Electrifying a Wot 4

[Chris Bott - Moderator]

OMG it took me so long to do! Over a week of messing about with videos.
I've had many video editing problems and a row with the software manuf, which ended with them sending me a new disk. I've had so many goes with the timing of the data finnishing way before the model lands!

I'll do a few more so I'm sure about the technique first and then could do a step by step.
With a bit of luck I'll get Dannys Fury on its maiden, and even one of my own planes.

Remind me about doing a video thread sometime.

[Danny Fenton]

Just don't ask how many days he has spent getting that to work

Bad news on the Eagle tree, any sign of a fuse or diode that may have popped? Allendale can probably sort you out.

It is good to see the power as you fly, AMP's next flight will include aeros so we will see what a loop and roll cost, its a big model to fly on just 2300 mah so I need to be careful.

Are you going to do a wrap up for some of those that are struggling to keep up Timbo? you are great at putting things in a way that we can all understand, I couldn't have got anywhere with this smoke taming without your articles and threads.

[Tim Mackey]

Chris Bott wrote (see)

Hi Timbo

I was a little worried about your cell count. The round can A123 cells also drop in volts under load but I wouldn't expect quite this much.

On this 6S graph, picking a 35A point shows a voltage of about 17.5V which gives under 3V per cell, but not much under. Chris

OK looked a little closer now - your A123 hard shells are 2300 ma right ? -  which is a bit stronger than mine ( only 2000  ) + you were using 12 cells  - at 37A ( 16C ) cell volts were 2.87 and at 57A ( which is pretty high @ 24C )  2.59V per cell.  MIne at 17C showed only 2.77, but as its a new pack, and allowing for metering errors etc, I guess its not far away. I admit that I was calculating my rig based on the pack holding closer to 13V under moderate load, and this is obviously un-realistic, although I should better 11.1V when 2 x packs are paralleled. If I get 12V and say 36A  then that's 432 Watts so getting pretty close to my original calcs...add an inch to the prop and I am there I think. Another problem I have discovered is that my old Jeti ESC seems unwilling to accept any programming to set a  cut-off change, and arbitrarily kicks in at 10V which is no good at all for Lifes...it also fails to accept any commands to change timing and seems stuck on inrunner settings of soft timing and high PWM - so a new ESC is on order.

Bad day at the office

[Chris Bott - Moderator]

That is a bad day Timbo.

If it's any consolation, I too have days like that when I wish I'd never got up. (recently too)
It does make the days when everything goes well feel even better!

I'm sure its the challenge that keeps some of us interested!

Chin up, you know it will all be OK in the end..

[Tim Mackey]

Danny, yes I will wrap it all up after final testing and decisions over the next few days...probably go for the Lifes on a slightly larger prop, as the wife needs lots of stick time oooerrr missus

[Tim Mackey]

Oh yeh no problem Chris..just a bummer about the data logger really - I could kick myself

"CU" tomorrow  - although most of my day is taken up already by other domestics

[Doug Ireland]

Just watched the video (shame about the nose-over but hey, we've all done it) and the embedded data stream. That must have taken either some clever software or a lot of patience to get it synchronised. Would it be possibl;e to transmit the data to a ground station and mix it to video in real time?

[Danny Fenton]

Hi Doug if you look closely the left undercarriage leg collapses, so a nose over was inevitable that was my first ever landing of a warbird with flaps and retracts, so don't think it was too bad, looking forward to the next flight.

We have thought of videoing the lcd panel that attaches to eagle tree and gives real time data, using a small video camera in the plane looking forward through the canopy, with the lcd panel in the foreground, but it all adds the dreaded weight

[Danny Fenton]

Timbo it was our clubnight tonight and was chatting to a guy that reckons the lipo shaped A123's are not A123's but are "apparently" using A123 chemistry. It would be very interesting to know if there are any markings on your packs that may give some sort of clue as to their origin. We have had several cells come from China over the last couple of years claiming to be A123 and they are not. I have been trying to find some data from A123 Systems website but it is not working properly. The developer kit still only lists the 26650 cans, and there is no mention on the site of a "square" pack. Also A123 Racing http://www.a123racing.com/html/hypersonic.html do not mention any pack other than the 2300 mah.......

