rrTV-PHOTO   New HD TV
HOME   rrTV-PHOTO   GALLERIES   MY GALLERY   HELP-FAQ
myHOME PM pmRR MEMBERS 370 ONLINE 74 EVENTS SEARCH REGISTER  START HERE
 
1 page851 viewsPOST REPLY
Thunder Power RC . Real Raptors . Mikado Modellhubschrauber

.
.
e-Electric Batteries & Chargers > Capacity Vs. Peak (C) capability
 
 
blytle
Heliman
Location: Maple Valley, WA

I recently purchased some True RC 2200mah 3 cell lipos for my Trex, and they worked great and have a published rating of 16C. Unfortunately after 3 months of use, they no longer have enough "Punch" to do anything but hover. When I recharge using the Astroflight 109, it tells me that the cells still are receiving about 2150 mah while charging - The same value they have always had.

LONG story for a short question:

Do LiPos have fail in such a way that they still have the same capacity, but not the same current capability?
05-08-2006 Over year old.
 
 
Rob_T
Elite Veteran
Location: Tualatin, OR - USA

Yes.

It's caused by increase in internal cell resistance. Better cells have a longer life time before it happens. Some cells over state their "C" capability and get this problem early on.

Do check that the connectors are not the cause- especially if you're not using Deans, Sermos or AstroFlight zero loss connectors.


Rob
Eco8, Piccolo Fun, Shogun, HB Elite CP, Trex 450XL CDE, Swift
05-09-2006 Over year old.
 
 
blytle
Heliman
Location: Maple Valley, WA

Thanks for the info Rob. I have since balanced the two batteries giving me problems and it hasn't helped. Something interesting that put the nail in the coffin was discovering that when I lightly squeeze the batteries I see the voltage jump up.

Just pissed that they only lasted less than 5 months when I have a thunder power 1320 still going strong well after a year.

Are there any batteries you're having good luck with that are easily found on the internet? At this point, I'm not worried about cost as much as durability. There's no point spending $10 less for a battery that lasts half as long.
05-09-2006 Over year old.
 
 
Rob_T
Elite Veteran
Location: Tualatin, OR - USA

For my Rex I usually use Apex 12C 2200s. On paper their spec might not seem that great but in practice they seem to be very good. (And I have flown my Rex with data logging on board, so that is an informed opinion based on some in flight measurements.) I've also had very good luck with Tanic 1050s (but they're too small for a Rex).

ThunderPower are the most popular it seems, and I know lots of people who think highly of them. I dont think they're worth the price premium they seem to attract, but many people would say they're the safe bet.


Rob
Eco8, Piccolo Fun, Shogun, HB Elite CP, Trex 450XL CDE, Swift
05-09-2006 Over year old.
 
 
blytle
Heliman
Location: Maple Valley, WA

Great!

I looked up the Apex and there are some great deals, especially if you have had luck with them, grabbed two of them today.

I guess I learned I need to add more of a budget for batteries then I thought.

Thanks again!!
05-09-2006 Over year old.
 
 
oldboldpilot
Key Veteran
Location: Southern California

LiPo's have a "do not exceed" flight temperature, and "do not exceed" minimum flight pack voltage.

If you bust either one of these, your pack life is going down, way down.

Flying past a 75% discharge is begging for a short pack life.
05-09-2006 Over year old.
 
 
blytle
Heliman
Location: Maple Valley, WA

I'm not sure about the temperature mine have been operating at. They feel warm to the touch when I'm done flying, but not "ouch" hot. As a guess I woud say 120 - 130 F.

As far as Depth of discharge, I tend to get about 12 minutes of flight time out of the 2200mah packs and when I put them on charge they are usually about 10.8 - 11.0 volts for a three series pack.

I've heard the NEVER EVER go there voltage is 9.0V per pack or 3.0V per cell. What do you recommend as the "Best for your batery" Voltage to not drop below? In other words, what at rest voltage constitutes 75% DOD in a 3 cell liPo.

Thanks

-Brent
05-09-2006 Over year old.
 
 
Rob_T
Elite Veteran
Location: Tualatin, OR - USA

On some of the high performance cells, the "dont go there" voltage is raised to 3.3V per cell.

I tend to adjust my flying time until I'm charging a little less than 85% of the labelled capacity of the battery after flying. For my Rex setup thats just under 12 minutes - I think my timer is set at 11 1/2, but I'm away from it and can't check just now. Obviously it will vary with setup, so you need to find whats right for your setup.

The fact that your AstroFlight charger says its putting back 2150 mah after flying makes me think you are pushing things a bit hard. My rule of thumb says for that size of pack you dont want to charge more than about 1850 mah (85% of 2200). I think you'll get better life out of your batteries if you cut down to about 10 1/2 minutes flying.


Rob
Eco8, Piccolo Fun, Shogun, HB Elite CP, Trex 450XL CDE, Swift
05-10-2006 Over year old.
 
 
blytle
Heliman
Location: Maple Valley, WA

Thanks Rob,

I'll have to admit, I do not fly until the ESC gives me the throttle down hint very often, but I have done that on occasion with these batteries, and almost always to 90 - 95% of capacity for a flight, as I said earlier 2100-2150 charge in for a flight on a 2200mah pack.

I'm glad I have the information now to better protect my next set of packs. I have to remind myself it's not worth the extra 45 seconds of flight time.

Thanks again

- Brent
05-10-2006 Over year old.
 
 
1 page851 viewsPOST REPLY
CanoMod . A Main Hobbies . Boca Bearings

.
.
e-Electric Batteries & Chargers > Capacity Vs. Peak (C) capability
  UPDATE SCREEN   PRINT TOPIC Advertisers 

Subscribe to This Topic

Saturday, May 17 - 7:25 am - Copyright © 2000 - 2008 runryder.com | email | link to rr | runryder needs cookie