HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 21, 2014, 09:00 AM
Airplane and Heli Flyer
V-Man's Avatar
Canada, QC, Montreal
Joined Dec 2009
1,669 Posts
Quote:
Originally Posted by oldsneakers View Post
The battery can supply (2.25 x 65 = 146) amps continuously.

So I though the 146 amps would be fine even if I flew wot the whole flight. I guess not. Not sure where I went wrong.
It may just have been a bad battery. As much as we'd like them to be equally perfect, LiPo manufacture has a lot of variance build into it.

I have a set of four Rhinos that I use for a landing trainer (high wing, slow flyer). They are charged and used in the same session, one after the other, so they have the same cycles and have been charged/discharged the same. Well, two seasons later, two are good as new, one is slightly puffed, and one will be retired soon as it's noticeably puffed and doesn't perform well anymore. Same manufacturer, same type, same flight use, different outcomes. Luck of the draw...
V-Man is offline Find More Posts by V-Man
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 21, 2014, 09:48 AM
Registered User
Joined Oct 2009
1,104 Posts
Quote:
Originally Posted by oldsneakers View Post
I didn't have time to make a thrust tube before I went flying with my upgraded T45, HK EDF unit, 80A esc and 2250mah 65C 4S. It was quite a bit faster than the stock configuration. The surprise upon land was the battery. It had ballooned up as if it were going to pop. Doing the math(as I understand it), I didn't expect it.

HK motor max amps are 68 amps. I tested it with this battery and it drew 65A.

The battery can supply (2.25 x 65 = 146) amps continuously.

So I though the 146 amps would be fine even if I flew wot the whole flight. I guess not. Not sure where I went wrong.
The problem is that there is no math you can do, at least not using any numbers printed on the battery label. Typically a good quality lipo can deliver 30C reliably at full charge, for greater longevity it is better not to push a lipo past 20C, there is no such thing as 65C. In your case your setup was actually still within spec, so either it was a defective battery or you drained the lipo completely causing it to puff.
nighthawk0077 is online now Find More Posts by nighthawk0077
Reply With Quote
Old Oct 21, 2014, 11:05 AM
Airplane and Heli Flyer
V-Man's Avatar
Canada, QC, Montreal
Joined Dec 2009
1,669 Posts
Quote:
Originally Posted by nighthawk0077 View Post
either it was a defective battery or you drained the lipo completely causing it to puff.
That's actually a good point -- if the voltage drops too low, you'll damage the battery. What was the final voltage?

I didn't think of it because I never bring my cells lower than 3.8V, except for my EDF jets where I allow them to go to 3.7V (or else I'm not in the air long enough ).
V-Man is offline Find More Posts by V-Man
Reply With Quote
Old Oct 21, 2014, 11:43 AM
nom
Registered User
nom's Avatar
United States, ID, Boise
Joined Mar 2011
1,806 Posts
Flight time is lipo capacity/amp draw x 60 minutes. So for your setup 2.25mah/65amp equals about 2 minutes of flight time at WOT which is a pretty short time. You won't get 2 minutes but something like 1:40 as you need to leave 80% capacity to keep your lipos in decent shape. I shoot for 60-70% max.

There is a great discussion in this thread about lipos in this thread:
http://www.rcgroups.com/forums/showthread.php?t=1767093

I also agree that it was a tired or defective lipo.
nom is offline Find More Posts by nom
Reply With Quote
Old Oct 21, 2014, 12:10 PM
Registered User
oldsneakers's Avatar
United States, CT, Hamden
Joined Jul 2011
309 Posts
Thanks for the replies.

I did not know how to estimate the flight time. Thanks for that nom. I just guessed on the time I could fly. And I did run it down to the ESC low volt cut off. Which is set to 3V a cell(the default). I just use a HK Cellmeter7 checker after flights which gives percentages. Which was at zero percent. So I guess that was the real problem. I've done that before and not ended up with a balloon like this was. It looked like it was going to pop.

