Moderator
I also have some Makita tools (excellent) but no cordless. The huge advantage is sticking with one brand. My Odd Man is one Hitachi impact driver with 3 LiIon batteries that built much of my shop, some decks and a lot of my farm construction. It simply won't quit.
JKJ
Originally Posted by Rich Engelhardt
Contributor
Bosch 18v cordless drill, first and only cordless tool I own, unless you consider all my hand tools, the ultimate cordless tool. Replaced batteries once, never again. Cost me more than a combo drill/impact driver kit. While the drill has served me well and I'll keep it until this set of batteries die, I still kick myself for not going with the combo kit.
Member
Mark when you say that you dont care for the battery life of lithium ion ,are you getting longer life from NiMH batteries ? I wonder if that is a climate thing ? I really considered Makita,a lot of trades were using them here in Alberta about 5-10 years ago. We had huge issues with the batteries crapping out. This was the main reason I went Milwaukee. Here in the hot summer to real cold winter lithium ion lasts about 2.5 times longer than any of the others.
Guest
Makita used to charge the batteries in 15 minutes. It's too fast for the cheap cells that are used. They just can't handle the amperage going back in. Lithium ion/polymer/iron batteries start coming apart chemically if they get pushed too hard. They also don't like going below a certain voltage, or they don't recover. That's why all of the new cordless tools hit a voltage cutoff and just quit, pulling any more juice out causes the voltage to sag too much damaging the cells.
Nihm batteries are a lot more forgiving.
Member
Well today is a good day ,I learned something.I actually like the way the batteries just stop when they need to be charged,instead of slowly winding down. Now I know why. Thanks, Martin.
Moderator
Good LiIon batteries themselves have circuitry to prevent being drawn too low and the chargers are designed to monitor and prevent damage from overcharging. The tiny cheap LiIon batteries used in micro RC heli and quad copters, for example, don't have the protection and the pilot is cautioned to land immediately when noticing reduced power. If drawn too low, the batteries cannot even be recharged, even if not fatally damaged. (BTW, these tiny things are great fun in the shop!)
My cordless tools or the batteries themselves have a push-button power monitor to check the charge. This can give you a heads up to have a charged battery handy. I suspect all the brands have this.
JKJ
Contributor
All I can say is I have NiMh makita impacts that are still running that are probably about 15 years old. I have a bunch of LXT's that we picked up in a tool lot from a guy who got injured and there were I believe 10 or 12 LXT batteries in the lot, a couple impacts, chuck drill, sawzall, circ, etc.. the 12 batteries were mix of the larger and the smaller LXT. Have probably had them for about 8 years and several of the LXT batteries are long since dead.
Like I say, my main beef, and Im sure its true with much of the new battery technology, is they are no longer rebuildable. It gets old buying $100 batteries when you can buy kit for a couple hundred plus.
Member
I agree, my Hitachi 18V won't give up the ghost at all. I keep waiting for the batteries to fail so I can justify going to buy another one, but they keep on chugging along. I had to jump start one battery that got too low, but it's never had a problem since.
Member
Same thing with computers...I paid $60 fixing a laptop which lasted less than two years after the fix. I am still kicking myself for not spending that money on a new laptop instead, which is faster, lighter and bigger (in harddisk storage). Lesson learned...mistake will never be repeated.
Simon
Guest
Typically it's not the battery that determines the cut off, it's the controller in the tool that does it. That might not always be the case or at all with cordless tools though.
Member
I am still using a Bosch 14.4v drill.... It still works very well so no reason to dispose of it. I also have some of the newer tech drills as well.
Robert
Contributor
Is the controller in the tool or in the battery? I have been waiting for someone to come up with a hack to rehab the Makita LXT's but everyone tells me there is a board in the battery that when it says the pack is dead there is no getting around it. It'd seem the battery status would have to be in the battery itself to disallow charging when its put on the charger.
