My Trex 700 electric conversion!! 12s, Power, Super light, Cheap packs, Fly all day!

[marlonm7]

First off, I've gained invaluable knowledge from this site and I want to say a huge thanks to HeliFreak for making this hobby (now addiction) lasting and very enjoyable! I rarely post but I feel this could help someone considering a 700E. It's a way for me to share and give back to this awesome community.
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I just completed my initial T-Rex 700 electric conversion!! Based on what I was using, I had no idea if it could even work but I was pleasantly surprised! Basically, I had a high power 12s setup for my 600 but unfortunately, I stepped up to 14t and the headspeed was probably too high for the plastic main grips because one of them broke off while in a high hover and the heli violently exploded! I got power hungrier and it indeed wasn't a wise decision to bump the headspeed beyond that before moving to metal grips. I also didn't have a 13T pinion on hand so I jumped from 12T to 14T, cutting down the throttle curves a bit, but I feel it was still in the 2400-2500 rpm range when one of the plastic grips broke off. Nobody was around mainly for safety concerns and thankfully too! Absolutely scary power!! I was really discouraged and instead of repairing the 600, I had a wild idea of transferring my electronics over to a 700! So I just bought a 700 knowing it would be electric from day one and migrated the 600 system over. I'm using a 12s 2100mah combo pack made from three 4s 2100 packs wired in series. Each 4s pack was only $62 so my 12s packs only cost me $186! They're also designed to handle hundreds of charge cycles while sustaining high charge rates so my wait time is only about 3 minutes between flights. I basically can fly my 700E back to back all day long. I'm truly amazed. I didn't think this balance could be possible on a .90 heli. My 700E is super light weight which helps make this possible. Perfect CG too.

Setup:

NEU 1910H/1.5Y on 12T
12s 2100mah combo pack (3 x Revolectrix 18C 4s 2100mah wired in series)
Revolectrix 15C 2s 750mah pack (for receiver power)
Align RCE-B3X 6V voltage regulator
3 x S9451 on cyclic
GY611/S9256 combo
CC HV-85 ESC
JR R921 receiver
X9303
2 x Cellpro 10s dual pack balancing charger
Sorensen 33V-33A rack mount power supply (Set to 15.7V)
Radix 690mm
2000 headspeed at 0 pitch
Throttle curve: 70 flat
Max pitch 9.5 degrees (That'll go up!)


I honestly didn't think it could've worked but it really does! This 12s combo is especially nice because I use these single 4s packs in my 450SE, two for an 8s combo on my 500, and until recently, the exact same 12s setup on the 600. Bear in mind I'm not at the hard 3D stage yet and I haven't fully wrung it out but it's extremely smooth with great power(especially in the first 90 secs) and super light weight. The main drawback is a 3 min flight time max. Even this works well for me though because I have 2 of those 12s pack combos and 2 Cellpro 10s fast dual pack balancing chargers. I always have 3 4s packs charging while flying so even though my flight times are shorter, the packs only take between 9 and 10 minutes to charge up and I only have to wait a few minutes between flights! Just wanted to let you freaks know it's been successfully done here! Below are pics of the setup and how the charging system works. Here are the main points with this setup:

- This shows that it's possible to easily convert to electric
- Perfect CG
- Cheap 12s packs!! $186
- 12s packs can be separated for a power Trex 500 8s or 450 4s setup
- 3 minute flights but only 10 minute charge times so almost no waiting between flights.
- After a full flight: motor temp is very warm, ESC temp relatively unchanged, 12s combo pack is mildly warm
- Super light weight and simple
- 700 frame helps protect packs much better than any other Trex because they're not mounted in front.

I have several 25C 4s 2200 packs that I'll try out sometime soon for comparison. I just wanted to share my findings and unexpected easy success. Hopefully this helps some freaks! Any comments or questions are welcome.


Marlon

[yarbsea]

Interesting, but 3 minute flight times would drive me crazy. Heck 6 mins on my 600E drove me insane having to always stop, get the heli and change batteries. Now factor in charging at the field (which I never did), and i'd seriously throw in the towel. But good luck to you!

[cbdane]

Cool. You're charging 2100mAh packs at 9.6A? That's close to a 4.5C rate. Yeah, that'll give quick charge times. Keep a fire extinguisher handy though. Remember that for them to truly be "cheap" packs, they've gotta last a few cycles.

