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knightrider
2010.12.28, 12:33 PM
I'm working with the Powerex MH-C9000 charger so I don't know the IR and Amps, the display only shows V and mah. My 750's are in the 625 range and my 900 are iun the 697 range.

does that sound correct? I recorded these values after executing the 'refresh and analyze' mode. Maybe I should try using the 'cycle' mode with three repetitions? Thanks

EMU
2010.12.28, 12:39 PM
Which 900 cells do you have?

knightrider
2010.12.28, 01:02 PM
Peak 900's and R1 Wurks 750's

rensuchan
2010.12.28, 01:40 PM
With two new packs of R1works 990's (900 mAh rated) I got results from 760-830 with all of them, so the 900's seem to be a little bit low. I don't own any 750 mAh rated batteries so I can't really speak for those.

Felix2010
2010.12.28, 05:46 PM
Hold old are your cells? How high are you charging@ (Amps)?

If your cells are new = Good. If they are older than 1 year = Maybe they are no good....

EMU, did you say in one of your posts you mention the MAHA chargers' limitations - The Zero-Delta Peak thing? How the MAHA chargers only charge to about 90% capacity or something thereabouts? I much prefer an adjustable Delta-Peak charger (ICE, MuchMore, etc.) So that you can be sure you maximize the 4 cell's voltage + capacity.

Oh, and about charging on the MAHA, one more thing: If you charge at over 1C (1xcells rated capacity), you will usually lessen the capacity of your cells. For example, charging Peak/Orion 900's @.9Amp (Around 1C) the the end-charging capacity usually will be higher than if you charged them say @1.8-2.0Amps (Around 2C).

doug01n
2010.12.28, 06:34 PM
Felix, charging above 1C will short the battery life, and no matter what charge you use, it will make it charge less mAh than charging @ 1C or less.

I just finished analizing my 7 packs, and I'll put the result here.. Some of the packs have 6 months to 1 year use, others have only a few weeks (no more than 3 cycles). All of them are R1 wurks cells:

Refresh & Analyse (charge 1A and discharge 1A):
R1wurks 990:
Pack 1:
791
767
693
690

Pack 2
652
620
616
597

Pack 3
591
585
582
578

Pack 4
565
531
531
528

R1 750 (charge 0,7A and discharge 0,5A)

709
650
648
629

615
594
563
553

545
535
531
525

I think this values are ok, but I'll try to mensure the capacity with another method: using PN discharger tray to equalize the cells for more than 6 hours, than charge it on Maha at 0,5C. I think I'll get higher numbers and more consistent results.

Anyway, I just group my batteries as I put above, and I'll try them tomorrow at our track. Than I'll tell you the results.

EMU
2010.12.28, 06:48 PM
Felix;
Yes, the Maha does not charge up to full capacity when it says done. They are roughly 90% charged, and then the charger switches to a trickle to top them off. When cycling in the maha, or doing the test function that charges, discharges and charges again, there is a 1h rest stage where I expect the charger to trickle the cells to top it off before the discharge function.

When I test, I typically charge the cells normally. Let them trickle for 10 minutes or so (same as I would when racing). Then I run the discharge function and see what the numbers are. I dont really use the analyze function, as it takes a little too long to test. one set of cells, and if I have 20 sets of cells to test, it can take a long time. A lot of times, I charge in other chargers, and only run the discharge function in the maha when testing cells.

Also, I seem to get lower numbers on my Maha than I did on my Lacrosse BC-900 with the same discharge rate. I tend to think that they terminate discharge at a higher voltage, or their method of calculating the capacity of the discharge may be slightly different. I got similar discharge on my Pulsar2 as I got with the Lacrosse. Which seemed about 50-100mah higher than the Maha gives me.

Felix2010
2010.12.28, 08:15 PM
I was just thinking (And ouch did it hurt!lol... Seriously though man! ---

What a bummer it is to find out that MAHA chargers end the charge cycle @90% of cells' actual capacity(I own the Wizard One 4-cell MAHA charger/analyzer). This sucks!
How many guys have done a full-charge (Not just a re-peak) of their cells right before a race, thinking they would have max voltage+capacity when the unit ended the charge cycle? Those guys might've only had around 90% of their batteries' capacity to run with and they wouldn't even know it...:eek:

I am not too keen on this.

Even though the Maha Wizard One MHC-9000 is a great unit for the $$$, having Completely-Individual cell charging&analyzing with spec data(And this is the #1 advantage of this charger unit) - Right Now, I am almost exclusively charging with my MuchMore CellMaster SP Edition RC charger. With the Muchmore I have to charge my cells in-line, which lessens accuracy of being completely-balanced charging of all 4 cells, but being able to manually set the Delta-Peak cut-off is so important to getting the utmost performance from our AAA NimH cells, IMHO.;) The fact that many of the Hobby-grade 1/10th-scale-type chargers offer Internal Resistance measurement of the pack being charged; Adjustable charging methods to suit your wants&needs (Linear charging, Pulse charging, or a combination;+Other methods); The use of a battery charging tray (A good one like PN's or the old-time fave Atomic Linear rack) can also have advantages over the MAHA's all-in-one plastic construction.
When charging 4 cells in series You have to check individual cell voltage via a voltmeter/multimeter before and after each charge/discharge; Even still the benefits of the "Gold Standard" 1/10th RC chargers, with ever advancing software, for example - Models such as the Cell Master Ultimate, the TC 1030, Eagle Racing CDC7.0, etc. - These chargers offer the best charge I think.

Just look at the races: Most guys I see use a combination of both a 1/10th scale-type hobby-grade RC charger, plus either a Lacrosse or MAHA Wizard One in order to get their cells the best they can be for racing:D For racing, I can't see a better option than the Tried-And-True "old-type" chargers usually used for Larger 1/10th and 1/12th scales.

BTW- I think the PN chargers are a great value! Need to try one of those... I only wish the Max.Discharge Amp rate was higher than 1A....

Mike Keely
2010.12.28, 08:45 PM
I have been looking into matching my cells but I want to match them by IR and average voltage. Not worried about the capacity of the cells. What are your thoughts on this. I know that I could get cells with 20-45 seconds difference in run time but if you matched 4 cells that had low IR and high voltage it should be a killer pack.

doug01n
2010.12.28, 09:30 PM
Does the voltage drops proportionally to the capacity? I mean... supose you have 4 battery packs with 1.5V each one fully charged, with 25mohms of IR, but 3 of them accumulated 750mAh, and one only 550mAh (supose this cell has vented, or something like that to compromise it's live).

How long this battery will keep up the high voltage, to give you the maximum performance? If it holds the voltage during the 5, 8 or 10 min of the main, ok... but........ if don't??

That's one thing I'm searching about now... Does anyone have something to tell us about it?

knightrider
2010.12.29, 03:10 PM
Thanks guys. I can't see the IR with my charger :mad:

my cells are only 1 month old but with 3-4 track days a week on them.

so I guess my charger will peak my cells 10 mins after 'Done' is displayed.

and I guess my capacity #'s are OK. those capacity #'s below are almost higher on the 750's than the 990's!!!

I would have thought capacity is a good matching method for consistancy, correct? since the pack can only discharge down to the cell with the lowest capicity, leaving some energy in the higher capacity cell. Therefore, without using the discharge option, running the car till it stops isnt' a good discharge method.

or am I way off?

EMU
2010.12.29, 03:32 PM
When 'done' appears, that is when the peak detection terminates charge. Then they trickle to top off.

I match by capacity... as my chargers dont state IR either. Not many do.

Running the car till it stops hurts the cells with less capacity. The cell will overdischarge, and lose even more capacity. I pull the car off when I feel the 'dump'.

hrdrvr
2010.12.29, 03:42 PM
When I test, I typically charge the cells normally. Let them trickle for 10 minutes or so (same as I would when racing). Then I run the discharge function and see what the numbers are.

What rates are your charging and discharging at for this test?

knightrider
2010.12.29, 04:16 PM
ah yes, I also should post my charge rates. Discharge = 1A (charger's max), 900 Peaks charge at 1A and the 750's - .8A

EMU
2010.12.29, 05:10 PM
What rates are your charging and discharging at for this test?

1A for each.

knightrider
2010.12.29, 05:42 PM
HM! So do you I should junk my cells since I sometimes do that?

knightrider
2010.12.29, 06:09 PM
Oh wow, I just let the 990's trickle and all went up .02 - .03. I guess this would have changed the capacity too. It doesn't seem this 'top off trickle' happens during the 'refresh and analyze' clycle.

What's ya'lls thoughts? thanks