Interesting you say there are no 65C batteries. I kind of thought things were fishy with the high C's x mah/1000 to get continuous amps. For purposes of sizing a system anyway. You get some unrealistical numbers.
oldsneakers is online now Find More Posts by oldsneakers
Reply With Quote
Old Oct 21, 2014, 12:17 PM
Registered User
ukbren's Avatar
United Kingdom, Derbyshire
Joined Aug 2011
595 Posts
I used to take my lipos down to 3.7v per cell but even with a 4000mah in the t45 I was only getting about 5 minutes (70mm edf). I decided to do some tests and let the battery come down with about 3.5v per cell, and now I get in the region of 8 minutes (5 minutes on a 2700 - both zippy flightmax).

I wouldn't let my lipos drop to anywhere near 3v - that's the lower limit of a lipo's life and you might struggle to get a charger to detect the battery below that. I thought my 3.5v was taking a risk!

btw, best way while you're learning the capacity of a battery is to chuck on a lipo alarm, set it conservatively and make a few flights. or fly for a short time (recording flight time), land and check the lipo. repeat until you exhaust the battery (to a 'safe' level).
ukbren is offline Find More Posts by ukbren
Reply With Quote
Old Oct 21, 2014, 12:24 PM
Airplane and Heli Flyer
V-Man's Avatar
Canada, QC, Montreal
Joined Dec 2009
1,669 Posts
Quote:
Originally Posted by oldsneakers View Post
And I did run it down to the ESC low volt cut off. Which is set to 3V a cell(the default).
Yep, that's the culprit alright. Keep in mind that under load the voltage drops even lower. If you hit the LVC there's a high chance you will ruin the battery.

I lost five(!) 3S packs that way. They didn't puff, but they won't hold a charge anymore (max 12.3V if at all), and can barely feed a motor (down to 5C maybe). I just ran them too hard.

But at least you got the plane back in one piece, which is all that matters, right?
V-Man is offline Find More Posts by V-Man
Reply With Quote
Old Oct 21, 2014, 12:34 PM
Registered User
oldsneakers's Avatar
United States, CT, Hamden
Joined Jul 2011
309 Posts
Quote:
But at least you got the plane back in one piece, which is all that matters, right?
Lol. So true.
oldsneakers is online now Find More Posts by oldsneakers
Reply With Quote
Old Oct 21, 2014, 01:01 PM
nom
Registered User
nom's Avatar
United States, ID, Boise
Joined Mar 2011
1,806 Posts
Getting the plane back is the most important thing!
nom is offline Find More Posts by nom
Reply With Quote
Old Oct 21, 2014, 01:58 PM
Registered User
Spain, GA, Ourense
Joined Apr 2014
6 Posts
Arrived

My T45 has just arrived, the box is and isn't a double box, though is thick and robust, capable of survive international postal companies, there are a lot of pics of it in this tread. Everything was almost ok, there is a small dent on the horizontal stabilizer (wacht pic), it looks that it was from origin, not because transportation, the tail parts came loose at the bottom of the box (pic 2). I don't know if it is only me or it happens to everybody, I had only bought 3 planes in HK, and all them have came with some kind of dent, scracht or bend, nohting serious but is annoying. The planes that I have got from other on-line stores in Europe, even in Spain, always come perfects, this is the third time that I said that I won't get any plane from HK, is good to buy pieces, lipos and other things but I have no luck with their planes. The last 2 from EU warehouse.
I said that the model was a pnf. Well, is more an all included kit, I have to cut the edges of the pieces of the cockpic and the nose, attach the hinges, clevises and push rods, put decals, and so on, at least I think that putting together this plane is going to be fun. Well I think this is too long. Later I'll write down another update.
Fredmd and everybody thanks for your advises
New Merlin is offline Find More Posts by New Merlin
Reply With Quote
Old Oct 21, 2014, 09:48 PM
Registered User
fredmdbud's Avatar
USA, MD, Frederick
Joined Jan 2010
4,040 Posts
First try w/retracts on the SAPAC/Global Fly/Cermark T-45

