RedBullFiXX

iTrader: (34)

Oddly enough, the opposite could be true
Long lines of waiting for tech at Big races (where lipos are temp/voltage checked), are negated at club races, where the temp/voltage could actually be of some benefit

I charge @2c for stock classes, and concentrate on other areas to improve

John Wallace2

When you are discharging at high discharge rates (30+) what volt cutoff do you use? I've been going down to 7.o volts (2 cell pack). At first there was improvement. But after a few cycles I noticed a fall off in the packs I've been testing, (MAH, MWH, IR and average voltage). I was talking to another racer this weekend and he said his discharger only went down to 7.8V. PS I use my old Turbo 35 for discharging and recording data.

frozenpod

iTrader: (1)

I only discharge my cells to check the numbers every 50 cycles or so.

When I cycle my race packs to check the numbers I use 30A discharge to 3.5V per cell.

I haven't tried discharging to a lower voltage in the last few years but in the passed have found discharging to 3.0V per cell hurts them.

20A would most likely also be enough to produce numbers for comparison.

PFKAOG

iTrader: (12)

2 cell can go down to around 6.4 when cycling and to around 7.4 for storage

John Wallace2

Again I was just experimenting with high charge/discharge rates and trying to document the change in performance. I was charging at 15 amps (the max I can do) and discharging at 30 amps down to 7V (3.5 volts per cell). Initially I saw a big drop in IR (as measured by the Turbo 35), but then saw an overall decline in the battery performance and IR went back up but not as high as it was initially. Just trying to figure out if discharging down to 7.0V too frequently is causing the drop off in performance or what? My buddy is charging at 30 amps and discharging at 30 amp but only to 7.8V after each run.

frozenpod

iTrader: (1)

Depth of discharge does effect cell life. Cycle life vs depth of discharge is not a specification we are provided with for RC cells but the greater the depth of discharge the lower the number of cycles.

Lipo battery manufactures for non RC applications ie portable devices recommend minimum discharge voltage of 3.5V per cell.

Pushing the cell further wont aid performance and may hurt the cell and will certainly reduce life. Discharging 3-5 times to 3.0V over 500 cycles probably wont matter but doing it every run will.

jedi

iTrader: (2)

Just read all 42 pages of this thread and found it very interesting. Just wondering what the difference is between the iCharger 4010duo and the 406duo aside from the ability to charge more cell? For TC use, will the 406duo do just as good a job as the 4010duo? Thanks

John Wallace2

I have the ICharger 306B and I can charge at least 25 amps and discharge at 30+ amps (with a battery as power source). So I'd say the 406 is more than adequate for TC use.

PFKAOG

iTrader: (12)

The 406 has a smaller foot print

slowpoke68

iTrader: (28)

question? does lipo's have a memory when you charge and discharge them at a high rate then later you charge at a lower rate for practice?should i use them the same way all the time?I've seen my ir reading go down on my packs for the first cycle but if i check them on the next cycle(next run on them for same car)they are a little higher.this is a mystery to me lately I've been try to use use them no more then twice in a day.i looking at maybe using bigger plugs 5mm on my new batteries instead of 4mm to see if the is a difference in performance.i have a icharger 4010 and i'm able to charge at higher rates easily but do i need too?this is what i need to figure out.

i race mostly 1 cell and the performance and efficiency of the battery,motor and esc means allot.

jedi

iTrader: (2)

John, are you using a 24 volt power supply to charge 2s batts at 25amps or will a 12 volt power supply do? If not, what is the maximum charge rate using a 12 or 14 volt power supply? Thanks.

DamianW

iTrader: (5)

No memory.

I charge my packs at the same rate every run.

Outlaw 44

iTrader: (17)

All that high charge/discharge rate hoopla is bull**** if you ask me.

Been racing oval for 22 years now. I think I have a decent feel for what actually makes my car go faster, that stuff isn't one of them.

I race in St-Hyacinthe Quebec, TOUR Spec class with the Salvas Brothers every two weeks, 146 foot runline on new CRC carpet. Two Sundays ago I was part of a 5-car field which all finished on the same lap (an average lap is about 3.6 seconds) after a 100-lap race. The race lasted about 6 minutes.

This past Sunday at the New Year's Dash in Oneida NY, Steve Salvas finished 2nd in the TOUR Spec A-main against some of the best drivers in the business, Eric had a 2nd or 3rd place car before getting involved in a wreck. this is just to give you an idea of who these guys I race against are.

I charge between 6 and 8 amps between qualifying and feature rounds, and never discharge between runs. I'll charge at 12 amps during practice just so I can hit the track again faster. There's no point in charging at a higher rate, my battery will just be done charging before my motor gets a chance to cool down from it's last practice run or before I can finish making changes to my chassis.

I've been running the same SMC 7000mah battery for all my practice/heat/main runs since I bought it new in June. I don't see the need for high charge or discharge rates period, I truly believe that the life span you lose in the battery isn't worth the infinately small extra ''punch'' I can't even feel on the track anyways. The battery still feels like it did back when I bought it, I think a less aggressive approach to charging has helped me keep it in good shape.

Before June 2014 I was running a used battery I bought from a fellow racer. When I went to the new battery, I couldn't feel any difference in speed. What helped me is working on the chassis, and managing my tires. Some hints from the Salvas brothers helped me on the chassis setup end of things.

Don't give into the hype.

Miholc

You are obviously not understanding how 4010 charger measures the IR.

IR can only be measured on the 4-wire Kelvin method, you can see more here: https://www.youtube.com/watch?v=N8QhXewcAXY

http://www.allaboutcircuits.com/vol_1/chpt_8/9.html

If you read instructions carefully you will note the charger gives you few different IR readings :-)


Now the answer what causes the IR to change. It is the temperature! Generally - more temperature gives lowe IR, but not all LiPo chemistries have the same behaviour. If you can controll the temperature you can heat up the cells from room temperature up to 110 F you will definately see IR decreasing.

Charging at higher amps heats up the cells, thus IR goes down. You can also cycle the lipos fast in sync mode on 4010... 1S goes nice with 40Amp discharge

Edit: Yes, you need to have also balancing conector setup for 1S to have IR measured correctly. Sorry...

I measured a lot of LiPos lately. No time for report yet :/

So far:
IR winners: LRP 7500 big mama at 40°C only 0.7/0.9 mOhm/cell on the test sample.
Capacity winner of 2S HC pack: LRP 7500, 7200mAh usable from 4.2-> 3.3V/cell @ 200W constant discharge.

Skiddins

Why not get the usable voltage test to stop at 7.5V etc for the pack?
No-one will be running a pack below as low as 6.6V unless they've forgotten to change it from the last run