Is it ok to....battery discharge question?

[Pyledriver]

I've used my Excal on a couple hunts and wanted to go ahead and discharge the battery all the way but wasn't sure how to do it effectively other than maybe just leave the detector on. I have the NiCd batteries and just wanted to be sure they went all the way down before charging back up again so they won't develop a 'memory'. It occurred to me that I might just be able to hook up the battery to a small DC motor and let it run till the battery drained. I'm thinking this would be a quicker way of discharging but wondering if that would cause a problem in any way? I'm also working on getting a peak charger setup but just don't have all the stuff together yet!

 

[kered]

Yes a small motor will do it or even a 12v car light bulb, either way just make sure the battery doesn't get hot

 

[John(Tx)]

I use a 12v car bulb to drain down my batteries. You will still have around 4-6volts after the 12v bulb goes dim, I then use the bulbs from my flashlight and the batteries will then drain down to about 2 volts. The light bulbs I use are from a cheap flashlight I bought at the dollar store. It's the flashlight that has 5 lights in a circle and are bright blue when they are lit. This takes me about 24 hours to complete, these bulbs have a very, very slow drain on the batteries, batteries don't get hot this way......Hope this helps. John

 

[Pyledriver]

Thanks! I may give it a shot this afternoon. I hunted about 4 hours yesterday and am planning on hitting a spot before work in the morning. I want to be sure I have a good charge!

 

[kered]

if you drain completely it will take a lot longer to get the full charge, i would say at least 15-16 hours so take that in mind or it might not be charged fully before you leave

 

[John(Tx)]

After I have charged my battery pack for 12 hours, I will disconnect the charger and test the voltage with my voltage meter, shows 14.88v, figured that was good enough, should I charge longer? Thanks......

 

[Mel Parker]

http://www.onlybatterypacks.com/up/pdf/batterycharginginstructions/NICAD%20INSTRUCTIONS.pdf

 

[kered]

Hot of the charger it will read higher than it is, let it stand half an hour then meter it, although that 14.88v sounds pretty good

 

[Critterhunter]

As I like to say, everything you ever wanted to NOT know about batteries and chargers can be found in this thread in this forum...

http://www.findmall.com/read.php?21,1178409,page=1

If you have any questions after that it's going to be where's the coffee to keep you from falling asleep, but you'll then know about all there is on the feeding and care of various battery types, including the specific packs being used on the Sovereign and other Minelab detectors. Also covers how to cycle (drain and charge) the battery for longer life and more run time, or to recover a bad pack that won't hold a charge.

Using LED flashlights to drain packs, even if they are near dead, is going to take you hours upon hours to do. They also offer no advantage over using a car light bulb other than a much more mild amp draw if you want to be real easy on the pack. Once the car light bulb goes out just let it sit on the battery for several hours afterwards and it will drain the last bit out of it, though any battery will bounce back in voltage once it's sat for a bit, so don't expect it to read "zero volts" once you take it off the load (light bulb). Letting it sit for a couple hours after the bulb goes out will drain it as good as it's going to get for the most part. Besides, those LED lights also require a certain voltage to work. Meaning, once those go out that doesn't mean the pack is dead either. Nothing wrong with using them, but it's taking you much longer than needed to drain the pack dead. So long as the pack doesn't feel hot when it's being discharged (meaning over amped) there should be no problem with using a DC motor, but I prefer the light bulb since they are designed to take the heat. If that motor isn't meant to run on 12VDC it may burn up over time, and brushed DC motors do not like a dropping voltage. An electric motor will try to do the same amount of work as the voltage drops, meaning as the voltage drops the amps will rise that it is consuming. Result is a very hot motor after a while. That's why compressors on condensors for central air go bad a lot. The CC (cooling contactor) relay gets a little carbon built up on the contacts, supply voltage to the compressor drops a bit due to the resistance, and then the compressor starts sucking more amps to try to keep up with the amount of work to be done due to the dropping voltage.