KenChoo

Quick question guys...was out today at a site with no electric sockets so I used my car battery to charge my packs and I think it stopped charging before the packs reached 100%. When I landed and plugged them back on the charger they read 9% charge left... My packs are Zippy 5000 25C. They still look fine and weren't hot (barely warm actually). I've restored them to storage charge at about 45% now. Question is, might I have damaged them severely, and whether I can continue to use them? Thanks, Ken

serious power

Hi Everette,
I posted some detail on the 'new battery - we'll see' thread re Brenners point above.
This is an extract as appropriate to this;

'Today's power plants put out 10kg+ static thrust.
Your 5000ah pack volt drop ,flight start to finish, is say 3.5 over an average of 38.5(no load).
That's a 9% drop in power.
These packs are say 120g heaver - that ,in Nialls case, increases his model from say 4850 to 4970.
That's an increase of 2.5%.
You say you don't notice a 9% power fall off yet you knock these packs due to a 2.5% weight increase. '

'The extra capacity also gives extra performance, relatively speaking, as the flight progresses - less % capacity used = less voltage drop !! '

The pack referred to is the Zippy 5800 at 1300g compared to a 5000 at 1180g.
The point here is that 'weight saving' may/does have a cost due to the compromise.
It will have a performance cost and a monetary cost.
I would advise that you carry as much battery capacity as you can - legally - in whatever brand choice you make.
The IC guys leave the ground with the same model weighing 5500g and it is likely the model was designed for IC anyway.

Brian

serious power

Ken,
Your packs will be fine - probably will stop performing 'good' a few ?? cycles earlier than they otherwise would - but this is the difficulty with this aspect of lipos. There is a disconnect between the cause and the effect.
Keep an eye on the IR's and try to not get below 20%.

Brian

wattsup

My Feedback: (1)

Hi Brian, I went back to that thread and read it again in it's entirety and found that it indeed made even MORE sense. I have to say I agree with you and Niall. I've never seen Jason agree with anyone. I suppose he has his own agenda and feels he is right no matter what! I'm in the process of ordering the Zippy 5800 25C 10s packs. If it's good enough for Brenner than it will be just fine for me. IMHO, the extra amount of weight that is added to the AUW weight is neglegible and compared to the smaller packs it is more than offset by the increased capacity and POWER! You've been a real help and I appreciate you sticking with me. Looking forward to flying with you one day, Everette

wagen017

Everette, I am still thinking about your packs dying after 70 cycles. On average, with any pack you should get to 150 cycles, with some better and some worse. I have had some packs retired after 75, some after 250+.
You might want to check your charger. I found out some chargers need calibration, you might be structurally overcharging some cells. Do you see any pattern which cells fail?

Volkert

wattsup

My Feedback: (1)

Hi Volkert, To answer your question, on occasion I've had individual cells die in the course of a flight indicated by a severe loss of power usually at approx 4-5 minutes into a flight. Generally
what I experience the most as these packs age is it taking longer and longer to charge, an increase in the IR's and increasing loss of power on each additional flight. I've even wondered if it could be the controller I've been using in both these planes_ie, Castle HV 80 series. Does this help? Everette

wagen017

Recognize exactly the first item you describe. Had that happening to me on my first electric flight ever with a new plane. Loss of power after a few minutes of flight. Immediately was able to land, one cell completely completely swollen. Post-mortum was I did not fully charged that cell and I did not realize that was important....
Gotta think a bit about the second bit you wrote.

Volkert

serious power

Hi Volkert,
How did you charge the pack ,I assume fully, and not charge one of the cells.
What were you using to charge and or balance the pack.
How did you diagnose this as the cause in postmortem.

Brian

Jetdesign

My Feedback: (8)

I've done this by accident (over discharged some packs), and haven't noticed the impact to the packs yet. I agree it's probably a decrease in usable life expectancy.

wagen017

Brian, when I charged the pack one cell did not make it to 4.2V, despite the fact it was charging with a balancer. It was lagging and made it to about 4.15V or so. I thought I could fly it, then recharge and slowly like this bring the pack to full life. That unfortunately, did not work out that well. This was a first generation Zippy, I then moved to Rhino 4900 which served me extremely well and are actually still flying in a friend's plane.

Volkert

wagen017

Isaac, sorry for hijacking your thread a bit!

Another, maybe related question: now with winter approaching here in the Northern hemisphere is there maybe anything special to do with regards to the first flight/charge?

For now I have decided that the first charge will be 1C, not at the usual 5C. Only after the first flight, when the pack is awakened, I will use full charge. Or is even that too much? I usually stop flying at about 5-7 degrees C.

Volkert

serious power

Hi Volkert,
Ah - That was just a faulty pack with one dud cell from the get go.
There were a lot of those being reported ,in various cheap brands, up until the last year or two.
This was NOT a charging or charger related issue so.
I believe also some of the so called 'nano tec,, ' cells are failing at relatively low cycle no's .

This is not to say that there is not a charging issue with Everette's pack - there may well be.

Brian

Anthony-RCU

My Feedback: (2)

Lots of good stuff here. Had to go to the shop and check some numbers. All 5s packs had some kind of break in and were charged and flown as 10s packs. Only the high C packs were charged at more than 1C. Mostly flying masters and some FAI using 3200 - 3500 mah per flight. Of course ther were a couple of way out there ones that turned into 4000mah charges but luckily those were not too frequent.

Started with several of the True RC 5000 10c. A few sets were replaced for puffiness and the rest dropped cells around 70 flights. Then went to the Zippy flightmax 5000/15c that worked well for 80+ flights before they started to puff and lose voltage. Great for an $80 battery that was 1160g.

Next tried 4 5s Rhino 4900/20c packs and had no luck. Opened the shrink and took out the extra wire to get the weight down and one set quickly lost a cell. Ordered another 5s and the other set dropped a cell. Started resoldering cells in one set and that one lasted about 40 flights before I gave up. The one with the mismatch now has almost 90 flights and is good for calm days in cool weather. One 5s still has good IRs but the other is struggling. I was surprised that this one came out of hibernation in the spring and don't expect it to hold on much longer. Everyone seemed to do well with these but me and for $130 they were quite a disappointment.

My favorites have been the Sky Lipo 4400/40c. Again bought 4- 5s packs and built two flight set that had great power until around the 80 flight mark. Still make good power but not as good as last year and IR numbers are up while charges definitely take longer. For less than $90 shipped they were a great deal. Lastly, Nano 4500/35c almost as powerful as the Sky 40c but got squishy quickly. Only 45 flights so far but at $130 a set they better keep going.

Wow, that is a lot of batteries! I usually buy two new sets each spring and all get flown each day until they fail. For me it seems to be initial quality and a little bit of luck for longevity. If I can get my packs to $1/flight I am happy. So far the zippy and sky have made it. I will probably buy another set of Sky 4400 in the spring unless some other new comer looks promising. Maybe one day I will spring for TP but I doubt it.

ytell

One more question here on this fuzzy subject,

Is it true that for longevity purposes it is better to store your packs half charged?

Do you guys charge or discharge your packs accordingly before winter time?

Thanks,

wagen017

Yes, I would recommend this. Don't leave your batteries fully charged!