How to Revive your Battery packs

[gmack5]

I posted this on the Ryobi site and thought that some of the "Newbies" here could also use the information.

One of the biggest reasons that a battery pack fails on a newer tool is that the operator uses the tool, then puts it back on the charger without totally discharging the battery. [8)]
What this does, especially with a NiCad pack, it to cause the battery pack to establish a "false bottom". [:0]
NiCad batteries have a "memory" and if you continue to put the battery back on the charger, without it's being totally discharged, it will ultimately begin it to recharge only to the point that you last put it on the charger, thus shortening the useful life of the battery. [}]
One of the things that you can do to "revive" the battery is to discharge it as completely as you can, then put it in the freezer for 24 hours, take it out of the freezer and let it return to room temprature for the next 24 hours, then recharge it. [:I]
This will usually revive them, in as much as the Freeze/warm up cycling seems to cause them to lose their memory. [8D]
It doesn't work every time, but it's well worth the effort to try it.

[monte]

Thanks for the tip. I have one pack that refused to charge. I'll give it a try today.

[Lefty]

Could one freeze the battery, then microwave it to cut the time in half?
[]

Not serious, and please don't try it!

[lago]

I tried that about a month ago on 2 of the Ryobi 14v batteries and it worked.

[SteveR]

Gmack,
Good post....I am trying this very thing on a battery now...hope it works.

Edit: Are there two types of batteries? If so, will this work on the other one too?

Thanks
Steve

[gjensen11]

Ok everyone please post your results..
thanks I'm gonna try this with some 14.4v today

[maxparot]

The other thing you can do to improve on this is to use a power resistor to drain the battery closer to zero volts.If you don't need the pack recharged any time soon leave the resister on for a few hours. Doing this before charging will greatly reduce the memory effect.

[Otter]

quote:Originally posted by maxparot

The other thing you can do to improve on this is to use a power resistor to drain the battery closer to zero volts.If you don't need the pack recharged any time soon leave the resister on for a few hours. Doing this before charging will greatly reduce the memory effect.

Ah yes, the good ol load bar. You can use light bulbs in series to do the same thing. When it cant light them you are ready to charge. I use 4 5w 12v automotive bulbs on my 18v batteries, works great, less filling.

[LCHIEN]

Guys, I'm an electrical engineer. I've designed equipment with batteries and studied the instructions from all the people who are experts on batteries. I believe in the validity of science.

Good Science
Yes, Nicads and Mimh to a lesser extent have memory. They build up an internal salt layer if repeatedly charged/discharged to the same level that prevents them from using all their capacity.
In order to keep using the full capacity of the cell, use it to the endpoint (which is around 0.9 Volts per cell, not less.)
In my experience, there's two primary failure modes. One a dead short, 0 volts across the cell and won't charge up. Two, weak cells that won't hold a charge.

Questionable science.
Putting a bttery in the freezer. This may or may not remove the salts. It may also fix a shorted cell - apparently dendrites or chemical growths can cause these shorts between electrodes. Maybe freezinf will break the dendrites. It certainly can't hurt since the pack is already shot. If it works, more power (literally, ha ha) to you. It's never worked for me but I believe its possible.

Bad Science.
Shorting your battery pack to drain it is very, very bad for the pack. So is a power resistor. So are leaving on flashlights. So is taping the switch on your drill to the on position. The best way to drain the cell is to use an electronic device with automatic low battery shutoff. These will pull power from the battery until the battery reaches the end point of ~0.9 to 1.0 volts per cell.
The technical reason for not putting an open-ended load drain on your cell is reverse charge. Cells at endpoint drop real fast below .9 volts if further discharged. Since not all cells are equal (that's why you should not mix cells new with old, different manufactureres, differetn production lots) in capacity even when made in the same lot, the weakest ones will drop real fast below endpoint (depleted) while the others are still at 1.2 volts (still disharging).

Remember charged cells give up current out their positive terminal
Cells chargeing have current go into their positive terminal.
Cells discharged or depleted in a pack still being used will have positve current going into their negative terminal (coming out the positve terminal of an adjacent charged cell) - thus reverse charging.

