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Old Dec 22, 2010, 11:46 AM
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Making a non-swappable LiPo swappable

Hi guys,

I'm fairly new to helicopters so I would appreciate your input.

I have a new G.T. Models 5888 coaxial helicopter which is great but the battery life is a bit limited. It has a 3.7V 180mAh flat rectangular battery inside the canopy which is zip locked to the front of the circuit board.

I'd like to move this underneath the heli and use a connector so that I can swap to a new battery when this one runs down.

There looks to be a circuit board inside the insulating cover of the battery so I guess I need to have this between ANY battery and the main circuit board connection.

So the plan is ....

1) keep the two wires going from the main board to the battery circuit board intact.
2)Unsolder the battery wires from the battery circuit board.
3) Solder 2 new wires from the battery circuit board to a 2 pin connector ( JST type )
3) solder a JST connector to the original battery terminals and some new batteries which I will need to buy.

Is there any flaw in the above that I need to be aware of apart from moving the centre of gravity ?

Also, suppose I buy a 3.7V 250mAh battery for example, will this charge and power the helicopter properly or should I stick to 180mAh ones ?

Thanks in advance for your help.

Steve
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Old Dec 22, 2010, 12:04 PM
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It is doable. I've done it myself on a S107. Just be careful to use a lipo that has that PCB board on it, this will protect the lipo from overcharging.

As for the 250 vs 180, all you need to check is the weight. Usually, more capacity = more weight = more weight to lift = less flight time = to original flight time.

EDIT

Oh and I've forgot to add, if you move the batt underneath the heli, you will unbalance it, you will need to counter weight the front. And to solder new wire to the heli's elec board, you need a few soldering skills. It's tiny!
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Old Dec 25, 2010, 03:24 AM
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Thanks for the reply.

I was planning to use the battery's PCD from the original battery on any new ones ( see my original post ) by putting this in between the batery and the main circuit board. Would a 250 mAh need a different battery PCD to a 180mAh battery ?

I've never come across a battery that had a PCD with it. Can you point me to a web link so I can have a look please.
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Old Dec 25, 2010, 03:30 AM
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I've never come across a battery that had a PCD with it. Can you point me to a web link so I can have a look please.
Syma S107s have them ... so do most of the 6010s. From what I'm hearing, any heli that uses a USB charger better have a charging protection PCB on the LiPo to prevent over charging and ruining the battery in short time.

You have to look very closely at the top of the battery where the power wired come out to see the PCB buried in the top of the battery.
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Old Dec 25, 2010, 05:14 AM
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There is some circuitry in the USB plug itself. A red LED turns on when the battery is charged so there must be something inside the USB plug I would assume.

So any ideas if the PCB on the original 5888 battery would be ok to use in say a 250mAh battery as well ?
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Old Dec 25, 2010, 12:57 PM
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There is some circuitry in the USB plug itself. A red LED turns on when the battery is charged so there must be something inside the USB plug I would assume.

So any ideas if the PCB on the original 5888 battery would be ok to use in say a 250mAh battery as well ?
Yes there is some kind of circuit in the USB plug, but it is not a charging regulation circuit. I think it's just a circuit that senses when the battery is at full charge ... meaning the charging voltage has increased to near the max allowed for a LiPo, which is 4.2 volts.

Many here have proven that the USB charger does not have a regulator because they have used it on a LiPo (the BestOfferBuy 6010 clone) that does not have the circuit board on it, and the result was a puffed up, over charged battery that was toast.
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Old Dec 26, 2010, 02:19 AM
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If you read the thread on the 5888 you will see that what you are attempting to do will burn your motors out very quickly

http://www.rcgroups.com/forums/showp...&postcount=211

Quote:
Originally Posted by gbjbasdw View Post
There is some circuitry in the USB plug itself. A red LED turns on when the battery is charged so there must be something inside the USB plug I would assume.

So any ideas if the PCB on the original 5888 battery would be ok to use in say a 250mAh battery as well ?
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Old Dec 26, 2010, 05:09 AM
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I'd agree with what Hayabusa Heli says. It's the PCD that sits between the battery and the main board that controls the battery charging otherwise this circuitry would need to be in both the USB cable and the controller because both sources can be used for charging and I don't think the Chinese would duplicate stuff they didn't need to becuase of manufacturing cost.

