ic-racer

Just got an iCharger to enable better LiPo battery management for competitive carpet blinky stock racing.

Put my existing 2 cell batteries on the charger and after full charge they read 8.35 with my voltmeter instead of 8.4. Is there some trick to setting the charge greater than 4.2/cell or are my batteries just shot.

BTW internal resistance reads around 20 milliohms per pack, so I suspect the packs are shot.

I'm asking here because searching for 'low voltage lipo' brings bring up only threads and info on over-discharged cells and not low voltage after full charge.

So my packs only charge to 8.35 and have high internal resistance. Any way to cycle them for improvement or should I get new packs for racing. Thanks in advance.

Also, for 17.5 Blinky rubber tire carpet Touring racing car how do you manage batteries for the rounds of qualifying and mains? Single battery and top it up between rounds? How many amps 1C or 2C or higher? Or do you use multiple charged batteries?

Odin544

iTrader: (93)

Which Icharger did you get?

Try looking here first. http://www.rctech.net/forum/radio-el...r-308-duo.html

You need to go in and adjust the end voltage. It may say 4.2 volts per cell on the charger but if it is coming off at 4.0 or 4.1 per cell then bump it up .1 or .2 volts per cell until it actually comes off at 4.2 per cell. But keep in mind that every volt meter will read slightly different. Some read a little high some read a little low. If I adjust mine, I use the volt meter at the track that they will be doing the tech inspection with.

I usually charge about 12 amps. Approximately 2c. I've gone as high as 20amps when I was short on time but I don't see any need to go that high on a regular basis. I run ORCA batteries so I feel plenty comfortable charging at 2-3c. I wouldn't do it with really cheap batteries.

I usually only have one lipo per car. And I just charge it between rounds.

vivo quevas

iTrader: (19)

You have to set the end voltage on your iCharger to get the charge voltage to 8.40v. Chances are the batteries are good. The charger needs you to program it.

ic-racer

I got the new 406 Duo. Looked to do almost all the important things the 4010 does but it is in a smaller package. I'm using a 45A/12V (540W) re-purposed computer power supply.

So, in our bigger races at the track we had battery 'tech' and they always told me I'm 'way under voltage' compared to the other racers.

I'll look through the manual and figure it out how to ramp up the target voltage so it is 8.4 after it comes off the charger. BTW, the manual is like an operating manual for a plane. It shows you what all the buttons do, but it does not tell you how to fly. So, even after reading the manual, I'm still a little in the dark about the proper way to prepare and manage a battery for stock racing.

Again thanks for the replies.

CraigMBA

iTrader: (22)

Not with a measured 20 Milliohms. They probably work fine, but good ones are like 4 or less.

A warning:

IF you adjust your charger endpoint (I think you should) and WHEN you get new batteries they will be over voltage for tech. At the TCS finals, I adjusted my charger so my 6 miliohm batteries and another racers 10 miliohm batteries came in at 8.41 (8.42 limit). Another racer gave me a battery to charge for him (about 4 miliohms, his charger cut him off at 8.29!) and when he went to tech it was 8.45. I fiixed it by charging it and then discharging it 50mha, was fine for the rest of the weekend.

Just be aware. And fast guys use one battery all the time.

avs

iTrader: (2)

initially with the icharger I also got low voltage and high IR readings. this was due to the charge leads. are you using a balance wire separate from the power leads?
with 1s I figured it couldn't matter too much, but I found the battery would charge in less time, report lower IRs and have much closer finishing voltage.

with 2s it could also be a safety issue with cells too much out of balance.

in the past I was juggling multiple batteries for a car when my charger max'ed at 5amps. now charging at 20amps(just shy of 3C with 7000's) and its pretty quick 15minutes or so.

John Wallace2

On the ICharger my packs are around 4 IR. If you cycle them at a discharge rate of 20 or 30 amps down to ~3.8V per cell that may help with the IR (at least that worked on some of my packs). Don't do this often as you will loose run time.

Still new to the ICharger but mine is set to 4.2 volts per cell and I find that the higher the charge rate the lower the terminal voltage I end up with (i.e., after the charger shuts off). It almost looks like it's over charging the battery. Am I doing something wrong? Many people are charging at 20 and 30 amps; so far I don't see it with the terminal voltages I'm seeing, but I haven't plotted the discharge curves to see if there are differences with the charge rate.

CraigMBA

iTrader: (22)

Its because you have good batteries.

You can lower the voltage cutoff.

slotracer577

You can also calibrate the charger to your tracks meter so the voltage on the charger is the same. then adjust your end voltage cut off to get the voltage you want when the pack is sitting.

1101

Just a thought.
Is .05v of a volt really going to make that much differnece ?
When were ANY of these meters last tested and calibrated
Do you really expect .3% accuracy , at all temps ? with cheap non lab-spec chargers ?

ic-racer

Now that I have had a chance to work the iCharger and read up more I found that I have one reasonably good battery with low internal resistance (5mohm/cell) and it does come right up to near 8.4 with the 'standard' 4.2/cell rate. I also just got an Aero-Model 90c 7600mA pack but I have not had it in a car or on the charger yet.

It seems the charge target voltage can only be set in increments of 10mV and the discharge can only be set in increments of 100mV, so getting a 'perfect' 8.4000 charge is challenging and probably not worth the effort.

avs

iTrader: (2)

the icharger's have an adjustable 'charge end current'. the default is 10% which means that with the higher charge rates the charge will stop sooner, no matter what condition the battery is in, although I suppose a higher IR will make it worse.

has anyone tried reduced this parameter to 1%. I would think the charge session would take a little longer, but hit closer to the voltage target?

CraigMBA

iTrader: (22)

Yes, but it's situation specific.

I was racing 1s carpet oval several years ago. My ICE charger stopped at 4.18v, and my car was off the pace (like .3 a lap). The fix was my buddy "re peaked" it on his Turbo35 to 4.21 and I went from being like in the B to TQ in one round with no other changes.

So, it's important if you are running single cell because the voltage is so low. If you are running two cell it's less so, but if you are charging to 8.28 and everybody else is going to 8.42 you are leaving some on the table for the first couple of laps.

The only calibration that matters is if you get DQd at the tech table.

John Wallace2

I assume your comment is in reference to my post? If so, what final cutoff voltage do you suggest for good batteries? As I said for my race packs, my ICharger IR is 4 for 2 cell packs.

CraigMBA

iTrader: (22)

Whatever it takes to get to legal voltage at your track without getting dq'ed. My Batteries need a 4.25v cutoff to get 8.42 at the tech table. That same cutoff makes a "good" battery 8.46 on the same tech table fluke meter.

Voltmeter in the charger reads 8.42 both times.

You'll just have to try it. Before I changed it, my batteries were at 8.35.