Lipos

[sheddy]

Advise needed,

I have two packs of intellect 5000 40c lipos. Will these last a 5 minute race in a 4wd buggy with a 5.5 brushless?

Only ran them in tc with a 10.5. Dont want to be running out of power.

Also any suggestions of where to get new lipos from? are the ones from hobbyking any good?

Cheers, Dave

[dobber]

Im sure these will last you conciderably more than 5 minutes. Probably nearer 20 mins. Im sure someone will confirm a more accurate figure in a bit

[RogerM]

Originally Posted by dobber

Im sure these will last you conciderably more than 5 minutes. Probably nearer 20 mins. Im sure someone will confirm a more accurate figure in a bit

Your not trying hard enough then ... 4wd really takes some juice!

I can run about 8mins to the Lipo cuto off (set to 3.2V/cell) with my 5500/90C Orions. Remember that we never get full capacity out of a LiPo, in fact I think that if you did a couple of times it would be near enough dead!
In a normal race I am pulling something like 2200mAh out of my cells.

2wd it's more like 1600mAh.

Your cells will be fine I'm sure.

[Cardnim]

Sheddy - you wont have a problem mate.

I run a 5.5t in my Cat on Speed Power 5000mAH 55C lipos and I get two races out of them if I had to. After 10 minutes they still arent near the lipo cut off of 3.6v per cell that I have set on my ESC.

Race on buddy!

@RogerM - something queer going on. You arent getting the capacity rated on those batts, or maybe the high C rating of your cells is sucking the amps out quicker? Either way, thats the fastest dropping batteries Ive heard of. 4WD doesnt take that much more juice than 2WD in mine (and the other guys I race against) experience.

[mattr]

I get about 10-12 minutes using a 6.5T/4wd on the same cells as RogerM, so 8-9 mins probably isn't far off for a 5.5T.

[cigbunt]

i guess it depends on the discharge rate vs the capacity,

correct me if im wrong but 40c 5000mAh should last longer than 90c 5500mAh..
but less punch

[Southwell]

I can still last with my old 4200's and a 6.5 in 4wd, and they're almost 3 years old.

[/tobys]

I'm with Rog - between 2000 and 2400 mah required to recharge my 5200 45c lipos on 4wd with 5.5 motor. That includes running a couple of warm up laps and doesn't seem to vary much on track surface - although lower grip takes less out.

In 2wd, somewhere between 1600 and 2000mah depending on motor (either 7.5 or 6.5) and track surface.

On that basis I can (and have) run 2 races on a single pack with 2wd but wouldn't attempt that on 4wd. I do prefer to charge after each race so that I have consistent power delivery.

[Col]

I generally use around 1500mah indoor at York in a B44 6.5. Done over 20 mins and never hit the cut off.

[mark christopher]

Originally Posted by cigbunt

i guess it depends on the discharge rate vs the capacity,

correct me if im wrong but 40c 5000mAh should last longer than 90c 5500mAh..
but less punch

way off assuming the most you can draw constantly is 40c the 5500 will last longer.
the mah is the capacity the 'c is the amotg of amps it can produce.

If you draw 10c constant the.5500 will last longer

[cigbunt]

Originally Posted by mark christopher

way off assuming the most you can draw constantly is 40c the 5500 will last longer.
the mah is the capacity the 'c is the amotg of amps it can produce.

If you draw 10c constant the.5500 will last longer

i was presuming the car would be using the extra c rating is this wrong

[mattr]

Originally Posted by cigbunt

i was presuming the car would be using the extra c rating is this wrong

I suppose it depends on the ESC/motor maximum current draw. I have tonnes of "spare" capacity on my battery, think the max ESC current is 120 or 140 Amps. As long as the battery can meet that, any "extra" should make almost no difference.

[VintageRacer]

i was presuming the car would be using the extra c rating is this wrong

It would only use it if the motor demanded it and with a 5.5 motor, I can see that it would.

Is there actually really a need for a 90C lipo?

At 90 x 5.5A this is a maximum current draw of 495A, even at the maximum of 8.4V that needs the resistance of the circuit to be as low as 0.017ohms. (at 7.4V, the resistance would need to be lower to maintain the 495A current).

Adding up data I have found for wire, esc and motor, the total for those is about that figure, give or take a few thousands of an ohm. That's assuming that all connectors and solder joints are zero ohms too.

Looking at it another way, the power rating of motors, a 5.5T Novak is rated at 420W which gives a current of 57A, a long way off 495A.

With current motors, it would seem that 5500mAh 30C or 40C cells should be more than adequate.

[losichris]

im fairly new to Lipos, as ive been out of racing for 4 years.
ive got a pack of Vampire 6200. Was the best method of charging/discharging/balancing them?

[VintageRacer]

Originally Posted by losichris

im fairly new to Lipos, as ive been out of racing for 4 years.
ive got a pack of Vampire 6200. Was the best method of charging/discharging/balancing them?

General recommendation is to charge at maximum of 1C (so 6.2 Amps for your pack) although there are increasingly packs that claim to be able to charge at higher rates.

No need to ever discharge them except in your car as they don't suffer from the same memory problems that NiMH does.

Doesn't hurt to balance as you charge them every time, but this is not essential, every few charges should be OK.

[losichris]

great, sounds fairly straight forward.
i used to charge my cells at 5A back in the day.

[bad man alty]

What speed controller u runnin with ur 5.5 mate. I run 5.5 n get 2 races of a 6500