3S or 4S over the 70mm fan 3800kv inrunner

[Dting26]

Edmund,

As rerequested, I started this new thread.

Here's the published test datas u shared;

@ 10v
Current: 29.6A
Thrust: 24.8oz
Power: 296W

@ 11.1v
Current: 34A
Thrust: 28.9oz
Power: 377.4W

@ 12.6v
Current: 39A
Thrust: 33.3oz
Power: 491.4W

Looking at the above, I believe 11.1v refer to 3S and 12.6v is for 4S. However, the full charge 3S lipo read 4.2v/cell, total output read 12.6, 4S read 16.8v.

I will try to see I can snap the reading from my meter and share it so that we all have better idea about the actual bench data for further discussion.

One thing I learnt from the seller about the Lipo batt., he explained higher C will provide higher current draw, here's the example;

2200maH, 20C ---- 44A max.
2200maH, 30C ---- 66A max.
4400mah, 30C ---- 132A max <<-- this is the batt. I used during flight
3000mah, 30C ---- 90A max <<-- this is the batt. I used on bench test

Rgds
David

[leonlio]

hot wires

From the previous thread, you mention the wires are hot during the test run. Did you check and see where is the heat coming from. If the ESC is very hot, the heat in the wires may be from the ESC itself and not due to the current in the wires itself.

40A ESCs usually have 14AWG wire (lower AWG means thicker wire), and can handle current in excess of 40A.

Edmond pointed out, something strange indeed. For the same test set of motor and fan the voltage increase and the current drawn is usually NOT linear. Current drawn should increase much more than the corresponding increase in voltage.

error in the specs?

Cheers,
Leon

[edmond22]

From the previous thread, you mention the wires are hot during the test run. Did you check and see where is the heat coming from. If the ESC is very hot, the heat in the wires may be from the ESC itself and not due to the current in the wires itself.

40A ESCs usually have 14AWG wire (lower AWG means thicker wire), and can handle current in excess of 40A.

Edmond pointed out, something strange indeed. For the same test set of motor and fan the voltage increase and the current drawn is usually NOT linear. Current drawn should increase much more than the corresponding increase in voltage.

error in the specs?

Cheers,
Leon

yar, and the poor fellow burnt the ESC and kaput one motor. I am thinking 4s is too much for that power system.

David, if you go HC site, and see that product page, you will find user comments below where one guy actually claims he is running 4s 30 over flights drawing in excess of 70+ amps! with no problems lol. Strange. The 12.6 I believe is representative of a assumed lipo 3s holding voltage at 4.2v per cell which will never happen in real life lol.

Definitely need to get a second opinion to the measure the current drawn. For the cables to get hot, something is building heat and you need to see where that is stemming from. Stalled motor, bad connectors, too thin a cables? Does the connector get hot too?

[blueangel]

My input on this overheating issue.

If all your equipment functions OK on the ground and then it went into overheat during flights, you may want to suspect on of the following :

Had you soldered extra length of cable from the ESC to the Lipo battery ?

My old EDF Red Arrows requires the ESC to be mounted to the rear of the fuselage where the EDF fan is seated.

That means I had soldered a red and black wire to the ESC cable so that it can reach the Lipos which is placed in the cockpit ( at the front )

Everything was fine, until one day when I decided to clock 1 minute less of flight time while conpensating with a lot of full throttle stunts, verticals, loops etc..

Within 3 minutes, I landed and to my surprise those 2 wires melted the skins and some parts of the copper wire were exposed.

My mistake of not getting proper gauge wires to match the current through the cables, from the Lipo to the ESC.

Perhaps you may want to look at any poor soldering, cheap connectors or under-performing cables.

[Dting26]

test data.....

thanks to all valuable input, as mentioned, I took the test again with 3S and 4S batt., here's the result;

3S 2200 mah, 25C : 33.7A, 317w
3S 3200 mah 20C : 38.0A, 427w
4S 3000 mah, 30C : 36.6A, 572w

ESC is more than warm for all the above, there is no extention cable used during the test.

Edmund, u are right, reading through the review, looks like everyone use only 3S, however, with 3S, to meet 500W, I am afraid current draw will be more than 40A and 2200maH may not able to make it, any comment?

Rgds
David

[edmond22]

thanks to all valuable input, as mentioned, I took the test again with 3S and 4S batt., here's the result;

3S 2200 mah, 25C : 33.7A, 317w
3S 3200 mah 20C : 38.0A, 427w
4S 3000 mah, 30C : 36.6A, 572w

ESC is more than warm for all the above, there is no extention cable used during the test.

Edmund, u are right, reading through the review, looks like everyone use only 3S, however, with 3S, to meet 500W, I am afraid current draw will be more than 40A and 2200maH may not able to make it, any comment?

Rgds
David

Bro the 4s data you have gotten doesn't look right still. Usually, when all else remained the same, when you increase the lipo in series, the current will almost surely go up. It is unlikely to stay the same or go lower. We normally have to change the motor (lower KV) to get a suitable amp draw within spec but still arrived at higher total peak power. Your measurements would have looked good if there was a change of a motor but there wasn't any.

[Babylon5]

My input on this overheating issue.

If all your equipment functions OK on the ground and then it went into overheat during flights, you may want to suspect on of the following :

Had you soldered extra length of cable from the ESC to the Lipo battery ?

My old EDF Red Arrows requires the ESC to be mounted to the rear of the fuselage where the EDF fan is seated.

That means I had soldered a red and black wire to the ESC cable so that it can reach the Lipos which is placed in the cockpit ( at the front )

Everything was fine, until one day when I decided to clock 1 minute less of flight time while conpensating with a lot of full throttle stunts, verticals, loops etc..