IMG 3369 (0 min 21 sec)
fredmdbud is offline Find More Posts by fredmdbud
Reply With Quote
Old Oct 21, 2014, 11:15 PM
Registered User
Joined Jun 2013
350 Posts
Wow! You have flaps too!! Nice. Looking forward for your flight report
oscarmok is offline Find More Posts by oscarmok
Reply With Quote
Old Yesterday, 12:56 AM
Registered User
fredmdbud's Avatar
USA, MD, Frederick
Joined Jan 2010
4,040 Posts
An immediate downside is that this is heavier than any T-45 I've built - 6S-rated motor, CS 10-blade EDF, retract assemblies, 5S battery for maiden. I have a feeling it will need a longer run than I've needed before, even with the flaps.
fredmdbud is offline Find More Posts by fredmdbud
Reply With Quote
Old Yesterday, 01:40 AM
Plane Fanatic
DeathWarmedUp's Avatar
Australia, QLD, Gympie
Joined Jul 2007
855 Posts
Nice job Fred. I have always thought about adding retracts but, yes, the added weight has stopped me. Be interested to see how it goes. Whats the AUW without battery?
DeathWarmedUp is online now Find More Posts by DeathWarmedUp
Reply With Quote
Old Yesterday, 02:39 PM
FireHawx
FireHawx's Avatar
United States, FL, Jacksonville
Joined Oct 2011
1,199 Posts
Quote:
Originally Posted by New Merlin View Post
My T45 has just arrived, the box is and isn't a double box, though is thick and robust, capable of survive international postal companies, there are a lot of pics of it in this tread. Everything was almost ok, there is a small dent on the horizontal stabilizer (wacht pic), it looks that it was from origin, not because transportation, the tail parts came loose at the bottom of the box (pic 2). I don't know if it is only me or it happens to everybody, I had only bought 3 planes in HK, and all them have came with some kind of dent, scracht or bend, nohting serious but is annoying. The planes that I have got from other on-line stores in Europe, even in Spain, always come perfects, this is the third time that I said that I won't get any plane from HK, is good to buy pieces, lipos and other things but I have no luck with their planes. The last 2 from EU warehouse.
I said that the model was a pnf. Well, is more an all included kit, I have to cut the edges of the pieces of the cockpic and the nose, attach the hinges, clevises and push rods, put decals, and so on, at least I think that putting together this plane is going to be fun. Well I think this is too long. Later I'll write down another update.
Fredmd and everybody thanks for your advises
This is definitely a builders jet. Loved both mine to the end(ccrash). But enjoyed the build. It can be made a very nice jet with a little work. I wouldn't use those tail feathers even if they came pristine. Use balsa. I used an old set of SkyAngel F86 wings and it was a perfect fit with only a little work and some CF. Good luck.
FireHawx is offline Find More Posts by FireHawx
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
New Product F4D Skyray 64mm EDF by FMS Model Joe 1320 Foamy EDFs 993 Oct 16, 2014 01:21 PM
Article G&C Hobby F-16 "Fighting Falcon" 64mm EDF from NitroPlanes Review Spackles94 Foamy EDFs 69 May 19, 2012 02:46 AM
Discussion Hobby King A4 Blue Angels EDF Jet airbagit13 Electric Ducted Fan Jet Talk 8 Nov 04, 2010 11:37 PM
For Sale Replacement 64mm EDF fan units for EDO and Hobby Lobby jets (REDUCED) The Don Aircraft - Electric - Jets (FS/W) 10 Dec 07, 2008 10:24 PM
Discussion broken fan on 64mm sapac t45 edf newguy2005 Foamy EDFs 0 Jul 19, 2008 04:44 PM