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  #1  
Old 04-21-2003, 11:59 PM
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Namuna Namuna is offline
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Battery Runtime Tests

I've been wondering for some time exactly what kind of runtimes I could get out of the different car batteries available. So I finally broke out my Peak Charger and went to work.

So, without further blah blah...Here's the details.

Tested:
- Stock Bit Char-G Battery (Nicad, rated at 50mAH)
- Stock ZipZaps Battery (NiMH, rated at 100mAH)
- High Capacity Battery (NiMH, rated at 160mAH)

Test equipment:
- Peak Charger (Dymond 'Super Turbo Charger')
- Modified charge stand

Test procedure:
Charging: The Peak Charger was set to a 1amp (1,000 mA) charge rate and it peak detected the voltage and stopped automatically when 'peak' charge was attained. Since the batteries had been sitting around for some time, I ran them through a few charge/discharge cycles until I got a more consistent result.

Discharging: The Peak Charger was set to draw a constant 200mA (it actually fluctuate between 200 and 210) while it automatically monitored the voltage. When the voltage reached a certain level, the charger automatically turned off.

While testing, each battery was run through several cycles of charging/discharging to get a 'truer' runtime.

Results
Stock Bit Battery: 3 to 4 minutes to 'peak' charge. Then a very consistant 8min 30sec runtime

Stock ZipZaps Battery: Approx 3 1/2 minutes to peak charge. Over 11min runtime

High Capacity Battery: Approx 5 minutes to peak charge. Over 20min runtime

What's it all mean
These are more 'scientific' tests, in a real world situation you'd be charging your car on the stock charger at much higher current and for shorter periods and it would be dependent upon the juice in the batteries you used. Still, the charge times aren't very much different, but the runtimes sure are!

Also, I had my Peak Charger set to discharge at 200mA...Your average motor uses considerably less juice (refer to my Motor Usage Tests in my sig), which means you'll actually get even LONGER runtimes than I posted if you charged for the same amount of time (at the same current)...Since I ain't about to spend hours and hours testing, I used a little bit higher current.

I'm not quite sure how the charger handled the voltage. It requires a minimum 12v input (the Power Supply I use feeds it 13.8v) and if I understand the workings correctly...It just pumps it all out to the battery being charged, but the battery only accepts as much as it needs. The Charger then monitors the pack voltage and shuts off accordingly. If this is true, then I've been overly cautious about using higher voltage.

I've got pics, but the gallery is still wacky (from the Server crash not too long ago). Once it's back up, I'll post more pics.
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  #2  
Old 04-22-2003, 12:58 AM
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cool beans...

is there a way to test the amperage i.e. the touque (corect me if i am wrong) , i have heard that the nicd's give a little more juice or am i just plain confused
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  #3  
Old 04-22-2003, 06:32 AM
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Very interesting stuff. It definitely raises some debate as to how long we should be charging our batteries. From the formula you listed in another thread, the 160 mAH battery should have taken about 11 1/2 minutes to charge, where it actually took only 5 minutes. This is assuming that I understood the formula correctly. The 110 mAH battery should have taken a little over 7 minutes to charge, but really only took 3 1/2 minutes. The 50 mAH battery was right on with the formula.

So the question is why the discrepancies showed up. Could voltage have something to do with it? Should we not be adding in that 20% fudge factor, as the batteries are more consistent than expected? Does the very high 1000 mAH charge rate, which is far more than double the rating on the battery, induce another timing variable? Or do NiMH batteries do something entirely more unpredictable than Nicad?

It almost looks like the difference between theoretical charge time and actual charge time is logarithmic.......

Thank you for performing the experiment. Very interesting stuff.
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  #4  
Old 04-22-2003, 11:14 AM
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vtheo,
The limiting factor on amperage is the PCB. It doesn't really matter how much a battery can put out, the PCB will put restrictions on it. If you refer to my Motor Tests (in my sig) I tested this to some extent.

Buzzbait,
I attribute the discrepencies to how my Peak Charger works. It monitors the voltage and stops charge/discharge based on 'Delta Peak'. But at the 1A charge rate (which is VERY aggressive) it's kind of like baking a cake at 1,000_°. The Charger sees the outside is golden brown and stops, but the insides are still a little uncooked.

