Cox Engines Forum
You are not logged in! Please login or register.

Logged in members see NO ADVERTISEMENTS!


How to use Li-XX batteries with standard receivers? Cox_ba12




How to use Li-XX batteries with standard receivers? Pixel

Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Latest topics
» Indexing COX cylinders
by balogh Today at 1:10 am

» 1/2a Skyray plans?
by 944_Jim Yesterday at 10:14 pm

» Postage stamp backplates
by JPvelo Yesterday at 8:52 pm

» my attempt at making an exhaust throttle for Cox .049
by roddie Yesterday at 8:20 pm

» Another of C.T. engines cleaned ---- Cox Tee Dee .09 --- Just today (3/26/2024) more Cox parts
by sosam117 Yesterday at 6:58 pm

» Cosmic Winds, - Big Guy, Little Guys, Silver Guy and Wounded Guy.
by rsv1cox Yesterday at 5:18 pm

» My friend Ramón, his Cox .09 & Cox .010
by MauricioB Yesterday at 12:31 pm

» Introducing our Cox .049 TD Engines
by Cox International Yesterday at 12:27 pm

» Parts Cox TD-4
by rsv1cox Yesterday at 8:40 am

» STUKA bomb dimentions needed
by latole Yesterday at 7:43 am

» On ebay a very special Cox engine
by davidll1984 Yesterday at 6:32 am

» Introducing the new - "QZ" RR-1
by Admin Yesterday at 12:51 am

Cox Engine of The Month
March-2024
balogh's

"COX Budapest" .049 engine



PAST WINNERS
CEF Traveling Engine

Win This Engine!
Gallery


How to use Li-XX batteries with standard receivers? Empty
Live on Patrol


How to use Li-XX batteries with standard receivers?

Go down

How to use Li-XX batteries with standard receivers? Empty How to use Li-XX batteries with standard receivers?

Post  dirk gently Sun Dec 16, 2012 5:54 am

Background:
Li-Pol and Li-Ion batteries are lighter than Ni-MH batteries of the same capacity. One might be tempted to use them as receiver batteries for IC powered airplanes. The problem is, a typical Li-XX 2 cell battery has a voltage of 7.4V, while standard receivers and servos operate in 4.8-6V range (which I guess is because they were designed during the Ni-MH era). To safely use a Li-XX, we need to drop at least 1.4V.

Solution:
Some people tend to use a voltage regulator with BEC in this scenario, but this is expensive and moreover adds weight, which defeats the purpose of having Li-XX in the first place. Coincidentally, 1.4V is exactly the voltage drop of two standard silicone diodes. The diodes are remarkable in that the drop is constant, regardless of current flow. Since my other hobby is guitar tube amps, I was using this method extensively to drop a constant amount of voltage. I'm guessing the same approach can be used for Li-XX batteries. Here's what did:

1. I collected a wire with a plug from a dead servo, two 1N4007 1A diodes (please note, the current rating of the diode is important) and some shrink tubing:
How to use Li-XX batteries with standard receivers? Dscf2330b

The cost of this is probably under 1$, if you have a dead servo. The only tools you need are a knife, a cigarette lighter and a soldering iron. The weight is 2g (depending on the length of the wire, mine is 8'').

2. I cut down the leadouts on the diodes and removed isolation from the wire:
How to use Li-XX batteries with standard receivers? Dscf2331r

3. I soldered the diodes to the wire. Please note that the white stripe on the diode denotes the cathode. You want to solder the diodes in opposite dirtections, with the cathode facing the positive (orange) wire:
How to use Li-XX batteries with standard receivers? Dscf2332p[img][/img]

4. I used some red small diameter tubing to isolate the diodes from each other. Then I used some larger black tubing to form a plug. You may want to use an actual battery plug instead, but I found that this works fine as is. I covered the leadouts of the diodes with tin to prevent oxidation:
How to use Li-XX batteries with standard receivers? Dscf2333r

