changing to a brushless motor, suitable ESC, think I would keep down to 2s packs because of the cost, might have a job to find a suitable motor because of how these new motors mount,not with the 2 screws as in the Mabuchi type fitting, but there we go again as I cant find out the difference between an outrunner and an inrunner motor or even what that bit means, thick or what!!!
Dennis.

[Tim Mackey]

Well Dennis, like most projects, it is best to break it down into small chunks, and avoid being overwhelmed by the big picture.
Lets do that for starters...
1)Most brushless ESCs have a cutoff of around 3v PER CELL based on the assumption that many people these days use LiPo,and the days of nickel cells for our hobby is limited. I really cant comment about ESCs designed for brushed motors, or indeed useage with nickel stuff, as I ditched both of these technologies around 4 years ago, and have never looked back.
2) Still dont understand a cutoff of 4.2V - and using 8.4V packs would be WORSE, 'cos these should not drop below 7V !!
3)C rate. This basically indicates the maximum rate that the pack /cell can be dischrged ( used ) at, and is a very simple formula. EG if a pack is classed as 2000m/a ( 2A ) and it has a C rate of 20, then it can discharge ( theoretically ) at 2A X 20 = 40A
Same pack but rated at 15C .... 2A X 15 = 30A and so on.....
4)YOu do NOT need to go to brushless motor, or ESC in order to use LiPo batteries. They are just a battery after all, the only difference ( well there are others, but one step at a time remember )is that each LiPo cell is nominal 3.7V, and fully charged is 4.2V
This means a typical 3s pack is 12.6V when full, so will whizz your brushed speed 400 around at fair rate of knots, with higher current too.. ( ohms law ) than your old 6 cell nickels ( 9+ v ).
5) The decision to use 2s instead of 3s is not to be based on cost at all.
2s packs will give totally different performance than 3s, and may be entirely unsuitable for the particular motor and prop.
Many motor prop combinations will simply not reach their performance design with a 2s pack, and others will simply burn out if using 3s...so you must decide first what motor prop is required for the particular plane, then choose 2s or 3s or more.... as appropriate.
This is a typical example of where things are totally different to IC.
6)Most motors these days have a high degree of flexibility in mounting systems, and a little "modelling" will ususally provide a suitable method in most cases.
7) Inrunner - the spinning bit ( armature / rotor ) is enclosed in the case, and the case with its magnets is fixed. They GENERALLY spin faster, but with less torque.
Outrunner - The windings on the armature ( stator ) are inside and staionary, and the outside bit with the magnets on ( rotor ) spin around the stator. They are often referred to as bell motor 'cos this outside bit is a bit like a kiddies bicycle bell. Normally chosen where slower revs but higher torque is required - for instance big props / slow flyers. Outrunners are the motor of choice in very many cases these days, as they are cheaper and easier to produce, and if wound correctly can be very fast revving like an inrunner.
8) Thick or what - not at all, thick is the person who does NOT ask :)

[Dennis Ainsworth]

Thats given me something to think about, but things are getting much clearer now. One thing I must correct on as it perhaps will make some difference as to selection of power pack and that is in my case the pack is for a Heli and not a prop, so as you can appreciate, you just cant let the motor run as you have a gear ratio to consider. By that I mean that in my Heli manual you have a chart giving the gear ratio and pinion to use for a given number of cells and how you want the Heli to behave, they quote for my model of motor a max number of cells as 8, normally they reccommend 7 cells for normal performance, hence why I said I would use 2s packs as from what you say 3s packs would take the voltage to high for my purpose and I would I think have a tiger by the tail with that much voltage, this is assuming that I am now on the right track with my thinking. I have always thought to myself that voltage is voltage no matter what type of battery pack it comes from and would agree with you that the ESC should work the same, that being so why do they state that the ESCs on sale are or not suitable for LiPo use.
Thanks for clearing up about the 2 types of motors.
At the moment I will have to stick to the old fashiond packs but that doesnt stop you wondering does it how things work and fit into your models in the near future.
Timbo I really do appreciate all your assistance, somehow suspect you are from my era or close to it, (75).
Thanks Dennis.

