cordless tool charger - need help

You guys know a whole lot more about this than I so please help.
The charger is a DeWalt 18v. The other day I pulled one battery down using the jig saw. I pulled the battery and, along with the other battery, began a recharge. One battery charged for about 4 hours which is historically a long time. I sapped batteries and the second one charged for 10 hours. I both cases, the indicator lamp on the charger kept flashing indicating that full charge wasn't achieved. Using my old analog VOM, I read 21-22v on both batteries. The charger appears to be putting out 27v. I'm afraid of overcharge and fire at this point.

Thoughts on how to proceed?
Thanks in advance.

If I run mine dead,before they go on the charger I'll put the in the frig for a few minutes to cool them down. If there're to hot the charger will throw a code and won't start the charge. Once they cool down it takes about 30 minutes to charge. Good Luck.

I go with Charlie N , a cool battery will charge quickly. I just let mine sit until they are cool. When on the job with the crew I sometimes work with, the first thing we do in the morning is put freshly recharged batteries in all the tools and put the take outs on the chargers. If and when during the day we will swap them again, let cool and put back on the chargers. Towards the end of the day we put the charged batters in a tool bag for the next morning. WE usually have 6 18 volts on the chargers and 4 of the 20 volts on chargers..crew of six.

1 battery had been 4 hours since drawn down. The second battery was days in the Dodge and we have temps the night before in the 40's. I don't think a hot battery is the issue.

get a new charger
I have and very much like a yellow 2 battery charger that charges Ni-Cad, NiMh, Li-On
or if you are thinking about going with 20 volt there used to be a 2 battery charger one side 18v other side 20 volt

Hello Steve in VA,

Sounds like the charger to me. Most of the time it will take about an hour to charge a battery + or -
20 minutes. 22 volts is the terminal voltage for a fully charged battery, and 27 or so is the open voltage for the charger. But it must have lost some capacity to take that long to charge a battery.I would replace the charger,

Guido.

Well, it sure sounds like I go charger shopping. Since the batteries both have 22v as cited by Guido as full charge AND the charger keeps pumping out 27v, then either the charger isn't shutting down properly or the indicator lamp for the charging state isn't reflecting the operating state.
Thanks again guys

Steve,
About 20 years ago I bought a cheap 18v B&D cordless drill from K mart. I got rid of the wimpy drill and junk Ni-CD batteries but kept the old school charger to use on batteries that my 18v dewalt charger can't charge.

I'll never buy another Li or Ni-Cd battery. I changes over to Ni-Mh batteries off ebay a decade or more ago. Ni-Mh batteries and Li batteries require a special charger from dewalt. This charger shuts down when batteries are charged. Old dewalt chargers never turned off. When you removed the battery it was hot, cooking the battery.

About 6 of my very old Ni-Mh batteries have an issue with the temp sensor and I can't charge them on the newer dewalt charger. However they will charge on the old school B&D charger at .25 amps. In theory, a 3000 ma-hr battery will be fully charged in 12 hours.

ALL Ni based batteries will self discharge to 50-75%. Some will self discharge faster than others, but they will ALL self discharge, even faster in a cold barn. Only battery that doesn't is the Li. However Li will give you less in cold weather too.

Back to charger. Get one off eBay, it will work.

Now I've made a battery maintainer using the old school B&D charger and 100 ohm power resistors. I have the ability to trickle charge 4 of my old batteries at 30-40 ma each. I made the trickle charger 6 months ago, without damaging a single one. It keeps my old junk batteries in the barn that can't charge on dewalt charger fresh and fully charged. I made a second trickle charger using 100 ohm resistors that will trickle charge 3 batteries.

BYW my Oldest Ni-Mh battery is the best one I have. My newest batteries that will charge normally, I carry in truck. I have a 18v dewalt charger in truck that uses truck battery.

Geo

18v B&D charger

Just don't let your Grandson take it to school .

I have battery tools where the OP manual warn, NEVER go directly from charging to use or from use to charging, as the battery can be damaged by internal heat.

I'm going to go on a different track here.

You said you drew the batteries down. Maybe you drew them too far? The charger may be in "recovery" mode, which takes longer than a normal charge.

Recovery mode is when one or more cells in the pack have been drawn down below a certain voltage level. You can't just blast them with high-rate charge voltage when they've been drawn down too far, or you will cause more damage than what's been done already.

The key is to switch batteries before the tool stops moving. So many times over the years I watch people run cordless drills until the bit won't turn anymore. It just wrecks the batteries.

Neither battery was completely flat. Once the drill slows noticeably, they're off to the charger.