PDA

View Full Version : My new favorite thingie, a Tx Lipo!


Pages : [1] 2

Drew816
07-11-2008, 02:13 PM
http://www.helifreak.com/showthread.php?t=80243

$20, these battery kicks A$$!!! 12.6 volts, charge it up on your normal Lipo charger and talk about voltage hold, phew! My old Nicad for my Futaba 9CHP was an 11.2 volt that with 20 minutes of flying drop to 9.8-10.2 volts; huh?!? So I've done 20 minutes of flying so far with the Lipo battery and it went from 12.6 to 12.5; OH YEAH!!!

I'll report long term on this but I'm pretty pumped; and considering a replacement NiCad is $40, why would you bother?!?

Mikej
07-11-2008, 02:47 PM
I have just bought a 2400mAH Nimh for 9.95 (about $20) - I did think about a lipo but I have got to the field twice recently to find that I had either left the DX7 truned on in it's bag or possibly had swtiched it on as I put it into the case. In both cases the battery was so flat that the Tx would not even switch on - I hate to think what might have happened had it been a lipo :wow2:

gpach
07-11-2008, 03:33 PM
Just got the 1800 for my DX7 and am getting the same results. No more draining of the battery sitting on the bench unused and about 40 mins and its back to 100%.

I did think about the TX being left on mike. Not a good thought. So far have never left mine on by mistake but it may be a good practice to unplug the battery when not in use.

ICCA
07-11-2008, 04:02 PM
I have just bought a 2400mAH Nimh for 9.95 (about $20) - I did think about a lipo but I have got to the field twice recently to find that I had either left the DX7 truned on in it's bag or possibly had swtiched it on as I put it into the case. In both cases the battery was so flat that the Tx would not even switch on - I hate to think what might have happened had it been a lipo :wow2:

That has been my fear also. I would like to try a lipo, but will only do so if I can have some kind of a low voltage cut off. The Tx has a warning, but that does no good if I'm not there. Is this kind of device out there? :dontknow

Dave

kahn10
07-11-2008, 09:18 PM
it wouldn't be to hard to make one but it would leave you with another big problem.the low battery alarm in your tx (unless adjustable) is set up for nicads/nimahs safe lipo cut outs way higher........so no beep beep no warning and NO TRANSMITTER :wow2:

marco

ICCA
07-11-2008, 09:39 PM
it wouldn't be to hard to make one but it would leave you with another big problem.the low battery alarm in your tx (unless adjustable) is set up for nicads/nimahs safe lipo cut outs way higher........so no beep beep no warning and NO TRANSMITTER :wow2:

marco

This is true, but if I'm flying, I SHOULD be aware of the voltage. They don't drop that fast. When it's on a shelf, or in it's case, who cares if it shuts off.

Dave

mjdee14
07-11-2008, 11:15 PM
Where are we getting these batteries for $20 ???? plz post a link..

Thx

I am also tired of the DX7 running down so fast.....seems like I charge it after every session....

gpach
07-11-2008, 11:28 PM
I didnt get mine for $20.00. Went with the Kong 1800 mah packs from RH. Was less than 1 weeks worth of smokes.:smokin:

daijoubu
07-12-2008, 12:01 AM
This is true, but if I'm flying, I SHOULD be aware of the voltage. They don't drop that fast. When it's on a shelf, or in it's case, who cares if it shuts off.

Dave
Still doesn't explain the guy on our local field that crashed into the golf course because his transmitter batteries were dead. We SHOULD do lot's of things. I still like warnings for when we don't do them. Piezos are pretty cheap. LEDs and meters worked for a long time. Any cutoff circuit could have a warning added.

mjdee14
07-12-2008, 12:05 AM
OK....for you elrical types....."twigitts" as we called them in the Navy.....

isn't 2400 mah....2400 mah whether it's being supplied by mnh or lipo? or is the real difference that your using a higher voltage on the lipo and therfore takes MUCH longer to get down to the tx cutoff voltage...

Kind of think I answered my own question......

Just wonder if we would burn up the TX :bomb:

daijoubu
07-12-2008, 12:21 AM
2400mah is 2400mah, but the cutoff voltage for Nickel batteries is 1v per cell. Your transmitter uses 8 cells. Cut off voltage is 8v. Mine will start beeping at 8.5v because the discharge curve gets pretty steep at that point. LiPO cutoff is about 3.3v per cell. A 3s pack has a 9.9v cutoff. At 9v you may damage the pack. KP claims they can run much lower... down to 2.2v per cell. That's a 6.6v pack voltage which should trigger our warning alarms.

kahn10
07-12-2008, 12:59 AM
the other thing is transmitting has quite a high power usage.spent more than 15 years with an r.t. strapped to my hip and lots of that time looking after a giant pile of them(god i hate them)i think having a lipo tx pack is an awesome idea.but with the way lipo voltage drops off at the end its possible that having an inline cutoff could go horribly wrong(the opposite to horribly right).ie rather have the low power alarm go off and accidently over discharging your tx pack(horribly right) than stop transmitting and totally lose control of one very angry flying lawnmower(horribly wrong):)

Graeme67
07-12-2008, 07:51 AM
Mate there is no way I would want a LV cutoff on my TX. I can see things going pearshaped with that scenario very quickly. The main advantage of a LIPO is the low weight - just what we want in a birds. I can't see the point in a TX. The standard 1500mah Nmh that the Dx7 comes with lasts me nearly 2 weeks of flying most days. When the LV alarm goes off I bring her straight in. It doesn't happen often as I charge her up once the voltage gets down to 9.5V.

Cheers
Graeme

mjdee14
07-12-2008, 10:03 AM
After reading everything and several posts on other sites and Horrizons tech page....I just decided to order a larger standard type battery.....2600 mah for 24.95 plus shipping....about $30....that should uffice...and not burn up the tx in the process...

I have never left my tx on yet (:arggg: = knock knock)

but I could see it happening and runing a good pack.

Now I can use the 2600 pack in the tx and keep the stock 1500 charged and in my field box....in case I have a really great day of flying and need it. I can fly thru 7 sets of packs on the hurris and have plenty of power left with the original pack....it's just if I start adding planks into the picture.

Drew816
07-12-2008, 01:33 PM
I'm not sure what the original batteries Mah was 'supposed' to be, but in all fairness it was a few years old. Regardless my battery would go from a complete charge to unusable in 35-45 minutes of total use. It had developed such a NiCad memory that it was pretty well worthless; however I'll keep it charged and in my kit so should I ever need a backup it's available.

So I got a 2500 mah replacement for $20, HALF the price of the original with more power and it's a Lipo. Advantages we already know, disadvantages, correct the Tx alarm is going to no longer be 'functional' but I charge my Tx like I recharge my flying Lipos so I don't ever expect to show up at the flying field with a dead or depleted Tx battery (if I do, see the above). I check my power on all my equipment before I fly and the T9CHP radio as Voltage right there so if I get into Lipo trouble territory I'll have to remember to swap. But I've never gotten to the Alarm point on my Tx anyway. Plus I jumped from 11.1 volts to 12.6 AND more Mah to back it up as well as it being lighter (hey, makes for a lighter Tx so that's a nice side benefit!) and cheaper.

We'll see, perhaps someday I'll report back I screwed the pooch, didn't check voltage and planted my bird; let's hope not, but I'll take a cheaper, lighter 2500 mah battery anyday over what I had! I wonder it there's a way to setup your radio to give an earlier warning? I'll have to check that out...

Happy Flying!

Mikej
07-12-2008, 02:04 PM
Drew,

It's not the low voltage cut-out bit that worries me but the behaviour of lipos when and over-depleted - from my understanding if a lipo gets drawn down too low then it can get volatile and can catch fire ?? When I left my Tx switched on and it went completely flat, after a minute or two of charging I turned the Tx on to check that it still worked and the voltage reader was 6.6V - wouldn't want to take a 3S lipo down to that.

Hope it never happens.

Cheers,
Mike.

kahn10
07-12-2008, 02:33 PM
not 100% sure mike but i think if you over discharge them all they are is ****ed.its to rapidly discharging them that makes them vesuvius.and i reckon your battery cover popping off as they swell would give ya that hey ....somethings going on feeling:DOH

Mikej
07-12-2008, 05:35 PM
After reading everything and several posts on other sites and Horrizons tech page....I just decided to order a larger standard type battery.....2600 mah for 24.95 plus shipping....about $30....that should uffice...and not burn up the tx in the process...


My $20 2600mAH arrived today, charged it up ready to go - I can't believe that I've finally found something that I can buy cheaper than you septics - I'm gonna buy another to or three of them to celebrate :YeaBaby::YeaBaby:

Drew816
07-12-2008, 09:45 PM
I concur, I don't think 'over discharging' them is going to cause an eminent EXPLOSIVO crisis; I guess in theory it 'could' but if it were all that common Lipos would have been pulled from the general market place a long time ago as how many knuckleheads have left stuff plugged in way too long with their equipment after all?!? I know I have on occasion.

I agree with Marco, you might killed you Tx Lipo if you let it get too low but other than that the threat of killing my $20+ investment... BUT unplugging it might not be a bad way to go for 1) safety's sake in case you're right MikeJ and 2) to insure it's not accidentally knocked into the ON position and then discharged to death.

Here's a Common Sense RC Tx pack by the way, no additional warnings or anything which may not mean anything but...

http://www.commonsenserc.com/product_info.php?cPath=37_27&products_id=32

mjdee14
07-12-2008, 11:08 PM
[quote=Mikej;cheaper than you septics - [/quote]

Septics ?? :thinking is that the Queens English? I'm getting the feeling it's not a term of endearment....:badair::bad

Mikej
07-13-2008, 01:29 AM
Septics ?? :thinking is that the Queens English? I'm getting the feeling it's not a term of endearment....:badair::bad

A bit of Cockney Rhyming Slang for our American friends - naturally it's a term of endearment :oops:

ke6d
07-13-2008, 08:27 PM
OK....for you elrical types....."twigitts" as we called them in the Navy.....

isn't 2400 mah....2400 mah whether it's being supplied by mnh or lipo? or is the real difference that your using a higher voltage on the lipo and therfore takes MUCH longer to get down to the tx cutoff voltage...

Kind of think I answered my own question......

Just wonder if we would burn up the TX :bomb:

I have been using an old TP prolite 3S 2100 in my DX-7 for over a year now. The transmitter has over 1000 flights on this lipo. As long as you don't forget to turn off the transmitter, the lipo pack would last a long time.
The DX-7 has a voltage readout on the screen. I normally fly for several weeks until the voltage readout drops to 11.0v, then I charge the the pack outside of the transmitter.

ukgroucho
07-14-2008, 07:59 PM
Lots of folks use LiPos in the Tx now ... I've been thinking about it but, to be honest, my DX7 pack (1500MaH NiMh I think) still lasts fo hours.. I did leave it switched on once and found it after 6 or 7 hours, still had some juice left.

The obvious advantages of LiPos in a Tx are that you can fit a higher MaH pack than the stock NiMh (or go lighter) and also you can leave them charged on the shelf for a number of weeks and just pick up and go... NiMh self discharges when sitting unused - well until someone starts providing Eneloop type NiMh packs for Tx use... I use Eneloops in my old Futaba 7CHP Tx that gets dragged out rarely for some foam planes and they hold charge very very well.

LiPos in a Tx do not need to be (probably should not be) high C rated... As I understand it, lower C rated LiPos (like 8C) tolerate being discharged down as low as 2.7v per cell without any significant 'damage'. High C rated (20 - 25C) really don't want to go below 3v per cell. A Tx is a low drain application and you should really not be using (e.g. a DX7) with battery voltage below 8.5v so you'd have to try pretty hard to run into issues with a suitable LiPo. Even if you did leave it turned on it would last many hours and all you'd do would be to damage the LiPo - it would be hard to get it to take charge.

LiPos can be recovered if you do this but you need to dial in some 'custom' charge parameters on a suitable charger... i.e. put a charger into NiMh charge mode and charge at 3v per cell with a very low current (say 0.2 amps). Not something I'd want to do with a flight pack that was going to discharge at 20C but it should be fine for a LiPo that is discharging at 0.1C in a Tx.

Rumour has it you can also jump start an over discharged LiPo with a 12v car battery... just a few seconds will be enough to get it from 'dead' to being willing to take charge (I guess you scare the crap out of it so it decides to co-operate again). I've not tried this and don;t intend to but if someone does want to give it a go then please video and post the 'saga' for us :)

Drew816
07-18-2008, 01:54 PM
Okay, it's been one week of flying with my Tx Lipo, I've got what 12-14 flights total, some setup testing on the ground and before leaving for the airfield and I've yet to recharge; my readings at the beginning of the week, 12.7 volts, as of today a few seconds ago on a tuning and setup test, 12.3 volts. This thing RULES!!!! :smokin:

Not sure what my total time 'on' was as I didn't reset my Tx timer (I'll do that this time of course) but I'm recharging the Lipo just for the sake of doing so and on my Cell Pro 4s it indicated 97% of fuel remaining. I'd guess 3.5 hours + though... :thumbup:

On my VERY tired Nicad pack that came with my three year old T9CHP Futaba Tx I would be able to get one flying session, say three to four flights and I'd go from 11.1 volts to 9.8-10 with a total 'on time' of same 30 minutes? :wow2:

I still agree, just don't leave you Tx on accidentally as you might kill the battery BUT in my case this Lipo has totally changed my flying setup as I used to be tied do my Tx's re-charge schedule and status, I've had several incidents where I had everything else ready to go AND the rare time to go fly but my Tx was too low and the trickle charging on it shut me down; some poor planning on my part admittedly but... And I have my Nicad in my kit as a backup just in case.

For $20 from HobbyCity for a 2500 mah Lipo; my friends it ranks as hard to beat IMHO!

Happy Flying! :cheers :cheers

ke6d
07-18-2008, 03:19 PM
I don't recharge until the voltage reading on the DX-7 shows around 11.0V. I normally fly 3-4 flights a day / 5 days a week. I charge my TX battery once every 3 weeks :)