I read all the thread that scotsoft's comment refers to some time ago. There seems to me to be no good reason why a 5888 helicopter motor should burn out because I'm using a 250mAh batttery unless it is run for very long periods. If the motors on the 5888 burn out then it means the model is one to be avoided in my opinion !

Still no answer to my original question....

Can the battery PCD from a 180mAh battery be used on a 250mAh battery ??
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Old Dec 26, 2010, 02:03 PM
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Still no answer to my original question....

Can the battery PCD from a 180mAh battery be used on a 250mAh battery ??
I wouldn't see why not. The PCD will still regulate the charging rate ... it will just take longer to charge a 250 mAh battery vs. a 180 mAh battery.
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Old Dec 26, 2010, 04:38 PM
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From what I can see, the PCB on these LiPo's performs the following:

1: Overcurrent protection - if there is an overload, it will cut power and not reset until the electrical load is removed.

2: Over discharge protection - it will cut power (rather abrubtly) when the LiPo is exhausted.

3: Over charge protection - it will terminate the charge when the LiPo hits 4.2V

It does not regulate the charging current. A simple series resistor can accomplish this, or an constant current IC regulator. You'll want to set the charge current to a 1C rate. (180mAh should charge for approx 1 hour at 180mA)

I had ordered some spare parts for my Falcon 8913 heli, and it came with a spare battery. I charged it with a 5 volt power supply with a flashlight bulb in series as a ballast. When the cell hit 4.2V - the PCB cut the charge and the light bulb went out.
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Old Dec 27, 2010, 03:11 AM
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As I am not thinking of changing the charging power source ( i.e. USB cable or transmitter cable ) then the over current issue goes away.

Sounds like I should be ok from what you've said.

I like your "bulb in series" experiment - very neat ! I guess the LED circuit inside the USB plug detects the cut-off in the battery PCD somehow and then lights the LED.
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Old Dec 27, 2010, 10:01 AM
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The "bulb in series" ballast regulator is a very old trick. I had a cheap NiCd trickle charger that was nothing more than a 7 watt night light bulb and a diode in series with the batteries you were charging connected directly to line voltage. There was a safety interlock switch that prevented the circuit from being energized unless the lid was shut to prevent shock.

The wall wart that came with the 4 channel toy heli has a two color LED in it. When the wall wart is plugged in, the green part lights up. When the LiPo is accepting charge, the red part lghts up and the light glows amber. WHen the PCB in the battery cuts off, the light goes back to green. They probably have the red LED across a dropping resistor so it lights up when the pack is accepting charge current.

I was thinking that those little LiPo batteries used in helis like the Blade mCX and mSR would be a good conversion because they have a connector on the end. You would just have to rig a holder in the right spot to maintain CG. I don't think those batteries have a protection circuit board, so you would have to use one from the original battery for LVC and HVC.
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Old Dec 27, 2010, 10:32 AM
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Originally Posted by gbjbasdw View Post

Still no answer to my original question....

Can the battery PCD from a 180mAh battery be used on a 250mAh battery ??
Yes. I've done it. I first made the mistake of keeping both the original 180mah board AND the 250mah board which was part of the new lipo. It took like 40 minutes to recharge my 6020 after just a 1 minute flight. I discarded the 250mah board and kept the 180mah one and the charge times went back to normal. Flew several cycles with no battery puffing or anything (then the flybar broke). It was like the old lipo was being used except it had more power, but the old lipo was already very weak so I don't know if it felt more powerful than what a strong 180mah would have felt like.
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Old Jan 02, 2011, 06:26 PM
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Originally Posted by gbjbasdw View Post
I read all the thread that scotsoft's comment refers to some time ago. There seems to me to be no good reason why a 5888 helicopter motor should burn out because I'm using a 250mAh batttery unless it is run for very long periods. If the motors on the 5888 burn out then it means the model is one to be avoided in my opinion !
Lee's observations in that thread were that the motors in the 5888 were the weak point... which is why he makes such a big deal about checking if they get too hot.
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Old Jan 03, 2011, 08:29 AM
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My motors seem to be fine so far ( fingers and toes crossed ).

I understand what Lee is saying but my own experiences have been that the motors seems fine but he has owned many more of them than I have !
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