Receiver Packs

Receiver Pack Care

NiCad Care

You can discharge NiCad packs with a #1157 automotive taillight bulb. However you must never allow the pack to fully discharge. If you do, you are taking a risk of reversing a cell. Disconnect the discharger when the light begins to go dim. A better idea would be to use a cut-out switch to prevent the pack from discharging below a safe point. For a 5-cell pack a 4.5 volt switch would work perfectly. The idea here is to bring each cell down to .9 volts. I wouldn't worry about doing this procedure on a receiver pack religiously. Once every couple of months should be fine.

When charging your NiCad receiver pack, the safest bet would be an overnight wall charger. However if you have a charger capable of charging a NiCad receiver pack you'll want the charger to see a higher voltage drop-off than NiMH would, when the pack is full. This is what the threshold setting on most chargers addresses. If you are using a charger that allows you to vary the threshold setting, you'll want it around 10-15mV for each cell. Therefore, for a 5-cell pack, you'll want to set it in the range of 50-75mV. The exact setting may vary between packs, and require some experimentation. Always start out on the low side and adjust upwards if you find you packs are not getting fully charged. You should generally charge at no more than a 1 amp rate for a pack with 1000Mah or more. For packs with less than 1000Mah, divide the total of Mah by 1000, and set the charge rate according to that if possible. So for a 800Mah pack, you should charge at a .8 amp rate.

Many high-end chargers will also provide you the capability of flex/pulse charging. This method of charging starts out at a fixed rate but at several points during the charge, it's interrupted with short bursts of discharging. This is often used to revive older batteries and restore much of their usefulness. This is used on NiCad packs, and isn't recommended for NiMH packs.

You should always make sure that your NiCad packs are discharged when they are stored. If you store a pack for a few days that's fine. However don't store the packs for a week, month, or any other prolonged period while they are charged. Doing so can affect their capacity.

NiMH Care

The discharge procedure for NiMH packs is the same as for NiCad packs. Again, you want to discharge until you reach .9 volts a cell, but no lower than that so that you don't reverse a cell. Again as with the NiCad packs, I wouldn't worry about doing this procedure on a receiver pack religiously. Once every couple of months should be fine.

When charging your NiCad receiver pack, the safest bet would be an overnight wall charger. However if you have a charger capable of charging a NiMH receiver pack, you'll need to set a much lower voltage drop-off point for when the pack is full. If you are using a charger that allows you to vary the threshold setting, you'll want it around 3-5mV for each cell. Therefore, for a 5-cell pack, you'll want to set it in the range of 15-25mV. The exact setting may vary between packs, and require some experimentation. Always start out on the low side and adjust upwards if you find you packs are not getting fully charged. When charging your NiMH pack, you should set the same charging rates as you would for a NiCad pack. Charge at a rate of no more than 1 amp for a pack with 1000Mah or more. For packs with less than 1000Mah, divide the total of Mah by 1000, and set the charge rate according to that if possible. So for a 800Mah pack, you should charge at a .8 amp rate. Flex/pulse charging isn't recommended on NiMH packs.

Probably one of the most significant differences in NiCad and NiMH packs is how to store them. When storing your NiMH packs, you should always charge them back up to around a third of their normal charge. Which, to say the least can be inconvenient. Who wants to sit around and charge their packs partially back up after they're done running. However it should be done. NiMH packs can be damaged if you store them fully discharged. While it's recommended that electric RC cars have their packs discharged after coming out of storage, I think that's usually overkill for a receiver pack. You should be fine in most instances by just charging the pack before you use it.

For more information regarding the differences between NiCad and NiMH packs, see my battery section. While it focuses on electric RC battery packs, most of the information applies to receiver packs as well.

Part One:	Introduction To The Receiver Pack
Part Two:	Wiring A Receiver Pack
Part Three:	Receiver Pack Care