question about my LiPo

bmxRRT · #1 09-07-2008, 07:20 PM

Hi, well, I own a rustler VXL, venom 11.1v 3s 20c 5400 LiPo, and vision peak ultra charger. I've charged and used this battery about 5 times without balancing it. I just recently got the blinky balancer. The past two runs the truck has gone into 50% (low power) mode and completely died 10seconds after 50% mode has kicked in. The battery in total lasts about 45min on the track. This happens even when I balance it. Is my battery damaged? When I plug it into the charger right after low voltage detection it reads 9.9v (which is .9v above min disch. volts according to venom). I figured it would run at low voltage mode for some considerable time, no?

(BTW I'm charging at 2.5amps, voltage at finish is 12.54 with balancing simultaneously.)

guver · #2 09-08-2008, 01:52 AM

It may be slightly damaged from overdischarge. You are getting excellent runtime.

chewie · #3 09-08-2008, 11:48 AM

umm you can charge at 5.4 amps and i would balance charge every time.

bmxRRT · #4 09-08-2008, 12:05 PM

My charger limits me to 2.5amps, it takes about 1 1/2hrs to charge.

Also: I connected my balancer this morning and it reads balanced, so as far as I'm concerned, the cells are maintaining the voltage.

rccardude04 · #5 09-08-2008, 09:39 PM

With lipos, as soon as you notice a drop in power, it's already dead.

What you are experiencing is normal. You absolutely do not want to run a lipo near its minimum voltage longer than you have to. It should shut off suddenly and that's it. Don't drive it any more.

-Eric

bmxRRT · #6 09-08-2008, 10:15 PM

ohhh ok. Yea I thought it would run at 50% power for a little, but I guess not....is it okay to leave my blinky attached to the battery when I let the battery sit for a few days? To maintain it? Or does it not matter...

rccardude04 · #7 09-08-2008, 10:59 PM

DO NOT leave it on the pack. If it's kind of low, it will discharge it to the point of no more battery left.

You only need to balance if you're changing the voltage, ie charging the pack.

-Eric

bmxRRT · #8 09-08-2008, 11:24 PM

oops, oh well I'm at work till 7am, hopefully it doesnt blow up on me

rccardude04 · #9 09-09-2008, 10:04 AM

As long as it was at least half charged, it will take a while for the parasitic drain to kill the pack, but it's really not a good idea to leave it on there.

-Eric

pasan · #10 09-09-2008, 02:22 PM

Also don't balance your cells after a run. Charge first, and when the voltage is up to 12v, attach your blinky to the pack and let it work while charging, and then you won't have to keep it attached for much longer after charging is done. As a rule of thumb, I remove the blinky after 2 minutes of inactivity. And it's always good to be in the same room with your batteries when they're charging.

bmxRRT · #11 09-10-2008, 05:43 PM

If the battery sits for a day or two, is it okay to repeak the battery before a run?

guver · #12 09-10-2008, 05:54 PM

It is ok, but the battery should not lose any charge in a few days. It won't self discharge in a year if it's average.

oops, I forgot to mention (after re-reading your original post) that 10 volts resting voltage is dangerously low (if not too low) and should not be run until the cut-off. The cut-off is there only as a last resort protection. If you normally get 45 minutes then I'd recommend shootin gfor 30 minutes and stop to recharge.

bmxRRT · #13 09-10-2008, 06:06 PM

ohh. ok. The pack says that minimal discharge volts is 9.0v, so I don't know. Hopefully it's not trashed, I'd think that if it was trashed it would run a lot shorter than 45minutes. I connected my blinky after a run and 1 cell was below 3.2v. They suggested a slow charge until that cell is above 3.2v. Mind you I can chose anywhere from .10amps to 2.5 with this lipo. I bet that cell is busted.

rccardude04 · #14 09-10-2008, 09:12 PM

Nah. You're probably fine. If not, just keep using the balancer and watch it to make sure it doesn't swell up.

Just remember, the less you run it down, the better. If it runs for 45 minutes, time the run for 35-40 minutes, and charge it back up. Your pack will last a little longer.

As far as repeaking, unless you let it sit for like a month, you should never really have to "repeak" the pack. LiPos aren't like NiXX batteries.

-Eric

guver · #15 09-10-2008, 09:26 PM

9 volts must be a LVC settting (a loaded minimum voltage) The minimum resting should be 10.5 volts. Some say 11.1 volts.

jakewolf · #16 09-16-2008, 04:19 PM

with that kind of run time i wouldn't worry about it