Date: Tue, 22 Sep 1998 14:38:52 -0400 (EDT) From: Marty Goodman MD KC6YKC Subject: DeWalt battery chargers John Whitley quite rightly noted that ALL smart DeWalt poewr tool battery chargers use voltage sensing only. I should note that all my experiences with DeWalt service and customer support folks were equally astonishingly positive, when it came to their simply and plainly answering detailed critical technical questions about the design of the product. I guess what confused me is John's initial impression that only a DW9104 or DW9106 will work. Perhaps he didn't see my "latest" (four months ago) post on this subject. In that case, for John, and those others who haven't see it, here it is (again): ---------------------------------------------------------------- Guide to DeWalt Chargers (c) Marty Goodman May 1998 (may be freely re-published only in NOT FOR PROFIT printed and electronic publications / services) As many on BikeCurrent know, I've been recommending DeWalt power tool chargers as a third party smart NiCd bicycle lighting battery recharger for quite a while. I've also noted that Black and Decker makes identical equivalent chargers. Important WARNING / Note: The DC output to the NiCd battery of these power tool chargers is HOT with respect to ground, to the tune of 110 volts AC, making it imperative that modified chargers be set up and used with care and only by knowledgeable tinkerers. Touching the charger output, or touching an exposed battery contact while the battery is connected to the charger, can result in a startling, or painful, or even potentally (tho fortunately very rarely) LETHAL shock IF you are also in contact with an earth ground (cold wet stone floor, cold water pipe, etc.) at the same time you touch the charger or battery contact. Modified chargers should be set up in a controlled area where children, pets, or curious adults ignorant of the dangers they pose cannot get at them! And should be used BY the tinkerer with care and respect for this potential danger. A knowledgeable tinkerer who is highly safety conscious can eliminate this shock hazzard by powering their DeWalt 9104, 9106, 9107, or 9108 charger (or equivalent Black and Decker charger) via a 110 volt to 110 volt AC isolation transformer. The model number I've mentioned most over the last two years was the DW9106. However, the venerable DW9106 has been discontinued. Some hardware stores and chains that carry DeWalt stuff MAY still have the 9106, and some of those MAY be closing them out at extra low prices. The normal retail price on the DW9106 was around $45. I picked up a couple for $10 each a while back from one chain that was closing them out. The DW9104 is IDENTICAL to the 9106, except for one sensing resistor on the circuit board. This resistor, R2, is 13,000 ohms in the DW9016, which is rated as having a 1.9 amp charging current. R2 is 15,000 ohms in the DW 9104, which is rated as having a 1.5 amp charging current. Both the DW9104 and 9106 are rated to handle batteries from 7.2 thru 14.4 volts, tho in practice I've used them successfully with batteries as low as 4.8 volts, and the technician at DeWalt, when I called about this, told me he thought they could be used down to a single cell (1.2 volt) battery, but that in any case the could be used with confidence on batteries down to 4 cells (4.8 volts), and that the rating on the package reflected ONLY the fact that the batteries made by DeWalt designed to fit in the hole in the charger were made in votlages ranging from 7.2 to 14.4 volts. NOT due to 7.2 volts being the lower limit of what the charger could handle. I believe DeWalt made yet another model of charger for this line of power tools, the DW 9105, I think, which was designed to run off 12 volts DC. If you can get such a charger at a good price, DO SO. For by powering it off a linear 12 volt DC wall source, you will eliminate any shock hazzard! And you will have the added advantage of being able to use it on the road, powering it off your automobile's battery. ------------------------------------------------------------- DeWalt switched to a different physical style of battery and battery contact. These batteries had higher power capacities, and to charge them quickly enough DeWalt completely redesigned their charger to put out almost twice as much current as the old ones, as well as redesiging the hole in the charger and the battery contact to fit the new line of power tool batteries. Their DW9107 was the first charger they put out (that I know of) in this series. It was rated to handle batteries from 9.6 thru 14.4 volts, but works fine in my experience with