Jetdesign

My Feedback: (8)

Would those of you using Power Unlimited batteries, from F3AUnlimited, care to comment on the longevity of these batteries? How many years have you been using your packs, what have you noticed over the span of two or more seasons?

I don't think I can afford a whole fleet (4 flight packs) this season. I would probably buy 2 flight packs this year and 2 more next year. Of course that keeps the issue of different batteries affecting weight and balance of the airplane, but if these things will last me a few years, then it is worth it through the first season.

rcpattern

My Feedback: (45)

Joe,

Just like any other pack, if you take care of them, they will take care of you. Especially flying Intermediate, you should never be pushing your packs. They are nice packs, especially for the money.

Arch

Jason Arnold

Hi Joe,

I fly FAI and use Power Unlimited packs. My ones are from the very early batches.

So far I've had three 5S packs puff badly on me. One at 85 flights and the other two at close to 140 flights each.

In my opinion, they are great packs. Low IR, great voltage under load, light weight and excellent performance.

FYI, my packs were manufactured by Fully Max.

Cheers,
Jason.

VerneK

Joe, I agree with Archie's comments.

Not commenting on any particular brand of batteries, my experience after nine years of flying electric leads me to expect 100 cycles on a set of packs regardless of manufacturer claims. If I get 100 cycles of useable competition flying on a set, I don't figure they owe me anything. Everything after that is a bonus. If I get less, I feel shortchanged. I take care of my batteries and monitor everything, particularly flight time, number of cycles, IR and all the rest. I've gotten some great batteries and not so great batteries, often times from the same manufacturer.

I long ago came to the conclusion that no two cells are created equal and there's not much our battery merchants can do about it other than change manufacturing suppliers as the need arises. Even feedback the merchants get from us is cloudy at best for them because they have no idea what we've subjected their product to. I guess what I'm saying here is don't put too much stock in endorsements for any particular brand, pro or con, unless you know firsthand what the owner subjected the packs to. As I'm sure you've read, one single case of over-discharge can greatly shorten the life expectancy of a pack, even though the owner may not see any immediate deterioration. The same guy may have long forgotten the over-discharge and then deem the batteries as bad after not lasting as long as he expected them to. How many seasons you get will depend on care, storage, number of cycles, and finally, how lucky you are in getting a pack made from a good batch of cells. All of that goes right down the drain if you don't take care of them as Archie suggested.

Verne Koester

desertrider49

My Feedback: (5)

All that leads me to this question, what is "taking care of them" ?

I'm sure I have read the answer here somewhere, but this may be a good place to remind us.

VerneK

Never discharge the batteries more than 80% of their capacity.

Make sure you have adequate cooling in your setup with at least twice the amount of air exit area than air inlet opening in your fuse. Monitor your battery, esc, and motor temps to verify your setup.

Never leave fully charged for more than a week. Less is better.

Break in your batteries for at least 5 flights, using no more than 50 or 60% of their capacity while avoiding any full throttle activity.

Discharge your batteries to storage levels and store in a cool or cold (not freezing) dry place. Thunderpower has lots of good info on this in their support section on their website.

I'm sure there's more I've forgotten to mention, but the above steps are a good start.

Verne Koester

underdw

My Feedback: (2)

I have not had the good experience of the other posters.
My first packs were new 12/10 and lasted 65 cycles until the first low-voltage cutout in 9/12. Slight puffing.
My second set was new 11/11 and lasted only 31 cycles until the first low-voltage cutout in 3/13. No puffing. Stored over the winter in the fridge.
I claim that I have not abused them, but I'm sure some will chime in and tell me otherwise.
My 3 year old 200+ cycle Hyperions are weakening, but still getting me though a flight.
...so just take this as part of the survey.

A further thought is that our experiences with these 2+ year old versions are really not relevant. It appears that the ones soon to be arriving at F3AU are entirely new/different/improved.

Dan

desertrider49

My Feedback: (5)

Regarding number 1 - never discharge below 20%

I'm an Intermediate, I fly my sequence in 6 minutes and immediatly land. When I start the charger (cellpro 10s) it usually says there is about 10-15% left. I know there is nothing that can be done to use less electrons, I was just wondering what you guys in the upper classes use. My batteries are 4400's.

VerneK

That comes under the category of setup. What you're pulling out of the batteries is directly related to how many amps you pull at WOT and your actual throttle useage in flight. There's actually a lot you can do to control how many electrons you use through prop selection, esc settings, and flying style.

