Dewalt (the glorified B&D's) is bringing out a new range of 36v tool which are bound to hit our shelves sometime this year, probabl initally through ebay and cheaper!!
These will obviously be in direct compo with the Bosch range and I be with a price tag to suit!!
Will be interesting to see how they go down, but for the average DIYe they will have no need for anything more powerful than 18v, so I tak it they are aimed at the professional.
Bet the hammer drill will have some umpth on it...
It seems to me that there are several different markets here.
- DeWalt and Bosch professional hammer drills. I am dubious about the point of a 36v cordless hammer drill, although it's interesting that the Bosch one is the same weight as the 24v product. Other than that.... Hmmm.
- Entry level drills using higher voltage battery packs. There have been spates of these with claims of " a pound a volt" etc. The battery packs in these will be questionnable at this price point. However this is a marketing man's dream, although his normal job is probably marketing of penile extenders.
- SDS drills. These seem to perhaps make sense at 36v for capacity reasons as long as they have good quality batteries. A typical user might be an antenna installer who doesn't want long power cords trailing up ladders. Plus, they can still be 4kg in weight.
- Circular saw. Also seems reasonable because the tool rests flat and is usually guided against something. The 18v ones don't have enough battery life to be worthwhile.
- Jig saw. I'm dubious about having a heavy tool here fro controllability reasons.
Of course what the manufacturers decide to make is something else.
Since pretty well all power tools use the same sized cells, the only real reason to increase voltage is to get a greater capacity, ie longer usage.
Because for the average cordless drill used for DIY drilling and screwdriving 12 volts or thereabouts is enough. A cordless SDS will be different, but not many DIYers would actually need one.
If you check out a cheap B&Q drill like their PPPro range you'll find their 18 volt types have actually less torque and poorer battery life than a 12 volt Makita. Because they use cheap poor quality batteries. And chargers. Go down the route of say 500 cycles of the batteries and the difference will be even more marked. If the PPPro is still working.
The higher the voltage, the more the tool weighs and the greater the bulk. For those making an impulse purchase this may seem a good thing. For those using them seriously for DIY - not.
My imitation Mkita 24 volt has just given up the ghost. It might be repairable if I coul only take it apart. It just won't though. The ratchet or something in the gear box has gone.
Not bad for a couple of years site work.
I still have a charger with 2 usable batteries of the cheapo Chinese quality. Fortunately I have a Power Devil whose 18 volt batteries I cooked on the wrong charger, Power Devils supplying about the worst chargers going that gave out almost immediately.
That left me stuck with a reciprocating saw, a circular saw and the drill no longer usable (the saws virtually unused.) The 24 volt batteries are the same male-female fiting as the drill's but the clips on the drill get in the way of full mating.
They still work though. So do I cut the clips off the 3 tools and buy a roll of Duck Tape?
I am tempted, though I might just use them with a 1/4" gap and try the tape until one or the other of us gives out. I might even be tempted to make a wire clip. It is not exactly elegant but I am such tight arse.
And the next one of the species I buy will be a DeWalt screwdriver. The little 12 Volt one with a gizmo for measuring screw depths. I fell in love with one that some Irish bog trotter was using along side me last summer. It made my huge 24 Volt look like a toy.
It was in the order of a couple of magnitudes a greater weapon. I kid you not! It just left me standing and did a far better job too. I had to keep guessing the depth, then go over my work to sink them while he was on the next run of screws. He was three or four times faster and only had to do the job once.
Is that actually right Dave ("they pretty well all use the same sized cells" I mean)? (I assume 'C's' or sub C's ?)
I believe capacity pretty well equalled mass where batteries are concerned but there are advantages running a higher voltage with less current re restance and voltage drop (therefore waste) etc (do any maker make use of this though?)
I mean you could have 5 x 1.2V 4Ah 'D' cells giving (simply) 6V @ 4A (24W) or 10 x 1.2V 2Ah 'C' cells giving the same power but with (potentially ) less voltage drop = less energy loss = last longer for the same size conductors (intercell, cell > motor > switch (or more efficient speed controller) etc)?
Higher v is no more efficient, since the motor windings are longer and thinner for higher Vs, and the opposite for lower.
Higher v does however mean shorter battery life, more potential failure points means a cell will fail on average sooner. Unfortunately marketing rules, so we see 24v 1.3Ah instead of 12v 2.6Ah.
