DX7 and Lipos?

[sgrim80]

Has anyone changed to a lipo in their DX7 instead of the stock pack? I have a friend that uses lipos in his transmitter and claims they last so much longer between chargings.

What lipo would someone recommend to put in a DX 7?

[Ticidytoc]

Take a look at Esprit Model. They list a pack that fits in the DX7.

http://www.espritmodel.com/

[Danal Estes]

Lithium do last longer, no question... but before you go there, be aware that the stock DX7 pack lasts a LONG time. I don't recall the numbers sitting here... but they made the pack bigger than the DX6 and reduced the power drain (at least when using the new receivers). Yes, the tranny "knows" whether the receiver is DSM1 (AR6000) or DSM2 (any of the new ones) and uses less power in DSM2 mode.

In short: Play with it stock for a while before you change it.

[BarnOwl]

I use a 3S 1800 Mah lipo in my Spectrum DX7. It's been in there for weeks and I hardly see the voltage bar shrinking.
The reason was not that I was not satisfied with the performance of the stock battery, but I sold my Nimh charger because TP promised a Nimh charge upgrade on their 1010 charger early this year.........
Anyway, you can use a lipo on this tx no problem.

[kgfly]

DX7 comes stock with a 1500mAh NiMH Tx battery (and a PITA 50mAh wallwart charger). It uses about 350mA in DSM mode (talking to an AR6000) and about 160mA in DSM2 mode (AR6100 or AR7000). That means you will get at least 3-4 hrs (DSM) or 6-8 hrs (DSM2). (See here for current draw test results: http://www.rcgroups.com/forums/showpost.php?p=6523231&postcount=659 )

However, apart from being larger capacity, the big bonus of going LiPo is shelf life. You can put your Tx away, come back in a week (or a month!) and it's still ready to fly. Same is not true for NiCd/NiMH.

Also note that Spektrum say that you cannot charge any battery above 1A via the Tx charge socket. So if you put a lipo in there don't try to charge it at 1C unless you charge it by taking it out of the Tx. Still, even at 500mA you will fully charge a lipo in 3 to 5 hrs.

I don't think the espritmodels Tx lipo is a great deal, take a look at these others:

http://www.commonsenserc.com/product_info.php?cPath=37_27&products_id=32
http://home.comcast.net/~truerc/ready_pack/ready_packs.htm

The one from TrueRC looks the best deal to me, 3S1P 2500mAh 1C for $30 and comes with the JR connector fitted and a balance lead so you can balance it every so often.

[sgrim80]

DX7 comes stock with a 1500mAh NiMH Tx battery (and a PITA 50mAh wallwart charger). It uses about 350mA in DSM mode (talking to an AR6000) and about 160mA in DSM2 mode (AR6100 or AR7000). That means you will get at least 3-4 hrs (DSM) or 6-8 hrs (DSM2). (See here for current draw test results: http://www.rcgroups.com/forums/showpost.php?p=6523231&postcount=659 )

However, apart from being larger capacity, the big bonus of going LiPo is shelf life. You can put your Tx away, come back in a week (or a month!) and it's still ready to fly. Same is not true for NiCd/NiMH.

Also note that Spektrum say that you cannot charge any battery above 1A via the Tx charge socket. So if you put a lipo in there don't try to charge it at 1C unless you charge it by taking it out of the Tx. Still, even at 500mA you will fully charge a lipo in 3 to 5 hrs.

I don't think the espritmodels Tx lipo is a great deal, take a look at these others:

http://www.commonsenserc.com/product_info.php?cPath=37_27&products_id=32
http://home.comcast.net/~truerc/ready_pack/ready_packs.htm

The one from TrueRC looks the best deal to me, 3S1P 2500mAh 1C for $30 and comes with the JR connector fitted and a balance lead so you can balance it every so often.

Any idea what balance lead? I need to know so I can get the right adapter for my cellpro.

[piwko4]

as far as charging the lipo througn the tx goes, i would def not do it.. take them out and charge them w/o the tx. dont want a lipo explodeing in your tx. just something i wouldn't want to chance.

[BarnOwl]

/ready_packs.htm

The one from TrueRC looks the best deal to me, 3S1P 2500mAh 1C for $30 and comes with the JR connector fitted and a balance lead so you can balance it every so often.

They won't fit: The DX7 has a battery compartment of 25mm deep, 32mm high and at most 105mm long! :shock:

**EDIT** Ignore this post: The proper battery is at the bottom of the page, I was looking at the top ones... :oops:

[stevehonn]

Although the supplied 1500mAh nimh pack gives long life between charges, one advantage of lipo's is the very low self discharge rates. Some nimhs have quite a high self dicharge rate so if the transmitter hasn't been used for a few weeks it would need a top-up charge, a bit of a pain if you're just out for an unplanned flying session, not a problem with lipos.

I've never been 100% convinced that nimh's don't suffer from memory effects, lipos certainly don't. Lipo's are also lighter so then you wouldn't even know you were holding the DX7 :) It might help balance a bit though.

[sgrim80]

/ready_packs.htm

The one from TrueRC looks the best deal to me, 3S1P 2500mAh 1C for $30 and comes with the JR connector fitted and a balance lead so you can balance it every so often.

