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Old 03-05-2005, 02:56 PM   #16
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one more thing to keep in mind if you deadshort your batteries, your first couple of charges might be false peaks. So I just changed the peak detect to .04 instead of .03 and viola my packs charged back to normal.

I did notice after dead shorting my batteries and charging them up fully, the car had a noticeable increase in punch.
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Old 03-05-2005, 08:09 PM   #17
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Quote:
Originally posted by David Alberico
no, some advanced chargers will even allow you to limit the amount of charge that goes into a cell. If I'm racing stock I will normally make sure that my battery is discharged to 5.1 volts at 10amps then limit the amount of charge to 3000MAH in my GP 3300's, this way it will under charge the pack. My packs just barely get warm and that's normally how I run it and as far as punch goes it stays about the same through the whole run.
I'm sorry David, but your information is incorrect. I would suggest all racers reading this thread that are looking for good information on charging and dead-shorting to disregard the posts by David Alberico.

David, I don't mean any offense to you even though you will probably take offense to my post. Please take the time to read and research battery information before you post. You information is flawed and incorrect in numerous ways, most importantly your statement that NiMH doesn't have a memory. It does have memory effect. Lithium and LiPoly (both lithium based cells) are the only rechargables that don't have a memory effect. It is also detremental to cells to under charge them as you have mentioned.

I apologize if you don't agree but many persons on this forum are very knowlegable about battery chemistry and care, and will be happy to concur with my statements.
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Old 03-05-2005, 09:35 PM   #18
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Old 03-06-2005, 01:30 AM   #19
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Thanks for all your comments.

Okay, I didnt post some facts, which could have made this thread more specific. Sorry

I'm exclusively racing stock, so runtime is not an issue.

I do have two chargers: A Nosram Sirius alias LRP Pulsar Sport and a Eagle CDC v6.0/B2. I tend to say both dont false peak, but I've never tried charging a dead shorted pack on these. What do you guys think?

I have 4 matched GP3300. One with approx. 30 runs on it, and three with around 15. Will it be bad to try deadshorting these now?

Now, the reason for this thread: I've been through many dead short threads, and I only found one comment about discharge voltage curve: A guy, made a experiment with two packs. One dead shorthed, the other wasnt. The dead shorted got better average voltage. But thing is, when the discharge voltage curves was compared, it showed up that the dead shorted one, was better for the first 450 mAh. After that point, the non-dead shorted was better.

So... I'm not talking about the discharge curve at the end, but in the beginning. Thing is, I dont like the voltage curve of a NiCd 1700 pack. Very punchy for the first rounds, and then they flattend... What I do like about my current packs, is that they are pretty consistent AND strong for the first 5 minutes.

Please lets the comment come
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Old 03-06-2005, 01:34 AM   #20
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Default About charging rates...

I havent made discharge curves of this, but at my experience, a 5 amp charge rate will result in a more flat and consistent discharge curve, than a 6 amp charge rate. As stated, this is only a subjective experience from the track. Have you guys any experience about this?

Also, I want some reasonably battery life, so I'm trying to keep my batteries peaking around 122-131 degrees F / 50-55 deg C.
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Old 03-06-2005, 06:15 AM   #21
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Cole, your temps are correct. Continue with that. 6 amps on GP3300s is proven not to hurt the cells and yes they have more punch.

Discharge voltage curves. I'm not sure who's experiment you were looking at, but Danny Sulivan and many other battery matchers have proven that dead shorting produces higher voltage curve averages. That doesn't mean the curve starts out higher than non-DS, it means the average across the whole curve is higher. Even if it shortens the runtime by 20seconds it doesn't matter to you because you aren't averaging anywhere near 40 amps which is what it would take to get to the "flat" part of the curve. Most people's problem wth DS is they try it on used packs (so I wouldn't try it on yours) and either kill the pack then swear it's the worst thing you can do or get lucky and make the pack better. Your best bet is to get new packs and begin with the first cycle. You will like it. Be forewarned though, if you purchase from a matcher that doesn't truly zap and cycle the cells correctly you might get a weak cell that can't take it. Best bet is to purchase from a good matcher like SMC, Kinetix, EA Motorsports, Thunder R/C, etc but not neccissarily in that order...
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Old 03-06-2005, 06:18 AM   #22
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Oh yea, forgot something- any charger without a lockout feature has the potential to false peak especially when training the first few cycles so yes, they all can, but all you have to do is pay attention to the temp. If they aren't over 115-120deg F, then restart the charger. That simple.
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Old 03-06-2005, 11:52 AM   #23
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If you watch the charge graph on a GFX while charging a dead shorted pack you will see that the voltage starts high then drops off after the first couple of mins. It then levels off and slowly rises like a non D/S pack. So if you dont have a "long lockout" feature, your charger sees the voltage drop early in the charge and thinks it has peaked. All you really have to do is watch the charger for the first few mins of the charge and restart it if it false peaks.