5. We're ready to go:
How to use Li-XX batteries with standard receivers? Dscf2334l


I will give it a try go tomorrow when I unpack my new servos. Since this is an experiment, I don't recommend it to anyone yet, please use at your own risk (although I can't see why it wouldn't work).
dirk gently
dirk gently
Gold Member
Gold Member

Posts : 429
Join date : 2012-02-03
Age : 41
Location : Poznań

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  Surfer_kris Sun Dec 16, 2012 6:14 am

I think it is much better to use switching technologies so that you don't waste the extra voltage, instead it is used to prolong the battery time.
Surfer_kris
Surfer_kris
Diamond Member
Diamond Member

Posts : 1893
Join date : 2010-11-20
Location : Sweden

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  dirk gently Sun Dec 16, 2012 8:05 am

That's a good point. ~20% of the overall poweroutput of the battery is wasted (dissipated as heat). I think this is acceptable. Please note, that a switching voltage converter also gives some power loss (albeit probably not as much as 20%). Given the very low weight of the diode-based solution, I guess you can afford to have a slightly larger battery to compensate for the loss of battery time compared to a switching device.
dirk gently
dirk gently
Gold Member
Gold Member

Posts : 429
Join date : 2012-02-03
Age : 41
Location : Poznań

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Sun Dec 16, 2012 8:40 am

How many/how big are the servo's Dirk?
If tiny/not many take a look at the hobby king step up
Device which allows use of one of the 130mah 1s lipo's
Very very low weight solution.
Or poss a small 2s with a small ESC instead of an expensive and
Heavier Regulator.
Or if you're say .40 sized and above (IMHO) the Powerbox
Digiswitch is unbeatable/ not cheap though.
Very Happy
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Sun Dec 16, 2012 8:46 am

Oh oh just read the whole thread.....
As for cost I bet you spent an hour with the
Soldering iron. Even at minimum wage thats
10 bucks of your time.
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  Kim Sun Dec 16, 2012 9:07 am

A possibly dumb question from someone with admitted ignorance of this subject:

Is the voltage of a Lipo battery dictated by it's internal workings, or were they engineered to match some industry standard? If the second part is true, is it then possible we might see a company step up with "plug-and-play" voltages from these batteries?
Kim
Kim
Top Poster
Top Poster

2022 Supporter

2023 Supporter

2024 Supporter

Posts : 8509
Join date : 2011-09-06
Location : South East Missouri

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Sun Dec 16, 2012 9:14 am

Already done Kim, Futaba and Hitec already produce hi voltage
Servo's with JR in hot pursuit. However they are v v ah say v
Expensive.
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Sun Dec 16, 2012 9:24 am

There are pro's and cons with everything of course.....
Lipo's REALLY don't like the cold I haven't flown my biggie
For a few weeks cos it has lipo's in it.
To give an indication... Yesterday we had max temp of 3 celcius
And my little glow stuff with nimh batts flew like they always do..
My foamy 3s yak flew ok while I had the lipo's warming on
Heater vent of car but as soon as batts were out doors for more
Than 10 mins they didn't want to work.

Dirk in my Bacaruda (2 hs50's) I have a 120mah nmih batt
It weighs 8 grams.
Very Happy
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  dirk gently Sun Dec 16, 2012 10:10 am

John Goddard wrote:Oh oh just read the whole thread.....
As for cost I bet you spent an hour with the
Soldering iron. Even at minimum wage thats
10 bucks of your time.
I guess minimum wage over at London is a bit different than down here Wink
Actually, the whole thing took me 10 mins, and that includes taking pictures while I was on it.
dirk gently
dirk gently
Gold Member
Gold Member

Posts : 429
Join date : 2012-02-03
Age : 41
Location : Poznań

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  andrew Sun Dec 16, 2012 11:01 am

Kim wrote:Is the voltage of a Lipo battery dictated by it's internal workings, or were they engineered to match some industry standard? If the second part is true, is it then possible we might see a company step up with "plug-and-play" voltages from these batteries?