Lastly Ah capcity and current output. NiCd D cells can give 60A a piece, I dont know what a sub c can do but it will be far above 1.3A for a 1.3Ah cell.
Yes. All the packs I've fixed - ie basic drills - use sub C size. But the capacity and peak current varies enormously from the worst to best. Hence 'cheap' drills going to higher and higher voltages to give a decent battery life - while the cells are new and working to peak performance. I'm just assuming that to the maker a 1 amp/hour cell costs less than half a 2 amp/hour one. Or pro rata. Otherwise it makes no sense - other than 'mine's bigger than yours' marketing - to go to such high voltage. DC motors need current to produce torque.
You require high current to produce high torque - like when driving screws.
I do have a cheap cordless drill - a PPPro 18 volt. And when the battery failed I re-celled it with Sanyos. You wouldn't believe how much better it worked in every way. Oh - and I bought a new spare from B&Q before doing this, so it was definitely a comparison between two new batteries.
But to explain further, the Sanyos cost almost as much as the entire drill
- even at reasonable bulk prices. I keep them in stock for fixing pro audio batteries so did it as an experiment.
Oh indeed. When I was racing electric cars in Ally Pally Palm Ct Hall (all them years ago) sub C's were 1200mA. The same size cells are now what 4000mA ? It was also kown then that a matched set of Sanyo's were much better than the supplied cells ;-)
Indeed (and I have done the same to rechargable torches / dustbuster etc) ;-)
But this was supposed to be high over low voltage rather than cell quality?
My EV runs from 48V and the conductors, switchgear (n cells) have to carry some 400A on pullaway. The voltage drop over all those conductors is quite high. One mod done to this model is to increase the battery voltage (double) hence reducing the current (for the same 'power') and realising a better range? There is no room for more battery capacity so it's simply a more efficient solution (or no one would bother doing it presumably)?
If you double the voltage on a cordless drill you would often end up with a higher reving motor so the gearing would be modified to bring the chuck down to the same revs as before .. bringing the torque back at the same time?
Granted .. but comparing like with like .."yes, current is a function of voltage" ;-)
So as the voltage goes up and the current goes down isn't it possible these 'cheaper' cells could survive better (as per your good cells = high current)?
Ok (and reluctant as I am to mention this) why does Drivels fantasy hybrid Primus thing have 240V worth (or whatever) of smaller cells and not 24V worth of bigger ones?
A decent SUB C NiMh cell will deliver over 200A. But typically should be held to 60A or so for extended operation.
In the end there is no difference between 100A at 9.6v and 50A at
19.2v...except in the latter case its easier to arrange without paralleling cells, and the switching and wiring is easier to make for he high voltage case....which is why the national grid runs at 160kV or more not at 12v :-)
With te advent of LIPO power tools and the ease with which these cells may be paralleled, it doesn't make as much sense to jeep jacking up voltages to get more power..but still its true to say that one wants to keep voltages below 50v or so for safety reasons..and currents below 50A or so for wiring and switching reasons...a lot depends on the semiconductor devices you use to regulate the motors...these tend to be able to reach 50v easily, bit not currents over 50A..in the ned its all down to cost...use what is cheap to use.
Doesn't seem to be the case. A good make 12v with the same peak starting torque as say a cheap 24 volt will invariably have longer lasting batteries. Of course it will have a better charger too.
Well for a start it uses a different design of motor.
But the real answer is there is usually an optimum for any use. And while high voltage may be necessary for traction use it doesn't follow it will be better for a drill. I'd say for the average DIY drill it's just a selling 'feature' - 'bigger is always better'. Different matter with very power hungry cordless tools like circular saws and SDS drills.
I think that the "bigger willy" factor is the main point for the low end.
Another factor in higher voltage/lower current, is in the power distribution from batteries to motor including cabling, switching, brushes, windings etc., all of which need to be stouter at higher currents.
There is a grain of truth in it though. With sensible cells (SUB C) at around 1000-2200 mAh. the only way to get more power and keep a decent usable battery time was to add more cells.
It is if you use ones at the bottom end of the range. As you say the capacity can vary by more than 50%. However, doubling the number of cells makes for a larger battery and therefore bigger and heavier drill. I doubt the savings in cable thickness etc due to the smaller current offset this.
I know it all goes back to the cheap v expensive cordless tools debate, but for me just one more thing in favour of buying quality.
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