[Tim Mackey]

Hi Danny, nothing on the packs...but I am beginning to doubt that they are "genuine" A123s. I have done a few more runs with them and have to say I am not exactly delighted with the results.

The picture shows the final arrangement I have settled on, due to the 4s LiPo pack being too powerful for the motor and ESC ( despite the motor specs leaflet )

2 x 2000m/a LiFePO4 packs ( 4s ) in parallel. 12 x 6 E prop.

On this setup ( static at the moment - a new Eagle Tree logger is due to arrive today repairs are apparently and unsurprisingly not feasible )  - I am getting 43A / 11.5V / 512Watts and 8700 RPM. With a fair bit of full throttle and some mid / low settings too, I got  around 10 minutes to LVC ( 9V ) ....and until the new ESC arrives today I cant get it any lower, so expect that full static run would be nearer 12 minutes, and flight time may well be 15 - 20 - I shall fit the eagle tree in the model for some real time flight testing. I forgot to check the total mahr consumed before disconnecting my whattmeter, so thought i would just monitor what went back in on the charge..however another problem.

The GT8 has a problem - as Chris has found out too - it stops towards the end of charge with an error message stating "connection break" and the data disappears so you dont know what went back in....and upon checking the pack with a DVM it only read 27.5V ( I charged in series at 3C = 6 amp ) instead of the expected 28.8V. I hooked it up again for another shot, and the same message occured, however the charger meter showed 29.4V before the error message re-appeared.

29.4V is 3.675V per cell, a little above the recommended 3.6V ( but still acceptable ) but of course, if I had just taken the pack off at the first error, the cells would have actually only been at 3.43 V instead of the recommended minimum of 3.6V. Obviously there is something amiss with the charger which aint good.... and I need to explore more - I will hook it up to the PC today and do some more testing.

I am disappointed at the packs ability to hold voltage under load - having expected them to be better than LiPo and they are obviously not.

Freshly charged and at only 11C they show 11.5V which is a drop from charged voltage of 2.9v .....therefore each cell drops from 3.6 to 2.87....thats a 26% drop. My LiPos only drop on an average load from 4.20 to 3.65 - only 15%. I know the A123s are supposed to have a nice flat dischrge curve too, with a sharp drop off at the end, but these things obviously drop down a fair bit straight away, and then actually continue to gradually drop further ( more like Lipo ) until the end.

At the moment ( assuming I can get a charger which works properly and I shall probably end up making one ) then the only real plus that I can see is the fast chargeability and considerably extended overall life ( no pun intended ) over polymer - and even that aspect is not yet proven.

So much for a cheapie trial

£80 batteries

£45 eagle tree logger

£12 ESC

£19 Motor

£8 props due to the suggested prop being wrong

I need to go and lay down now....

Catch you later with more results.

[Former Member]

[This posting has been removed]

[Chris Bott - Moderator]

Timbo

I have a rule - I try never to add up the costs of a project any more...

[Tim Mackey]

I have rule too - trouble is the missus hits me with it when she adds up the cost - I cant hide all these damn online purchases - too many  "confirmation of your order" emails

Eric...youre dead right on that score ! 

[Danny Fenton]

I am really sorry this isn't going to plan Timbo, It is a real pity we aren't geographically closer, I have four brand new cells here that you could have tried. Something doesn't sound right with the packs you have. Maybe Chris can recall the stats we got from the "fake" A123's we tried from China last year, I know they were dissapointing to say the least.

[Tim Mackey]

No worries Danny...its all part of the game....keeps me busy

I am off to the field later today for trial runs -  just waiting for posty to deliver the new logger. Also will be trialling my IC engined ( sorry I swore ) Spifire after extensive mods over the winter...she has not flown since last summer.

Later matey

[Danny Fenton]

okay well good luck on both counts

[Chris Bott - Moderator]

Timbo your wife must be a clone of mine, my sympathies mate!

[Tim Mackey]

Just returned from the field - E logger never arrived before I left although its here now, so good old manual info only

Flight was OK, not ballistic but then I didnt want or expect that, found I needed a bit more WOT (no pun intended) than I thought, but it flew pretty well, It did have a 52 in before so unsurprisingly it is noticeably slower ( and much quieter ) Flew for 10 minutes exactly before noticeable drop off in power - would have expected more, although did not take it to LVC which I have set on the newly fitted ESC at 2s LiPo figure of 7V.

