Battery Experts Please...

[Derek Arita]

I have two NiCad drills and two NiMH drills. All the batts sat for about 6 months, pretty much unused. Since braking them out and using them, almost all of the NiMH batts have gone south, but the NiCad batts keep on tick'n. What's going on?

[Doug Hobkirk]

Were the batteries fully (or mostly) charged before they started sitting?
When you say they are dead, do you mean they won't take a charge?
Out of curiosity, what brand(s) are they?

[Paul Ryan]

Derke,

I learned alot about tool batteries recently. I have 2 batteries that are in need of replacement or repair. There are a couple of sites that had a lot of useful information. Try voltamanbatteries.com and primecell.com Both of these companies are indeed trying to lure your business, but they provided some interesting info on the difference between NiMH, NiCad, and Lithium. I was thinking I would like to change to the new Lithium tools but now I am not so sure. I like the weight savings, but the run time and durability isn't the same. I also learned alot about proper care and storage, much different that I have always been told to do.

[Derek Arita]

I think most of the batteries were stored as they were, which was mostly discharged. I was in the radio controlled car industry for a while and learned to store batteries fully discharged. In fact, we used to put a load on batteries while in storage in order to keep them from gaining back any of their charge. I ran all of my current batteries down as far as possible on their drills. I have 1 Makita drill/driver, a Makita impact driver and a Panasonic drill/driver.

[Andrew Joiner]

I've had the same problem. All the info I find is inconsistent on getting the best life from batteries.

I was going to go lithium, but not until I get more proof on the $ to lifespan.

My next cordless purchase will be the tools that have the cheapest (including shipping) batteries. That seems to be the best for value.

[Bill Bezilla]

Ni mh batteries should be stored at full charge and room temperature.

Storing at discharged state or at extreme temperatures will result in permanet loss of capacity. Also nimh batteries have a fairly high self discharge rate so periodic charging during storage is recommended.

[Eric Gustafson]

I work in the aerospace industry and used to work closely with a guy we called Dr Battery. He was a phd and the only thing he did was research batteries, battery chemistry and conduct tests. Well I conducted the tests and reported back to him. I also had access to his library and read up on the subject. This was some time ago, so nicads were the rechargeable of choice, but lithium were coming along and I did explosion testing to them.

What I can say about nicads will go in the face of what most owners manuals will say that come with your tools, and conventional wisdom, but here goes:

If fully discharged/recharged, nicads will last about 500 cycles. If partially discharged/recharged they can last more than 2X that. However, partially discharging a nicad will reduce its total capacity... slightly. About 5% is all. Fully discharging the cell a couple of times removes that "memory" with a big caution. You must discharge each cell individually. If you discharge the entire pack, you will likely incrementally damage one cell in the pack. Nicads vary in capacity at manufacture. So there is always one weakest cell. (Except in matched-cell packs, which only the RC hobbiests do at great expense!) When one fully discharges a pack, that one cell will go into reverse current once its voltage reaches zero. At that point, the electrolyte in the battery forms gases, pressure builds in the cell case, and eventually, the gas vents through a safety valve at the top of the cell. This reduces the capacity of that cell and the pack. Repeat this discharge cycle and the pack will fail prematurely.

My advice for Nicads is to keep them cool and fully charged. They lose 10% of their charge each month, so if you are not using them, it is good to recharge them periodically. I have read that Lithium pack like partial discharges, but am not as familiar with them.

[Douglas Brummett]

I have two NiCad drills and two NiMH drills. All the batts sat for about 6 months, pretty much unused. Since braking them out and using them, almost all of the NiMH batts have gone south, but the NiCad batts keep on tick'n. What's going on?

I think you have already picked up some pretty sound advice and information. I will toss in my experience. I have a 9.6v nicad dewalt impact driver that has served me well for years. I have always had some issue with batteries, but mostly ignorance on my part in leaving the batteries on the charger. I would get about 6 months of factory level service and then they would decline in charge holding capacity to worthless in another 6-12 months. I could deep cycle them a few times and get some life back, but it was starting to get annoying.