This is negative charging, it actually makes the cell go negative in voltage and causes undesirable, irrevesible chemical changes. THis causes battery pack failure of the won't hold charge sort.

So... use your drill 'til it slows down a whole lot, then stop. For certain, Don't run it past stall (like leaving the switch taped in the on position). Don't leave a flashlight on, don't put a dumb resistor on it. Do use a smart device, CD player, smart charger, computer that has low-battery shutoff. (yeah I know its hard to find electronics that take tool battery packs).

Guys, rechargable batteries are one of the least reliable things we humans manufacture.
Personally I avoid them whenever I can. The only battery tools I own are a drill and a screwdriver.

sorry for the long explanation. Couldn't stand it any longer.

[Lefty]

Also interesting to keep in mind. It is a widespread belief that if a battery is left on concrete it will loose its charge. I'd been told that years ago (before my age of reason) and believed it until fairly recently. I looked around on the internet for why this was so and found it wasn't.
Just thought I'd share my ignorance.

[SteveR]

I saw this info. on another forum and kept it for future reading...

http://www.buchmann.ca/chap10-page1.asp

That future has not arrived yet....so if someone actually reads it, lemme know in simpleton terms what you got out of it...I am all eyes

Loring....Wow....lots of info. there. So from what I gather in your explanation is that freezing is a possible solution in theory. And do not fully drain.

Is there any fix to ones that are already hurtin'? I have a total of 4 18V dewalts..2 of ea. flavor. I have a ridiculous system of having to keep them all lined up in chargers and rotating them once one gets low and that does not take much time at all. I think I read on this forum someone had some rebuilt? I would prefer to buy lumber instead of batteries...maybe corded tools are not that much of a pain after all[)]

edit:

quote:Guys, rechargable batteries are one of the least reliable things we humans manufacture.
Personally I avoid them whenever I can. The only battery tools I own are a drill and a screwdriver.

I think this just confirmed my corded tool comment
:end edit.


Thanks for any and all input!!!
Steve

[Jim Boyd]

I have done the discharge/freeze/recharge thing before and it worked 50% of the time. What Loring says about reversing the polarity by totaly discharging a battery is a fact and the results can be quite shocking[:0] While working at the Wally World auto centers I have seen this more than once on returned car batteries.

[maxparot]

Bad Science I'm sure....
Since battery packs are connected in a series configuration having a single or a few cells go into a reverse charge is a wives tale. The point of a too low charge is posible but that is more a problem with the automatic solid state chargers thinking the pack is bad because of the low voltage. This is not a problem on time based charger power supplies but those type tend to cause battery failure due to overcharging or memory problems due to undercharging. For this reason manufacturer use Solid state (voltage sensing)chargers but do not include a battery conditioner mode(drain mode)as in "smart chargers"
This would increase the cost of the charger and increase the time required for a complete condition/charge cycle.
Finally manufacturers would much rather sell you a new pack for $60 then try and sell you the better charger with the drill and have to raise the price of the drill by $15 in a tight market.

[monte]

Very well done Loring! Nice to have another EE around here.

[LCHIEN]

quote:Originally posted by maxparot

Bad Science I'm sure....
Since battery packs are connected in a series configuration having a single or a few cells go into a reverse charge is a wives tale. The point of a too low charge is posible but that is more a problem with the automatic solid state chargers thinking the pack is bad because of the low voltage. This is not a problem on time based charger power supplies but those type tend to cause battery failure due to overcharging or memory problems due to undercharging. For this reason manufacturer use Solid state (voltage sensing)chargers but do not include a battery conditioner mode(drain mode)as in "smart chargers"
This would increase the cost of the charger and increase the time required for a complete condition/charge cycle.
Finally manufacturers would much rather sell you a new pack for $60 then try and sell you the better charger with the drill and have to raise the price of the drill by $15 in a tight market.

You missed the point. Reverse charging happens during discharge. One or more cellz gets depleted first while the others are still giving up charge and it gets reverse charged. Has nothing to do with the supplied chargers.