[marlonm7]

Originally Posted by yarbsea

Interesting, but 3 minute flight times would drive me crazy. Heck 6 mins on my 600E drove me insane having to always stop, get the heli and change batteries. Now factor in charging at the field (which I never did), and i'd seriously throw in the towel. But good luck to you!

It's the trade off for dirt cheap packs and low mah. I personally would much rather have shorter flights and almost no wait between flights as opposed to longer flights but > 10 min waits. I hate waiting! Charging in the field is really no different because I park very close and let the car run while the packs charge inside.

But in any case, certainly not the setup for you.

Marlon

[cbdane]

Originally Posted by marlonm7

Charging in the field is really no different because I park very close and let the car run while the packs charge inside.

Wow. 4.5C charging rate, inside your car?

[fireup]

Originally Posted by cbdane

Wow. 4.5C charging rate, inside your car?

Yes, 4.5C without a balancer, be very carefull. I've seen my share of lipo fires and they were all due to no balancing while charging.

[marlonm7]

Originally Posted by cbdane

Cool. You're charging 2100mAh packs at 9.6A? That's close to a 4.5C rate. Yeah, that'll give quick charge times. Keep a fire extinguisher handy though. Remember that for them to truly be "cheap" packs, they've gotta last a few cycles.

These Revolectrix packs are the only packs I know of that are designed for a 3C charge rate. I've been charging all my Revolution/Revolectrix packs at 3C minimum for over a year and a half now and they're still going strong...at least the ones I haven't crashed hard. I've been charging at 10A on two of those same kind of 4s packs for over 80 cycles now. Still holding their charge and pop very well and usually stay in balance for the most part. Never had a problem. But yes, that's the only way this kind of system is even possible. Even at the high rate I charge, I fully expect to get at least 200 cycles out of each pack.

Marlon

[marlonm7]

Originally Posted by fireup

Yes, 4.5C without a balancer, be very carefull. I've seen my share of lipo fires and they were all due to no balancing while charging.

These chargers are very advanced. First, they check the pack to see if it can even accept the charge rate safely. If not, it'll halt with an error code. Even while it's pumping at that high rate, it's balancing at the same time. You can see the balancing connecters and main discharge leads connected in the pics. To top it off, if cells become unsafely imbalanced, it'll automatically reduce the charge rate and balance mid stream before resuming the high rate charge. It's bulletproof and I've been seriously spoiled by this system. I could never go back. I started off with the Polyquest 4, then moved up to the ThunderPower 1010C with balancer. I've found the Cellpro system to be superior in every way. Just my personal experience.

Marlon

[marlonm7]

Originally Posted by cbdane

Wow. 4.5C charging rate, inside your car?

Yes! The trunk works very well.

[HeliSmith]

Wait where's the muffler again?

Oh and btw your nitro is UGLY! No nitro slime anywhere.

Edit:
That thing looks sweet. I couldn't give up the smell of nitro but dang man nice job.

[marlonm7]

Originally Posted by HeliSmith

Wait where's the muffler again?

Oh and btw your nitro is UGLY! No nitro slime anywhere.

Edit:
That thing looks sweet. I couldn't give up the smell of nitro but dang man nice job.

Darn! I was hoping nobody would notice it was missing! I didn't strap it down properly before my maiden flight and lost it in the weeds! lol Thanks! My unfortunate incident with the 600 is the only reason this even happened. Looking back on it, I'm actually happy because this .90 is yet another level up from the 600 in stability. I'm finding that running 2000rpm on the 690s at 9.5 degrees of pitch on this .90 is about as punchy as the 600E at 2100 on 600s at 12 degrees. So it seems that the power to weight ratio is even better than I was expecting. A part of me still doesn't believe how well this is working. Thanks.... and please rock that 700N for me!!

[Bobbyk]

You are very creative, didn't know the Neu 1910 can take up to 12s.

Thanks for sharing.

Robert

[marlonm7]

Originally Posted by Bobbyk

You are very creative, didn't know the Neu 1910 can take up to 12s.

Thanks for sharing.