My NiMH batteries were inherited in a NOS Makita that had likely been sitting for about 5 years. The batteries were fairly poor upon opening the box. One was shot, but the other would charge and hold a decent level. Within a couple of months both batteries were not working too great.

Well, I moved and had the drills in storage for a year. I fully charged them all prior to packing them away. My results mirror your own. The NiMH came out pretty well useless. The nicads were not great, but still functional. With a deep cycle they worked well enough to carry on.

Last month I sent the NiMH packs and one nicad pack in for a rebuild. I swapped the NiMH over to nicads and got all 3 packs rebuilt for about $100 using mtobattery.com . Gotta say they had a fairly good turn-around and the batteries are all running great now. I don't see any issue in swapping over to nicads on the Makita, so I think it was a good call there. So for now I am once again all nicad in the shop.

[Curt Harms]

I got a couple 4 pack AA batteries from Jason at MTO. They have a brand that they claim won't self-discharge. I've had 'em in an electric can opener (heavier draw) and a TV remote (very light discharge). So far so good on both uses. No apparent self discharge issues and good life. $11 for 4 AA's.

HTH

Curt

[Ray Dockrey]

I got a couple 4 pack AA batteries from Jason at MTO. They have a brand that they claim won't self-discharge. I've had 'em in an electric can opener (heavier draw) and a TV remote (very light discharge). So far so good on both uses. No apparent self discharge issues and good life. $11 for 4 AA's.

HTH

Curt

Sanyo makes some that are called Enelopes and they are the same way. Come fully charged ready to use and when charged they will keep their charge. Can get them at Walmart for about the same price.

[Chris Padilla]

Sanyo makes some that are called Enelopes and they are the same way. Come fully charged ready to use and when charged they will keep their charge. Can get them at Walmart for about the same price.

I can vouch for the Sanyo Eneloops. They have an extremely low leakage current compared to other recharagable batteries like good old Duracell or Energizer.

Basically, when the batteries are fully charged there are parasistics within the battery that act like a resistor conneting the two terminals of the battery. This slowly bleeds off charge over time.

I recenlty picked up a nice battery charger than can tell me the capacity of each battery so I can find the bad ones or the ones that simply aren't holding voltage any longer. It will also deep discharge the batteries to help with the memory issue and then fully charge them.

[Phil Green]

Guys,

I'm freezing my stones off here in Upstate NY and reading this thread brings a question up. My shop is unheated, so I put a couple of 18v Dewalt batteries I have on the charger with a small shop light on them. The idea behind this is to keep them from freezing.

Question is, I thought having them on the charger and under the light would be the best way not to lose them to the cold weather. Am I wrong on this??

Phil

[Chris Padilla]

Guys,

I'm freezing my stones off here in Upstate NY and reading this thread brings a question up. My shop is unheated, so I put a couple of 18v Dewalt batteries I have on the charger with a small shop light on them. The idea behind this is to keep them from freezing.

Question is, I thought having them on the charger and under the light would be the best way not to lose them to the cold weather. Am I wrong on this??

Phil

Phil, Depends on how cold the stones are! I dunno...do the batteries on the charger feel warm? If not, then I'd say it is too cold for the charger to keep them warm enough to work well for you. It might be best to keep them in the house during the winter.

[phil harold]

You can get your batteries rebuilt

I had 2 makita nimh 18 volt batteries done here 2 months ago
great service

http://mtobattery.com/store/index.html

[Dave Sabo]

My next cordless purchase will be the tools that have the cheapest (including shipping) batteries. That seems to be the best for value.[/quote]


I think this is the worst way to decide. You are really only buying batteries the tools kinda come at no charge. Look at the better brands - a pair of replacement batteries is about the same as buying a whole new kit. SO, if that's the case you should get something that has the best "battery" technology, not lowest replacement cost. Panasonic and Festool lead the category by a wide margin when it comes to longevity. The only way to save a few bucks, is to have your cells recycled by one of the battery rebuilders.

I'm sure in your cheap sceneario that Ryobi or Harbour Freight will win hands down. Those tools will not be anywhere near the quality or have features that the top brands do. Their batteries will also be the worst performing from the get go.