Keep in mind that this comes from someone who is admittedly ignorant on almost all subjects.

Battery voltages were generally set based on industry need rather than by the physics and chemistry associated with battery design. For example, my first R/C Tx required a 90v cell to drive the vacuum tube filaments.

I believe the original specifications for the nickle based cells, NiCd and NiMH, were set by industrial, military and aviation standards. The original voltage was 1.25, but most nominal voltages quoted today for these cells is 1.2v. When the lithium technology came on the scene, nominal cell voltage was set to 3.6v or an equivalent of three nickle based cells in a series. The 3.7v rating of LiPo's is really more related to advertising hype (i.e., higher watt-hours) and, to some extent, tied to looking at the average voltage from discharge curves of the different lithium types. The lithium cells are all rated at 4.2v fully charged and 3.0v at a safe discharge voltage. Depending on how flat the discharge curve remains when loaded at .5C from a full charge 4.2v down to 3.0v, average cell voltages may vary from 3.6v to 3.8v for differing lithium chemistries. LiPo averages 3.7v.

I doubt that the R/C communitity can generate sufficient buying power to move the manufacturers away from the industry standard.
andrew
andrew
Diamond Member
Diamond Member

Posts : 1807
Join date : 2011-08-11
Age : 76
Location : Western Kentucky

http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  dirk gently Sun Dec 16, 2012 11:08 am

Actually, the voltage of a single cell of any given type is dictated by how "far away" electrochemically speaking, are the materials of the two electrodes from each other. How many cells are put together might be an industry standard, for example, you can find the regular alkaline batteries with 1.5, 4.5 or 9V (corresponding to 1, 3 and 6 cells, respectively). But you can't make a LiPol that is 2.4 or 4.8V, it will always be 3.7.

What could happen, is manufacturers could come up with 3.7V receivers and servos (I guess it is actually happening, to some degree at least).
dirk gently
dirk gently
Gold Member
Gold Member

Posts : 429
Join date : 2012-02-03
Age : 41
Location : Poznań

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  ahrma_581 Sun Dec 16, 2012 11:23 am

re. servo lead colors: something doesn't look right. Red is positive, black or brown is negative (ground) and yellow, orange or white is normally the servo signal lead. It looks like your loom would be feeding battery positive to a receiver signal pin. Or am I missing something?
ahrma_581
ahrma_581
Gold Member
Gold Member

Posts : 290
Join date : 2012-03-21
Location : Sonoran desert

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  andrew Sun Dec 16, 2012 11:41 am

ahrma_581 wrote:It looks like your loom would be feeding battery positive to a receiver signal pin. Or am I missing something?

You're correct. I'm not aware of any major manufacturer that splits Rx power with the signal wire in the middle. The colors used are for JR -- and as you noted, brown is negative, red is positive. If he is plugging into an additional loom, then it may be adjusted there; if it is plugged into a typical Rx, then it could be problematic.
andrew
andrew
Diamond Member
Diamond Member

Posts : 1807
Join date : 2011-08-11
Age : 76
Location : Western Kentucky

http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  dirk gently Sun Dec 16, 2012 12:15 pm

You guys are right, I messed up the wiring. Corrected now.
Btw, I gave it a run and it seems to work without any problems.
dirk gently
dirk gently
Gold Member
Gold Member

Posts : 429
Join date : 2012-02-03
Age : 41
Location : Poznań

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  andrew Sun Dec 16, 2012 1:23 pm

When LiPo's hit the market with high power/weight ratios, flat discharge curves and high capacities, I started looking at means to use them in my smaller planes. I had already switched to NiMH from NiCd's, but most available smart chargers did not have low enough charge rates to form charge the smaller batteries, so I ended up building a constant current charger which worked pretty well. The other problem with NiMH's is the high self-discharge rate, so unless I topped off the night before, a spur of the moment trip to the field could be dicey. LiPo's have a low self-discharge rate, can be easily balanced with smart chargers and are not as finicky about initial charge cycles as NiMH.

