Dead Battery

[blaxbb]

We just took a battery out of summer storage to try to test some things before brunswick and it is completely dead.

It wont charge and reads 0 volts on a multimeter.

Is our battery toast or is there any way to revive it?

[vivek16]

have you checked all the wire connections and stuff?

besides that I have no idea. Those lead acid batteries are pretty good at not dying.

-vivek

[Kevin Sevcik]

Lead acid batteries are, in fact, remarkably good at dying. That is, if you don't store them properly. See, SLA charges are stored in sulfate ions. When you charge the battery, you force the ions into solution in the electrolyte. Conversely, when you discharge the batteries, the sulfate ions come out of solution and bond with the lead plates, forming lead sulfate and giving up their extra electrons to create current and all that. So far so good. The problem comes when you leave a highly discharged battery just sitting around. All the lead sulfate originally forms as a very loose highly divided mass. But left to its own purposes, it slowly coalesces and forms lead sulfate crystals. Which are highly stable and which won't dissolve back into the electrolyte just because you'd like them to. This is called sulfation, and every bit of sulfation your battery undergoes removes that little bit more of its capacity.

So, in summary, SLAs should be stored well charged. Preferably on something putting out a float charge to combat self-discharge.

As for your particular problem, in addition to bad wiring it, your SLA could be suffering from sulfation. However, it could also have a shorted cell or an open. There's plenty of this that can go wrong in there that you won't be able to see.

[Jimmy Cao]

There's 2 possible reasons why it's dead.

1) The terminals are loose or there is some disconnection in the terminals/leads. This is easy to fix. Just tighten whatever is lose, or replace the wires if they're broken.

2) The battery is internally disconnected, or completely shorted out. Lead Acid can build up on the sides of the battery, and if they fall off, they can completely short out the cell, resulting in insane loss of voltage.

Usually, however, if you battery is only internally shorted, it would still have a very low voltage (not 0), so I do not suspect this. Check the electrical connections, and if they're good, I would suspect that there is a disconnect somewhere inside the battery, and such an issue is hard to fix.

[MrForbes]

I'm with Kevin, if you want lead-acid batteries to last, you need to use them regularly, or at least charge them often.

Get your programmer to play with the robot during the summer, and cycle all the batteries.....

[blaxbb]

hmmm okay we were reading right off of the terminals so I guess we are buying a new battery

[Alan Anderson]

A really most sincerely dead battery that acts like it isn't even there when you connect it has probably been mistreated by using the wiring as a handle. The stress on the terminals can break the internal connections. That's not necessarily true of every totally dead robot battery, but it's likely enough for me to use this as an excuse to warn people.

Don't pick up a battery by the wiring. Just don't.

[Al Skierkiewicz]

Brian,
There is an alternative. It is possible that your battery somehow discharged through contact of the terminals or connector. This would normally show some voltage when checked with a voltmeter but not always. When the battery is discharged to this point, the circuitry in the charger does not recognize that a battery is connected and therefore does not turn the charger on. AS a last ditch attempt to revive, you will need a variable power supply and some method of looking at current. In this method, you would start out with a minimum voltage (1 volt) on the power supply while monitoring current. Connect the positive output to the positive battery terminal and the negative output to the negative battery terminal. Energize the power supply and monitor current. If it skyrockets (i.e.several amps) then the battery is likely shorted and it must be recycled. If the battery draws no current then it is likely open (internal damage usually from a fall) and the result is the same, recycle. If it draws some current then slowly advance the voltage without letting the current get over 1 amp or so. This step requires very close monitoring of the current and heating of the battery. If you can advance the voltage to 5 or 6 volts without running the current above 1 amp then let the battery charge for about fifteen minutes. Remove the power supply and measure the voltage of the battery. If it maintains some voltage above 5 volts, then try putting it on the regular battery charger. Charge for an hour or so and then test the battery in your robot. If it runs the robot for a few minutes, then you have been successful. Put it back on the charger and watch it periodically. It might take the full four hours to charge. Check for battery heating as well. If all is normal, then use it for practice.

[Wayne C.]

We just took a battery out of summer storage to try to test some things before brunswick and it is completely dead.

It wont charge and reads 0 volts on a multimeter.

Is our battery toast or is there any way to revive it?

a battery isnt truly dead until its flattened on the turnpike.......

WC

[Elgin Clock]

a battery isnt truly dead until its flattened on the turnpike.......

WC

Or stabbed in an off-season competition by a Team 25 driver via the robot. :p
LOL

[Wayne C.]

Or stabbed in an off-season competition by a Team 25 driver via the robot. :p
LOL

Sorry- therefore IOU 1 Battery- you can collect it on I-95 about 1 mile south of exit 13A in the center lane......

:p :p :p

:cool:

(ps- of course that battery is "free of charge")