There seems to be quite a variance in battery label numbers from different battery matchers and there's really only one way to check your on track battery performance.
First it doesn't matter what your discharging with all your going to do is to form a base line to compare your packs.
A GFX , Integy16x7, 16x8 , Tekin or anything that will discharge at a constant rate of 30 or 35 amps will work fine . "15 - 1157 bulbs "
Charge your pack up as you would normally do on race day and discharge it checking the voltage every 60 sec to the 300 sec mark.

Example ------- 5 sec 5.39 volts
60 4.99
120 4.95
180 4.90
240 4.83
300 4.75

These are all at 30amps on a GFX , the average discharge voltage for this pack in a 5 min run [300 sec] was 1.242 volts per cell , which really is the only thing that matters, forget that your pack has 485 sec of run time, on track voltage is key!

Remember this is just a reference and you really can't compare between different dischargers , even the same model , as none of these mentioned are laboratory grade units and do fluctuate.

I've spent alot of time playing with batteries are don't claim to be an expert on this , but if you label your packs this way I think you'll find the better performing ones.

Hope this helps :thumbsup: :wave:

Well... not really. How do you know your motor is only going to use 300 sec off of your pack? A mod motor can easily drain a 3800 pack in 5 minutes. In oval racing even stock motors can average over 30 amp draw rates.

While I agree that everyone should use their own discharge & record keeping method, using a cutoff of 300 seconds is really not sound advice.

As I mentioned the first time , the discharge rates are up to you and you probably have to adjust the perameters for your type of racing.
WELL--- Most racers will find this beneficial.

Best bet would be to discharge to the batteries "useful" voltage limit. I've found that a pack generally becomes used up on the track when the voltage falls 1 volt per cell. At that below that point the pack loses it's punch and doesn't have enough voltage to carry much speed.

A foam sedan with a STOCK motor can draw over 50 amps if you hit a board or get stuck....modifieds can drain over 100 amps in the same situation....

So, say you nail a board and romp the throttle.....and kill 10 seconds of runtime in less than a second....now you are farther down into the curve.

Besides, 300 seconds is not very accurate, as rarely do we finish in exactly 5 minutes....

To accurately test a pack, you should discharge down to .90 per cell and take your readings from that....

It's all relative though....a good pack s a good pack....

Later EddieO

battery voltage # are almost useless anyway just buy packs from a good matcher and go racing can't remember when i have had a bad pack anyway to much emphasis is put on batteries motor etc chassis and driver is what wins races anyway

Well put GILYHANTREE!!!!

Just shows no matter how much you try and help other racers they don't really want any help and just p + m when they get beat. oh well : :(

battery voltage # are almost useless anyway just buy packs from a good matcher and go racing can't remember when i have had a bad pack anyway to much emphasis is put on batteries motor etc chassis and driver is what wins races anyway

I am with on on that. I do belive you need a good motor though. I ran last year with sub-par batts. at the end of the off-road season, and I still finshed in the top three every week.

My .02 cents.

Jerry

Every 30 sec's is probably a little more accurate as most popular dischargers check every 5 sec's. 11 #'s vs. only 6

Some manufacture's are building av. voltage cutoff adjustible points into their next model so this will all be figured for you in the near future.

Unless you race in the top level classes at your track this is probably unnessesary information !-------unless you enjoy electrical knowledge as a hobby. :wave:

Just shows no matter how much you try and help other racers they don't really want any help and just p + m when they get beat. oh well : :(

I appreciate your program that you started this thread with. I've been in R/C for over 25 years, planes and cars, and if there is one subject that will stir up conversation/controversy it's battery maintenance!

The old cliche' - 10 different questions = 10 different answers applies here more than any subject I can think of.

So, here is my summation - a consistent battery maintenance program (BMP) is what is important. So you have baseline information to compare the battery packs you have. If you change your BMP all your numbers will change.

regards,
Scott

a wise man once said VOLTAGE plus Motor equals WINS ............From the Funniest RC racer ever .... Steve "Sean Combs" Fuime.


ROCKET

My two cents... You should NEVER compare battery numbers from one matcher to another... not voltage, not run time, not nothing... Same is true for comparing your numbers from a GFX, etc... to someone elses...

Heck I'm not even totaly sure comparing your own numbers is of too much value, unless you really know what your doing... and understand how there are MANY variables that can make your numbers go up or down and/or be unreliable...

Basicly... I think the best advice is... find a matcher you trust and/or have had good results with previously... buy the best you can afford from that matcher... and well... Do your best to maintain your packs and maybe learn as much as you can while doing it...

If your car isn't setup well... Voltage nor motor will do you any good. Most average drivers would do better working on their chassis and/or driving then buying the most expenesive highest voltage cells and motors.

[QUOTE=If your car isn't setup well... Voltage nor motor will do you any good. Most average drivers would do better working on their chassis and/or driving then buying the most expenesive highest voltage cells and motors.[/QUOTE]

Well said!

