Charging Instructions for 4200 Ni-Mh Cells

The newest generation IB and EP 4200 cells have extremely high voltage and current flow characteristics, so special care must be taken when using these cells. Please use a quality charger specifically designed to charge Ni-Mh cells and that has adjustable peak detection or thermal charging capabilities.

How do I take care of the IB and EP 4200’s? When you first receive your new packs please follow these instructions for best results. Perform a "Soft Cycle" by charging the pack at 4 AMPS for about 10 minutes and then immediately discharge the pack at a high rate (20 to 35 AMPS) to 1 Volt per cell or 6 Volts for a 6 cell or 4 Volts for a 4 cell pack. Follow this by equalizing the pack using an equalization tray. As soon as the lights go out on the tray, fully charge the pack at 5-6 AMPS.

What should I set the peak detection threshold at? Whatever it takes to get the batteries to 125-130 degrees farenheit when the charger shuts off. This is assuming that battery charger and pack are at room temperature (75-85 degrees Farenheit) when charging. Do not use a fan to cool the batteries during charging! On a turbo 35GFX I find that a .03 (30 millivolts) value works best for a 6 cell pack (.02 for a 4 cell pack). Some may find this setting is to high or to low for their chargers so please start with a lower peak detection value and work your way up to the proper temperature range in order to avoid damaging the pack! Once you have established the proper peak detection value for your charger then leave it there! After the first charge you can skip the first (Soft Cycle) and charge at 5-6 amps as usual.

What if my charger does not have adjustable peak detection? As long as the charger shuts off before the cells
reach 130 degrees F you should be fine. If the charger shuts off at a much lower temperature you just will not get the full benefits of the packs.

For short term storage (less than a week). Please note that these latest generation 4200 IB and EP cells significantly self discharge due to their extremely low internal resistance . After use. (if you charge the packs more than once a day do not discharge between uses), I recommend you charge the packs at 5-6 amps for 5-10 minutes and put them away. When using the packs for racing, charge the pack so it finishes charging as close as possible to using the pack for your race. Every 3-4 weeks I recommend discharging and then "balancing"* the cells in an equalization tray before charging them. Only use an equalization tray that stops discharging before the cells reach .5 volts or higher. You should only leave the pack on the tray only long enough for the led’s to go out. You should charge the cells up immediately after equalization. If you leave your pack(s) in a completely discharged state for any length of time damage to the cells will occur.

For longer periods of inactivity more charge must be left in these cells. For storage longer than two weeks I recommend fully charging the packs. Expect a temporary decrease in performance after long periods of inactivity.

* Ni-mh cells do not form a "memory effect" like Ni-cads so equalization is not used for that purpose but rather to balance the cells so they all start charging from the same point.

My packs aren’t taking as much of a charge as they did when they were new. What’s wrong? First off all Ni-Mh cells will lose some capacity after a few cycles. If you race with Modified motors, (especially below 8 turn winds) this problem will be more noticeable. With low wind motors that draw a very high amount of current you can actually cause damage to the cells by exceeding their maximum rate of discharge. This is even more critical in 4 cell racing. Also after several discharge/charge cycles your packs will begin to get "out of balance". This means some cells have more of a charge left in them than others within the same pack. Once the cells are out of sync and you charge them, the cells that started out with more charge in them will peak (reach full charge) before the other cells finish charging. The charger may overcharge these cells and possibly cause damage to them while not fully charging the other cells in the pack. You charger cannot see what is happening to each individual cell since it is hooked up to the battery pack in series. It only takes an average of what’s happening with the whole pack. For this reason it is imperative that you discharge and equalize your packs on a regular basis.

How many times a day can I run these packs? If you are a backyard basher I would expect 3 times a day would be about the limit. This is assuming you let the pack cool down thoroughly between runs. At least an hour and two hours would be better. If you are racing, I would limit use to twice a race and let the packs cool down between runs.

What about step charging? There are lots of theories about step charging, pulse vs. linear, flex charging, and lots more. My personal feeling is this. A batteries performance is mainly limited to the internal structure (hence why some cells are better than others). As long as you fill it all the way up (without overcharging it) you will get the best performance from the cells that you can. The only effect I have seen is that lower rate charging will make the power last a bit longer and higher rate charging makes the pack run a little faster. I personally use linear charging at 6 amps for the type of racing that I do (offroad).

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