I'm more interested in what my CellPro tells me I put back into a pack rather than what percentage it says I have when I start a charge which I have found to be unreliable at times. I fly Masters with 5000mah packs and typically put back anywhere from 3200 to 3800mah depending on wind conditions and the overall condition of the packs. As packs age and deteriorate, you'll use more throttle stick to get the same performance with a resultant increase of mah per flight. With a 5000mah pack, 80% equates to 4000mah. As long as I'm not putting more than that back in, all is good. With a 4400 mah pack, you shouldn't be putting back more than more than 3520mah which is 80% of your capacity. If you're putting more than that back in, you're hurting your packs and should be checking your setup with a Wattmeter, if you haven't already. With a little research right here, you should be able to find proven combinations of motors and propellers to compare to what you've got.

I'm pretty much electrically stupid so that's exactly what I do. I check to see what's working for others and then copy it. I'm switching motors this year for the first time in 9 years and already did the research to see what was working for other pilots and matched it. Before I go up for my first flight, I'll check to see what my amp draw is with a wattmeter to make sure it's similar to what others are seeing with this combo and to use as a baseline standard so I can re-check it later if I start seeing an increased draw from my batteries based on what I have to put back in after a flight. Hope this makes sense and helps.

Verne Koester

Jetdesign

My Feedback: (8)

I have been horrible to my packs. they have all probably been over discharged, i don't know if i have ever made it 5 flights of easy flying, and most have had full throttle climbs by the second or third flight. does it make more sense for me to get 4 sets of cheap packs, and practice logging and taking care of them, before investing in the power unlimited packs?

truthfully the most important thing for me is probably to have all my packs the same, so they weigh the same and balance the plane the same. i need consistency.

I am sick of supporting Hobby King - really prefer to go through F3AU, but I also don't want to piss money away if i am not going to properly take care of the packs.

rcpattern

My Feedback: (45)

You can't go by that percentage. I've seen it be way off. You need to pay attention to how much it puts back. On a calm day I can fly an FAI F sequence around 3600mah and that is flying fairly large. If you are using that much in Intermediate you are using way too much throttle. Most guys I know flying Intermediate are under 3000 for a sequence.

Once again though, verify what it puts back in, not what it says as soon as you plug it in.

Arch

rcpattern

My Feedback: (45)

Joe,

The best thing is if you are going to fly electric then learn to take care of the packs. Its not difficult, it just takes paying a little more attention. Use a timer and listen to it. No packs will handle constant punishment. The steps Verne outlined aren't hard to follow and they do work. Treating packs poorly can also be dangerous. Most, if not all, Lipo fires I've heard or seen have usually occured with a previously crashed pack or one that has been abused.

Arch

Stuart Chale

One thing that I don't think was mentioned is that lithium poly packs deteriorate over time even without abuse. Keeping them cold when not in use helps but most of us do not finish a flying session charge to 50% and put them in the fridge. Now you not only need a generator to bring to the flying site but a small fridge in your workshop. Wait a minute a small fridge could be a good thing

Changes in lithium poly chemistry may have changed some of this but I remember reading on a non hobby site I think, that after 2 years of normal use (not abuse) and not refrigerated, that a Li Poly pack would be down about 20% by normal aging. Some sport hobbyists may not notice the 20% loss but we certainly do.

Stuart C.

Silent-AV8R

Randy - Arch is dead on here. Flying Intermediate I typically used 2,500 to 2,600 mAh of capacity. Flying the Advanced sequence now I am typically using 2,800 to 3,200 per flight out of my 4,400 packs depending on conditions.

I also agree with Arch that the capacity your charger tells you when you start charing is typically not very accurate. The only way to know what you used is to know what you put back into the pack. I think I've mentioned this to you at the field. This is the same reason that those nifty little voltage meters that tell you "what's left" are not really worth much beyond confirming that a pack is in fact fully charged if you are not sure.

Chris Moon

My Feedback: (8)

The key to battery longevity is keeping them cool. I have an article coming out in a future KFactor about this topic. Virtually every plane I have seen does not have adequate cooling and this above all else determines cycle life (assuming you don't routinely overcharge or overdischarge). Look at the guys who almost always get good cycle life and their procedures and the cooling arrangement inside their planes and it differs from the guy who gets 30-40 cycles from a set of batteries. These results are very consistent, some always have good results while most cannot match their results and it is just a matter of setup and procedures.

