Optima 9 - To Powerbox or Not? (2024)

Jan 06, 2021, 04:34 AM

• #1

Mtn_Commando

Thread OP

Discussion

I'm about to start build of a 60cc model. I plan to use six 14kg servos for AIL/ELEV, one 20kg servo for the RUD, and two 6kg servos for THR/CHK. The rx is an Optima 9.

These will be powered by two 2S 2000mah LiFe's.

I know that the Optima 9 will accept two batteries on any open channel ports, and will automatically modulate the voltage of the two packs.

My question is...is the Optima 9's bus capable of handling the higher current of all the high-torque servos that I'll be running on the control surfaces? Or should I use a Powerbox?

Cheers.

Jan 13, 2021, 09:57 PM

• #2

Mtn_Commando

Thread OP

I emailed this question to Hitec support. Here's the response, in case anyone else was wondering the same thing:

Good thing, saves me a few hundred bucks.

Jan 14, 2021, 10:21 AM

• #3

Xpress..

Jan 15, 2021, 09:55 PM

• #4

Mtn_Commando

Thread OP

Would I though? Because remember, I'm planning to use two separate batteries each hooked up to the rx via a separate channel port.

Feb 10, 2021, 10:21 PM

• #5

Xpress..

Quality servo connectors are rated to 5a continuous for around 30 seconds, 10a burst for a small fraction of a second (half this number for lower quality units). Your servos can probably draw 3-4 amps a piece, maybe more. If we do this math, you can expect somewhere around 25+ amps continuous draw to be forced through 2 connectors only capable of supplying a combined 10a continuous for 30 seconds. Are you willing to take this risk and potentially bottleneck your setup, causing a brownout? Or would you rather play it safe and spend a little extra to ensure your pride and joy remains in tact for a long time? Food for thought..

Feb 10, 2021, 11:44 PM

• #6

Mtn_Commando

Thread OP

Point taken. Since starting this thread, I decided to use two receivers in the same airframe for full redundancy. That option necessitates a distribution board, and thus I've decided to go with the XPS X16.

Cheers.

Mar 29, 2021, 08:56 PM

• #7

RCPilot8

That is a good point about current limits for the connector hardware in the Rx which Express makes. I'm putting together my first large model ~50cc and will be using seven of the D645 servos (2.6 amp max each) with an Optima 9. An idea I had is to use a few Y-harnesses to connect the LiPo battery power into three different slots on the Rx with a servo on the other leg of the harness. This will split the heavier wires off the battery into three different feeds to the Rx and servos. What do you guys think of this approach?

I am also thinking of using a separate smaller LiPo to feed power via the SPC connector to the Rx. This would help ensure good voltage feed to the Rx even if the servo battery sees fluctuation. Do I need to worry about how I power up the batteries? Does the SPC battery need to power on first or does it matter?

Thanks
Chris

Mar 30, 2021, 04:10 AM

• #8

Mtn_Commando

Thread OP

I'm not sure that you can use a Y-harness with the intention accepting power from one y outlet while outputting servo signal from the other outlet. I'd recommend you try it out with a cheap servo first to see if it works, then repeat it with however many servos you were intending to repeat this setup with.

Separate battery into SPC is a good idea. I don't think the sequence matters, either one will still feed the bus and will boot up the receiver.

Apr 05, 2021, 08:02 PM

• #9

RCPilot8

A good post on this was made by Xpress.. in the Optima 6 discussion on 25-Feb-21

"SPC only powers the receiving circuit, it doesn't power the servos. ..., power can be Y-harnessed into any port on the Optima 6."

So I am thinking to try two or three Y-harnesses to divide power along the servo connection buss. The plan is to solder the power wires to some heavier switch output wire to divide the current... anyone else out there try this?

Thanks

Apr 06, 2021, 11:07 AM

• #10

Xpress..

A y-harness is fine, but keep in mind the more failure points you add, the more likely it is you will have a failure.

The AFHSS protocol only communicates to 1 receiver at a time effectively. This is solidly true with Optima receivers, but only partially accurate with the other receivers since the other receivers just intermittently listen at the same time. If your intention is to use true dual receiver redundancy, then look to other radio systems for reliability.

Apr 07, 2021, 07:24 PM

• #11

Mtn_Commando

Thread OP

Yes, I've moved to OpenTx + FrSky rx since.