Cordless Tool Battery Short Charge?

I have a project coming up where I would like to use my cordless Drills. One of them still has power in both batteries, but I am afraid that the charge is not sufficient enough to last through the tasks I have to do.
According to the instructions (Yes, I acutely read and kept them) the max charge time for the batteries is five hours. Being that the battery is not totally out (I know, I can put a bungee around the trigger and run it down, but don't want to if I don't have to) can I put it on the charger for, say for the sake of argument, two-and-a-half hours, just to give it (them) a boost?
No, these aren't the best cordless tools in the world, but they are what I have and they do the job better than I had ever anticipated.
Thanks for any knowledgeable input.
__________________ Bill Waller New Eagle, PA
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Bill Waller wrote:

What type of batteries does the drill use? Some types of batteries will take a "set" if short cycled. With other types it doesn't matter.
See: http://en.wikipedia.org/wiki/Rechargeable_battery
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Jack Novak
Buffalo, NY - USA
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There is a widely popular misunderstanding about DISCHARGING batteries (NiCd & NiMh: most likely one of the two types is yours), NEVER drain your battery pack to no output; i.e. drill stops turning. When you do this, you drop the voltage in the cells to a point that internal polarity reversal can occur. When this happens, your pack is damaged beyond reasonable repair; you can try to isolate the bad battery within the pack and replace it with exactly the same mah rating cell AND it must be exactly at the same charge level as the remaining cells: almost impossible and I wouldn't recommend it.
The best way to manage your rechargeable batteries is to use them until they noticeably start decreasing output; i.e. drill starts slowing down. Stop using that pack. Wait for it to cool (1 hr) if it is warm to the touch and then charge it fully. Keep it in the charger for no more than 24 hours which gives the charger time to trickle charge the battery. Remove and store it unattached from the tool until you are ready to use it. If you aren't going to use it for an extended period, 2 months or more, then store it with a full charge and then every couple of months, top it up in the charger. The problem often occurs when batteries are left for an extended period of time and their voltage drops low enough to allow internal polarity reversal to occur. Then when you go to use them, they are completely dead and usually won't take a full charge anymore. You may or may not be able to use them again as you once did.
If your packs take only a short charge, then they are most likely damaged beyond repair as described above.
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wrote:

This sounds like the charging called for in the harbor freight tools "drillmaster" line of cordless drills. They use a dumb charger- one that doesnt have the brains to detect when the pack is full. It continues to charge at the same rate no matter what the state of charge is of the pack. What's the brand of drill that you have? Most of the better (even mediocre ones) now come with an intelligent charger, one that can tell what the state of charge is, fast charge to 90-95% capacity, then switch to trickle charge for the rest. Least in my little experience . Pat
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maico wrote:

<snip>
Cell reversal occurs when the cells in the battery discharge at differing rates and one cell discharges to zero before the others. Cell reversal occurs at below one volt. The drill's turning power would be useless long before reaching one volt. See:
http://en.wikipedia.org/wiki/Nickel-cadmium_battery#Cell_reversal
and
http://adsabs.harvard.edu/abs/1982STIN...8233836Z
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Jack Novak
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Yes and no. The events are mutually exclusive: you don't require differing discharge rates for polarity reversal to occur. If the pack discharges uniformly: approx. same rate per cell then you can have reversal in potentially all of the cells. It may also occur if the cells discharge unequally, which is all the more reason not to fully drain the pack by holding a drill on until it stops or the like in other cordless tools/equipment because you don't know how low the cell with the most discharge goes.
The cell(s) need to drop below .9 volts for polarity reversal to be possible. A 'pack' is made up of cells, that when new and fully charged are (typically) 1.2 volts/cell, e.g. a 14.4 V pack has 14.4 V/ 1.2V/cell = 12 cells. To make up 14.4 V, the cells are connected in series, therefore, if ALL of the cells drop to .9 volts equally, you will still have 10.8 V in the pack which is enough to keep the drill turning.
Keep the drill running until it stops and you will most certainly damage one or more cells within the pack. This will deter fully charging the pack.
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maico wrote:
> Yes and no. The events are mutually exclusive: you don't require

Nickel-cadmium can tolerate some cell reversal, which is typically about 0.2V. 0.2V x 12 cells = 2.4V out of a 14.4V pack. Long before reaching 2.4V (0.2V per cell) a 14.4V drill's torque would be useless.
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Bill was not talking about using the drill, he is talking about draining it completely: "Being that the battery is not totally out (I know, I can put a bungee around the trigger and run it down...<snip>". His thoughts were that by completely draining the battery and then fully charging it, he would have a better working battery. This is not true and can do more harm than good.
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Thank you Jack, for understanding the question. The question is now, however, moot. That part of the project was finished yesterday. I used my antique Makita corded drill for making the bores and my old 12V B&D to drive the screws. Its batteries were either new and freshly charged or had been run down enough that I was not afraid to run a full time cycle charge. The 18V in question still has enough charge to do some work before I put it on the charger, but I got away without using it.
I know that many in the group poo poo B&D, but that 12V drove a whole lot of #10x3" screws yesterday and even had enough umph to put in the last two 8" timber screws from McFeely's. Yeah, I know, who woulda thunk. __________________ Bill Waller New Eagle, PA
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Actually Bill, it's Michael (maico) per the last input in the quoted text of your reply above; no issue though.
Hey, if a tool works for you and you are happy with it, use it.
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<SNIP>

Sorry Michael. Definitely, my Oops. :-( __________________ Bill Waller New Eagle, PA
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