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Old Dec 23, 2012, 07:11 PM
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DX7s Li-Po Battery Charging

I have installed a Spektrum 2s1p 4000mAh Li-Po battery in my new Tx, but am concerned that the built in charger in the transmitter is only a trickle charger running at a very low rate and as a result it is taking forever to re-charge the battery ( 24 hours or more) to get it up to max volts (8.2v - 8.4v).

It would have been a lot smarter to have provided an adapter lead with the Tx so that the Li-Po pack could be easily removed from the Tx and charger externally with a standard high performance Li-Po charger, which should be able to charge and balance the pack back to at least 8.2v in about 1 hour.

Any comment from the Spekrum Development Team
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Old Dec 23, 2012, 08:03 PM
PGR
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The DX7s will only charge a LiPo pack at a 200mA rate so it will take ~20 hours to charge a depleted 4000mAh pack. The DX7s charging circuit has built in voltage and current regulation so the only practical way to charge the pack faster is to disconnect it and charge it with an external charger.

And it's very unlikely that you will get any kind of official response from "the Spekrum Development Team" in this thread or this forum.

Pete
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Old Dec 24, 2012, 05:38 AM
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I did as Pete says and charge it with the regular charger. I made an adapter from a servo extension as the pinout width is the same. I set the charger for 2 amps so it took a little less than 2 hrs to charge.

Gord
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Old Dec 24, 2012, 06:34 AM
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Haralson County GA. USA
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A X Max wish of mine is that people would post in the correct Forum Area.

Everything in RC uses batteries but that doe not mean B % C is the best forum.

Surprise ther relly is a Radio Forum as well as arout 300 other specific forums.

http://www.rcgroups.com/radios-135/

Charles
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Old Dec 24, 2012, 06:52 AM
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MPI makes a plug that will work but you will have to solder banana plugs on and be very careful of polarity. Apparently Spektrum's polarity is backwards from the other brands.
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Old Dec 24, 2012, 07:24 AM
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There's nothing wrong with charging it in the TX. In my experience the TX cuts off the charge at 8.2v which will prolong your battery life as well. You have to remember this is a low discharge battery, not a high discharge one like you use in your planes.
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Old Dec 24, 2012, 09:13 AM
PGR
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Quote:
Originally Posted by ForsheeMS View Post
MPI makes a plug that will work but you will have to solder banana plugs on and be very careful of polarity. Apparently Spektrum's polarity is backwards from the other brands.
Just to clarify something here, unlike the majority of transmitters you CAN'T charge the DX7s through the built-in charging jack with a programmable NiMH or LiPo charger.

The DX7s has a NiMH/LiPo charger built into it and the 12V charging jack powers that internal charger. In other words, there is no direct connection from the charging jack to the battery pack and if you try to charge the DX7s with an external NiMH or LiPo charger you WON'T be able to charge it any faster and you'll probably BURN UP the internal charger.

It also won't help to use a bigger 12V DC power supply. The charging rate of the internal charger is fixed at 200mA. I've charged my DX7s in the field by connecting it directly to a car battery and it didn't charge any faster than with the supplied 500mA 12V DC wall wart.

And for what it's worth, the 12V jack in the DX7s is polarity independent meaning that you can power it with either polarity and it will work fine as long as it's 12V DC.

Pete
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Old Dec 24, 2012, 11:33 AM
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Quote:
Originally Posted by PGR View Post
Just to clarify something here, unlike the majority of transmitters you CAN'T charge the DX7s through the built-in charging jack with a programmable NiMH or LiPo charger.

The DX7s has a NiMH/LiPo charger built into it and the 12V charging jack powers that internal charger. In other words, there is no direct connection from the charging jack to the battery pack and if you try to charge the DX7s with an external NiMH or LiPo charger you WON'T be able to charge it any faster and you'll probably BURN UP the internal charger.

It also won't help to use a bigger 12V DC power supply. The charging rate of the internal charger is fixed at 200mA. I've charged my DX7s in the field by connecting it directly to a car battery and it didn't charge any faster than with the supplied 500mA 12V DC wall wart.

And for what it's worth, the 12V jack in the DX7s is polarity independent meaning that you can power it with either polarity and it will work fine as long as it's 12V DC.

Pete
Pete, thanks for clearing that up. My post was definitely a little misleading. What I used was the MPI part number 2810 plug. Soldered on some banana plugs and removed the battery from the Tx hooking it directly up to my iCharger 206B. I am not charging through the charge port on the Tx. This way I know when the battery is fully charged rather than guessing at it.
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