Best 9x battery? 2S Li-Ion 18650 cells

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Ozzy
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Best 9x battery? 2S Li-Ion 18650 cells

Post by Ozzy » Sun Jul 08, 2012 9:11 am

The 9x runs off 5v, 3.3v and 2.5v internally, so 2 Li-Ion 18650 protected cells are a great 9x power solution.

Compared to a Rhino 3S LiPo and LiFe 9.9v packs, Li-Ion 2S protected cell pack has these benefits (IMO).
about 1/3 the cost,
lighter weight,
more capacity (run time),
compatible with LiPo chargers (some chargers do not have LiFe compatibility),
Li-Ion is a more rugged physical cell,
Li-Ion with individual cell protection is more robust than non protected LiPo & LiFe packs.
less wasted battery wattage (for the 9.9v LiFe or 3S LiPo packs),
and less heat in the Tx 5v linear voltage regulator. (worst case, full charge 3S LiPo is 12.6v, minus 5v = 7.6v, times ~150mA = 1+watt of heat dissipated in the 5 volt regulator), the Tx uses ~0.75 watts (5v x 150mA)

2 cells Li-Ion protected cells can be bought for ~$4.5 on ebay shipped. Cut the plug off the 8 AA cell battery holder then add a charge and balance plug for $1.5 for a total of ~$6.

Currently my 2500 mAH 2 cell Li-Ion pack lasts 16 hours in my er9x with HK Blue LED back light always on. From what I hear, the old frequency bands (27, 29, 40, 50 & 75MHz) RF modules needs ~9.6 volts, but not sure anybody is still using those old bands. Does any of the telemetry RF modules need more than 5v?

The low voltage battery alarm will come on with the 2S solution, but with er9x firmware, just adjust the low voltage battery alarm to 6.0 to 6.5v (EDIT: 7.2v would be better). With out er9x, there is a mod to add a 8.2K resistor in parallel to the 5.1K resistor (use 0603 SMT resistor and solder right on top, no solder mask scraping on PCB) .

If there is a high capacity (2200mAH+) 2S LiPo pack, please post info, cost or link.

Post your solutions with cost and run time.

Any thoughts, comments, suggestions or better solutions welcome?

Thanks,
Ozzy
Attachments
9x Li-Ion 2S1P 3000mAH resize.JPG
Two Sanyo 3000mAH 18650 cells with plenty of room to add er9x programming connector in the battery bay
Last edited by Ozzy on Sat Dec 15, 2012 5:45 am, edited 4 times in total.


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jhsa
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by jhsa » Sun Jul 08, 2012 8:19 pm

I would never use protected cells in my tx.. There are cases of the protection circuit cutting in mid flight and the plane crashing.. I prefer (if for some reason the voltage goes too low) to damage a couple of batteries than losing my model for something like this..

Just my 2c

João
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Kilrah » Sun Jul 08, 2012 8:28 pm

I use a 2500mAh 2s lipo, works perfect, and is enough for my all my TX modules, including the 35MHz one if I use it.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by kaos » Mon Jul 09, 2012 5:20 am

which 2500mah 2S lipo you have to fit in the 9X batt compartment?
I have been looking for one that fits but never found one.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Ozzy » Mon Jul 09, 2012 8:20 am

The most common secondary (rechargeable) cell in the world is the Li-ion 18650, this is 18mm Diameter by 65mm long, why they add a 0 is beyond me. The protected cells are 2-3mm longer due to adding the protection circuit. These cells fit and the battery cover goes on without problem. There is also 17670 cells (17mm by 67mm), but are less common.

Good point João.

Kilrah, do you have a link to your LiPo pack, I would like to check out its specs/price/dimensions?