I found out several things. Many of the smaller servos have higher stall currents and higher operating currents than the standard sized servos. Secondly, a lot of the sub-micro servos don't run on 6v --- however, with the advent of spread spectrum, this seems to be slowly changing.

There are 3 DIY options available for handling voltage regulation.

1) Use a series of diodes to drop voltage. Simple, but ...... A fully charged 2s LiPo will meter 8.4v. With two diodes, you've got 7 volts out and a 4.8v servo may end up being toast. Secondly, output voltage is directly related to battery voltage. If you use 3 diodes to force down voltage, a nearly discharged LiPo running at 6v will have an output of 3.9v which can cause a reset of some of the 2.4 GHz Rx.
Should you choose to use diodes, I would suggest something like a 1N5400 or 1N5401 rated at 3A continuous. All the 1N400x series are rated for 1A --- the only difference is peak reverse voltage rating.

2) Switching voltage regulators are efficient, but a little more expensive. Secondly, the component count for the circuitry is higher than for fixed linear regulators. If it weren't for the needed components (many require an inductor) and higher cost, I would use these.

3) LDO fixed linear regulators. This is my choice. They are not quite as efficient as switching regulators, but they are inexpensive and have a minimal component count to be used -- available with a 3A 5v rating. With an LDO, you can maintain 5v constant output at 3A down to about 6.3v input (5.5v for a Fairchild chip).



Last edited by andrew on Mon Dec 17, 2012 7:53 am; edited 1 time in total
andrew
andrew
Diamond Member
Diamond Member

Posts : 1807
Join date : 2011-08-11
Age : 76
Location : Western Kentucky

http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Sun Dec 16, 2012 3:35 pm

Dunno how many servo's you guys get thru
I tend to use quite a few.....
The only one's that (in my experience) are a
6v no no are Jr even their 200 buck ones
Don't ask how I know.....
As for Nimh self discharge get Sanyo eneloop
Cells cos they do NOT discharge, again little
More expensive but no problems in life
Only solutions Very Happy
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Sun Dec 16, 2012 3:59 pm

Ps
Perhaps this needs a thread of it's own but......
Even on my tiny stuff (ie the peewee'd
Bacaruda) are all ball linked.
Which helps not stall servo's. Bit surprised they
Don't seem to have caught on in the C/l world either
But I guess control slop isn't an issue for those Guys.
You'll notice 2 things,-
1 more accurate control.
2 your batteries need less charging cos
The servos aren't struggling and drawing more current.

Give them a try you'll never use a z bend ever again.
Wink
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  dirk gently Mon Dec 17, 2012 3:26 am

John, this plane is actually called "Bacaruda", not "Barracuda"? I can't find it on google, can you please show me how it looks like?
dirk gently
dirk gently
Gold Member
Gold Member

Posts : 429
Join date : 2012-02-03
Age : 41
Location : Poznań

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  John Goddard Thu Dec 20, 2012 6:21 am

Hi Dirk
Sorry about confusion the story went a little like ........

How to use Li-XX batteries with standard receivers? Pictur10

It's an FMK Models Mini Rainbow which as you can see I first had an 010 in.
After beer one Evening I drew the P40 type teeth on...

A few days later there was a 'muscle car' thread on here where one of the guys mentioned Plymouth

which prompted me to,-



That's where the Bacaruda da da legend was born.
Smile
John Goddard
John Goddard
Diamond Member
Diamond Member

Posts : 2447
Join date : 2011-11-24
Age : 59
Location : Leyton North East London

Back to top Go down

How to use Li-XX batteries with standard receivers? Empty Re: How to use Li-XX batteries with standard receivers?

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum