armourbl

iTrader: (44)

Going to be running it in an E-Maxx. Drive train has some upgrades to handle brushless. More concerned about using the right batteries at this point more than anything.

I have a pair of 2S 20c 5000Mah. Will that be enough? Or will I need more juice to help keep motor and ESC temps down?

ben

jzemaxx

iTrader: (5)

More then enough....gear it for about 35-40mph......it will run a good solid 20-30mins bashing.

Duster_360

iTrader: (21)

If your Emaxx weighed more, you'd need at least 25Cs. But as light as an Emaxx is, think you'll be fine. Just watch lipo temps when you start.

armourbl

iTrader: (44)

I need to find a way to weigh this thing. I'd say it is heavy. It has a lot of metal upgrades.

Here is what Castle Creations support had to say to my question.

"5000mah 30C minimum recommended. The higher the C rating the better. Anything lower and it can induce ripple current and damage the controller."

ben

Duster_360

iTrader: (21)

Thanks - thats a change, it used to be 25C and 5000mah (125amps) now they've upped it to 150amps.

That changes my situation - I've run my Flux many times with 25Cs so I guess my lipos need upgrading. Hmmmm...not sure about that.


My 3906 has only the UE TI cednter drives and the UE drive cups needed to make that change, other than that its pretty stock atm. Mine weighs 9lbs 2oz (no batts), so you have a reference.

armourbl

iTrader: (44)

I wish they had been more descriptive with their response. I currious if their suggestion was based on a full out setup or not. Not really knowing much about it, but I'd assume that if you have things throttled back quite a bit that you'd be less likely to have issues with a lower C rating.

On their site they are pushing the A123 6S packs. Seems like they expect you to run as much juice as possible.

All I know is my old Hacker motor was insane with the Mamba Monster and the same pair of 2S Lipos I was planning on using.

ben

armourbl

iTrader: (44)

Found this post in another thread. It explains the ripple thing and how it can affect the ESC.

http://www.rctech.net/forum/6909839-post11.html

ben

idbasher

iTrader: (3)

Zippy 5000 mah 20c 2s packs is what I run in my setup, my trucks geared for 35mph and it will do standing backflips at 1/2 throttle. you got more then enough punch with those packs.

V0RT3X

iTrader: (8)

I ran the ERBE on that 20C 5000 Turnigies for 20$ geared for 38mph with no problems. Weren't even warm.

OG RC 10T

iTrader: (41)

You have two batteries. 20c + 20c = 40c You should be fine.

Yosh70

iTrader: (17)

I'm fairly new to this hobby but I know that is not even close.
Running in series, the voltage is doubled. In parallel, the Mah (or runtime) is doubled.

The discharge rating is not doubled....who told you that?

So if I had 2 lipo's that had a 35C rating, you think I'd have a total of 70C?
That would be awesome....but it cant happen.

OG RC 10T

iTrader: (41)

I didnt mean it litteraly and should have clarified. If you have one motor pulling amperage at a rate of 35c, and one 20c battery, the motor is pulling more amperage than the battery is able to give.

If you have one motor pulling 35c from two sources ( two batteries ) there is a total avalability of 40c.

If you double your voltage, the amperage draw (or c) is shared between two batteries. If he has two 20c batteries, in his application, he will be fine and will not damage his packs by trying to draw more current than thay are rated to discharge.


http://www.cameronsoftware.com/ev/EV...ryPhysics.html

Understanding Lithium Polymer Battery Specifications:

Lithium Batteries are also know as LiPo, Li-Po, LiPoly, and Li-Poly. What do all the lithium battery specifications mean? The values that are the most important are:

•Pack voltage (depends on cell count; each cell is 3.7 V)
•Capacity (mAh)
•“C” rating (describes the rate at which power can be drawn from the battery)
Lipo Battery Cell Voltage

The nominal voltage of each cell in the pack is 3.7V, but this can go down to 3.3V during discharge, and up to 4.2V when fully charged. A battery pack is composed of two or more cells put together in series for increased voltage, or in parallel for increased capacity. A 2 pack with 2 cells in series would be rated at 7.4V (2x 3.7V).

The battery pack configuration is denoted by the number of cells in series and the number of cells in parallel. A 3s2p pack would have three cells in series, and 2 cells in parallel, using a total of 6 (3×2) cells. A 4000mAh 3s2p pack would have a capacity of 4000mAh (2 x 2000mAh), and a voltage of 11.1V (3 x 3.7V). It would internally consist of six 3.7V 2000mAh lithium polymer cells. The cells would be doubled up (the 2p part of 3s2p) to get 4000mAh, and there would be three in series (the 3s part of 3s2p) to get 11.1V (3 x 3.7V).

The “C” Rating

The “C” rating describes how quickly a battery can be discharged. A 2000mAh LiPo battery with a “C” rating of 1C continuous would mean it should not be discharged any faster than 2000mA or 2A, which would take one hour. A 2000mAh pack rated for 12C continuous would be able to discharge at 12 times its capacity (12 x 2000mA = 24000mA or 24A) at which rate it would discharge in 1/12th of an hour. Using a pack with a higher C rating than you require will leave some room for safety, and extend the life of your battery.

Continuous Current:
If you know how much continuous current will be drawn and the capacity of the pack you want to use, you can easily determine what C rating you require. If you are drawing 5A from a 1320mAh pack, simply take the current and divide by the capacity: 5A = 5000mA, 5000mA / 1320mAh = 3.8C.

Burst Current:
LiPo batteries are also given a C rating in terms of burst, which is how quickly the battery is able to discharge for a short time. A burst rating of 20C would mean a 2000mAh battery could supply 20 x 2000mA = 40000mA or 40A for a few seconds.

armourbl

iTrader: (44)

That is the concensus that I got from the guy at the LHS last night. He could have sold me two new batteries, but he didn't.

I'm going to need to read your last post when I have more time, at a glance it looks like good info.

Thanks,

ben

Duster_360

iTrader: (21)

I guess we're going to go thru this again. Ben, I'd ask Castle - the last time this was asked (think it was on RCM in the Castle thread..??), Castle said their lipo spec was per lipo, not the combination.

Think about it - other wise you could run 5000 15Cs and I know where that will get you - in line at Castle to have your smoked MMM repaired.

armourbl

iTrader: (44)

Despite the fact that I should be able to run my 2S 20c packs without issues, I'll probably still pick up some 30c minimum soon. Better safe than sorry. I'm sticking with 2S though so I can still use them in some of my other vehicles if I want or need to. For example, I really don't expect to ever run the E-Maxx at the track, or at least not often. So, I'll be able to use its batteries with my short course trucks and get more time at the track as a result.

ben