Using the calculations and manually charging would result in a more thoroughly charged battery...At the cost of shortened lifespan (unless you actually charge at the recommended rate, which is something wacky like 16mA for 16hours for the 160mAH battery)
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  #5  
Old 04-22-2003, 01:27 PM
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You should try a dual cell car with two 200mah NiMH batteries. Over an hour runtime?
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  #6  
Old 04-22-2003, 02:03 PM
bluemax_1 bluemax_1 is offline
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Hey Namuna, what peak charger do you have, and what's it's charge range/capacity? Also, how much did it cost? I've got a decent charger but only for larger cell packs. It's the Intellipeak Digital Pulse charger and it only charges 4-8 cell packs, with variable rate from 0.5 - 7.0 Amps. The discharge function is so high it can't be used for anything smaller than sub-C cells. (2.0 or 10.0 A selectable)

Was wondering what charger you have that can charge single 1/3AAA cells and set a discharge rate as low as 200mA, and what charge method does it use? Mine uses -ve delta V for NiCad and 0 delta V for NiMH batts.

*edit* Whoops, just noticed that you state that it's a Dymond Super Turbo Charger. Still curious about the available range in charge/discharge rates and how much you got it for though.

Last edited by bluemax_1; 04-22-2003 at 02:06 PM.
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  #7  
Old 04-22-2003, 02:51 PM
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Namuna Namuna is offline
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Here's the specs page for the Charger.
http://www.rc-dymond.com/Chargers/20156SuperSmart.htm

When I got it, months ago, I paid $109...But the price has come down to $99.

And for the regulated Power Supply, I use a Pyramid PS-15KX (13.8v @ 10Amps)
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  #8  
Old 09-12-2003, 02:39 AM
oldtamiyaphile oldtamiyaphile is offline
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Sorry Namara, but your testing is totally inaccurate.

The fast charge current for these cells is C3 or 150ma for a 50mah cell.

You should NEVER exceed 300mah. At 1 amp (!) the cells cook themselves. Because they get so hot, voltage drops and the peak charger senses this voltage drop and 'thinks' they're full, when in fact they have less than 50% of their capacity.

You realise that a 100% full 50mah cell, drained at 200mah will give you 15mins, don't you?

So your cell was half full.

The 160mah cell should last for 48 mins.

Again, your cell was less than half full.

I get well over one hour of runtime from a stock ZZ with a real peak charge.
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  #9  
Old 09-16-2003, 05:08 PM
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Well, if the batts can take more voltage and just use what it needs? Hey namuna, can you do the same test with the same batts to see if they handle higher voltages the same way?

oldtamiyaphile, you seem like "a cell is half full" kinda guy.
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  #10  
Old 09-16-2003, 06:04 PM
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ty namuna and oldtamiyaphile for taking the time to share.
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  #11  
Old 09-16-2003, 07:33 PM
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Thanks for your input OTP...

But now I'll have to disagree with a few of your comments.

"Sorry Namara, but your testing is totally inaccurate. The fast charge current for these cells is C3 or 150ma for a 50mah cell. You should NEVER exceed 300mah. At 1 amp (!) the cells cook themselves."

Okay, then explain why a standard Bit Charger puts out the FULL Amperage of the AA batts in the charger? At a measured range of 2.2 to 2.5A (for Alkalines) that puts it at 'fast charge current' of about C50. If Tomy thinks C50 is okay (even for a short charge), I'd say my C20 is rather conservative compared to that.

You'll also notice in my post that I said I used a higher current because I wasn't in the mood to sit there for HOURS AND HOURS for testing purposes...I tested mutliple times, until I got CONSISTENT results (True peak or False peak, consistent results is consistent results).

"I get well over one hour of runtime from a stock ZZ with a real peak charge."

That's cool, I myself get bored after 10-15 minutes.
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  #12  
Old 09-17-2003, 02:24 AM
oldtamiyaphile oldtamiyaphile is offline
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Yeah, I don't normally run my car for an hour either, just for run time tests...

2.2amps huh?

Let's do the math.

50mah cell charged @ 2200 - 50/2200*60 (to get minutes) = 1.36

The cell would be 100% full in about one and a half minutes.

We all know that's not the case at all. My controllers are modded with 6-10x charge caps, and they still give me less than a full charge (I don't want to drive for longer than a 10x charge anyway).

Tell who ever 'measured' that charge current they need a new meter, or learn how to use it :lol:

It's been ages since I measured charge current, but I think I got 300ma.

in a real world situation you'd be charging your car on the stock charger at much higher current and for shorter periods

You sure about that?

Your results might be consistent, but they aren't really measuring runtime are they?

They're measuring the cells pain threshold, which is why the quality cells (Tomy and the 150mah) recorded simular results per mah, while the cheaper ZZ cell didn't fair as well. Cheap cells are less tollerant of overcharging. Charged in your manner, the cells will be lucky to see 100 charges, instead of 500+
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  #13  
Old 09-17-2003, 09:37 AM
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Alright, what are we talking about here?

When I say I tested using a charge rate of 1A, my results were based on such...I concede that I should be clearer that charging at 1A on such small capacity batteries isn't going to produce the maximum capacity because it's aggressive, but as I said I didn't feel like sitting around for HOURS to test several batteries.

