How can you tell if a battery is dead?

[1stxrunner]

How can you tell if a battery is dead? I have three of them that will not charge. I put them on the charger and in about a min. there done. I put them in and get nothing. I know its not the charger because I just bought a new one today and still get the same thing.

[eVaDeR85]

Well if youve for sure narrowed down that its not the charger and they still wont take a charge, then its for sure the batteries themselves. But just to make sure I would take the batteries to my LHS or to a friend who has another charger and try them just to make sure.

[highroller]

whatype of battery are they. With NiMh batteries they have a tendency to false peak making you think there is a problem with either the charger or the battery itself. Try setting charger a little higher on the voltage detect setting and regardless of what you learned concerning NiMh discharge them after use, plus the lower you can get the voltage discharge first at a higher load (10-20amp) then at a lower load of about 2amps until cell voltage is around .25 volts or 1.50 volts for a 6cell pack. Allow the pack to cool at room temperture (1-3hour) before attempting to charge and use again in the same day.
Stick packs will be hard to determine if a cell is bad, the only way of getting an idea is the bad cells usually get much warmer than the good cells in as little of 1-5 minutes of charging. With cells built inline (side by side) configuration the positive and negative terminals are exposed and makes it much easier getting a voltage reading to determine the condition of cells. At rest the cells usually show the same voltage levels, however when charging or discharging loads are applied cells then may show some form of decline. Cell voltage should be in the 1.38 to 1.50 volt range to be considered good, higher voltage may indicate an increase in resistance, while a voltage voltage 1.30 and below means the cell is loosing it's abilty to hold voltage (runtime may have gotten shorter, but charging time may increase). During discharging the bad cell(s) may drop quicker in their voltage levels while the better cells voltage stay higher.
A string of lightbulbs is the cheapest and easiest method of building a discharging use 5 for a 10amp discharger or 10 bulbs for a 20amp load and one single (1157 auto taillight) for deep discharging. If you don't use a cutoff device then remove the bulbs when they start to dim.

[tcr]

I think it is time to break the pack and then measure each cell with a multimeter. After charge, compare their voltage(Volt) and their current(Amp). If it could not hold any of voltage or current throw it away. It is a good chance for you to regroup and match the cells. Have fun! ;)

[BCat125]

You can usually tell if the battery faulse peaks a lot or if the cells heat up faster than normal. At least thats how i can usually etll.

[1stxrunner]

So is there something I can do to keep them from faulse peaking??

[highroller]

Yes, you can reduce some of false peaking problems by discharging the pack a little lower in voltage. Each cell over a period of cycles (uses) will discharge to different voltage levels, if the voltage varies by a big difference then it causes most chargers (even the high end) to false peak. Use approx a 2amp load or 1 1157 bulb to discharge the cells further. Depending on type of cell take it down to .25 volts per cell or 1.50 volts for 6cell packs. If they are assembled inline (side by side) use a equalizing tray to discharge the pack, it should first be discharged to .90 volts (5.40volts for 6cell, 3.60 volts for 4cells) then equalized so cells are closer to the same levels. Deeper discharging gets cells closer to the same voltage levels, which allows them to charge closer to the same levels, may increase runtime and pack may perform better all around with less of the false peaking.
Panasonics are more delicate and shouldn't be deep discharged below .25 volts while the GP3300, Sanyo HV (3000, 3300) can be discharge lower in voltage to between .05 to .25 volts. Although I dead short GP3300 for racing, I don't recommend just anyone do it or you ruin a perfectly good battery pack pr can cause injury to yourself. If these are unmatched stick packs they generally start out with cells that are not as matched in voltage as the matched cells are - these too will become unbalanced after a period of use.