Robert

These motors are torque monsters!! That 1910/1.5y is a 680Kv motor so 12s(50.4V) would run it around 34,000rpm which is perfect for it's 30,000rpm max speed. It works great! To be honest I wish Castle's high voltage ESCs supported up to 16s(67.2V) so I could try a 1910/2y(520Kv) or 1912/1.5y(532Kv). Because of my combo setup, it would be as simple as adding another one of those same 4s 2100 packs to the series and making another deans series adapter. After all, I can charge 4 packs at once. No ESC that I know of can handle 16s though. Playing with high voltage power combos is a lot of fun and my current setup gives me a number of options.

[t-rexn8]

Wow is there any modifications to the frame to mount the motor? What motor mount is that?
Nice job.
You got to get some larger packs man

[marlonm7]

Originally Posted by t-rexn8

Wow is there any modifications to the frame to mount the motor? What motor mount is that?
Nice job.
You got to get some larger packs man

Thanks. I actually got two 6s 4800 packs back when I was running my 600 stock. I have no real desire to make a 12s 4800 combo though mainly because I know that means longer waits between charges...not to mention I only have enough for one 12s pack. I'm not about to drop $650 on two more 6s 4800s!

Mounting the motor is really the only work involved. This is what you'd need:

- A Trex 600E motor mount
- 4 x 3mm x 12mm socket head cap screws (to secure motor mount)
- 4 x Specialty washers for Trex 600 (not required)
- 2 x Home Depot's "3/32 FERRULE & STOP SET" (SKU #7331-526 I believe) for perfect spacing of the motor mount between the frame. It's where the ropes are.
- Loctite
- A drill (I used a press for the new holes in the motor mount itself)
- A ruler

I mounted the hard way since the frame was already together before drilling the holes for the mount. I can give you the exact vertical and horizontal spacing if you decide to do it. You will probably need to drill 3 holes in the top of the motor mount if you want to duplicate my setup(including motor). I felt a little uncomfortable using the stock mounting holes because the shaft on that particular NEU motor is short. That meant the frame holes closest to the gears would've been drilled closer to the edge than I would've liked. Once you know where the holes are to be drilled, it only takes a few minutes for the mod. But you must take your time and make sure the holes are accurately placed for obvious reasons. It's not much work and I've already done a lot of it for you.

[OTA]

Interesting project, and thumbs up for innovative and creative solutions.
I dont know about your flying style, and subsequent amp draw, but with my own experience of 12S, the 2100 packs would suffer EXTREMELY short life in my use. They would be pushed to burst level at each flight and probably very close to burst into fire.
I have used some Evolite V2 2500 packs and they is going well above 70degrC, and is close to RIP after less than 40 cycles. My TP V2 3300 packs is much better, but also they is getting decent warm (+50degrC). My new Outrage 3000 packs is also getting over 50degrC.

I cant imagine that a decent powertrain on a 700E would draw less amp, and by that your power setup doesnt make sense to me.

[Windbreaker]

What about using A123 packs?

Perhaps have two packs of 8 cells for a total of 52.8 volts, 2.3 AH. The Cellpro chargers can be set up to work with the A123 cells, and you can charge eight cells at a time.

[matchbox]

I really like the idea; and its amazing that it works. In my experience i found that high series cell counts with lower capacity packs, end up with a very high pack Impedence and the cells end up burning up large amounts of power in heat.
If i was going to do it; i would use 10 cell 4400- 4700mah range.
Thanks for giving use something to think about!

[oldschool269]

great idea , thanks for proving it does work .

you can fly with less than a 3000 ma pack , although i would probably go to 15s with 2100's


3 mins is fine , short for circuits , but more than enough time to bend my mind at the sticks.

Thanks for posting , get a balance charger .

Jason

[oldschool269]

Originally Posted by OTA

Interesting project, and thumbs up for innovative and creative solutions.
I dont know about your flying style, and subsequent amp draw, but with my own experience of 12S, the 2100 packs would suffer EXTREMELY short life in my use. They would be pushed to burst level at each flight and probably very close to burst into fire.
I have used some Evolite V2 2500 packs and they is going well above 70degrC, and is close to RIP after less than 40 cycles. My TP V2 3300 packs is much better, but also they is getting decent warm (+50degrC). My new Outrage 3000 packs is also getting over 50degrC.

I cant imagine that a decent powertrain on a 700E would draw less amp, and by that your power setup doesnt make sense to me.

TIME to GO 15s !!

Jason