Couple of battery questions?

Hi Guys,

Got the 8T sorted now and have the iCharger 208B and the Hyperion 6500mah 35C 4S pack.

The 8T is pretty uncontrollably fast on 4S, does anyone here use maybe 3S with Truggy to make it a little more driveable for racing, etc.?

I've put the MMM ESC punch control to 70% but still it's pawing at the sky!!

Should I keep with 4S and up the punch control to 80%+ or maybe use 3S perhaps? Let me know your thoughts guys?

Also, my charger can do normal, fast and balance charge for lipo, do you guys ALWAYS balance charge your lipo's only? Is it unsafe/unwise to use fast/normal charge function?

Or is it that you can use fast charge but maybe only a few times before then doing a full balance charge?

[magman]

First 3s in a truggy is not enough unless combining them for 6s. I always balance my li-pos when charging...just for piece of mind. Your pack can be charged at 6.5amps...so when setting your charger, see how many amps. are at normal/fast.

You say that it is uncontrollable on 4s? What motor are you running? In my mbx-5T I am running 5s w/the ccneu 2200kv set up and it is very fast. My punch control is set at 50-60 I believe. It will still wheelie w/a 1/2 pull of the trigger. What I do is set the epa for my throttle on my radio to 75-80% and I get really long run times.

Originally Posted by magman

First 3s in a truggy is not enough unless combining them for 6s. I always balance my li-pos when charging...just for piece of mind. Your pack can be charged at 6.5amps...so when setting your charger, see how many amps. are at normal/fast.

You say that it is uncontrollable on 4s? What motor are you running? In my mbx-5T I am running 5s w/the ccneu 2200kv set up and it is very fast. My punch control is set at 50-60 I believe. It will still wheelie w/a 1/2 pull of the trigger. What I do is set the epa for my throttle on my radio to 75-80% and I get really long run times.

Appreciate the advice, I'm running the 8T with the MMM / 2200 combo. Never thought to drop the EPA on the TX, might give that a go!

Sounds prudent to use balance charging at all times and certainly when I'm at home then I balance charge at 6.5amp if I'm in no hurry. My pack can be charged up to 5C but my power supply at home is only 10amp/12 burst and so I stick to 6.5, or 8amp if I'm in a hurry!!

I was really thinking of when out in the field, using the charger with a car/leisure battery to get a quick charge to get going again. Was thinking of using a balance charge at 2C to get a quicker recharge time, but the option is there to go higher of course, maybe 3C? Also the fast charge function on the charger too....

[suicideneil]

If memory serves, the fast charge option just uses a shorter CV phase (first is CC = constant current, then it switches to CV = constant voltage when it gets harder for the charger to pump in those electrons..), so the pack comes off the charger with say a ~90% charge, the cells sitting around 4.0-4.1v per cell rather than the full 4.2v; its the CV phase at the end of the charge that can take a while, since thats when the cells get balanced out usually (if there is any imbalance to start with that is).

Im never in enough of a hurry to use anything but normal balance charge mode myself.

In see quite a few people using 3s in 1/8 buggies, but they are lighter and less demanding than 1/8 truggies- thats not to say it cant be done, but you'd have to watch temps like a hawk to make sure the batts and esc arent gobbling up too much juice. You can always drop the gearing too if possible.

As for turning down the throttle epa, I dont like that idea myself even though I see alot of peeps doing it with no problems- main concern is that the esc is most efficient at 100% throttle, so turning down the epa forces the esc to run at partial throttle even though its at 'full' throttle on your trigger finger. Driving style and having a lighter touch of the throttle can reduce wheelies, as can adding some exponential to the throttle curve using the castlelink.

[E-Revonut]

I agree with neil. Lowering the epa is not the best solution! Not only is the esc most efficient at 100% but if you are that fast that lowering the epa still keeps you at the speeds you want then your gearing is shigher than needed which will increase the amp draw on startup and acceleration. I have heard that torque is a direct relation to the amp draw, so the more amps your trying to draw the more torque the motor produces, resulting in uncontrollable speed. I would suggest using a smaller pinion gear

[nitrostarter]

Learn to drive! Thats simple. Brushless is pure power unlike nitro!

Hmm....might try winding the punch control up to 80% then and see how that feels before playing with the EPA.

Curently at the end of an open fairly WOT run then yesterday the battery was just about warm, as was teh ESC, but the motor read 120f, is this OK? I had a look at the sticky on the Q&A and this suggested whilst OK then it might be undergeared? If it's undergeared then surely a bigger pinion might help all round, lowering motor temps perhaps and also meaning the acceleration is a little lower?

Sounds like I should stick to balance charging only on the charger side of things, although when using a car battery out in the field then I might try charging at 2C, so 13amps.

[suicideneil]

120 is cool for a motor, no worries there. Gearing up may well lower the motor temp, and decrease acceleration a little, but then your topspeed will climb at the same time, resulting in an even harder to control setup. If the track is too tight to make use of all that speed and power, concider a slower motor (1600-1800kv range), or dropping down to 3s.

Thanks guys, might gear up one tooth on the pinion, this will indeed tone down the acceleration and to be honest the higher top speed wouldn't be achieved on the track anyway, so this might fit the bill.....maybe reducing the motor temp a touch at the same time.

Might see if i can borrow a 3S from a friend to try too....

[lambchops]

what motor you using beanie?

I allways balance my lipo's every 3rd or 4th charge but then they take over 2 hours!!

Using MMM with 2200kv

Think I'd be a bit nervous to not balance charge them every time at the moment!!