3S LiPo in a DX7 - Re-visited

[scallybert]

I was thinking about this, and re-read a previous thread: http://www.rcheliaddict.co.uk/f45/dx...version-14581/ .

AIUI, the only problem you've really got is that 3*4.2V > the 12V the DX7 is happy with. The sugestion is not to fully charge the LiPo , so the voltage stays below 12V.

Another concern is that the mechanical cycling of the rear cover and/or power connector for charging might lead to a premature failure.

A further thought was what would happen if a regular NiMh charger (12V 150mA, it says here) was inadvertantly plugged into the DX7.

In general, this is a no-no. No balancing, not set-up for LiPos.

On the other hand, it's not going to charge >12V, so is unlikely to overcharge a cell (provided LiPo is periodically balanced). Which might also get around the issue of powering the TX a >12V.

So I wonder if using the regular charger with a 3S LiPo might not only be safe, but actually a good idea. Hmm.

Thoughts ?

[Ade_Law]

i never charged my 9x2 through the charge port when i had a nicad/nimh battery. took too long so always pulled it out the tx to charge.

never any issues with the lid or connections.

if anything with a lipo its better as you leave it plugged in the tx and charge through the balance lead only so your not disturbing the connection to the transmitter.

i used the outrage tx lipo in my 9x2 for about 6 months and never saw any issues with >12v all the internal electronics will be regulated down so that they see a constant voltage no matter what the state of charge of the battery.

dont worry about the paranoia, lipos for tx's have been around quite a few years we would have heard of issues by now if there were any.

Ade

[unwind-protect]

i never charged my 9x2 through the charge port when i had a nicad/nimh battery. took too long so always pulled it out the tx to charge.

Don't suppose you can remember the name of the connector that the 9x2 uses for its battery connection. It'd be really handy to be able to fast charge mine, too!

[J-S-Q]

The one thing that puts me off this idea is if you ever forget to switch off your Tx then you could have a serious problem with over discharging the battery, li-po fire etc.

[Ade_Law]

the tx discharges at such a low rate that it would just damage the lipo. You leave a nicad switched on and it will damage it too tho.

lipos fire up because they are being aggressively abused. discharged too fast or over voltaged due to bad charging.

Ade

[Ashley Davis]

agree with Ade, a slow discharged lipo doesn't catch fire.

[SRH990]

I though most transmitters will switch themselves off when the battery gets down to a certain voltage?

I've had a 3S lipo in my 9X2 for a good while now and even when fully charged it never shows over 12V on the screen.

[DT39]

I was thinking about this, and re-read a previous thread: http://www.rcheliaddict.co.uk/f45/dx...version-14581/ .

AIUI, the only problem you've really got is that 3*4.2V > the 12V the DX7 is happy with. The sugestion is not to fully charge the LiPo , so the voltage stays below 12V.

Another concern is that the mechanical cycling of the rear cover and/or power connector for charging might lead to a premature failure.

A further thought was what would happen if a regular NiMh charger (12V 150mA, it says here) was inadvertantly plugged into the DX7.

In general, this is a no-no. No balancing, not set-up for LiPos.

On the other hand, it's not going to charge >12V, so is unlikely to overcharge a cell (provided LiPo is periodically balanced). Which might also get around the issue of powering the TX a >12V.

So I wonder if using the regular charger with a 3S LiPo might not only be safe, but actually a good idea. Hmm.

Thoughts ?

I debated on this one a few months back and did a load of looking around at other forums and here but there is no reason not to use a lipo in DX7 from what i found. I got rhino 2620 off the bay (fits perfect) and it's been great only charged (via balance lead) it once in the 2 months i have had it and that's flying couple times a week + about 2hrs a week on phoenix.
I looked up the voltage regulator that's in the DX7 on CPC and RS website and from what i can remember it was good up to about 16v so that made my mind up.
DX7 has got a cut off voltage that you can change in the service menu but i can't remember what they are though.

[J-S-Q]

Ok I was just a bit nervous about the prospect of a LiPo fire as I have left my Tx on once or twice by mistake -I also wasn't aware that the DX7 actually had a cutoff voltage, I thought it just started beeping for low battery -does it actually switch itself off altogether then?

[scallybert]

i used the outrage tx lipo in my 9x2 for about 6 months and never saw any issues with >12v all the internal electronics will be regulated down so that they see a constant voltage no matter what the state of charge of the battery.

dont worry about the paranoia, lipos for tx's have been around quite a few years we would have heard of issues by now if there were any.

AIUI, it's the regulator that gets taken out, rather than the internal electronics (Linear mode, so greater battery volage => more power dissipated by regulator.)

I remember seeing an article of dire warnings on a Spektrum/Horizon web-site - but can't find it now.

I guess I shouldn't worry...