Within 3 minutes, I landed and to my surprise those 2 wires melted the skins and some parts of the copper wire were exposed.

My mistake of not getting proper gauge wires to match the current through the cables, from the Lipo to the ESC.

Perhaps you may want to look at any poor soldering, cheap connectors or under-performing cables.

Hi Blueangle,
Beside having good soldering and a thicker gauge wire, it is not a good practice to have a long cable between the Lipo and the ESC.(Long Wire at the 3 phase is acceptable provided you use 2.4Ghz))
Why, because long cable is inductive. During high surge (sudden high power demand),the negative E.M.F. generated is high enough to destroy the ESC.

The long cable at the 3 phase are AC do not generate high enough negative E.M.F. (to destroy the ESC) . However, the 3 phase generate RF noise that can cause glitches to the normal crystal type receiver , especially if the wires are significantly long. The 2.4Ghz is impervious to this noise .

Overall , where possible it is wise to keep all the connecting wires and the 3 phase wires as short as possible.


Cheers

[Dting26]

Bro the 4s data you have gotten doesn't look right still. Usually, when all else remained the same, when you increase the lipo in series, the current will almost surely go up. It is unlikely to stay the same or go lower. We normally have to change the motor (lower KV) to get a suitable amp draw within spec but still arrived at higher total peak power. Your measurements would have looked good if there was a change of a motor but there wasn't any.

Edmund, if refer to P=VxI, I don't have doubt, with same load (i.e. fan size), to achieve same wattage, the motor will have to draw more current from 3S than 4S and reason for going for lower KV motor is to have higher torque.

By the way, I am having the model which Freeman had it way back in 2007, u were in that forum exchanging opinion as well (do a search under "F14"). In fact, I follow the set up except the product made;

Freeman's set up :-

70mm EPF Ducted Fan x 2
EPF 3900kv in-runner (Mega equivalent of 16/15/3) x 2
Dualsky 40Amp ESC x 2
2200mah Lipo x 2

Mine set up :-

70mm EPF Ducted Fan x 2
EPF 3800kv in-runner x 2
Hobbywing 40Amp ESC x 2

In fact, I maiden the plane with 2x 3S 2200mah 30C, however, the plane don't seem to have enough power to get lifted, that's why I change to 1x 4S 4000 mah 20C, it works but the ESC can't take it since the current drawn is hitting more than 90% to the rating... which i think

I recalled your watt/lb requirement, I wonder how Freeman made it with just 40A ESC and 3S 2200mah batt. as this bird weighted more than 1600gm with all items in .

Apparently, to avoid unnecessary lost, I stop the repair and hang up this bird until I have enough information on the root cause.

Rgds
David

[leonlio]

...

Just add an external BEC unit and disable the BEC circuit on the ESC and it should be OK.

Cheers,
Leon

[a.c]

Hi,

intending to get the following for my multiplex twister.

70 mm ducted.
3800kv inrunner.
80amp esc turnigy.
2650mah 3s1p 40c.

Izit enuff to power it?

Have not bought anything yet from hobby tity.
Maybe can advise on my selection, as I do not understand all the number you all mention.

Regards

[a.c]

Hi,

intending to get the following for my multiplex twister.

70 mm ducted.
3800kv inrunner.
80amp esc turnigy.
2650mah 3s1p 40c.

Izit enuff to power it?

Have not bought anything yet from hobby tity.
Maybe can advise on my selection, as I do not understand all the number you all mention.

Regards

Forgot to mention an external BEC turnigy 3A UBEC with noise reduction .

[leonlio]

EDF Rule of thumb

Basically I use this simple rule of thumb for my EDF.
250W of power for every 1lb weight.

e.g. my current F-18E fighter is about 750g (1.5lb) therefore uses
250x1.5=375W motor/esc setup.

My jet is able to perform standard fighter jet maneuvers eg. loops, rolls, split-S with great ease...


Just don't expect it to go lightspeed.

Cheers,
Leon

[f22]

hi

Edmund, if refer to P=VxI, I don't have doubt, with same load (i.e. fan size), to achieve same wattage, the motor will have to draw more current from 3S than 4S and reason for going for lower KV motor is to have higher torque.

By the way, I am having the model which Freeman had it way back in 2007, u were in that forum exchanging opinion as well (do a search under "F14"). In fact, I follow the set up except the product made;

Freeman's set up :-

70mm EPF Ducted Fan x 2
EPF 3900kv in-runner (Mega equivalent of 16/15/3) x 2
Dualsky 40Amp ESC x 2
2200mah Lipo x 2

Mine set up :-

70mm EPF Ducted Fan x 2
EPF 3800kv in-runner x 2
Hobbywing 40Amp ESC x 2

In fact, I maiden the plane with 2x 3S 2200mah 30C, however, the plane don't seem to have enough power to get lifted, that's why I change to 1x 4S 4000 mah 20C, it works but the ESC can't take it since the current drawn is hitting more than 90% to the rating... which i think

I recalled your watt/lb requirement, I wonder how Freeman made it with just 40A ESC and 3S 2200mah batt. as this bird weighted more than 1600gm with all items in .

Apparently, to avoid unnecessary lost, I stop the repair and hang up this bird until I have enough information on the root cause.

Rgds
David

Bro, try this setup:-
wemotec ducted fan 70mm x 2
HET 2w-20 motor x 2
Hobbywing esc 60A x 2
batt 5000mAh(for my Rafale from Rcwarbird)4s setup

[f22]

hi

Bro, try this setup:-
wemotec ducted fan 70mm x 2
HET 2w-20 motor x 2
Hobbywing esc 60A x 2
batt 5000mAh(for my Rafale from Rcwarbird)4s setup

photo attached...

[f22]

haha

photo attached...

ignore the 1st pic, wrong attachment...