Battery conditioner for 18v DeWalt

Since the battery technology changed a few years ago. I doubt that you will improve your battery life. I pitch my batteries after a year here in the SW USA.
I am really amazed that a fire company would even consider a battery tool for extractions. Your engine should have a generator. I would think that you would be using line voltage for your saw-zall.
I suggest that you forget about the batteries for extraction and get back to the "powered" method. My 18v Dewalt saw-zall with a 8 inch wood blade lasts about 10 minutes with a fresh battery and charge. Then it takes about 30 minutes to recharge. Even with 3 batteries your on a coffee break before the victim is out of the wreck.

I would suspect that these are unrecoverable - running the thing until it stops is as good a way as discharging the battery prior to recharge as most things. You could wire up a couple of 12V lamps in series as a load and find a sutiable relay that trips out at the right sort of voltage, if you wanted. Stick a battery driven clock on, if you want to know how long it took.
I have seen 18 Volt drills being run off 3 6V lead acid batteries in series - with the batteries on the operators utility belt. That seemed to be a pretty good compromise between portability and endurance. The batteries can then be as large as the operator can manage, but the exisiting battery also has to be in place for balance.

I can give you exactly what you asked for in the bigger paragraph above. What you describe is exactly what I built for experimenting with batteries - an adjustable discharger with elapsed timer. Simple, cheap, reliable and fail safe. Sounds good? Don't be too fast at thinking so. Read on. As to the word "conditioner" in the second paragraph - doubtful that it would help.
You got two excellent replies, in my opinion. I can't add to the first, I don't have experience as a fire fighter. In the second, Palindr :-) me mentioned that running it until it doesn't work will discharge it just fine, and that is correct. When it still runs, but is ineffective, charge the battery. (Running it ALL the way down by taping the switch ON is NOT what we're talking about.) His circuit recommendation (if you just *must* do it) with the light bulbs is right on. But instead of searching for a relay, it is easier to use a TL431 "programmable zener" to drive a transistor to operate the relay. That way, relay selection is simple - just use one of those cheap 30 or 40 amp automotive relays.
Even with a nice discharger circuit that automatically turns itself off when the batteries are discharged to the correct level, I don't know if you will improve battery performance much, if at all. That said, if you are going to proceed, it should be considered mandatory that you have automatic shutoff. If you discharge the pack too far, you definitely risk damaging it. The selected relay will do that, as will the TL431/transistor/relay.
Ed

Have you tried to contact DeWalt directly? That should be your next step.
Objective: Looking to buy for or assistance with building a battery conditioner for an 18v DeWalt sawzall.
Background: I'm a volunteer fire fighter and on the rescue team of a fire and rescue department. One item we purchased about two years ago was an 18v DeWalt sawzall and three batteries. We have used this for vehicle extrications. We rotate the three batteries as 1) in the saw, 2) spare with the saw and 3) in the charger. Over the past two years, the sawzall has only been used a few times. At present, the batteries will only power the saw for about three minutes with no load.
On one hand, we are happy that we have not had a lot of vehicle extrications. But, this means each battery may go for many months without any use. We would like to buy/build some sort of battery conditioner to put a load on the battery before the battery goes into the charger. We have found some conditioners for 12v systems, but nothing for an 18v system.
A couple of us non-electronic folks have talked about some sort of system that uses light bulb(s) to put a load on the battery. Along with some sort of relay that opens the load circuit when the voltage drops below some predetermined level. Maybe even including some sort of resetable timer to measure how much time it to took before the relay opened up. This may give us some indication of the overall health of the battery.
Does anyone out there have any sources for an 18v conditioner system or can someone provide some assistance in building a conditioner system?
TIA -- Email hint - Everything after the @ is spelled backwards.
There are only 10 types of people in the world: those that understand binary, and those that don't.

On Sun, 23 Jan 2005 21:39:03 -0800, mg wrote (in article ):
It's not the conditioning, it's the charge cycles.
A charge cycle = placing the battery in the charger, regardless of its condition. If it's flat or if it's nearly-fully charged, that is one charge cycle.
If you're continually cycling your batteries (in tool, spare, in charger), this means that you're eating up your batteries' life even if it's seldom getting put to work. Conditioning the batteries before charging won't extend the life, by much, if at all.
I echo the other recommendations for pitching the battery tool in favor of a corded saw. Even at best, with new, fully-charged batteries, you don't want to find yourself with only X minutes of power and still needing saw power, in your job.
A good news group to ask questions like this in is chem.electrochem.battery Many who participate in that group have much experience with battery charging, etc.
Good luck,

On Mon, 24 Jan 2005 18:30:09 -0800, DaveC wrote (in article ):
er, rather:
sci.chem.electrochem.battery