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Old 8th September 2007, 01:13 AM   #21
rjb is offline rjb  New Zealand
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If you can get it for free or cheap, even if the battery pack is stuffed its worth it. I have two other battery drills, including an 18v one, and this model Makita is the one I use most. The lack of a torque setting and variable speed is not really a problem. Its light, small and powerful. And very very tough. Being small it gets into tight places better than most.
Yes, the new Makitas better in some ways, but not the new cheapies.
Its not too difficult to replace cells in the pack.

Re maintaining Nicad cells, they do have a definite life, usually 500 to 2000 charges depending on quality, but maltreatment will shorten this considerably. However sometimes recovery can be made. OzMikeH will probably improve on this but here is my method. (Note the following does not apply to NiMH.)

Never overcharge, as once the battery is fully charged, the energy goes as heat, (feel the battery-if hot its too much) but don't undercharge either. Manufacturers chargers with either voltage or temperaturer sensing are good.- If a simple uncontrolled charger is supplied, as normal with cheapies, (no cut-out when charged) use a time switch on the mains.

At least every three times, discharge fully by running drill till it stops before recharging. If using a cheapie charger, do this every time and rely on the time switch for correct charging.

If the battery does not charge, it will have gone high resistance and charge current will be very very low. In this mode the battery will never charge. This can often be broken down by forcing current through the battery from a higher voltage source, possibly double or more the normal voltage. It may take several days. However once the cell resistance starts becoming normal, the current will rise quickly, so a current limited souce must be used.
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Old 8th September 2007, 07:59 AM   #22
Eva is offline Eva  Spain
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In general all battery packs (NiCd/NiMH/Li-Ion) should be recharged as soon as you notice reduced speed or torque, as this happens when one or more of the cells have gone empty and are starting to work reverse biased.

Reverse biasing damages cells and results in permanent capacity loss thus leading the weak cells to become weaker and weaker because they will take less and less time to become empty while the other cells are still charged allowing the user to continue using the drill.

Charge unbalancing between cells may obviously arise after a few cycles. NiMH can be balanced with patience and trickle charging at or below 0.05C without damage. NiCd life is reduced by any kind of overcharging, those are hard to balance without at least very slight damage. For Li-Ion, 4.2V (current limited to C) may be applied to each cell for a long enough time in order to guarantee that all cells are fully charged, at this voltage they progressively stop taking current as they become charged without damage.

BTW: Speed control and clutch are really useful features.
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Old 8th September 2007, 09:31 AM   #23
Cobra2 is offline Cobra2  Norway
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I used Makita about 10 years ago, 9,6V & 12V, and remember them beeing very strong, and had a very good gear-box; could shift from high(2) to low(1) while torquing down a screw! (without stopping!).

Arne K
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Old 9th September 2007, 02:52 AM   #24
OzMikeH is offline OzMikeH  Australia
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I bought a whole drill for $20 at the supermarket because it was 12 volts (for car battery lead afterward) and I only needed to drill 2 holes. Make sure whatever you buy is faster than 450 RPM. 1800 to 2000 RPM is good.

Agreed. running the drill flat WILL eventually destroy the cells by reverse charging them. Leaving on charge all of the time and overcharging causes dendrites. Dendrites are conductive crystals that eventually short the cell out.

Pack revival, for AA, C or D sized cells NiCd only. Scale up the currents for really big ones like 5A/H cells. If working with large cells wear safety glasses, a face shield, welder's jacket and remove all conductive things from your hands. These things can blow a belt buckle apart like a firework.
Leads, cells and loads will get hot, if anything gets too hot stop, wait for it all to cool down. then proceed. Never discharge unattended.

Take the pack out of the housing, leave the cells connected, look for any white growths on the cells, if these are excessive the pack is stuffed. If they aren't leaky number the cells from one end of the string to the other with a marker pen. small growths can be cleaned with some distilled water and your sister's toothbrush. dry thoroughly afterward.

measure and record the voltage on each cell, should be within 0.05V on a really good pack. If any are 0V or just above refer to the dendrite blowing procedure at the end.

