Questions/thoughts about a lipo in the DX7

[najones]

I've looked into putting a lipo into the DX7 in the past and I know that people who do it love it.

There are 2 down sides to the lipo, though:
1: Possiblity of charging with the wrong charger
2: Transmitter cutoff is too low for lipo batteries

Problem 1 has been handled by flipping the charge port so that is no longer aligned with the case, thus preventing the charger from use.

I was just thinking about using a diode to drop the voltage from the lipo so that the transmitter would read .7V lower than the battery. This isn't my idea, I believe I read it from a thread or review. This allows the low voltage alarm to trigger .7V higher on the battery, so that problem is solved.

It also seems that it would protect the battery from being charged as the diode wouldn't allow power to pass that way. Is anyone using a diode to protect the transmitter from a lipo fire?

Nathan

[capebob]

Why don't you just buy a similar or higher capacity NiMh battery at a much lower cost. A milliamp is a milliamp no matter what kind of battery you use and you will greatly reduce the chance of destroying your transmitter. Of course you could remove your battery every time you recharge. :roll:

Bob

[najones]

I agree about the ma thing, and I doubt I would do the conversion anytime soon. I was mostly just asking a question to see if anyone is using a diode for protection of both the timer and charging.

The other factor is that lipo sits fully charged much longer than a NiMh fully charged.

[Hummer6]

I been using the www.maxamps.com transmitter lipo pack for my DX7. This battery has been working great. I cut a plug off of the wall charger and charge that battery with the normal radio plug at 1.5 amp. I charge once for the whole week-end of flying.

[ChasHeliCop]

I am using a FP 3s pack with no problems. put a mini-dean's connector inline, so I just disconnect to charge. I don't rely on the "low voltage" on the Tx, since it only takes an hour or less to charge the lipo, I simply pull it and stick it on the charger while doing my pther packs. MUCH much more convenient than the NiMH packs, and no more overnight charging, plus it last longer. On my other DX7, I did the DE Mod and have the NiMH packs which last longer now. Just my 0.02 worth

[Pinecone]

1) Spektrum does not support the use of lipos and claims to have seen Txes damaged by their use.

2) If you ever leave your Tx on, you will kill the pack.

3) If you ever screw up charging, you can destroy the pack and the Tx (melt down)

I run a 2700 mAH NiMH pack. Works great, and can last longer than a lipo due to more mAH.

The only reason I can see for a lipo is that if you forget to charge your Tx, you canfast charge at tehfield. But if you can't remember to occasionally charge your Tx, what else did you forget. :)

[najones]

1) Spektrum does not support the use of lipos and claims to have seen Txes damaged by their use.

2) If you ever leave your Tx on, you will kill the pack.

3) If you ever screw up charging, you can destroy the pack and the Tx (melt down)

I run a 2700 mAH NiMH pack. Works great, and can last longer than a lipo due to more mAH.

The only reason I can see for a lipo is that if you forget to charge your Tx, you canfast charge at tehfield. But if you can't remember to occasionally charge your Tx, what else did you forget. :)

The diode would seem to protect 2 and 3. The diode would possibly also help issue 1 because it would drop the voltage of the battery for the transmitter, thus not feeding the transmitter too much voltage.

LiPo's have most/all of their capacity above 3V per cell, which means that the transmitter could use all the mah from a lipo battery. NiMh seem to, I don't claim to know, discharge much more linear than a lipo, which seems to means that when the transmitter goes into low voltage cutoff, their is still a decent amount of capacity left in the batteries. Is this true? If so, a mah is not a mah, because a lipo supplies all of its mah's at a higher voltage and then just drops off quickly.

[gww528]

1) Spektrum does not support the use of lipos and claims to have seen Txes damaged by their use.


If Spektrum claims to have seen Tx damaged by Lipo use. What is the damage and how is it caused by the Lipo?

Thank you

[ChasHeliCop]

I suspect the Lipo fried my stock voltage regulator, but I have see them go out with the stock battery also. It just gave me a reason to do the DE Voltage Regulator Modification, now all is great. I still love the convenience of the Lipo in the Tx. particularly the fact I can pull the pack and have it fully charged, ready to fly in less than an hour. I recharge at 11.1v so I don't runn it down too low, and I only have to charge about once a month.

The biggest disadvantage is it voids the manufacturer warranty.

[Bigglesworth]

-------------------------------
The diode would seem to protect 2 and 3. The diode would possibly also help issue 1 because it would drop the voltage of the battery for the transmitter, thus not feeding the transmitter too much voltage.
-------------------------------

I like the diode idea, and agree with the above.
As an extra bit of info, you could drop the voltage by 1.2 volts with two diodes in series ( --K|--K|-- ) if you think 0.6 volt is not enough.
That would make the tx read 8.4 volts when the lipo pack is at 9.6 volts (3.2 volts per cell) and the tx would read 11.4 volts with a fully charged pack.

Just my 2.2 cents worth including GST:thumbdown:, I'm going to stick with just one diode all the same.

[gww528]

What is the DE Voltage Regulator Modification mod?

