Bottlehead Forum

General Category => General Discussion => Topic started by: Cary on August 20, 2014, 04:39:14 AM

Title: Discharging nicad batteries
Post by: Cary on August 20, 2014, 04:39:14 AM

What is a good way of discharging nicad batteries other than leaving them on? Can I use a bleeder resistor like in discharging a cap? If so what should be the value of the resistor?

Title: Re: Discharging nicad batteries
Post by: mcandmar on August 20, 2014, 04:53:18 AM

Got to ask, why do you want to?

Personally i would just connect them to a load like a small light bulb.

Title: Re: Discharging nicad batteries
Post by: Grainger49 on August 20, 2014, 06:42:14 AM

I use a resistor under 20 Ohms. 

They charge better when fully drained.

Title: Re: Discharging nicad batteries
Post by: Natural Sound on August 20, 2014, 10:46:40 AM

There are "smart chargers" that offer a controlled discharge before charge option for NiCads. NiMh cells don't have a memory effect so you can charge them whenever you want without discharging. That's why I use NiMh. If you do decide to use a manual discharge method make sure you don't discharge the cells too much or too fast. You will shorten the life of the battery significantly if you do.

Title: Re: Discharging nicad batteries
Post by: Grainger49 on August 20, 2014, 11:02:00 AM

If you are charging AAs I have a great charger, the LaCross BC-700.  It discharges and charges and tests AA batteries.

This is one of those "smart" chargers.  It and Low Self Discharge batteries cured my camera problems about 4 years ago.

Title: Re: Discharging nicad batteries
Post by: Natural Sound on August 20, 2014, 11:44:53 AM

Quote from: Grainger49 on August 20, 2014, 11:02:00 AM

If you are charging AAs I have a great charger, the LaCross BC-700.  It discharges and charges and tests AA batteries.

I use one of those too.

Title: Re: Discharging nicad batteries
Post by: Tickwomp on August 21, 2014, 11:50:17 AM

Many years ago I was pretty heavily involved with 10th scale electric buggies and used 7.2v and 8.4v NiCad packs.  My primary charger had the ability to fully discharge, but in the heat of the battle, I needed to discharge several packs at once and I was using the charger to charge or top off a pack. 

I soldered together about 10 single element tail light bulbs together with a battery connector.  I made several of these and they were did a good job pulling the packs down evenly without overheating them.  The talk at the time was this load was very similar to what the motors were pulling and it helped the battery packs stay matched.  I don't remember how far I would discharge, but I would I would monitor with a voltmeter and pull them off at a certain point. 

Seemed to work well enough and I was still using this method when I moved up to 8th scale gas.

Tick