Let me start by saying this certainly won't be as comprehensive, nor as scientific as many of the other more experienced tester's threads. Rather, this is meant to be a general idea of what kind of real world results you could expect to see with these two packs.

I have several Gens Ace packs ranging from 2S 450's up to 4S 2500's, all 25C, and all are performing extremely well. I needed something in this 3S 1600mah size for a profile jet. Knowing the performance of Gens Ace, and having heard some talk about the Sky packs, I thought I would order both to do a comparison. Seeing that most people who have tested Gens Ace packs have found them to be more in line with other brand's 30C-45C packs, I decided to compare the Gens Ace 25C to the Sky 40C.

Both packs were purchased at the same time from Hobbypartz.com, both roughly $13 and some change, and both have exactly the same number of cycles. The Gens Ace came perfectly balanced at 3.83v per cell. The Sky Lipo came with a slight imbalance, 3.77v 3.82v 3.83v. I independently charged cell 1 up to the rest, and then completed a full charge on the whole pack. Since then the pack has remained well balanced. The Gens Ace weighs 138g while the Sky is only slightly heavier at 144g. The two packs are similar in construction, well assembled, appropriate size wiring for this size pack, flexible silicone wiring on both the main leads and balance leads. The Gens Ace pack is noticeably shorter in length, although a touch thicker than the Sky pack. They both came with the typical red 4mm bullet connectors, but I changed them out to Ultra type connectors. The IR's were nearly identical for the two packs, measured using my iCharger 208B at 70* F, packs fully charged, Gens Ace 4 5 5=14 and the Sky was 4 4 5=13.

I did roughly 3 low C discharge cycles followed by 2C charges prior to the following 10C and 20C discharges below. The 10C discharge I did down to 10% capacity remaining, the 20C discharge I stopped it at 20% remaining capacity. As you'll see in the graphs, they both performed nearly identical in both test, and both did very well in my opinion. Considering that the Gens Ace is 25C and the Sky Lipo is 40C, I'd have to give the win to Gens Ace, but I'd feel comfortable recommending either pack, although I would personally not choose to buy a Sky pack that is less than 40C. Looking at some of the other graphs in the Battery Graph Vault, I'd concur with what most of the other test packs have shown, that Gens Ace 25C packs are conservatively rated, or maybe more accurately rated, and perform as well as most other brands 30C+ rated packs. It's also nice to see that the Sky Lipo packs are showing promise, at least in the high C rated packs. How they both hold up over time remains to be seen.

Gens Ace
http://www.hobbypartz.com/98p-25c-1550-3s1p.html

Sky Lipo
http://www.hobbypartz.com/77p-sl1600-3s1p-40c-3333.html

Another factor is the way the main wires leave the pack. If your lipo slot is limited, the GensAce wires come out sideways so will not easily fit more narrow slots. I prefer the SkyLipo over the GensAce just for that...assuming both have similar longevity.

Thanks for this comparison. I really want to get some new packs for my electrics but couldn't decide between the Sky Lipo 40c and the Gens Ace 25c. For a 3s1p there is about close to a 5 dollar difference between the two with the Sky Lipo being cheaper.

Gens Ace could easy carry the label 40C

Or....

Are all other brands overrated and does Gens Ace have the first real C rated packs???

See also here, where they are compared to other brands as well:

http://www.rcgroups.com/forums/showthread.php?t=1352332

I have the Gens Ace 25c (2 packs) and Sky Lipo 40c (1 pack) - 4s / 2200mah packs. The battery packs are identical physical size and weight. Sky lipo has 8 cycles and the Gen Aces only 3-4 cycles. Not much of a cycle sampling but both brands are performing the same so far. Based on my calculation I'm pulling only 6-7c from the batteries.

Originally Posted by dude_109

Another factor is the way the main wires leave the pack. If your lipo slot is limited, the GensAce wires come out sideways so will not easily fit more narrow slots. I prefer the SkyLipo over the GensAce just for that...assuming both have similar longevity.

I agree with you on this. I prefer the SkyLipo arrangement better. The SkyLipo wiring configuration just fits better in my plane. I had to cut the packaging on the Gens Ace to bend the wire leads to make them fit.

As you you said, assuming similar longevity, I would take the SkyLipo, few bucks cheaper and no weight / size advantage with the 25c pack.

I ended up ordering the SkyLipo packs. Will see how they perform in my heli and 2 planes.

Originally Posted by EricJ320

Let me start by saying this certainly won't be as comprehensive, nor as scientific as many of the other more experienced tester's threads. Rather, this is meant to be a general idea of what kind of real world results you could expect to see with these two packs.

I have several Gens Ace packs ranging from 2S 450's up to 4S 2500's, all 25C, and all are performing extremely well. I needed something in this 3S 1600mah size for a profile jet. Knowing the performance of Gens Ace, and having heard some talk about the Sky packs, I thought I would order both to do a comparison. Seeing that most people who have tested Gens Ace packs have found them to be more in line with other brand's 30C-45C packs, I decided to compare the Gens Ace 25C to the Sky 40C.

Both packs were purchased at the same time from Hobbypartz.com, both roughly $13 and some change, and both have exactly the same number of cycles. The Gens Ace came perfectly balanced at 3.83v per cell. The Sky Lipo came with a slight imbalance, 3.77v 3.82v 3.83v. I independently charged cell 1 up to the rest, and then completed a full charge on the whole pack. Since then the pack has remained well balanced. The Gens Ace weighs 138g while the Sky is only slightly heavier at 144g. The two packs are similar in construction, well assembled, appropriate size wiring for this size pack, flexible silicone wiring on both the main leads and balance leads. The Gens Ace pack is noticeably shorter in length, although a touch thicker than the Sky pack. They both came with the typical red 4mm bullet connectors, but I changed them out to Ultra type connectors. The IR's were nearly identical for the two packs, measured using my iCharger 208B at 70* F, packs fully charged, Gens Ace 4 5 5=14 and the Sky was 4 4 5=13.

