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Old 01-18-2004, 04:36 PM   #1
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i was wondering what voltage and wattage light bulbs to use when building a discharger? how should i wire it series or paralell?(using ni-cad for stock racing)
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Old 01-18-2004, 04:48 PM   #2
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Car brakelight 12V 21W bulbs, wired in parallel.
Use as many as you want to get the discharge current you need.
Approx 1.5-2A per bulb.
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Old 01-18-2004, 05:01 PM   #3
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I use 1157 dual filament bulbs. Each one pulls about 2 amps.
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Old 01-18-2004, 06:11 PM   #4
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i dont know much about discharging,i am bit cloudy on the finer points of batteries,charging and discharging. for example i have some 1700mah (high voltage!want to try them in stock) 4 cell packs i want to use in my carpet knife. all i know is-that ni-cads have memory and should be discharged. but i dont know at what rate,how many amps ,ect.. if you were to use these packs,how would you do it?
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Old 01-19-2004, 12:17 AM   #5
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sean,

What is the best amp rate to charge Ni-Cads at? There is really no best rate for all conditions. Charging at higher rates will give the cells a higher discharge voltage curve with less run time. Charging at a lower rate will yield more run time with a slightly lower discharge curve. The higher the rate at which you charge the greater the risk of "venting" a cell. It will also shorten the service life of the pack. I recommend charging your packs at 5 amps for stock racing. Charge your packs at 4 amps for modified racing.


Should I Flex my cells on every charge to keep the Internal resistance down? No. We have noticed that flex charging your cells repeatedly seems to flatten out the performance of the pack. A linear charge yields the best results for racing. Use the "Flex" mode for conditioning purposes only.


How do I take care of my cells after racing? After your race is over discharge your cells down to approximately 5 volts (6 cell pack) using a string of lights or other resistive load and some kind of cutoff device. Note: cooling your pack under a fan while discharging them will help to increase pack life. If you don't have this equipment then run your car until it slows to a crawl.. Then after the pack cools down place the pack in an Equalization Tray. Not all trays have a diode built into them. Make sure the one you use does. You may remove them from the tray when the lights go out or leave them in until you use them again. See next question.


What about dead shorting: does it really help?
PLEASE READ THIS! This is a subject with very strong opposing opinions.
The NI-Cad engineering handbook from Sanyo states the following information which directly pertains to dead shorting cells: "If a cell is left connected to a load for a long period of time, the cell will eventually become completely discharged to 0V. If this occurs the polarity of the positive electrode will become negative and the electrolyte may easily creep. Therefore avoid leaving a cell connected to a load for too long a time". What this means to you is when you short a wire across either an individual cell or the entire pack the voltage will eventually drop to 0 volts. The longer this load is left attached to the cells the greater the risk of damage to them. "Voltage depression" which is the removal of the energy in the cell is required to obtain maximum performance from your cells. But you must not let the cells reach 0 volts. This is why we designed our Smart Tray II with a diode built in. It prevents the cells from reaching 0 volts while still removing the energy from the cells.
If you do try to dead short your cells please heed the following warning! Soldering a wire across charged cells could cause an explosion! If you are not an experienced racer then I strongly urge you not try this practice! If you leave your cells in an equalization tray until you use them again you will achieve better results than dead shorting without the risk of damage to the cells or yourself. We understand that most racers cannot afford a Smart Tray II for every one of their packs. Leave each pack in the tray overnight and the next day remove them from the tray and store them in a cool place. Right before you charge your packs up again, place them back in the tray until the led's go out. This should only take a couple of minutes.

Can I charge my cells the night before and re-peak at the track? Yes you can but expect slightly lower performance. For best performance charge your pack so it peaks about ten minutes before your race and re-peak right before your race.


Aren't all cells cycled at 30 amps better than those done at 20? No. The purpose for cycling cells at 30 amps is to "weed out" the weak cells. This is not necessary for any type of racing where your cells are drawing an average of less than 20 amps. Actually some 20 amp cells that would perform exceptionally well in say stock off-road racing could be ruined by cycling them at 30 amps. Sanyo technical specification sheets recommend a maximum discharge rate of 10-C. This means ten times the rated capacity of the cell. Example: an RC2000 is rated at 2000MAH or 2 amp hours. Ten times this rating would be 2amps X 10 or 20 amps. However we have not noticed any adverse effects of matching the RC2000's at 25 amps*.There is some merit however in cycling cells at higher amp rates when the type of racing you are doing exceeds a 20 amp average discharge rate. Footnote: The new RC2400 with its increased capacity seems to hold up better to a 30 amp discharge rate.
* We did notice a slight deterioration in performance of most RC2000 cells repeatedly cycled at 30 amps.
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Old 01-30-2004, 12:56 AM   #6
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Quote:
Originally posted by WC
Car brakelight 12V 21W bulbs, wired in parallel.
Use as many as you want to get the discharge current you need.
Approx 1.5-2A per bulb.

Dont's use more than 10 bulbs seems u juzz need to discharge to 20amps, otherwise your cell will be in reversal
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Old 01-30-2004, 03:59 AM   #7
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thanks for all those tips proudwinner.
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Old 01-30-2004, 04:41 AM   #8
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NP.
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