GW E3D UPGRADE
 

I have a GW E3D, & 3 Sanyo 2600 Mah NiMH packs!
The motor is Hacker C40 12 T & 40 amp ESC!
Can someone inform me of how to change from NiMH to LiPoly packs?
Some say there's more to it than just batteries!
Like the ESC must be changed out!
I also have the EMC geardrive, 5.1:1----
I will truly appreciate any help!!!
Don Jeune
[email protected]
[8D]

RE: GW E3D UPGRADE
 

Here is the minimum you will have to do.

First, you need to determine if you can program the cutoff voltage on the ESC you currently have. If you can't program the cutoff voltage, then you will need to replace your ESC to fly Lipo's and not risk damaging them.

If you need to replace your ESC, Castle Creations makes some very good Lipo compatable ESC's, and the new Jeti ESC's (the BLUE ones, not the RED ones) are Lipo friendly too.

You will then need to determine how many Lipo cells you are going to need. Lipo's are not 1.2 volts per cell like Nimh and Nicd's. But, they are either 3.6 or 3.7 volts depending on brand.

Your cutoff voltage will need to be high enough to not let the Lipo cells drop below 2.5 volts minimal. But, be sure to read the manufactures suggestion. I have seen some cells where the minimal voltage is close to 3.0 volts.

You will need to know how many amps you will need to pull (max). Lipo's cannot supply the amps a Nicd or Nimh cell can. You will need to get the manufacturers information on the Lipo's you have to know what current they are rated too. To get a Lipo pack to supply high amp loads, you will need to set some packs up in parallel and in series. Setting the pack up in series will get you the voltage you need, where the parallel setup will get you the current capacity you will need. As an example lets say you had what would be called a 3S2P pack. This is a pack which has 3 cells in series, and has two in parallel. There is a total of 6 individual cells in this pack. Two sets of three in series and then the two sets wired in parallel with each other.

Whatever you do, before you take a jump into Lipo's, be sure to get on a good website to read all the warnings about them. They are great, but cannot take the abuse that a Nicd or Nimh can. And when Lipos are abused, they tend to burn and take planes, cars and houses with them.

Also, make sure you get a charger that is Lipo capable. Standard Nicd and Nimh chargers cannot handle the special charging needs of Lipo's. And again, check the manufacturers recommendation for charging. Abuse a Lipo during charging, and they will at best be ruined, and again, they can burn.

I hope this helps. Good Luck.

RE: GW E3D UPGRADE
 

On anything bigger than a park flyer, you want to time your flights anyway. You can't afford to just plop the plane in the grass wherever the LVC kicks in. Power to get back to the runway, and full power for a go-around is a necessity. Having a programmable LVC is not as important, as you should never be flying the plane to LVC anyway. You've already got a rough idea of how long you can fly on 2600mAh. If you put a 5000mAh LiPoly on the plane, it's perfectly valid to assume you can fly roughly twice as long, but it's a good idea to "test the waters" by flying a few minutes, landing, and checking voltage. When you start getting down near 3.0 Volts per cell, add up the total time, and you have your total flight time. It's a good idea to "sneak up" on that flight time over the next few flights, gradually extending your flights each time and measuring voltage immediately afterward.

Converting from NiMH to LiPoly involves all the precautions that Latch66 described above. Having a programmable LVC is not bad idea, just not absolutely necessary IMHO. Latch66 mentioned that each LiPoly cell is rated at 3.7 Volts, which mathematically would tell you that each LiPoly cell is equivalent to three NiCd or NiMH cells. In practice, we abuse our Nickel-based cells because they can take it. Under load, they typically show about 1.0 Volts per cell. LiPolys can't take it, and when properly sized, their voltage depression is much less severe. They will hold around 3.5 Volts per cell under load, and in practice, are approximately equivalent to 3-1/3 to 3-1/2 Nickel-based cells. Two LiPolys in series are equivalent to a 7-cell NiMH pack, and three LiPolys equivalent to 10 cells.

I would assume you're running the typical 10-cell E3D setup, since you didn't mention cell count that I noticed. That means you need 3-cell, or 3S (S for series) LiPoly packs, with enough of them connected in parallel to handle the current drawn by the motor at full throttle. How many in parallel will depend on the brand. I would guess given that the E3D has traditionally been a 40 Amp, 10 cell plane, that you're drawing somewhere in the mid to high 30's for current at full throttle.

While I can't recommend a specific brand, my calculations are based around the Kokam 1500 cell, which is a pretty good deal for an 8C cell right now. For your purposes, three 3-cell Kokam 1500 packs in parallel, or a 3S3P configuration would be perfect, giving you 36 Amps continuous (well over 40 Amps for short bursts) and 4500mAh capacity

RE: GW E3D UPGRADE
 

When I switched to lipoly, in the E3D's I simply replaced the 10-cell sub-c packs with 3S4P thunder power packs (1/2 lb lighter than the sub-c nimh). Now using 3S3P, (3/4 lb lighter than sub-c) and with these new cells, 3S2P would be just fine. When I notice any power drop, I land. No change in ESC although that would be a safer way to go. My very first 3S4P thunder power pack has been flown over a year now, has 400 cycles on it, and will be going back to them soon so they can test and see what sort of capacity reduction has occurred. At first I was flying 1/2 hour flights with it, but the novelty of that wears off quickly and I found myself flying 2 or 3 10 to 12 minute flights per charge. What I've found is that the power is rather flat during discharge with lipolies (no gradual decrease), so when you do actually see a decrease, you simply land then, and you're still well into the safe range regarding minimum voltage. I'm flying things from 100 watts (3S1P 2100's) to 2500 watts (10S4P 1900's) , and everything in between. No special ESC's. I'm not saying that's the best thing to do,.. a properly set LVC is of course better,..then you don't have to depend on your own self control to land at the appropriate time,.. but it's not an absolute to have a programmable LVC.