I would think the pro LiFe battery comments would come flooding in, :)

Thanks
Ozzy


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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Crucial » Mon Jul 09, 2012 3:53 pm

I have both the 18650's and the 3S LiFe batteries. I think they are both a fine choice. The 1500mah LiFe fits a little easier but takes up more overall space than 2 18650's.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Kilrah » Mon Jul 09, 2012 6:53 pm

I use the 3s 2500mAh TX pack from HK and remove one cell / make 3 packs out of 2 ;)

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Measuredpath » Mon Jul 09, 2012 9:54 pm

I use 2 trustfire 2400mAh batteries soldered into series with a balance plug attached. Works perfectly.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Crashj007 » Wed Jul 11, 2012 9:20 pm

Measuredpath wrote:I use 2 trustfire 2400mAh batteries soldered into series with a balance plug attached. Works perfectly.
Do you charge thru the balance plug or do you have a separate connection?
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Measuredpath » Wed Jul 11, 2012 9:26 pm

I charge using a separate connection. Once I get the rest of my bits that I am waiting for in the mail, I am going to clean up what I have right now.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Crashj007 » Wed Jul 11, 2012 9:31 pm

I have a multi-position mini-DIN now that has the three balance leads and + and - power leads. The adapter cable hooks right up to my charger. I'm wondering if I really need all five leads since I have two more TXs to modify eventually. If I need only the three lines it is much simpler to do.
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Measuredpath » Thu Jul 12, 2012 6:16 am

Here is what it now looks like after I finalized my setup. Forgive me for the grainy photos as the 2.4 aperture wasn't enough.

What you don't see is how I glued the ends so they are sealed contact points, then I wrapped it in electrical tape in a tight fashion.
Image

Image

Image

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Ozzy » Fri Jul 20, 2012 10:20 pm

I put a thermal couple on the 5 volt regulator ground tab (case temp), ran the radio at three different voltages, simulating fully charged battery packs.

3S LiPo 12.6V 120.6F 49.2C, 12.6v - 5 = 7.6v x 150mA = 1.14 watts of heat

3S LiFe 10.8V 111.8F 44.3C, 10.8v - 5 = 5.8v x 150mA = 0.87 watts of heat

2S Li-Ion 8.4V 99.4F 37.4C, 8.4v - 5 = 3.4v x 150mA = 0.51 watts of heat

Tx uses 0.75 watts (5v x 150mA)

This data shows the surface mounted regulater is heat sinked well (into the ground plane of the pcb), so that there is no fear of over heating with the extra voltage turning into heat, even on 120F days.

Adding other RF modules, second LCD, ect will burn more power in the regulator.

Also tested the limit where the 5V output is not regulating, at 6.7 volts it was still regulating, under 6.7 volts, the 5 volt line drops, so 6.7 7.0 volts is minimun battery voltage. The 9x looks like a standard linear regulator droping 1.7 volts typical, but 2.0v is max (as Gohst pointed out, thanks), as a LDO would drop 1.4 max volts.

Ozzy
Last edited by Ozzy on Tue Jul 24, 2012 9:08 pm, edited 1 time in total.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by calla969 » Sun Jul 22, 2012 10:56 pm

I use a Cellpro 4s charger that charges through the balance lead. Is it possible to have a single lead for powering the TX and charging the pack? Can I charge through the charge port on the TX? What's the best way to charge?

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by FriedOnion » Mon Jul 23, 2012 7:08 am

How did you get the solder to stick onto the terminals? when I tried to solder onto mine, it would never really bond properly so I ended up using AA holders (I use 4x AA size ones)

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Rob Thomson » Mon Jul 23, 2012 8:40 am

You need two things.

1. Lots of flux paste.
2. An iron with a lot of muscle.

Thing with batteries is that the suck the heat away fast! You need your iron up to about 400c, the do the job fast to avoid damaging the cells!

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by FriedOnion » Mon Jul 23, 2012 9:39 am

I was scared of damaging the battery so didn't have the temp too high... also I don't have any flux... It doesn't really matter now, my AA holders work fine, but it does stick out the back :oops:

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by jhsa » Mon Jul 23, 2012 10:16 am

That's how I do it.. hotter soldering iron but less time with it in place..
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by ReSt » Mon Jul 23, 2012 10:20 am

And using a not to small tip for the soldering iron

Reinhard

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Crashj007 » Mon Jul 23, 2012 7:18 pm

If you try to charge thru the existing charge port, doesn't the diode drop interfere with proper Lithium charge voltages?
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Ozzy » Mon Jul 23, 2012 8:22 pm

If you use a Dremel tool to scuff up (clean) the metal where your going to solder, it makes it's a lot easier to solder, specially on AAA, AA, C, D cells (these cells have some oxide prevention layer on them). And has been said, a hot iron for a short solder time is less damage to the cells. There is flux in almost all solder (rosin core).

