DEAD-SHORTING YOUR NIMH BATTERIES
When it comes to either getting an extra edge or just simply keeping up with the competition, RC racers must constantly utilize different charging and discharging processes. Now, it has become increasingly popular to utilize the
"dead-shorting" process when racing with newer NiMH cells. This includes the popular Gold Peak (GP) cells, as well as the newer batches of Intellect (IB) cells.
"Dead-shorting" is basically the process of short-circuiting a cell, or crossing the positive and negative leads. When utilizing the dead-shorting process with the right kind of cell, dead-shorting will increase voltage and decrease internal resistance; the combination of these two changes will yield a noticeable increase in power. Dead-shorting can have either positive or negative effects on run-time, depending on which method you use. Here, I will outline two different dead-shorting methods, one for applications that require maximum power (such as stock and 19-turn racing'excluding 1/12 scale on-road), and one for applications that require maximum run-time and high power (such as modified and 1/12 racing).
Dead shorting can be a dangerous process if performed incorrectly. Please be sure that you fully understand every step outlined in this article before attempting the process. Please be careful, use common sense, and do not skip any steps. Nexus Racing does not accept any responsibility for any harm caused to you or your equipment by performing the process incorrectly.
Accessories Required: at least one low-amp discharging tray.
IMPORTANT: Your battery pack must first either be dumped or discharged to a cutoff voltage before you can proceed any further (unless the battery pack is new, new matched cells have already been discharged during matching). It is best to use a 20 or 30 amp discharge rate for this, but a 10 amp rate will work fine. If using a discharger with an automatic cutoff, set the cutoff to .90 volts per cell. If using a bulb-type discharger, disconnect the battery as the bulbs dim. Only after doing this can you proceed to one of the following sets of instructions (depending upon application).
DEAD-SHORTING METHOD 1
ACHIEVE MORE RUN-TIME AND POWER
* decreased internal resistance
* increased voltage
* increased run-time
* Battery will be more likely to false-peak during charge. To avoid this problem, either use step charging, temperature detection charging, or a long-lockout feature (all available on the MuchMore Cell Master).
Step 1: Equalize Your Individual Cells
After your pack is either dumped or discharged to a cutoff voltage (or if your pack is brand new), equalize your individual cells on a low amp discharging tray. If using a tray with resistors/indicator bulbs (such as the MuchMore Zero-V), disconnect each cell as its indicator bulb dims. If using a tray with an automatic cutoff (such as the Novak Smart Tray), set the cutoff to .90 volts per cell. The pack?s voltage will have rebounded a bit after being initially discharged, so traying to a .90v cutoff could take a few minutes (since you will be using a lower amp rate to discharge).
Step 2: Store the Battery
Once equalized, you can store the battery for however long you wish. It is best, however to not store your battery for more than three weeks without putting a cycle through it.
Step 3: Dead-Short the Battery on a Discharge Tray
About 30-45 minutes before you begin charging the battery, place it back on the discharge tray. If the tray has an automatic cutoff option, disable the cutoff or enable dead-short mode. This step, leave the battery in the tray and allow it to dead short until you are ready to charge.
Step 4: Remove From Discharge Tray and Charge Immediately
When you are ready to charge (a maximum of 1 hour after beginning to dead-short), remove the battery from the discharge tray and then begin charging it immediately. Do NOT begin charging while the battery is still in the tray.
Repeat all of these steps every time you run the battery. Use ONLY a discharging tray to dead-short for this application. As always, it could take one or two cycles for a new battery to ?come to life?. It is best to run the pack a maximum of twice per race day.
DEAD-SHORTING METHOD 2
ACHIEVE MAXIMUM POWER
* decreased internal resistance
* increased voltage
* maximum power
* battery will be more likely to false-peak during charge. To avoid this problem, either use step charging, temperature detection charging, or a long-lockout feature (all available on the MuchMore Cell Master).
* decreased run-time
Step 1: Tray the Battery
After your pack is either dumped or discharged to a cutoff voltage (or if your pack is brand new), discharge your individual cells on a low amp discharging tray with no cutoff. Resistor-type trays (such as the MuchMore Zero-V) work best for this application. After your cells discharge/dead-short for at least 1 hour, proceed to Step 2 (while the battery is still connected to the tray).
Step 2: Long Term Dead-Shorting
There are two options for performing this step. No matter which option you choose, the pack will take a long period of time (days) to reach 0.000 volts. Plan to allow the battery to dead-short for at least 5-7 days before running it again.
OPTION 1 (PREFERRED): Simply leave the battery pack in the discharging tray and store it this way. This option is preferred because discharging trays do not cause cell reversal?this is when a battery?s voltage falls below 0, which is harmful to the cell. The disadvantage to this option is that you will require a discharge tray for each pack that you would like to dead-short. Newer trays, such as the MuchMore Zero-V, offer convenient stacking posts to occupy less space.
OPTION 2: First, while the battery is still dead-shorting in the discharge tray, connect the positive and negative leads of the entire pack with a line of solder (i.e. connect the positive lead of cell 1 to the negative lead of cell 6. After doing this, you can remove the pack from the tray and store it.
This option sometimes leads to cell reversal, which can be harmful to the battery. It does not, however, require a discharging tray for each of the battery packs you wish to dead short (hence it is a cheaper alternative). Your best option could be to dead-short using trays for your newer or better packs, and solder for your older or practice packs.
Step 3: Remove From Dead-Shorting and Charge Immediately
(Perform this step after at least a week or so of dead-shorting)
When you are ready to charge, abort whichever dead-shorting process you chose and then begin charging it immediately. Do NOT begin charging while the battery is still in a discharge tray or shorted with solder.
Repeat these steps every time you run the battery. As always, it can take one or two cycles for a new battery to "come to life". If you choose to run a pack more than once on a particular day, follow the instructions in 'Dead Shorting Method 1' for the second run. The run-time lost during this method is permanent, but negligible for stock and 19 turn racing, especially with the higher run-times offered in today's newest NiMH cells.
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