batteries at least down to 6 volts (and probably lower. It puts out 2.8 amps of charging current during fast charging. The current model in this line that's being sold is the DW9108. This model puts out 2.8 amps of current when fast charging, and is rated to handle batteries from 9.6 volts thru 18 volts. This current model is available at Home Depot priced at $50.00 plus tax. Its circuit board is very similar to, but NOT identical to, that of the 9107. There's an extra chip on the board, and some minor circuit changes. I have very limited experience with the 9108, but have every reason to believe it will handle the same range of batteries as the 9107. The CURRENT model DeWalt charger that can be run off 12 volts DC is the DeWalt model number DW9109. It's rated to handle batteries from 9.6 thru 18 volts. The equivalent Black and Decker charger is model number 980178. Retail price should be around $75. I don't currently know what, if any, charger is made by DeWalt in the same line as the DW 9107 and DW 9108 that will run off 12 volts DC. If they DO make one, it would be desireable because of the easy ability to remove the shock hazzard from the charger, and to run the charger off a car battery. But it is also likely to be quite expensive, as such a charger would require an added DC to DC converter to step UP the 12 volts DC for charging purposes. Summary: DeWalt power tool chargers that run off 110 volts AC fast charge model number current status stated bat voltage range ------------ ------------ -------------- ------------------------ DW9104 1.5 amps discontinued 7.2 - 14.4 DW9106 1.9 amps discontinued ? 7.2 - 14.4 DW9107 2.8 amps discontinued 9.6 - 14.4 DW9108 2.8 amps current model 9.6 - 18.0 DW9109 ?? current model 9.6 - 18.0 *** *** powered off 12 volts DC. No Shock Hazzard. Can be used in a car. Note: The case of all four of these models, and of the Black and Decker equivalent chargers, is held together with four SECURITY type torx screws. You need a T15 size SERCURITY type (hole drilled in the middle of the bit) torx bit to open these cases up. Such bits are widely available at well-stocked hardware stores these days (tho in times past were hard to obtain!). Black and Decker addendum: Black and Decker has, I'm told, CEASED to make power tools for the commercial market, leaving that to their "DeWalt division". They no longer make high quality power tool chargers under their own name. Only now under the name "DeWalt". HOWEVER, they USED to make the same chargers named above under the Black and Decker name, but with different model numbers, and called "UniVolt" chargers. Here are some model number equivalents: DeWalt Black and Decker ------ ---------------- DW9104 97104 (7.2 thru 14.4 volt batteries / 1.5 amp charge) DW9108 97016 (9.6 - 18 volt batteries / 2.8 amp charge) DW9109 980178 runs off 12 volts DC DC to AC converter addendum: Some folks may wish to try using an AC power input type DeWalt charger with a power inverter, that provides 110 volts AC off automobile 12 volt DC power. This MAY work, but then again it may not. For the square wave from these inverters MAY cause problems with the DeWalt chargers. Then again, it's possible they will work just fine... or even better. I just don't have any experience with this. --------------------------------------------------------------------- (1) Note that ONLY DeWalt and Black and Decker chargers are useful. This is because only they sense battery charge state EXCLUSIVELY by periodically sampling battery voltage. The other brands (Makita, Milwalki, Ryobi, etc.) of power tool charger-battery systems either rely on or at least use an internal THERMISTOR that's inside the battery pack, which connects to the charger via a THIRD contact. Since your pack lacks this thermistor, it can't be effectively charged "generically" using those other brand chargers. And getting the right thermistor to modify your pack is difficult. (2) If trying to charge a NiteRider or other battery that has a barrel type plug conector on it with a modified DeWalt charger, I recommend using an in line female barrel connector (like the one you cut off your exising NiteRider power supply) AND sheath that in some vinyl tubing, in such a way that you can't touch the hot metal of the sides of the connector, but still allows plugging and unplugging your connector. You might put a bit of a notch in part of the vinyl sheath to make this work. This helps reduce shock hazzard. Tho anyone really safety concsious shouuld also use an isolation transformer on the 110 volt AC input to the charger. --------------------------------------------------------------------