I have heard that some guys remove the dead short wire 45 mins before they charge and they say it helps with the false peaking. I dont know if this is true as I generally only let them sit for 5 or 10 mins before I charge.
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Old 03-06-2005, 12:04 PM   #24
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I've been following these dead short posts all along also....

I've been considering doing it with my 12th scale packs.... I have no problem making runtime, I'm looking for more punch....

Anyone else doing it in 12th? My biggest concern is not maiing the 8 minutes...

Gotta do a few cycles on the GFX and see what times I'm getting....
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Old 03-06-2005, 01:36 PM   #25
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I'm racing with Fukuyama packs, so I'm quite sure, I wont get problems here
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Old 03-06-2005, 01:40 PM   #26
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This is the post, I'm referring to: http://www.rctech.net/forum/showthre...*&pagenumber=3

The first on this page, that start with "Originally posted by gee-dub" "i got a pair of yok gp3300 packs awhile back"
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Old 03-06-2005, 06:08 PM   #27
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Quote:
Originally posted by vtl1180ny
I've been following these dead short posts all along also....

I've been considering doing it with my 12th scale packs.... I have no problem making runtime, I'm looking for more punch....

Anyone else doing it in 12th? My biggest concern is not maiing the 8 minutes...

Gotta do a few cycles on the GFX and see what times I'm getting....
Deadshorting 4 cell 1/12 pack is not recomended, Be carefull
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Old 03-06-2005, 06:10 PM   #28
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Quote:
Originally posted by tminus3
one more thing to keep in mind if you deadshort your batteries, your first couple of charges might be false peaks. So I just changed the peak detect to .04 instead of .03 and viola my packs charged back to normal.

I did notice after dead shorting my batteries and charging them up fully, the car had a noticeable increase in punch.
Wow , Howell NJ. I grew up there for 28 years now live in Point PLeasant. I used to live off Aldrich rd near Jackson border.
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Old 03-06-2005, 08:04 PM   #29
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Cole, to help try and answer your question... a guy here at the track was wondering the same thing about voltage curves and all. He started 2 new packs. 1 dead shorted... one not. Through out the life of the battery, he found that the dead shorted battery did indeed have a higher average voltage when cycled on his GFX at 30amps. But at the end of 300secs discharge (using the graph feature on the GFX) he found that the non-dead shorted battery had a higher voltage at the end of 300secs than the dead shorted one. So this told him that the DeadShorted battery will give him more voltage for the first 2 minutes of the race. But after that it will drop off more than the nonDeadShorted one. So the delima was... do you dead short for more punch at the start with higher "average" voltage. Or not dead short with a more consistant voltage throughout the race with more volts towards the end of the run?
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Old 03-06-2005, 10:14 PM   #30
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I agree with John Tag on the subject of 12th scale...

I don't recommend deadshorting 12th scale batteries at all. Stock or mod.

If they were only 5 minute races it would be fine, but with 8 minute races even in stock 12th you are pushing the limits of even good battery packs if you have your motors tuned up for a lot of amp draw.

I recommend discharging 4 cell packs to 3.60v as a pack or .9 per cell on say a novak discharge tray. Store them like that. On race day put them on the discharge tray down to zero and let it sit in the tray for 10-20 minutes and then take them out and put them on charge. That seems to work really well for stock and mod 12th. If you won't use the packs for several weeks then putting a 300 second charge into them seems to help them from degrading over time.

For 6 cell touring car stock and 19 turn I think dead-shorting the batteries is the way to go. You still should have 80-120 seconds of run time after the race is over even with dead-shorting.

$.02
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