DYNOMOHUM best post on here ......

ROCKET

Yes dynomohum is correct , but its always good to have your own battery stats just to monitor your packs.
You can't compare battery numbers no more than motor numbers these days.

I've got one battery co. I've done business with for a few years and quality of product and customer service is top notch , ---so for the most part thats all the thought thats needed, take their advise on all maintainance !

When you do test your packs keep good notes and make sure you duplicate every step the same , batt cold temp , ect.
I even solder all connections to make sure the perameters are the same.
Only check your batteries every 15-20 cycles , more often is just using them up.
GOOD LUCK , GO RACE , HAVE FUN, DON'T SPEND MUCH TIME THINKING ABOUT THIS :wave:

I can say I rely on good numbers. At my local track we do 150 lap mains with stock 4 cell sk cars. equal to 9 mins or more. Last week we did 175 laps which was a little over 10 mins of race time. Thats a true test of your "numbers" on the pack. I can safely say I depend on my matcher and has come through many many times. I did 175 laps on a pack that was IB 3800 1.185 435run time at 35amps about 8 secs of runtime left after race. 8 amp motor at 2 volts on turbo 35. Buy the best you can, there is too much of a battery war that you cant keep up with unless you have LOTS of money. Same thing with motors-do your own or have someone at your local track do it every 6 or 7 races.
Ken K

Todays 3800 matched packs are all outstanding compared to even to what was available a year ago !
BUY FROM A TOP, HIGHLY EXPERIENCED MATCHER AND YOU'LL HAVE NO PROBLEMS.

I won't put all the numbers out here , but checking your batterys every 30 sec's , starting with 5 sec on a GFX at 35 amps to 300 sec most of my packs average out to 1.217-1.218 volts.

Rodney S.

The voltage curve is about the same with 4200's , just slightly!! longer.
Don't run out and buy them just for a bigger battery MAH number. :thumbsup:

I won't put all the numbers out here , but checking your batterys every 30 sec's , starting with 5 sec on a GFX at 35 amps to 300 sec most of my packs average out to 1.217-1.218 volts.

Rodney S.

Rodney,
Are you just adding the volts at 5 -30 - 60- 90- 120- 150- 180- 210- 240- 270- 300 seconds and then dividing by 11 ?
Then taking that average and dividing by 4 to give the volts per cell.

If I add up my values at those marks and divide by 11 = 4.912727
then divide that by 4 = 1.228 per cell

The voltage curve is about the same with 4200's , just slightly!! longer.
Don't run out and buy them just for a bigger battery MAH number. :thumbsup:

Have you cycled 4200's if so can you email me your results on the curve?
eric.hutkay@beldenblake.com

thanks
EH

Not that it matters much for me because I run 8 minutes and can dump pretty easily but there is some merit to using a time cutoff for oval racing.

Step one is to determine the average current used on the track for your class. It's not the best but it's a start.

Then discharge to about the discharge time you would run on the track and take voltage numbers as above.

Average to find the best voltage pack for racing.

This is the only way to compare packs that don't have the same runtime and would be the only time that I would do it.

I noticed with my latest IB's I got this week that they have the same overall pack voltage so I thought hmm no real differences between my old and new packs.
B
ut if you look at voltage after 120 seconds, they are about 2-4 points higher through the end of the curve. Should really finish strong compared to earlier batches.

And I agree with Fred B
If you have a pack of 380, 4.82 and a pack of 410, 4.80 which is better for stock or 19T racing, you wouldnt know unless you analyzed the curve. More than likely they would be about the same on the track.

erock1331 ,

Thats some very stought packs you have as our highest av. dis voltage for 300 sec is 1.220 volts per cell.
Whats your cell labels say ??? I've got some 1.209 35a packs which are almongest my worst I've ever bought.

I've only checked a few 4200's and the 300 sec curve is pretty much identical at 35 amps but the overall run time is longer , 6-7 minutes plus maybe 20-30 sec's.

Most good 3800's will ''discharge'' at 35 amps to over 4000 mah's , plenty !!!

I've seen the new vs. older pack results also and the 3800's taken care of properly are VERY tough and will last a long time.
Your talking a few hundreds of a volt difference.

erock1331 ,
Whats your cell labels say ???

411, 1.208, 1.8 @35

I would agree with the fact that you really need to have some baseline with which to compare your batteries. I find it really useful to determine which packs are my best and which are my worst. They can sometimes differ by 30 seconds or more! In the graph I have attached, you can see that at 300 seconds, the best and worst differ by about 2 tenths of a volt!

just my $0.02
Chuck

Thanks Chuck ,

2 tenths of a volt is huge when it comes to battery voltage !

And thats at 300 sec , not the full run out of the pack.

Rodney S.

