Batteries and what I found

[bensid54]

I have six batteries that are 2200 mha three cell 20 c and two batteries that are new and are 2250 mha three cell 35 c. It appears the c rating is very important when it comes to multi rotor. With the 20c I get just under eight minutes of flying time with the 35c I get eleven minutes of flying time and used more of the mha. The 20C batteries are Turnigy from Hobby King the 35C batteries are Pulse are from Rotorquest so brand name may figure into it too. Anyway this is one way to get longer flight times.

 

[sixshooterstang]

C rating is not directly connected to your flight time. FLight time and capacity are more related to the brand and such you buy. It can vary. A battery marked 5000mah could be under or overrated. I have had batteries charge quite a bit over the rated mah from 3.6v per cell before.

 

[bensid54]

Well battery brand could well be the biggest factor here after all Turnigy is the cheapest brand you can buy. The quality matches the service that Hobby King gives , I'm done with them.

 

[sixshooterstang]

their shipping speed and shipping prices are awful. customer service is nonexistent

 

[PeteDee]

Wow you guys must be shopping at a different Hobby King than the one I shop from, the basic Turnigy packs are great, Zippy Compacts are excellent, service has been first class, refunds on faulty items no problems, sent the same day, here to Australia in a few days, must have saved thousands of dollars over the years.

I must say that I am particularly careful when choosing what to buy and have had a few duds but have also had some really outstanding items at fantastic prices.

Ben, 20C packs on a quad, what the hell were you thinking?

Cheers

Pete

 

[Benjamin Kenobi]

I think brand is very important. Your lipos are the life of your multi. It's not like you can glide home if they fail:nevreness:. I go 40C as the higher C ratings tend to be better quality overall. I went with GensAce last year and have now spend over £1000 on them as they just last and are really consistent. 2milliohm internal resistance after one year of operation is just brilliant.

 

[bensid54]

I'm still very much a rookie and every step for me is a learning curve, but I am learning.

 

[sixshooterstang]

My rule for C rating has always been to calculate the max continuous discharge and leave a little leeway between that and the amperage at max throttle.

So lets say I have a 4s 5000mah battery rated at 40C. If I multiply the capacity in Amps by the C rating that is max discharge.

5A*40C=200A max discharge. So if my copter at full throttle draws 0-185A then my battery is safe.

 

[deluge2]

Well that's an interesting calculation, and may work because full throttle is rarely used and never for more than a few seconds at a time. However the issue is not so much battery safety as aircraft safety. It's generally accepted that so called continuous max discharge ratings for lipos are mostly a marketing gimmick. This is borne out by the absence of any accepted standard method or test conditions to measure such a value. It may be true that within a single vendor's product line, higher discharge ratings correlate with 'quality' however comparing across manufacturers is risky.

By definition, discharging any lipo at 1C takes about an hour (if you're willing to approach 100% discharge). 10C discharge takes 6 minutes. Continuous discharge at 40C would take 1.5 minutes. I don't think 4 or 6 cell battery would last long at that discharge rate, if it even survived the first cycle. So the max continuous discharge ratings are basically BS.

Steve

My rule for C rating has always been to calculate the max continuous discharge and leave a little leeway between that and the amperage at max throttle.

So lets say I have a 4s 5000mah battery rated at 40C. If I multiply the capacity in Amps by the C rating that is max discharge.

5A*40C=200A max discharge. So if my copter at full throttle draws 0-185A then my battery is safe.

 

[bensid54]

I think the biggest difference between a higher C rating and lower is the ability of the craft to stabilize itself better and faster which in the long run could save on battery drain because the current spikes would be shorter lived on a higher C rated battery than a lower C battery.

 

[sixshooterstang]

Even if they are gimmicks, better safe than sorry. Could always calculate your own C-ratings if you have a way of measuring amp draw, time, capacity used and voltage all at once.

 

[photobobga]

I've wasted too much time fiddling with batteries and it's not worth saving a buck or two when it comes to flying expensive equipment with cameras attached. If you want to talk to the manufacture directly and get their personal recommendation as to what you ideally need call MaxAmps in Spokane, WA. They custom make every battery with your specific connectors. And from what I've found their pricing is right in line with the others. http://www.maxamps.com/
They offer a money back guarantee plus a Lifetime Warranty
-Bob

 

[bensid54]

Something new to add to the list. I used to stack one battery on top of the other, but to save on weight I got rid of my leg extensions and laid both batteries on the top deck one on either side of the GPS antennae to get the CG as close to craft centre as possible. Funny thing now the batteries that got me just over 6 minutes are now getting just over 8 the other batteries that got me ten minutes are now getting over 11.5 minutes and with only 100 mha more charging input for most of the batteries. Mind you now I have to adjust my gain the pitch seems rather jumpy but it does a much better job of coming down in a more stable way than it did with the batteries stacked on top of one another.

 

[Thalios]

Your difference in flight time has nothing to do with "C" rating. You're comparing the worst brand in terms of duration with a good one.

Take a 55C Turnigy Nanotech and compare it to your 35C Pulse, and i'm willing to bet that the Pulse will still outlast the Turnigy.

 

[bensid54]

You are right quality makes a difference but on the other hand the higher the C rating the shorter the drain time because the quad can correct its attitude faster and sooner.