Battery Experts Please...

[Brent Leonard]

Never let NiMh's discharge completely, it kills the life. NiMh's allowed to remain dead for as little as one week can ruin the battery. NiMh's have no memory like the NiCad's. NiCad's can & should be stored nearly dead and should be run to near dead before a recharge, but not totally dead. Keep NiMh's cool, heat kills em quick. NiCads don't love heat, but can withstand it better than NiMh's. Always allow all batteries to cool completely before recharging.

Storing NiMh's require an occasional recharge every so often as they slowly discharge.

Your NiMh's crapped out because they sat without a charge.

[Jason Abel]

NiMH batteries are extremely similar to NiCads but with higher capacity. They will develop a symptom very similar to the "memory" issue commonly found in the older NiCad batteries. When you start experiencing trouble with NiMH batteries they DO need to be discharged completely and cycled through multiple charge/discharge cycles to wake them up. I would also argue that storing a NiCad without charge is not what we would recommend either. If the voltage of the battery drops down below the cutoff voltage of the charger it will reject your battery as defective. We recommend storing all Nickel Based batteries fully charged and most importantly not on the charger. Heat kills NiCad, NiMH, Lithium, and PB batteries. Some are obviously more resistant than others but the NiMH cells we use will accept usage in higher amperageand higher temperatures than the NiCads on the market today all with a lesser self discharge rating. As a "general" rule though NiMH does self discharge a little faster than NiCad.

Jason
MTO Battery

[Vic Damone]

The individual cells of a battery are subject to self-discharge. With older batteries, some of the cells may lose their charge more quickly than others. As conventional chargers switch off when the first cells have reached full charge, the other partly charged cells never receive the full charge. The user becomes aware of this effect in the form of inadequate battery capacity, also referred to as age or memory.

Hilti chargers are equipped with a "Refresh" button on the charger. The button is pressed as the battery is inserted in the charger and it's released when a yellow indicator lamp lights. The yellow lamp is lit as long as the charging in refresh mode is taking place. I may refresh a battery once in every fifty cycles.

Hilti asks that as soon as you notice the battery losing its charge it should be recharged.

After owning yellow and blue cordless drills and considering the new battery purchase over buying a new tool I decided to spend a few more dollars for the Hilti. That was almost six years ago and these Hilti NiCads work as strong and long as the day I purchased them. I now own three Hilti cordless tools.

[Eric Sayre]

As Jason stated, NiMH batteries will discharge faster than NiCad (as well as lithium ion.)

I've owned many rechargable batteries. Through research and experience I've learned that NiMH discarge quickly, but they can produce more power in a sudden burst. That is their payoff. That is what makes them great as camera batteries.

I've never seen that to be a plus for battery powered drills & saws. It seems to me as if Lithium Ion may have the overall edge for power tools.

Eric

[Jason Abel]

Lithium may have the edge for weight and short term performance but they are no good as far as overall life expectancy and temperature sensativity. Use the lithium batteries in sub freezing temperatures sometime and note the difference. NiCads and NiMH will also perform less but the difference is drastic on Lithiums. We also rebuild a bunch of Segway battery packs and the lithiums are having tremendous problems with poor life and being troublesome in general. The NiMH packs are lasting at least 2-3 times longer and cost almost half of what the lithiums do.

Bottom line is that lithium technology is great but it is technology that has not matured yet. They are EXTREMELY close and I believe very soon more reliable lithium technology will emerge that is more affordable. Until then I stand by the Nickel based batteries as they will provide you with more watts of power before needing to be replaced than a lithium battery will (according to the charge/discharge cycle testing we did on multiple brands).

Jason
MTO Battery

[J. Z. Guest]

I've had that happen to NiMH batteries too, mostly Energizer AAs.

NiCd has half the energy density of NiMH, but twice the shelf life. (holding a charge) They're also lighter. But they do self-discharge pretty quick also.

I'm so glad to have gone to lithium. They're more expensive, but for someone who doesn't use them every day, they're beautiful. Brings the convenience back to battery-powered tools.

I had a Makita 12 V drill/driver with NiMH and they didn't have a good shelf life, but they also didn't stop working. I just needed to recharge them. Seems like Makita has stopped making NiMH and gone to NiCd and lithium only.

