Trex 800 hv with Lipo 2s, no bec

[roddrigo]

Hi Guys, I'm new to the forum and new to HV servos. I'm putting together a Trex 800 with HV servos, Spektrum satellites, 3gx and APS system.
Mi question is: Can I really plug the 2S lipo directly into the 3gx? No bec? Will the electronics be able to deal with the voltage drop as the battery charge goes down?
Thanks for any help an sorry for the poor english (I'm from Brazil).

[nu66ie]

Welcome!

Yes, it can handle a 2s lipo, or two. It would be best to run two power inputs to the 3GX, on the bottom two ports. Also, consider running two receiver batteries to achieve this. The redundancy and increased flight count is worth it. I run two 1350mAh 2s on my 800 and get six 3D flights. I use a Spektrum dual I/O switch to power the system.

Good Luck

[roddrigo]

Hi Nu66ie. thanks for your reply. With the kit, comes a Two-way Step-down voltage regulator that supposedly sends 5,1v to the ruder servo. Did you use it with your 800? If the servos are all HV why they send this with the kit?

[nu66ie]

Your welcome.

I have never used them. I actually give them away. The regulator included I guess is for those who want to run another brand of tail servo. The Align HV in the kit will handle the 7.4v without any problems.

Another option is to run a pair of 6.6v LiFe packs. Since your not doing 3D, the increased performance you get with a 7.4v 2s LiPo may not be needed. Again, the 3GX, Vbar, ect, prefer to have dual power inputs.

The LiFe batteries are more durable and have longer cycle life, and most important, they are allot less volatile. They have a very flat discharge curve till they are dead, this is why meters do not work well for calculating capacity. In other birds, I have used the Hyperion LiFe packs and recharged them at 4C.

[roddrigo]

Thanks for the help! the Heli is ready and flying great!

[Heli biggie]

So no bec. Just 2 more batteries? I like that , my kit is on the way. So your saying the 3gx is ok with all that voltage? Do you have any pics? Of setup please, so you just use normal servo plug on battery.
Can i use 2100mah batteries? For more flights? Thanks.

[Bonkievan]

The 3gx is good for 8.5v.

2x2100mah 2s would be ok. Just be aware of space and weight constraints v a few more flights, although with an 800 this is not such an issue. I use one of these Y-harnesses but if using 2 batts you´d just need 1 servo lead per lipo.

From memory my 800pro pulls around 250-300mah, per sport style flight, from my 2200mah 2S

[Heli biggie]

Just a normal servo wire? What color is positive and negitive ? Thanks . Is that a big enough wire?

[CrazyCrash]

250mah to 300mah, i.e. 0.25Ah to 0.3Ah. If I am not wrong, it meant system draw 15A (0.25A x 60min) to 18A (0.3A x 60min) per minute. Can single servo plug from battery handle such current without issues. Look like each HV servos draw about 3A to 4A.

[Bonkievan]

Originally Posted by CrazyCrash

250mah to 300mah, i.e. 0.25Ah to 0.3Ah. If I am not wrong, it meant system draw 15A (0.25A x 60min) to 18A (0.3A x 60min) per minute. Can single servo plug from battery handle such current without issues. Look like each HV servos draw about 3A to 4A.

As far as I was told and have read, a servo lead is good for 4-6amps approx. I'm assuming that's continuous as servo amp draw can spike higher than that, I'm sure.

I've had no issues running both my 700 and 800 (both Hv) like this, so long as you run at least 2 leads into the FBL powerbus. Some run 3 for this very reason.

[Heli biggie]

So run 2 seperate 2s lipos to the 3gx. Or put the 2 lipos together and then split again. Do some run 3 to power up rx? Is it safe to just use 2 sats?

[Heli biggie]

So are you guys using 2 sat or a rx and sat??

[Bonkievan]

Originally Posted by Heli biggie

So are you guys using 2 sat or a rx and sat??

I run a 2 dsmx Sat setup. Good for neater, less wiring but not so good if you want to get full telemetry, for example. You need the external Rx to get Fades / losses info etc but apart from that, everything else is available.
Some just like using a full Rx regardless. I personally don't, as above, because you have all the FBL to Rx wiring lumes to contend with.

I ran my 700 dfc Hv with 2 Sats off the 3gx for a time plus a 2s 2200mah+2 lead y-harness into the 3gx and it worked without issue.

[Heli biggie]

Sounds perfect , i run 2 sats alone on a 450 but i was just asking others opinion, thanks. Any pic of your setup?

[Bonkievan]

Originally Posted by Heli biggie

Sounds perfect , i run 2 sats alone on a 450 but i was just asking others opinion, thanks. Any pic of your setup?

Just sent you a Pm.

[kittiwat1]

I have the 800E Trekker and only use one 2s 3000 mAh Lipo to power the electronics. l get 4 flights and voltage still reads 4.0

[songer121]

im sorry but using 2 lipos at the same time to power the electronics is dumb IMO. its just not necessary to fly around with an extra battery for nothing. just get 2 or 3 of the pulse rx batteries, either this one: http://www.helidirect.com/plurx-3600...es-p-26536.hdx

OR this one: http://www.helidirect.com/plurx-2550...es-p-26537.hdx

BOTH will fit just fine and will get you easy 4-5 flights with the 2550, and more with the 3600.

then once you get your rx batteries buy this: http://www.amainhobbies.com/product_...l-JR-Y-Harness

All the pulse rx batteries are super good batteries and work great! and they come with ec3 and JR/Futaba connectors.

and that's all you will need!!

[Bonkievan]

Originally Posted by songer121

im sorry but using 2 lipos at the same time to power the electronics is dumb IMO. its just not necessary to fly around with an extra battery for nothing. just get 2 or 3 of the pulse rx batteries, either this one: http://www.helidirect.com/plurx-3600...es-p-26536.hdx

OR this one: http://www.helidirect.com/plurx-2550...es-p-26537.hdx

BOTH will fit just fine and will get you easy 4-5 flights with the 2550, and more with the 3600.

then once you get your rx batteries buy this: http://www.amainhobbies.com/product_...l-JR-Y-Harness

All the pulse rx batteries are super good batteries and work great! and they come with ec3 and JR/Futaba connectors.

and that's all you will need!!

Why is having redundancy on your electrics dumb?
Dropping a cell or having an issue with only 1 x 2s pack will most likely result in losing your Heli. Agreed, very unlikely but its a possibility all the same.

It's just another safety net and certainly not dumb, imo.

[Vinger]

Running two packs parallel without a diode in between will give you zero redundancy, as one pack failing will take out the other one or burn your wires.

[buto]

All I just picked up a used (like new) T-Rex 800 E with the stock 120 HV Esc (Castle) and stock HV servos.
I am planning on using Spektrum AR7200BX for flybarless and recevier with a sat. I have read all of the above posts and picked up the y harness and a Pulse 2s 5000mah to power the electronics. My question is what do I need to do in the ESC programming. I do have the Caste link set up and software already. I have a Pulse stick 65c (2) 5000 MAH to power the motor. Please let me know if anything does not sound correct. Better to ask than cook something. I will want to run it at a low head speed until I get comfortable with it.