Moderator
I know nothing about the differences between battery control circuits in power tools compared to other applications. Perhaps things used to be different or are different now from when I studied this. (The more I read, the more I was impressed with the complexity of the ubiquitous batteries in my cell phone and iPad.) In addition to internal temperature and over-pressure sensors and vents, I understood internal battery charge/discharge protection was commonly implemented. Some stuff from the Battery University, "BU-304b: Making Lithium-ion Safe" from a year or so ago:
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Li-ion commonly discharges to 3.0V/cell. The lowest permitted “low-voltage” power cut-off is 2.5V/cell. It is not advised to keep the battery at that level as self-discharge could bring the cell to its cut-off voltage, causing the battery to go into sleep mode. Most chargers ignore Li-ion packs that have gone to sleep and a charge is no longer possible. (See BU-808a: How to Awaken Sleeping Li-ion.)
In the ON position, the internal protection circuit has a resistance of 50–100mOhm, lower on power packs. The circuit typically consists of two switches connected in series; one is responsible for the high cut-off, and the other for the low cut-off. Larger packs need a more careful design than a smaller battery, and single cell packs for mobile phones and tablets get away with a voltage and current limit in addition to some intrinsic cell protection. (See BU-802a: How does Rising Internal Resistance affect Performance?)
Some low-cost consumer chargers may rely solely on the battery’s protection circuit to terminate the charge. Redundancy is paramount for safety, and unknowingly to the buyer, low-cost consumer chargers may be offered that do not have properly functioning charge algorithms. This could be a vehicular charger for a mobile phone or an e-cigarette.
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The better chargers sense conditions independently: In addition to internal cell safeguards, an external electronic protection circuit prevents any cell from exceeding 4.30V on charge. In addition, a fuse cuts the current if the skin temperature of any cell approaches 90°C (194°F). To prevent the battery from over-discharging, a control circuit cuts off the current path at about 2.20V/cell.
I certainly am no battery guru but my friend Joe is, he knows everything. He probably knows about the typical power tool implementations. I'll try to catch him and ask.
BTW, anyone interested in electronics and batteries might browse the Battery University site.
JKJ
Contributor
I have a lot of Makita 9.6 stick batterytools. 6-7 drills, 2 right angle drills, jig saw, clippers, flashlight etc. Good enough for me. If they made a lion battery to fit I might try.
Bil lD.
Guest
Most cases.... most, the ESC (electronic speed control) is what has the low voltage cut off in it. A battery is just cells wired in series or parallel to achieve a certain voltage or Mah rating, or both. I think Li-Ion is similar to a Li-Po battery for voltage, 3.7V per cell. Whereas Ni-Mh and Ni-Cad are both 1.5v per cell. Li-Po is a way better battery in terms of performace and size, but they're volatile and if they aren't charged correctly have this nasty habit of starting fires that can't be put out.
I only know anything about batteries from flying RC planes, and racing RC cars. There it's all controlled by the esc. I'm about 90% sure that's how the lithium packs in my Panasonic drill and impacts are too. New stuff in regards to cordless tools? No idea. Some of the DJI quadcopters have smart batteries, so maybe companies are doing it with tools as well. It makes the battery that much more expensive.
Battery tech and brushless motors have come a long ways even in the past few years. As has charging. To charge my Li-Po packs, I use a $400 charger with a separate power supply so it's getting clean DC. Thats also how I know you can't pack the amps back into a lithium battery the way Makita used to do it and not cause some harm to the pack.
The chargers should be keeping track of the voltage of each individual cell and balancing the voltage between them. That's why the Lithium batteries have multiple terminals, but the tool only has the two prongs. Over charging damages the chemicals, as does allowing the voltage to go to low. It will adjust the amperage that is being applied to the each cell as they get closer to the end voltage as well. The charger I use for RC stuff will measure the resistance in each cell, if one is going bad, I know it pretty quick and dispose of it.
All really useless stupid stuff you don't need to know unless you're into RC stuff. Tools, drop it on the charger, when it no worky, get a new one.
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