Ozzy

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Gavinxman » Fri Nov 02, 2012 1:58 am

not 1 link

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by ShowMaster » Fri Nov 02, 2012 3:45 am

Caution. I know it's done all the time but...
The real issue is the heat may cause the internal pressure contacts of the battery to fail, usually later. The internal connections ate not welded or soldered, but basically spring contacts. That's why solder tabs are welded on got soldering.
The real question to I do it all the time is how much your plane is worth compared to a $7-20 pack with proper connections?
It's one thing to do it for yourself, another to suggest it's ok to so many new flyers reading our posts.
Just thinking, not judging.




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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Ozzy » Sat Nov 03, 2012 5:30 pm

ShowMaster wrote:Caution. I know it's done all the time but...
The real issue is the heat may cause the internal pressure contacts of the battery to fail, usually later. The internal connections ate not welded or soldered, but basically spring contacts. That's why solder tabs are welded on got soldering.
The real question to I do it all the time is how much your plane is worth compared to a $7-20 pack with proper connections?
It's one thing to do it for yourself, another to suggest it's ok to so many new flyers reading our posts.
Just thinking, not judging.

ShowMaster
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There is only one spring in a Li-Ion cell, it is at the positive end of the cell, right under the + contact. You can see the pressure vents (usually 4 small holes) on the positive connection. If you flood enough solder to fill these holes or have solder flow though the holes, then I would be worried about compromising the safety vent.

The plus and minus of the cell are spot welded inside the cell, not spring contact connection. I know this from my 21 years RC racing on road electric cars. Back in the Ni-Cad days, we would "zap" each cell with ~4000 amps (yes, that is 4000 amps via a huge cap charged to 100 volts, then switched on via 16 paralleled large SCR transistors, current measured with current probe connected to scope), to weld the internal contacts better. This lowered the internal resistance of the cell. On a 6 cell sub-c pack, this would give an average of ~0.45 volts more voltage at 36 amp draw over 4 minute race. Until 3 years later when others caught on, we had a huge power advantage.

Oz

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by kaos » Thu Dec 13, 2012 4:56 pm

Another great alternative for the Tx batt. http://www.hobbyking.com/hobbyking/stor ... duct=16529

2650 mah 3S lipo, as is, it is a perfect fit in the batt compartment. But running 11.1 V. Get two of these and make them into 3 2S 2650 mah, it becomes perfect for er9X/T9X.
Just be aware the width of the lipo is a perfect fit, when you solder the leads to make 2S make sure it does not stick out to the side (there is plenty of room at each end), solder it a little pointing to the end.

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by Ozzy » Sat Dec 15, 2012 6:10 am

jhsa wrote:I would never use protected cells in my tx.. There are cases of the protection circuit cutting in mid flight and the plane crashing.. I prefer (if for some reason the voltage goes too low) to damage a couple of batteries than losing my model for something like this..

Just my 2c

João
Hi João,

I normally do not use protected cells, I was given some to test for a client (as a side job I test notebook batteries for form, fit, function, quality and safety, this pays for most of my RC hobbies) and they did what they are supposed do, cut off if output voltage is to low, this number is 2.50 volts per cell for a Li-Ion and depending on the cell mAH rating over current protection, tested at 6 .1 amps. So if your Tx is pulling over 6 amps (when it required 0.15 amps) you just about have a fire, LOL J/K. And if 15 plus hours is not enough flight time then your Mr endurance of flight (wonder what she says in bed :D ). I sold them cells when I did my 12th 9x to er9x mod and am using high quality 3000mHA Sanyo cells now, just under 20 hours run time with HK Blue back light always on.

Thanks for your good input João!

Ozzy

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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by jhsa » Sat Dec 15, 2012 1:48 pm

It's just one more thing that can go wrong.. ;)
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Re: Best 9x battery? 2S Li-Ion 18650 cells

Post by LTMNO » Sun Feb 24, 2013 8:44 pm

I have bought the trustfires. Very happy thus far. :-)
8.2v full charge.
15hrs before a voltage drops to 7.2
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