Now, I use the Ryobi 18 V One+ series. I have some old NiCd packs for it, which I use in the tools I use frequently, such as the shop vac and dustbuster. I use lithium in about everything else.

Ironically, after many years of using lithium tools, I now use corded more than I used to. It is so convenient to have full, no-excuses power without the weight of a > 18 V battery, no matter how cold it is.

I highly recommend the One+ series from Ryobi. They're not as high grade as Makita or Milwaukee, but they're as good or better as the entry and medium level DeWalts.

[Paul Ryan]

Jeremy,

I have to respectfully diagree with your opinion on the ryobi 18v tools. I bough a set some years back and the batteries lasted less than 6 months. I didn't use them every day but a few times a week. After about 5 months the batteries quit holding a charge over night. I would charge them up and by the next morning they we dead. If in a tool they were still usable but had a very short run time. I changed to a crapsman and have been very happy. The 19.2 is heavier but has lots of power. I have had them for about 4 years. The 1st tool pack was a drill and a light I bought about 4 years ago, and one other those batteries has finally died. The other pack a hammer drill and a circular saw is about 3 years old and those batteries are still going strong. I recently sent my dead battery to voltman to get rebuilt. I couldn't decide on rebuilt or buying new. But after reading reviews on the new lithium batteries from the rebuilders, they believe the new batteries wont have that long of service life. So I decided to keep using what I have. I like the weight reduction of the lithium but since I only use my tools a couple time a week, I couldn't justify the cost of lithium that will probably won't out live my older NICD's. The problem is the cost of 2 battery rebuilds cost the same as a new crapsman tool with batteries. But the rebuilt batteries are suposed to be better than what you would get new. The tools that I have a still in very good condition so I will see what happens.

[Andrew Joiner]

Lithium may have the edge for weight and short term performance but they are no good as far as overall life expectancy and temperature sensativity. Use the lithium batteries in sub freezing temperatures sometime and note the difference. NiCads and NiMH will also perform less but the difference is drastic on Lithiums. We also rebuild a bunch of Segway battery packs and the lithiums are having tremendous problems with poor life and being troublesome in general. The NiMH packs are lasting at least 2-3 times longer and cost almost half of what the lithiums do.

Bottom line is that lithium technology is great but it is technology that has not matured yet. They are EXTREMELY close and I believe very soon more reliable lithium technology will emerge that is more affordable. Until then I stand by the Nickel based batteries as they will provide you with more watts of power before needing to be replaced than a lithium battery will (according to the charge/discharge cycle testing we did on multiple brands).

Jason
MTO Battery

Wow, this is interesting Jason. Do you list the test results on your site?

[Pete Shermet]

I had a Ryobi 12 v Torque Force drill that the batteries were discontinued and I went to :
http://www.batterybuyer.com/
I had great service but I had to exchange the top case with my originals as they were keyed slightly differently (Sears) I sent them the procedure for my mods.
You should try to jump start them as many chargers need to detect voltage before they will start to charge. Take a set of jumper leads and hook + to + and - to - from a battery charger or your car battery, (yes even if it's 18 volt) for 30-60 seconds. This will impart enough charge to allow your charger to begin the charge cycle unless the pack is completely toast.
Best Regards
Pete

[Jason Abel]

We do not list the testing publicly. About 1.5yr ago we did and all the sudden our discharge curves starting showing up on other peoples websites as their own... but you can visit this website http://www.batteryuniversity.com/parttwo-36.htm for a graphical comparison. These results are similary to those we found but our tests were done at higher voltages so that would explain some of the variences.

[Andrew Joiner]

We do not list the testing publicly. About 1.5yr ago we did and all the sudden our discharge curves starting showing up on other peoples websites as their own... but you can visit this website http://www.batteryuniversity.com/parttwo-36.htm for a graphical comparison. These results are similary to those we found but our tests were done at higher voltages so that would explain some of the variences.

Thanks Jason,
Really great when someone who has a business gives one of his sources away for free. More important to me is you didn't just say "trust ME I'm the expert"

Needless to say I will study at the Battery University.

[Bill Wyko]

Give this a try. Connect them to a charged battery. Let them pull from them for a while. Then try to charge them. This works with optima batteries for cars. Migh work for you. Got nothing to loose.