Cheap Guy

Everyone (especially Hobby City) is out of inexpensive/cheap 2s 4000+mah 20C lipos. Would I have any issues running a 4000mah, 15C on my EZrun 35a/13t combo?

(Sorry to post ANOTHER batteries thread. [sm=red_smile.gif])

ScottStaypuff

Somebody correct me if I'm wrong but the punch of the 15c lipo should act like a very good nimh pack. Run time should be about 30% longer than a 4000mah nimh too, at least thats what a racer friend reports.

BigTb17

A 4000 mAh 15C battery should be capable of 60 amps. Should be more than enough for your setup.

Slo-V Flyer

Actually....... 4000 mah is 4000 mah mah = milliamp hours. So that's like saying a gallon of water would last more in a bucket than a bottle.... see what I mean?

Now, as for the 15C lipo vs a nimh... the Lipo will still be tons better. as someone said earlier, 4000 mah 15C is about 60 amps, which is great for what you're using.

rebuilder

If it is actually 15c continuous it will work fine......................but, be careful some companies(mainly chinese and Hong kong) list the burst rating, the one your speaking of could be a 10c which wouldnt be much better than a high quality NIMH. Heck, i've seen 5c's out there.

FoamyVictim

To answer the the original question, YES, it will work fine.

Cheap Guy

You were exactly right! I read the listing again, and sure enough, the continuous rating was only 10C, the burst was 15C. I did find one that matched the Zippy 4000mah lipos I'm running - 25C/30C burst for $35.00 shipped. I think I'm going to try it out.

ScottStaypuff

The guy racing said he used to use 1000mah in a race with his nimh packs on average. Now only uses 600mah a race with his lipo. I think that less power is wasted to heat with Lipo due to lower internal resistance.

rebuilder

Yes, they do have those deceptive lisitngs.................another good Lipo choice may be the Rhino....have you heard of that, HobbyKing i think. 20c+ 4000+ for like 40 bucks for 3s pack.

Lilredmachine

You are correct. but unfortunately we don't live in the perfect land of make believe where everything is 100% efficient. A lipo pack has lower internal resistance and gives off less energy as heat whilst running than a nimh pack, hence a nimh pack and a lipo of the same capacity will not last the same length of time. The nimh will always be out of juice first.

Be careful with the rather conservative rating on your ESC too, Hobbywing rates by the fet amp capacity like some other manufacturers, however they rate @ the 100 degrees celsius rating of the fet. Which will bring the amp rating down considerably. No system runs at 100 degrees celsius though, your esc is unlikely to see anything over 90F whilst running. Hence it's actual continuous rating will be a lot (and I mean a lot) higher than 35a. So don't skimp on the batteries aye?

HeliStyle

My Feedback: (2)

on that ezrun setup, I am running ebay mystery 11.1v 2200mah lipos, 15c with a 20c burst, and they run perfect. Batteries never get any hotter then warm, and I get about 12-15 minutes run time on one pack when the lvc kicks in. At $35.00 for two packs you can't beat it

HeliStyle

My Feedback: (2)

and I forgot to mention, I am running the 35amp ezrun esc, for the past 5 months with no issues.

eaterofdog

My Feedback: (1)

I have a couple of those (they are too small for my helis) and I run them in parallel on my Firestorm. This gives me a 4000mah 11.1v lipo.

HeliStyle

My Feedback: (2)

yeah, I had two left over from my exi450 heli, and I knew I wouldn't get much if I sold them, so I just decided to use them in my stampede, they work great

eaterofdog

My Feedback: (1)

HobbyCity has 2000 of the hardcase lipos right now.

Cheap Guy

WooHoo! Going to order three right now! Thanks!

eaterofdog

My Feedback: (1)

Sure thing. You got lucky, they'll be gone by this weekend.

Access

The total current*hours (current over time) that passes through one 4000mAH pack will be the same as another, regardless of any differences in internal resistance. Internal resistance is in series with the battery, so you see it as a voltage drop as you draw more current. But a 4000mAH battery (that survives) will have 4000mAH capacity, no matter how you run it, mAH does not even take voltage into consideration. What you see with the insufficient battery is a voltage drop that will either lose speed or cause the characteristic dropout where you lose power altogether with that battery, plus the battery becomes extremely hot and perhaps fails prematurely.

You also can't depend on a ESC current-limiting when it get to its max rating. The power and current draw is based on a certain motor run with a certain voltage, and if the ESC cannot provide that current, then you're going to have a problem.

ScottStaypuff

Access maybe I'm confused here but are you trying to dispute that the nimh will run out first?

Access

If you have two batteries of the same actual rating, yes. The NIMH may underperform or it may even fail due to temperature, but if it doesn't do either of these, a 4000mAH battery is a 4000mAH battery and it will provide the exact same amount of current over time. It's a subtle difference, between power-over-time and current-over-time: take 2 vehicles, (A) with a NIMH and (B) with a high-C LiPo.

1) If driven similarly, ie. exact same throttle movement, (A) will underperform, but the runtime will be equal.
2) If driven differently, ie. (A) with more agressive throttle movement than (B), such that the performance of (A) matches (B), then (A) will run shorter.

ScottStaypuff

Sounds like we're all in agreement then. Whichever way its said, Lipo is better.

HeliStyle

My Feedback: (2)

hmmm

all I know is my 3000mah 7.2v lipo out lasts my 4200mah nimh, my wife runs the rustler with the 4200mah nimh and me in my stampede with a 3000mah 7.4v lipo, and I get longer run times by far

ScottStaypuff

I did not realize this fact until this week. It really shrinks the percieved price gap between Nimh and Lipo. I'm Lipo all the way now. [8D]

HeliStyle

My Feedback: (2)

me too, I have alot of high capacity nimh packs too, I really dont use them anymore. Lipo is so much better and nowadays you can get a lipo at the price of a nimh

Cheap Guy

To add to Heli, all I know is that my 3300mah nimh batteries from Radio Shack cost $25. No brainer.

I normally don't push a product, but for you folks who are interested, when I bought my first three Zippys, they went fast!