I will see how much goes back in - providing the bloomin charger doesnt give me the disconnection fault message.

I may just try the 11 x 7 rather than the 12 x 6 once I have some flight data from eagle tree - its only a 500 watt motor.

Spitfire went well with its new mods - very pleased... 

[Chris Bott - Moderator]

That sounds like a successful evening to me.

On my charger I dont think I get the "connection fail" when I'm on a balance charge. Not absolutely sure about that yet.
Definately does it on a 7A field charge (not balancing) so Danny has lent me a wattmeter to put in circuit for the time being.

"parcels law"  applies to you too. I can almost cause a delivery to happen by leaving the house breifly when I'm expecting something.

Sounds like the batteries are still useful for training then? 10 minutes training with a rest while you charge (and fly something of your own )

[Tim Mackey]

Yep I reckon so. I will do quick summary of it all to finish off the thread, but it will have to wait a while as we are actually going out tonight,( a rare event for us )  and to something that has nothing to do with aeroplanes at all, model or otherwise. yes I will put the trusty wattmeter in circuit with the charger - good and simple idea - then I can capture the info. I have also bought the LCD panel with the new logger, so will fit it on the model I thinkj for its next flight, which will be on our Sunday club fly-in...are you guys coming ?

[Chris Bott - Moderator]

Fly In?  Where?

[Tim Mackey]

Here you go Chris.... I did send the info to Danny, but as you have not activated " message me" in your profile I couldnt get you!

I also posted it on the forum a while back here

[Chris Bott - Moderator]

Thanks Timbo, I really thought I had "message me" ticked, I have now!

This is a real shame, because we have a caravan and the wife likes Rhyl, but we are already committed this weekend. Also, I've rather overbooked my flying for the whole summer, so I'm desparately trying to claw back some "brownie points" with the whole family (3 teenagers too) at the moment. So unfortunately I won't be there

I hope you have some really good weather and I'll see what can be done next year..

Hope you don't hold this against us when it comes to any of our 3 funflys?

[Tim Mackey]

Nah....I understand - I hope to make it to at least one of yours - brownie points permitting.

Ill send you the full schedule for our events. 

[Tim Mackey]

On Sundays flight, I achieved only just over 8 minutes of actual flight, yet first time out with exact same rig I got 10 minutes and landed with some to spare.Numeric instrument display data shows low pack V of 8.60 ( 2.15V per cell ) yet power had all but disappeared ( nearly failed to make it to the strip ! ) even though LVC had not cut in. I thought these things were supposed to stay good right to the end down to 2v or even lower ! Total capacity used in flight shows 3051 from a 4000m/a pack, so only ¾ of supposed available capacity ( yes I know I wont actually ever use ALL of it ) Recharging back home put back only 1650 m/a over 24 minutes @ 3C - very odd.

Dials also show 1048 RPM before the throttle is even touched as evidenced by the Zero current draw, it even showed 103 RPM whilst the motor was stopped right at the end of the flight as I was disconnecting the pack ? Also I noted that the temperature gauge had blanked down to a series of dashes across the display window at 8 minutes 6 seconds which I assume is the point at which the taxiing had stopped and I disconnected the temp sensor in order to cycle through the dashboard display screens. Interestingly even at that point RPM was showing as 607 yet again I KNOW the motor was stopped again proven by the zero current draw.

Still disappointed overall with these new cells.... and unless I change motors or prop right down ( neither of which I fancy doing at the moment ) I will be dangerously over-cooking the motor on 4s LiPo.

However, I may just try one session with them just to compare things

Anyway, heres a first look at the graphed data…I hate graphs until I have taken time to fully read them clearly, and these are not easy if you are plotting several parameters - pity they didn’t have a facility to spread the data over 2 or more sheets, ( maybe they have and I haven’t figured it out yet amongst all the myriad of user changeable stuff including far too many options to change silly things like the shape size and style of borders )

Clicking should make it big enough to read.

Incidentally due to the scaling, pack current goes off the scale but was showing as average 21A and maximum 49.