What are some good numbers for 4-cell 4200 packs at 240 sec. discharging at 30 amps? Thanks

At 30;should be 5.02-5.05 @ 240 sec.

Dang, most of mine are in the 4.85-4.90 range?

What are the label #'s? The formula used by battery matchers is add .015 to the 35 amp # to get a 30 amp #.Ex: 1.237's@35 would be 1.252's @ 30 x's 4 should be 5.008,and 99% of the time with the RT loss the voltage will increase.I looked at my sheets from the past and 99% of mine were 5.02 or better,and i was never privy to the super,laid back for Mr.super pro racer packs.Use either the SMC or the TQ website for info on proper care,and the SMC site has the conversion info.

DK, the voltage is nice but without runtime it is a little misleading. what was the total runtime of your 5.02 - 5.05 packs??

DK, the voltage is nice but without runtime it is a little misleading. what was the total runtime of your 5.02 - 5.05 packs??

He wasn't saying 5.02 to 5.05 overall, but rather at 240 seconds with a 30A discharge.

He wasn't saying 5.02 to 5.05 overall, but rather at 240 seconds with a 30A discharge.


I realize that but if they were 5.04 @ 240 seconds with a total runtime of 500 seconds they are awesome. If they were only 410's thats another story.

Only if you're racing mod, otherwise what difference does it make? Lets say you're racing 13.5 and your motor is drawing 30A (which is about what they do). At 240s into the run the motor is getting 5.04V whether the pack is a 410 or 500 just determines how long you have to watch it discharge after the race.

Clearly, you speak for DK, thank you for your input.

I don't even know him, but whatever.

I think we were discussing voltage,but at the time mine were 480-90's @ 30.And too,we all know it is a matter of our cycle program,how it is set up.For an apples to apples,we should be as close to the tmatcher program as possible.99% of the time we'll be 30-40 secs. off the labels,but the 42's seem to be close on label voltage #'s.Just mho,and it won't pertain to anyone else.

Thank you DK

Only if you're racing mod, otherwise what difference does it make? Lets say you're racing 13.5 and your motor is drawing 30A (which is about what they do). At 240s into the run the motor is getting 5.04V whether the pack is a 410 or 500 just determines how long you have to watch it discharge after the race.


I would have to agree with that 100%

I was using 'real battery numbers' years ago, and never understood using an 'average voltage' beyond what I was using...

ie: STOCK, if you pulled like mentioned above, 30 amps for 240+ (I always add ONE extra lap to my estimated time) seconds...I didn't care if my pack DUMPED Completly 15 seconds later or 1 minute later...cause I wasn't going to BE THERE.

MOD racing is/has been different, because w/ MOD instead of figuring out WHAT Voltage I had for 240 seconds... I would adjust the AMP draw until the battery DIED in 240+ seconds...then test for voltage at THAT amperage.

Since we now do 5 min. (300 second) races, I've adjusted the times and numbers to do that...

I would have to agree with that 100%

I was using 'real battery numbers' years ago, and never understood using an 'average voltage' beyond what I was using...

ie: STOCK, if you pulled like mentioned above, 30 amps for 240+ (I always add ONE extra lap to my estimated time) seconds...I didn't care if my pack DUMPED Completly 15 seconds later or 1 minute later...cause I wasn't going to BE THERE.

MOD racing is/has been different, because w/ MOD instead of figuring out WHAT Voltage I had for 240 seconds... I would adjust the AMP draw until the battery DIED in 240+ seconds...then test for voltage at THAT amperage.

Since we now do 5 min. (300 second) races, I've adjusted the times and numbers to do that...

Thats the exact reason this thread was started , there has to be a more
accurate system than what we're recieving now.
Todays labels tell you nothing about the average in a 4 or 5 min race .

Somebody needs to develope this and at the same time get rid of the arkaic
.9 , that number needs to be at least 1.0 or higher.

I personnally cut off my 4 cell testing at 4.5 volts , forget the runtime.

Seems like most understand this reasoning :thumbsup:

Somebody needs to develope this and at the same time get rid of the arkaic
.9 , that number needs to be at least 1.0 or higher.
:thumbsup:

Have you looked at a TQCELLS pack lately...Cutoff is 1 volt.

As much as I havn't used many of their cells , I applaud them for making the
voltage cut off more realistic :thumbsup:

Now just print the average voltage for 4 min and 5 min

Have you looked at a TQCELLS pack lately...Cutoff is 1 volt.

For comparison sake , it does make a 1 volt cell show slightly better voltage,

so shop apples for apples.

Hopefully others will follow suit shortly

For test purposes ,,,, I've been setting my disc voltage cut-off at
4.8 for 4 cell and 6.0 for 5 cell.

Any decent pack will go for 345 + sec's @ 35 amps before it hits this point.

You can equalize how ever you want from there.

All your doing to go below those cut-off points is create alot of excess heat

ENJOY THE RACES :wave: