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Old 05-22-2006, 12:59 PM   #1
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Default Nooby Super Brain discharging help, please.

Just as an example, I have a 2400mah that I ran until the truck slowed SIGNIFICANTLY. It still had 7.50 or so in it. So, I ran it in truck until it stopped. Still had around 7.40. Ran truck with wheels off ground until it stopped. Had 7.40. Hooked straight to an extra motor I had laying around until IT stopped. STILL had 7.40.
I have Super Brain 969 that had some loose wires when I got it, so I fixed them. I followed the discharging instructions as I understood them (could very easily have MISunderstood), and when it stopped, you guessed it, I watched the meter climb right back to 7.35-7.40.

Help me out here. We may have already ruined a couple of batts by not discharging correctly, and DONT want to lose anymore.

Some hints at maybe "reviving" these seemingly dead batts would also be GREATLY appreciated.

Thanks

Last edited by oMONSTERo; 05-22-2006 at 01:01 PM. Reason: clarification
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Old 05-22-2006, 01:08 PM   #2
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Well when you place a load on the battery the voltage will drop, and when the load is removed the voltage will go back up. I suppose the real question is why are you using Ni-cds? They really are unnecessary now, ni-mhs are so cheap and so much better.
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Old 05-22-2006, 01:20 PM   #3
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Default No

NOoooooo, the REAL question is in MY original post. I hope someone will actually try to answer it.

But to answer YOUR question, as if it were relevant, these batts CAME with various trucks we have purchased. If we buy JUST batts, we buy NIMH.
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Old 05-23-2006, 02:08 AM   #4
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I will try to answer. What is the question?

Your batt seems acting normal to me.
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Old 05-23-2006, 03:47 AM   #5
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As has been said, the packs will have a voltage drop when palced under load (ie. when driving it around or running it), however when you take off the load and place it on the meter, there's no load and the voltage climbs again.
If you had a cutoff voltage in your speedy, garrunteed you'd stop running as the pack drops below the cutoff.
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Old 05-23-2006, 07:46 AM   #6
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Default So,

What good is discharging to 5.4, if the batts are gonna go RIGHT back to wherever it was?
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Old 05-23-2006, 09:46 AM   #7
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An open voltage reading really has nothing to do with dischargeing. Racers and battery matchers seem to recommend dischargeing to "condition" the pack. (or make it better some how) Pleaase fill in the quote with whatever you want to call it. I prefer to call it dischargeing or emtying and I would say there's little benefit to it for nimh batts.

Whether the voltage springs back up or not (it always will unless there's a tapering load down to zero) is normal and irrelevant because you are simply emptying the batt. The battery you described originally is considered "emty" or dead and has no useable capacity left.

An open voltage reading also is not nessesarily an accurate indicator of remaining capacity in a nickle type battery.
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Old 05-23-2006, 08:10 PM   #8
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Default well

How bout someone walk me through a discharge session on a MRC Super Brain 969?
Hook up the battery, hit "discharge" button, set discharge rate (.20 - 3.00?, what should I use?), push start. Is that all there is to it?
What is supposed to happen next? What readings should I be seeing, and when? How long should it take? Isnt the battery supposed to REMAIN at the suggested 5.4 discharged voltage?

"The battery you described originally is considered "emty" or dead and has no useable capacity left."
So, as long as the discharger took it to 5.4, it doesnt matter if it climbs back up to whatever?


Sorry for not "getting" this right away, we've never dealt with discharging before.

Thanks for your patience

Last edited by oMONSTERo; 05-23-2006 at 08:11 PM. Reason: correction
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Old 05-23-2006, 10:52 PM   #9
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I would not use an MRC 969 To discharge your packs, If you still want to make sure you have a fan blowing on the charger to keep the heat down. Your doing it correct. Hook up the battery to the charger, select discharge, You want to set it at the max, 10 amps. It will take a while(my guess would be 10 to 15 minutes). If their is any life left in the packs you will want to cycle them and that may bring them back a bit. To cycle them your going to have to charge them then discharge them, you will need to do this for at least 4 cycles. When you discharge them you will need to let the batteries cool off before charging them again. I would only cycle them 2 times a day. You also need to discharge Ni-cads after every use, Make sure they don't get to hot. Ni-cads are not like NiMhs, Ni cads develop a memory, this is why you must discharge before you charge..I'm "old school" so i do remember the how to's on Ni-cads.. I hope this helped.
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Old 05-24-2006, 09:05 AM   #10
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I would agree, I think you did everything right.

The only thing is you may have been under the impresion that a "voltage" reading is an indicator of remaining capacity. On a li-po battery an open (resting) voltage is directly related to whether or not the batt is full or empty.
On a nickle type battery it is still somewhat an indicator, but during the discharge the voltage drops way off and then as soon as the load is removed it will spring back up to a "nominal" voltage of 1.2 volts and measuring it will not give a clue as to it's state of charge.

I think you got it anyways , it's kinda like pressure in a long garden hose. The pressure in the hose (with it plugged) is no measure of the total gallons of water you have in the tank. Once flowing the pressure may drop way off and as soon as the flow stops it will boing right back up. Storage tank may be near full or near empty. Maybe a dumb anaolgy.
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Old 05-24-2006, 09:34 AM   #11
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in order to discharge your packs correctly you should get a discharger, 20a or 30a, with a .9 cutoff. or else use a charger with a 30a discharge rate. running the motors in your truck til they stop, and then on a motor outside a vehicle until it stops is not a really good way to do discharge. Spend 20-30 bucks and get a reactor 30, or another comparabgle discharger, I am using 10 1157 lightbulbs (deans stand, 20a) with a racers edge cutoff swith and then when I try to use an integy 0-30 tray to help equalize, should just buy one or a smart tray for those purposes. I rarely use my Integy 16x8v6 for discharging, but I have, and it discharges from 0-30 amps. I am also assuming that you are using sub-c's, I am not to sure on the smaller batteries.
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