[Tim Mackey]

That depends on whether you mean you are aged 75, or were born in 1975.
Either way, N/A for me !!
If its age 75 - well done for being so interested and technically competent at your "good age" -if only I could persuade my father ( aged 89 ) to stop being such a technophobe now !!
Yes, of course, you are correct - I should have spotted the Heli bit in your first posts, I apologise. In truth, you are using the wrong type of ESC completely for a Heli. Unlike a plane, a Heli should NOT be flown until the LVC operates ( actually nor should a plane either as it could mess up the battery permanentley ) and most ESC designers have a HELI specific conroller ( JES certainly do )and these do NOT have an LVC or PCO ( power cut off ) at all, relying instead on the flyer recognising a reduction in available powerr, and landidng ASAP.
7 cells will show around 9.8 - 10V fresh off the charger. A 2 cell lipo will show 8.4, which may just be a little too low, but may be worth a try. remember that the 2s pack will be a LOT lighter than a 7 cell nickel, and this higher power to weight ratio will make the eggbeater oops sorry Helicopter fly better. 8 cells will be 11.2 - 12v and is a little closer to the 3s LiPo at 12.6V but note the next bit !
The reason they state the ESCs are not suitable for LiPo is purely down to LVC. It is designed to cut / reduce power to the motor when the cells hit around 1.0V or so. Some even get down to .8V ( some of my Jetis for instance ). This is per cell, so they are either programmed manually for the cell number, or auto detect it. That means for a 7 cell it SHOULD cut power to the motor at about 5.6 - 7V and so on. Now that just happpens to be the same sort of voltage that the 2s LiPo should be stopping at too, and many ESCs actually state that the 7cell nickel setting is good to use for a 2s LiPo.
I still do NOT understand the statement that "the majority quote 4.2V cut off" NONE of my ESCs ( around 15 at present ) state this.

The jeti 350 Eco is suitable for 6 - 12 Nickel cells, which is a voltage range of ( maximum ) 9 - 18.
A 3s Lipo would probably show as a 9 cell pack, and the cut off would occur at around 9V which would be fine for a 3s liPo.

[Dennis Ainsworth]

For sure I wasnt born in 1975, wish I was though.
Now you have hit the nail on the head about the LVC as thats whats causing me trouble, it cuts in in a very short time and doesnt give me time to do anything as the motor is switched off. I have been looking for an ESC without LVC but cant find one, the only ones I can find are ones without a Brake or the facility to switch the brake off. Thats where I was getting confused with thinking the Brake cut the motor. I dont get you when you say you shouldnt fly unless the LVC is operating because when mine does the motor aint working.
If you can tell me who sells the ESC I want I should be a good way into succeeding.

Type Battery Cutoff Voltage
A 5-8 cells NiCd/NiMH 4.2V
B 2 cell LiPo 6V
C 3 cell LiPo 9V

The above is a copy from Microns web page and seems to be about normal for what I find, perhaps I am interpreting it wrong.

[Tim Mackey]

Try John Emms at Puffin models - he specializes in Jeti gear ( which is the best available anyway ) and the one you need is the
jes 300 heli
http://www.puffinmodels.com/
TELEPHONE him though...very helpful knowledgeable guy.

[Dennis Ainsworth]

Have tried them and they dont have it, nobody seems to, except that I did find one that specifically quoted to use the Jeti 300H, no brake and no voltage cut off and the firm is Hobby Lobby, in USA, no problem there, ordered it and just had an email from them to say it has been despatched already.
Had this problem about 3 months ago, I was rebuilding an OS40 Surpass 4stroke and I wanted a set of the socket allen screws for it as they are a special size, nobody in UK had them including Ripmax who are the agents for OS, but a big model firm in USA had every spare in stock for OS engines so I ordered the set and they were sent the same day I sent the order and they were here in about 4 days. I have a set on back order with a firm over here but I think that they have shelved it. Doesnt seem right when we have to go abroad for stuff, doesnt give you much feeling to buy their gear in the first place. I now regualarly get their monthly catalogue as well.
Will let you know when it arrives, You never know, might be tempted to try LiPos.!!!

[Allan Jordan]

Hi Dennis, Did you try Just Engines? They usually come up trumps.Regards Allan J..TTFN

[Dennis Ainsworth]

Hi Allan, thanks for your input, I dont think there was anybody I didnt try but with no success. as a model engineer as well as building helis etc I pretty well know all the firms that can supply these bolts and none had them, mostly due to the fact that OS use an odd size, crafty move on their part as you are fairly well made to get them from them. Its an old dodge that even stems from pre war times, I can remember that Austin cars even had their own thread and sold their own taps and dies, Morris were the same as well.
Cheers Dennis.