Get lots of croc clip leads, discharge the whole string through an appropriate resistor for 0.75C (3/4 of the cell's amp/hour rating)
Monitor each cell's voltage VERY closely.
(optional step to speed it up: as each cell falls below about 0.4V short the cell with a 1 ohm 5W resistor.)
as each cell falls below 0.1V short it out with a wire link.
continue discharging until all cells are shorted out. you will need to reduce the resistance of the load once half of the cells are shorted.
When all cells are shorted with wire links disconnect the load and leave it for a couple of days with each cell shorted out.

Will submit another post for the charging procedure.


Dendrite blowing:
Get a bench supply, current limited for 4C (4 times the cell's amp-hour capacity) and 5 volts. get some heavy leads with banana plugs.
Double check the polarity of the cell, hold one banana plug in each hand, at this stage you will experience an overpowering urge to call out the word "Clear!" loudly.
Hit the cell with a 2 second burst of current.
check the cell's voltage with a meter. If the dendrite has been cleared the voltage will have jumped up to about a volt. the cell has been revived.
If the voltage is still zero hit it again for 4 seconds, NEVER EXCEED 4 SECONDS. repeat as required, If the cell remains at 0V after 5 or 6 attempts it is U/S.
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Old 9th September 2007, 03:22 AM   #25
OzMikeH is offline OzMikeH  Australia
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After your pack is well and truly discharged remove the wire links.

Set your bench supply for 1.4V per cell, current limited to 0.1C.

connect the supply to the battery (make sure it's the right way around!)

After 10 minutes measure and record the voltage of each cell.

repeat measurements regularly, If any cell is increasing in voltage too fast it is faulty. individual cells can be replaced but rebalancing will have to be done much more often. If a cell is faulty discharge the whole pack again do the same to the new cell, then install the new cell and start the charge again. Try to use a replacement cell that is as equally worn out as the rest of the pack.

keep charging and check every cell regularly. Charge for 18 hours.

Carefully reassemble the battery pack, write the date on a zip lock bag, put the battery in and store it in the fridge (NOT freezer!). If you are in a humid area put a small amount of dessicant in the bag too.

Remove the pack from the fridge to warm for 2 hours before use. It will remain charged for about three months if stored in the fridge. Don't top it up every three months. Use it then charge it.

After use (until it just begins to look flat) charge the pack on your bench supply instead of the charger that comes with the drill. 16 hours at 1.4V per cell at 0.1C current limit. Set an alarm or a timer. If using a timer to switch the bench supply off charge the pack through a diode and don't forget to add 0.7V to the charge voltage.

Using your batteries like this your cells will last a very very long time.
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Old 9th September 2007, 03:26 AM   #26
OzMikeH is offline OzMikeH  Australia
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For determining the amp-hour rating of a 12V cell use a 7810 and a 10 ohm resistor. discharge the pack through the constant current load and plot time against voltage.

use a 7805 and 5 volts for a 7.2V pack.
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Old 14th September 2007, 05:48 AM   #27
owdi is offline owdi  United States
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I have a cordless Makita drill, and it is my favorite tool. I like quality tools, and this thing puts a smile on my face every time I use it. I have two 12v 2 Ah batteries, and rarely need to change the battery during a day of speaker building. 16 torque settings, 2 speed settings and a keyless chuck make it a snap to use.

I once dropped it from a ladder, and it fell 10 feet onto concrete. It thought that was the end of it, but all it did was snap the plastic housing out of place. The drill still works, and a few whacks from a rubber malet realigned the housing.

The drill failed me only once, when I was drilling Jatoba. This stuff is more than twice as hard as oak, and I had dull non-carbide bits, so I had to fall back on my classic Milwaukee hammer drill.

Anyway, I'm just rambling. I <3 Makita drills. Mine is available as a refurb from amazon.com for $70 + shipping, but you're across the pond, so it'll probably cost you twice that.

Dan
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Old 14th September 2007, 08:02 AM   #28
TroelsM is offline TroelsM  Denmark
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Hi all.

Thanks for the valuable feedback.

I found a used Bosch 9.6V (green series) with a fast charger for ~26$ with shipping.

I have one just like it (blue "pro" series) and it works very well. It has ~10 torque settings, two gears and is nicely balanced. The battery is refurbished with 3aH cells.

Somewhere in the stash I have a complete motor-gear-assembly from a similar Bosch, so all-in-all I should be set up for years of speaker-building :-), even if one of my Bosch´ fail.

Regards TroelsM
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