Thank you

I suspect the Lipo fried my stock voltage regulator, but I have see them go out with the stock battery also. It just gave me a reason to do the DE Voltage Regulator Modification, now all is great. I still love the convenience of the Lipo in the Tx. particularly the fact I can pull the pack and have it fully charged, ready to fly in less than an hour. I recharge at 11.1v so I don't runn it down too low, and I only have to charge about once a month.

The biggest disadvantage is it voids the manufacturer warranty.

[Pinecone]

New item at Spektrum:

Heads Up, Use the right batteries in your Spektrum transmitter for best results
Monday, March 17, 2008

Warning concerning use of non-standard transmitter batteries

Spektrum transmitters are designed to be operated on 9.6 or 4.8 volt Ni-cad or NiMh batteries only. Use of Li-Po or other power devices operating at higher voltage can add heat to the system, possibly overloading the power regulating transistor for reduced output. Despite what aftermarket battery manufacturers might suggest, use of non-standard batteries offers decreased reliability of your Spektrum. Our service department has received failures associated with Li-Po packs.

For increased flight time, please use increased capacity NiMh cells, like the JRPB5011 2500 Sanyo pack. Charge these packs with the JRPC223 9.6 volt 270mAh output charger.

[LITHIUMSTATIC]

I've been running a 3s lipo in my DX7 since Christmas without any problems. I know MANY others that do the same thing without problems too. It wouldn't surprise me is if Spectrum is just throwing that statement out to cut down on risk of TX damage. You know what happens if a tx goes bad and is under warranty? They get to fix it.

[gww528]

New item at Spektrum:

<snip>
Use of Li-Po or other power devices operating at higher voltage can add heat to the system, possibly overloading the power regulating transistor for reduced output.
<snip>


The Dx7 Spektrum NiMh battery fully charged registers at 11.8 volts in the TX. The concern is the higher voltage. You can add a diode to your Lipo battery connector and drop the voltage to the appropriate Spektrum TX voltage of 11.8 volts.

Hope that helps

[ChasHeliCop]

What is the DE Voltage Regulator Modification mod?

Thank you

DE Mod is the installation of the Dimension Engineering Voltage Regulator in place of the stock regulator in the Tx. It takes some soldering skills to do this successfully, and of course voids the Manufacturer warranty. DE also makes BEC's and Lipo sheilds.

http://dimensionengineering.com/appnotes/spektrum_mod/spektrum_mod.htm

Cost is $15 = $1.50 shipping

http://www.dimensionengineering.com/DE-SW033.htm

[sparky]

The manual recomends not using Lipo. And I am curious as to why you would want to when the OEM pack is 1500ma and the Lipo pack is 1500ma. Why would you want to take the risk?

[LITHIUMSTATIC]

The manual recomends not using Lipo. And I am curious as to why you would want to when the OEM pack is 1500ma and the Lipo pack is 1500ma. Why would you want to take the risk?

Because I only charge my TX once a month...... maybe even six weeks. Very nice just grabbing the radio and knowing it's going to be ready to rock.

[Yardape]

I've just completed the Dimension Engineering voltage regulator swap. Was really quite easy, cut the pins and replace with the new one. Voltage was at 10.3v when i swapped a couple hours ago...it's just dropped to 10.2v. With a lipo onboard, probably have to charge once a month tops? it's a toss-up max amps packs or flight power tx packs? Anyone have suggestions?

[LITHIUMSTATIC]

I got mine from True RC. $30

[rcmarty]

I bought the true rc pack also. 2500 mah and fits better in batt compartment than a fp or tp pack.

modded and repinned the balancing tap to fit a eflight charger.

the eflight chargers are a more moddest end voltage charge

i just pop the back off the tx and connect up the charger. End up with 12.3 - 12.4 volts every time.

Had this pack in my 9303h also , works great.

I would think the oposite with a higher voltage pack .. a stronger signal to transmitt with rather than a sagging voltage to get powered off of. Could be wrong though.

I also put a piece of fuel tubing in the charge jack location over the pin , this prevents the nicad charger from being used should i ever loose my mind (i have kids so its plausable)



Martin :)

[Yardape]

I went for the Kong Power...they are supposedly less prone to puff. So far with the d.e. 3.3 v regulator, and lipo combo...i put back about 1000-1200 mah every 2 weeks...50% of the lipo used in 2 weeks...gotta love that...

[tungym]

I have been using 3s lipo over the last 3 years, in my T7CHP, DX6 and DX7 (+1.5 year). Never have any problem. Except once an old lipo puffed inside my T7CHP, as I forgot to switch it off.

Putting a few diode will be an good idea if over voltage is a concern. But why not just charge your lipo to around 12V.

IMO, I have another more horrible issue. The Tx drain the lipo so gentle that once my Tx suddenly shut down during bench testing. The 3 cells (also new lipo) reads 3.3V, 3.3V and 0V. DX7 reads 11.1V few minutes before the shut down. I still cannot figure out the exact reason as I certainly balance charge my lipo. The pack works perfect after complete recharged and has been used for another 3 months since then.

Now, I recharge my pack whenever DX7 reads 11.5V. But I certainly will put in a diode soon, for exact safety.

[Buzzkill]

As soon as Spektrum or JR makes a lipo it will suddenly be ok to use them.