They won't fit: The DX7 has a battery compartment of 25mm deep, 32mm high and at most 105mm long! :shock:

The vendor that sells them says they fit. What makes you think not?

[BarnOwl]

Sorry, my mistake, was looking at the wrong packs at the top of the page.......This is the one Kenneth means, it's 24 x 21 x 101mm, a perfect fit!
http://home.comcast.net/~truerc/ready_pack/2500TX.JPG

[Heli_harry]

I would think that the stock battery is the better way to go.

It lasts a Long time between charges, and if you mess up and leave it on the Li-po will be ruined.

Good Luck!

[sgrim80]

I would think that the stock battery is the better way to go.

It lasts a Long time between charges, and if you mess up and leave it on the Li-po will be ruined.

Good Luck!

Too late...already got one. I really like it so far!

[Filby]

What about the fact that the lipo is lightre than the DX7 nimh pack? Does this fix the problem witht eh dx7 being base heavy?



Fil

[PsychoPilot145]

What about the fact that the lipo is lightre than the DX7 nimh pack? Does this fix the problem witht eh dx7 being base heavy?


Actually, the DX7 is perfectly balanced, it's just that the eyelet for the radio strap is not centered with the CG. Notice that it is about 3/4 towards the top of the radio. That's what makes it out of balance.

Move the eyelet down to the bottom of the power switch, or use a bolt through the eyelet with a ring over the bottom of the power switch and hook the strap there. The bolt extension works great, and does not void the warranty.

[BarnOwl]

Move the eyelet down to the bottom of the power switch, or use a bolt through the eyelet with a ring over the bottom of the power switch and hook the strap there. The bolt extension works great, and does not void the warranty.[/quote]

Wont the bolt be in the way of the power switch? Is it still easy to switch on and off?

[Jermo]

well if you up the charge current to 100mAh on the charger it would fully charge from zero in 21 hours. From the web max charging for NiMH is capacity/10 so 1500mAh/10 = 150mAh charge rate max (***EDIT: this is for non-max peak detecting chargers..ie wallwart type. most Manf allow up to 1C rates with a peak detect charger). Time to charge is determined by (capacity * 1.4)/charge rate. So (1500mAh * 1.4)/100mAh = 21 hours. That assumes it's totally dead.

Many Lipo chargers have a NiMH/NiCad mode with adjustable parameters..ie pack capacity and charge rates. Just have to rememeber to get the polarity correct (DX7 is reversed if I recall).

Edits to add more detail.

[dutch_anykey]

Hi Jermo,

I have a dx7 as well with the stock nimh battery...but i cant find any charging rates on the sticker of the battery...The kit came with the stock charger....that one i cant use here in netherlands since it is 110V 60hz...
I charge it with my robbe powerpeak ultimate charger..but to be on the safe side i put it on auto detect since i dont have any real data on this nimh battery ..but the current doesnt get high enough to make it a quick charge.. ( i forgot how many milli amps it actually was)
So for the questioncan i safely charge it with 1C setting (program the charger for nimh 1500 mAH and 1C charging current and the amount of cells)...

Im curious about the rest of you guys, are you actually using the stock overnight charger...or a C pump that will turbo charge this thing, which in my case also charges my lipos :D

thanks,
Maurice

[Jermo]

From my reading the key part to charging over C/10 rate is having a peak charger specifically for NiMH batteries. So without knowing your specific charger I'd have to say I don't know. If your charger has NiMH settings then you should be all set. The charger I have sets Battery Type, Voltage, Capacity, and charge rate/type.
Just note the charge jack on the DX7 is fused so if you go over current you'll know quick.

[DavidH]

Maurice,
Yes you can safely charge the 1500 mah pack at 1.5 amps. Would not make a habit of charging it that rate all the time. But will not hurt it. As for charging long term. 150 to 250 mah charge rate will be fine.
To charge the battery at higher rates you will have to take it out of the radio. It is a 3 amp fuse in the radio. I doubt it is going to take a charge rate much over a 100 mahs without blowing the fuse.

David

[dutch_anykey]

Thanks guys,

Just what i wanted to hear. As for taking out the battery..i was already doing that...luckally i already read about blown fuses before on the forum.

thanks,
Maurice

[BarnOwl]

Sorry, my mistake, was looking at the wrong packs at the top of the page.......This is the one Kenneth means, it's 24 x 21 x 101mm, a perfect fit!
http://home.comcast.net/~truerc/ready_pack/2500TX.JPG

I actually have been using this pack for about 25 flights now, I hardly see the voltage dropping. It's a winner!
I charge the lipo outside the tx on the 1010/210 combo at 1C.

[PsychoPilot145]

Wont the bolt be in the way of the power switch?

Only if the eyelet is ninety degrees to the radio. While not my idea for the bolt, I discovered that rotating the bolt about twenty degrees top left, frees up the switch. If left at 90*, then yes, it is hard to get at the switch.

The CG for the radio is pretty much centered at the the switch. This works perfectly.

[Filby]

No offense intended but that solution looks crap.

Barnowl: Did the lipo change the balance of the Tx?

[PsychoPilot145]

No offense taken. I'll take practical functionality over looks any day. The only thing that looks worse, is the transmitter sloping backwards at 45* when you are trying to fly. :)