Chris Moon

My Feedback: (8)

The Power Unlimited 25C-4900 packs are being discontinued and are replaced by the 35C 4500 and 35C 5100 packs. We did this because the 35C packs are simply more powerful and less critical to heat than the 25C packs. The 35C 4500 packs are comparable to the old 4900 25C packs in weight and the 35C 5100 packs are a little heavier. We have 100s of the new 35C packs in use worldwide and the feedback has been 100% that they are even better than the25C 4900 packs which were good enough to have been selected by several competitors in the 2011 F3A World Championships.

A true higher C pack will have lower internal resistance vs a lower C pack and will maintain a higher voltage under load and thus better power available. The only limiting issue is the very high C packs (45C-65C) packs get very heavy and make it hard to use for a weight limited event like F3A. Also, the average discharge for us is not particularly high so there is a diminishing value to the really high C packs.

KGSS28

What is the max temp that we should stay at or below measured right after landing ?

Silent-AV8R

The general rule is to stay under 140 deg F as much as you can.

KGSS28

Great, no problem then.

Thanks

Chris Moon

My Feedback: (8)

Yes, 140 degrees F is the accepted upper limit but it's not "ok" to be at 139F consistently. There is no reason to be that hot if you have proper cooling unless it is 115F outside that day. Always strive for the lowest temp for your batteries in operation, ambient air temp +20F is great and ambient +30F is probably the minimum acceptable temp rise. If it's 75F outside, it's not ok to be at 130F, your goal should be 95F to 105F at most. This is where most people fall into the trap where they see their packs at 110F in April when it's cool out and figure they are ok but then we see battery failures when it gets hot outside. Don't think in terms of what's my battery temp, but what is the temp vs the outside temp today?

Remember damage to your packs is cumulative, the damage you do in April does not show up until July /August when they "suddenly" fail.

KGSS28

I always temp after each flight. In looking back at my records I have never recorded one above 122F in mid August at 100F ambiant temp.

I believe record keeping is also important . It is a good way to spot little changes like IR inching up etc. sometimes you can notice a problem before it is apparent in the air.

Chris Moon

My Feedback: (8)

Excellent point! Nothing will tell you the condition of your battery as the internal resistance reading. It also will help determine if your "genuine 30C" pack is really such or is just a repackaged 20C or 25C which does happen more then we realize. Comparing IR numbers is not easy unless you are using the same charger or IR meter as the means of testing IR are not the same from manufacturer to manufacturer. With most people now using Celllpro chargers, a good 25C pack should be about 2.5-3.5 and a good 35C pack about 1.2-2.2. Keeping track of the IR numbers will help you see a cell going bad way before it actually becomes too weak.

JAS

My Feedback: (2)

I've done a couple of things on my planes to help keep the air flowing around the batteries. Since 04 I've used clear packing tape (2-3mm depron also works) to 'seal' the bottom of the canopy to keep the air down around the batteries. The other thing I started to do is to close off the area under the battery tray with some 3mm depron. I attach it to the front cross support, down and around the bottom of the fuse. That way no air goes under the tray and out the exit's, now it goes up over the batteries before exiting. I did this on my Envision and the batteries were 15 degree's cooler, and that was June/July FL weather. I thought about other airflow 'directors' for the batteries, but the canopy tape and air dam seemed to work well enough.

For me I like to break-in my packs for 10 flights, 4 minutes a flight, no full throttle for the first 5. This also gives me plenty of time to practice my rolling maneuvers. I learned how to do the Rolling-8 in F before the Nats with the Sensation this way and it worked out just right.

pvogel

I've seen this advice (and a 3x exit area instead of 2x variant) before. But if you look at a lot of the pattern ships out there right now (i.e. the Griffin here: http://www.f3aunlimited.com/webstore...s/Griffin4.jpg) you see that the exit holes are, at best the same area (and I think a little smaller) as the inlets. I haven't seen many people modifying the venting of their composite birds should we? Why don't the manufacturers follow this approach?

Peter+

Jetdesign

My Feedback: (8)

The 3x exit area is a rough estimate. There is nothing set in stone saying it has to be that. Exit area could be 1:1 if the flow was straight with no restrictions. The extra area is to compensate for a non-direct flow path. Even on the same airplane, two different setups would technically need different exit areas to equal the same airflow.

And, all this assumes you need 100% capacity of the intake area. Most of us don't know how much of an inlet or exit we really need, but the rule of 3:1 outlet to inlet is thought to be a safe assumption that you are maximizing your inlet area.

Nothing is ever that easy.