"Tell who ever 'measured' that charge current they need a new meter, or learn how to use it :lol:"

Here's a thought, how about along with your snide remarks, perhaps you also include the PROPER way to test?

I was the one who measured the charge current. My method was to put my DMM leads on the charge prongs (to close the circuit) and read the output from there. My belief for testing the output from there is that if there was any current filtering from the PCB (in the TX) then testing at the charge prongs (with no load) should show the proper current that was being pushed to the car battery. I considered putting the car on the charger first, then reading the output but I thought the output of the battery would interfere with the reading.

Obviously your 300mA findings are in contradiction. I'd like to know your 'proper' way to test then.

"Your results might be consistent, but they aren't really measuring runtime are they? They're measuring the cells pain threshold..."

Actually, I'd say my test did BOTH. As I've said I didn't feel like sitting there forever waiting for the full/proper charge, so my C20 charge rate shows what these batteries are capable of (as far as 'pain threshold') and what you can expect to see as far as runtime because of it.

I've always had respect for what you've had to say OTP (still do), but I'd appreciate that if you're going to take the stance of 'knocking me down' or belittling my findings, that you at least do so AND give the PROPER info (or share your own findings). The work that I've put in, in hopes of bettering the hobby, has been to HELP people, not to make myself look like an omniscient guru...So I've got no problem with taking criticism if my work needs fixing, but if all you've got is criticism (and little to no info on how to do it right) than I'd rather you didn't respond at all.
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Old 09-17-2003, 11:04 AM
oldtamiyaphile oldtamiyaphile is offline
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Ok, then you don't know how to use a mulitmeter.

Snide? Saying that when it's true is a truth statement and not an attack...

What you did was just short-circuit the charger. You're lucky you weren't using Ni-Cad/Mh because you would have gotten 100amps, smoke, burnt fingers, a melted controller and possibly a fire.

Think about this, if the Tomy controller put out the full current of the AA's, what happens if you use Ni-Cads that put out 100amps?

The only way to measure current across a circuit is to break the circuit and measure across the open terminals.

In this case, lift one side of the car off the charger and connect the meter across the (now open) terminals. Should read around 300ma.

This sort of stuff is second nature to me, I assumed I'm not the only one here who knows how to use a DMM, but...you've clearly held this belief for some time and never been set straight.

But if you just looked at the maths I provided, you'd know that a 2.2a charge current is just not possible, you don't need to measure it to know that. Therefore I knew that the 2.2a figure was flawed, because I've measured it and the maths proves it's impossible.

Electronics begins with maths.

I considered putting the car on the charger first, then reading the output but I thought the output of the battery would interfere with the reading.

This is heading off topic into general electronics theory, but, 'electricity takes the path of least resistance'. Since the multimeter is a short circuit (0 resistance), you can put whatever else you want across the circuit and it's won't affect the reading. However, in this case, (assuming you already have some charge in the Ni-Cad)you'd be shorting out a Ni-Cad and would have gotten a much higher reading (and the fire as you may remember )

Actually, I'd say my test did BOTH.

I'll give you that, though the pain threshold is purely by accident. I still feel that it's not a 'runtime test' if the batteries are only 50% full.

I too reply here only in the interests of furthering the hobby. As you know I don't come here much, but there were too many points that needed addressing, and stood unrefuted/unquestioned/undebated for four months.

If people think these cells should be charged at 1a+ then it's to the detriment of the hobby, particularly since the same cells are used in Epochs and Yokomos where replacing them every 100 charges or less, isn't quite so cheap.

Moreover, in an Epoch (and Yoko) where a peak charge (real) gets 22mins, it's worth charging slower and getting the longer run time.

Mainly, I wanted people to know:

Not to charge above 300mah
These results are for cells only about 50% full, much less in the case of the ZZ cell.
Fully charging (not overcooking) a cell is actually good for it.

And if I've taught you to use a DMM, that's a bonus
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Last edited by oldtamiyaphile; 09-17-2003 at 11:18 AM.
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Old 09-17-2003, 11:33 AM
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Okay, now THAT'S helpful stuff.

As to why I accused you of being snide...

Snide:
adj: expressive of contempt.

The comment "Tell who ever 'measured' that charge current they need a new meter, or learn how to use it :lol:"

Then "Snide? Saying that when it's true is a truth statement and not an attack..."

Truth Statement would've been something like: "Those meter readings are inaccurate"...Adding the extra pieces of 'needs a new meter or needs to learn how to use it' with the 'lol' part makes me think 'snide'.

Etiquette aside, I appreciate you taking the time to add some solid info (yeah yeah yeah about the DMM )
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