RC18 battery question charge/discharge

[aramis]

Hi Guys.I recently bought an RC18T.Great little truck.Anyways,I race all gas,and the last time I raced electric I was using NICADS.My question is what rates should I charge and discharge the NIMH batteries these cars use.I have the 1100 High Voltage batts from Reedy that use GP cells.My charger is MIMH ready,so I have no problems there.Thanks for any help,Jeff

[Sherminator]

Jeff, a small battery like the one used in your RC18 probably shouldnt be charged at more than 2 amps.. ive never discharged them but i would try at 3-4 amp discharge and go from there..if you charge or discharge them too fast they will overheat. you want the batteries warm to the touch not roasting hot

[SquirrelNutz]

WOOOAHHHH!!!!!!!

Sherm is very correct in saying 1 to 2 amps to charge.

However.....

NiMh batteries SHOULD NEVER be discharged!!! you will be damaging them! Nicad you do but NiMh you do not. It is best to run Nimh to where it is almost dead but not quite. going down to a zero level will damage them. When you get to that point then charge them and leave them charged when stored.

[aramis]

Thanks Guys,but I have a question as to not discharging them.My charger has a setting for discharging NIMH batts.I also noticed that the matched sets have a discharge rate on the stickers.(the ones I saw said 10 amps)It also gave a charge rate of 3 amps(I am going to stay at 2 amps).I would say the car is pulling around 10 amps during acceleration,so why would discharging at a similar rate harm them?Do these batts have any memory issues?If not,I would not discharge.As I said,I am used to NICADs and these are new to me. Thanks Again,Jeff

[RC10racer89]

WOOOAHHHH!!!!!!!

Sherm is very correct in saying 1 to 2 amps to charge.

However.....

NiMh batteries SHOULD NEVER be discharged!!! you will be damaging them! Nicad you do but NiMh you do not. It is best to run Nimh to where it is almost dead but not quite. going down to a zero level will damage them. When you get to that point then charge them and leave them charged when stored.

NIMH batteries can be discharged, you do when you run them in your cars, thats kinda the point ;) Discharging them will not damage them, but (and this is what I think you might have been thinking of) if you use a bulb discharger or another discharger with out a voltage cutoff, you run the risk of reversing a cell if you discharge the battery completely. This will basically ruin a good battery back.

Like Squirrel said, you should be fine running down the NIMH cells in your car. They don't have the same "memory" issues that NICADS do so you don't really need to discharge them.

However, many racers who use the larger sub-c cells in their race vehicles will use a battery tray with a variable voltage cut-off or a programed cut-off to equalize their matched battery packs. This makes sure that all the cells in a matched pack have the same voltage when you charge it back up again. Since your not running matched packs, and because your running smaller cells anyway, this is not needed or doable in your situation. I agree with Squirrel when he says that the best thing to do would be to just run down your batteries in your car.

One more thing to note is that if you plan on storing your NIMH packs, is that NIMH cells store better for long periods of time with a partial charge left in them. This is obviously not true of nicads.

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGGJ0&P=7

[aramis]

NIMH batteries can be discharged, you do when you run them in your cars, thats kinda the point ;) Discharging them will not damage them, but (and this is what I think you might have been thinking of) if you use a bulb discharger or another discharger with out a voltage cutoff, you run the risk of reversing a cell if you discharge the battery completely. This will basically ruin a good battery back.

Like Squirrel said, you should be fine running down the NIMH cells in your car. They don't have the same "memory" issues that NICADS do so you don't really need to discharge them.

However, many racers who use the larger sub-c cells in their race vehicles will use a battery tray with a variable voltage cut-off or a programed cut-off to equalize their matched battery packs. This makes sure that all the cells in a matched pack have the same voltage when you charge it back up again. Since your not running matched packs, and because your running smaller cells anyway, this is not needed or doable in your situation. I agree with Squirrel when he says that the best thing to do would be to just run down your batteries in your car.

One more thing to note is that if you plan on storing your NIMH packs, is that NIMH cells store better for long periods of time with a partial charge left in them. This is obviously not true of nicads.

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGGJ0&P=7Thanks,that is some good info.The reason I am asking about discharging is the fact that we run 5 minute races at my track.I am only using a little over half of my run time,and then recharging.I was worried about the batts developing any sort of memory,and falling flat at the 5 minute mark.Since it appears none of this is the case,I wont worry about discharging before I charge.Thanks Guys,Jeff