I did roughly 3 low C discharge cycles followed by 2C charges prior to the following 10C and 20C discharges below. The 10C discharge I did down to 10% capacity remaining, the 20C discharge I stopped it at 20% remaining capacity. As you'll see in the graphs, they both performed nearly identical in both test, and both did very well in my opinion. Considering that the Gens Ace is 25C and the Sky Lipo is 40C, I'd have to give the win to Gens Ace, but I'd feel comfortable recommending either pack, although I would personally not choose to buy a Sky pack that is less than 40C. Looking at some of the other graphs in the Battery Graph Vault, I'd concur with what most of the other test packs have shown, that Gens Ace 25C packs are conservatively rated, or maybe more accurately rated, and perform as well as most other brands 30C+ rated packs. It's also nice to see that the Sky Lipo packs are showing promise, at least in the high C rated packs. How they both hold up over time remains to be seen.

Gens Ace
http://www.hobbypartz.com/98p-25c-1550-3s1p.html

Sky Lipo
http://www.hobbypartz.com/77p-sl1600-3s1p-40c-3333.html

Gens Ace 3S 1550 25C is rated for real world use

vs. Sky Lipo 3S 1600 40C is rated until the point of explosion.

but they perform about equally.

The Gens Ace weighs 138g while the Sky is only slightly heavier at 144g.

6gram more is this 50mAh that the Sky LiPo has more in capacity.

My point: Gens Ace do carry the sticker 25C, but are in fact 40C packs.
Their 25C is underrated...or all other brands are overrated.

Originally Posted by EricJ320

The Sky Lipo came with a slight imbalance, 3.77v 3.82v 3.83v. I independently charged cell 1 up to the rest, and then completed a full charge on the whole pack. Since then the pack has remained well balanced.

A short update.... The Sky Lipo has not stayed very balanced as time goes on. After having sat at storage voltage for anything more than a couple of days and the low cell drops .08v-.1v below the other 2 cells. With such a large difference it's hard for my charger to balance the cells before it stops charging because it reaches it's charge rate/5 cutout. I've also had to remove it from parallel charging as I see it pulling down the same cell in the Gens Ace pack.

I'm not ready to make a conclusion on the Sky Lipo brand based on this one pack, it could be just that, this one pack is a bad apple. I will pay attention though, and see if others do well with their packs, or if Sky possibly has some quality control issues if others have similar issues.

Hummm...that is a fair amount of imbalance. Have you checked the IR of the weak cell again.? I have 2 smaller 2s1p 800mah packs for my Uflys that are 30c and they never are more than .01v difference per cell even after 2 weeks on storage charge.

Originally Posted by EricJ320

A short update.... The Sky Lipo has not stayed very balanced as time goes on. After having sat at storage voltage for anything more than a couple of days and the low cell drops .08v-.1v below the other 2 cells. With such a large difference it's hard for my charger to balance the cells before it stops charging because it reaches it's charge rate/5 cutout. I've also had to remove it from parallel charging as I see it pulling down the same cell in the Gens Ace pack.

I'm not ready to make a conclusion on the Sky Lipo brand based on this one pack, it could be just that, this one pack is a bad apple. I will pay attention though, and see if others do well with their packs, or if Sky possibly has some quality control issues if others have similar issues.

Could it be the parallel charging that is causing this? I read of similar reports with other brands when parallel charging on another forum.

I have several 6S 3000 to 3300 mah 30C lipos with balance of within 0.03V always after discharge. I don't parallel charge.

Originally Posted by ridge_racer

Hummm...that is a fair amount of imbalance. Have you checked the IR of the weak cell again.? I have 2 smaller 2s1p 800mah packs for my Uflys that are 30c and they never are more than .01v difference per cell even after 2 weeks on storage charge.

I haven't re-checked the IR's, but I will and report back.

Originally Posted by alexf1852

Could it be the parallel charging that is causing this? I read of similar reports with other brands when parallel charging on another forum.

I have several 6S 3000 to 3300 mah 30C lipos with balance of within 0.03V always after discharge. I don't parallel charge.

I don't believe so. I've been parallel charging for almost 2 years, with many many packs and have never seen anything like this before. One downside to parallel charging can be that it could hide a bad cell if you aren't on top of checking your cells individually. I'm kind of a fanatic about caring for my packs, so I'm always checking my packs, after charge, after flight, before charging, and after storage, even if it's only a couple of days. This one pack, no matter what I do to it, after a few days that one cell drops dramatically.

The fact that this pack, and this specific cell came with a fair amount of imbalance is the real issue. I was able to balance it by charging that one cell as a 1S to match the others. And now, after only 10 or so cycles, if that, it's showing the same amount of imbalance even after it's been balanced. I think it's just a bad cell, it still works, and seems to put out power still, but for how long is the question. I'd say it will eventually fail before the other cells do, but how long that is, and how many cycles is anyone's guess.

Yeah, my experience with two imbalanced packs (not skylipo) was they needed 3 or 4 cycles to get so they could remain in balance. So I agree with you after 10 cycles, sounds like the cell is bad.

I wonder how blue lipos compare to skylipos, for the 3s 5K pack size I use, they're about the same price.

My SkyLipo 1000mah 3S 40C pack arrived with center cell horribly out of balance...can't remember exactly but well over 1V difference. I had to nurse that cell back to life. I always balance charge and so far its been holding up in EDF usage.

I have 3 x 2s1p 800mah BlueLipos that I bought about 5 months ago. Currently one will not hold a charge. I was never really impressed with the performance in my UflyS compared to the SkyLipos.