charging nicads

[barry]

I recently return to the hobby after a 20yr break and have gone straight to using Lipos in my touring car. I really like the ease of use and maintenance.

However, I have just acquired a Tamiya Mini which came with 4 1500 nicads. I also have a 2200 nicad which was bought as a back up to my lipo but have never needed. They're all sealed stick packs.

My problem is I'm not sure how to charge them! My lipo charger also charges Nicads and Nimhs, so no problem there, but I don't know the settings to use. Back in the 80s, we had simple chargers made up of a steel plate with ceramic resistors on the back, with wires leading the stick pack and car battery. After a race we'd connect a car headlight bulb till flat then charge for 15mins for the next race. Easy!

So my questions are:

what amps can I feed my 1500 and 2200 stick and for how long?

what is this peak rating thing?

my charger takes an age to discharge, so is it safe to use the car headlightmethod (about 10mins to discharge iirc)?

Many thanks,
Barry

[cjm_2008]

barry,

sorry for not replying to your pm.... been mega busy.

if your charger has adjustable delta peak settings (sometimes referred to as cutoff voltage or similar) you need to dial that into your charger.

from memory, it's normally a drop-off of 0.2 of a volt or so. nicad voltage under charge drops when the cells reach full capacity.

google is your friend

generally, use high currents (four amps or so) for punch, lower currents for duration.

have you run the mini yet?

[neiloliver]

0.2V is too high, 5 to 10mV per cell is a better -dV setting.

Depending on the settings on your charger, I would suggest the following to start with; youcan increase the charge rate to 2C later once you know everything is working OK.

Constant Current setting (not CVCC used for your LiPo)
1C Max (1500mA for your 1500mAh packs)
Max time of 1.2hrs
Max temp of +50°C
-dV of 60mV

Neil

[barry]

Thanks both.

Originally Posted by cjm_2008

have you run the mini yet?

Took it out today and loved it!

Barry