Re: You are correct
 

QUOTE]Originally posted by Dr.Bot
The charger went bad. It was an old model - I liked it because it had a meter so you could see the charging rate. I tried another battery and the same thing - I put a voltmeter on it at
zero load it was floating at 12.6 volts - as soon as it tried to charge a bettery it went to over 18! So that charger is on the scrap(er recycle) heap! Too Bad. I think I lost too much electrolyte from the Exide to salvage it for bench use. Fortunatley the acid didn't ruin anything the baterry was sitting on a slab of particle board. Neutralized the spill with baking soda - plop plop fizz fizz oh what a rekief it is. [/quote]
Dr. Bot,
If I was you, I would go get the charger off the scrap heap and throw the batteries on there instead!
When you put a battery on charge (providing that the charger is working OK) and the voltage goes up way beyond normal, 18 volts in your example, then this is a sure sign that the battery is heavily sulfated and is not in 'prime' shape. The sulfation has the effect of raising the internal resistance of the battery, making the current go high, while keeping the charger output low.
As for the electrolyte leaking out, this is another indication that the battery is toast. These batteries are Valve Regulated Lead Acid and have a gelled electrolyte. In theory, they are sealed to avoid any loss of moisture from the electrolyte as once its gone, it can't be replaced as in a flooded lead acid battery. When a battery is on charge and the voltage rises, the plates begin to give off a mixture of hydrogen and oxygen - in a flooded battery, this can be seen as a stream of bubbles. In a VRLA battery it can't be seen, obviously, but it still takes place. This begins to occur when the battery voltage gets to about 2.3 volts per cell or 13.8 volts for a 12 volt battery. In a flooded battery, this results in 'gassing' and the need for having to add water to the cells periodically. In a VRLA battery, you cannot allow this 'outgassing' or the electrolyte dries up. The dilemna is, if you stop the charge when the battery is at 13.8 volts, then it will not be fully charged and will gradually lose capacity and become sulfated. To get around this problem, the battery is 'Valve Regulated' in that the 'Valves' are set to withstand a certain pressure without opening and allowing the out-gassing of the moisture. Internally, the hydrogen and oxygen gas is re-combined back to H2O and retained in the cell. If an incorrect charger is used on a VRLA cell and does not sense the gassing voltage has been reached and cut back the current, then the pressure will quickly build up inside the cell and the 'valves' will open. Once they open, the battery is doomed as they are not able to close again and the battery will quickly lose the moisture from the electrolyte during charge until it eventually dries out completely. This is why the battery that you mentioned was oozing electrolyte from its valves - the battery voltage was at 18 volts and the plates were gassing a lot. These bubbles of gas cannot easily pass through the gel, so it expands and forces its way out of the open valves.
As I mentioned above, if you stop the battery charge at 13.8 volts, then it will not be fully charged. We get around this problem by using a different charge profile than we would for a flooded battery. A simple flooded profile is a taper with dv/dt where the charger tapers the charge - as the voltage rises the charge current tapers off and when it hits a pre-defined voltage indicating 80% charged then it goes into the dv/dt (Voltage against Time) finish stage and completes the charge. The return of charge factor is about 1.15 which means for example, that for every 100amps taken out of the battery, then you have to put back 115 amps from the charger to get to where you can use the battery to give you 100 amps in output again. With VRLA batteries, the charge factor is a bit more efficient <>1.06 and the charge profile used is more controlled (IUI - constant current/constant voltage/constant current) so that the battery does not gas profusely and lose its moisture. That is why it takes a long time to re-charge a gel battery as the finish current is very low to avoid raising the internal pressure and blowing the valves, but allowing the battery to take a full charge.
Whew, this was intended to be a quick reply - hope that somebody finds it helpful.

Dave,
You certainly were very technical in your discussion. I would like to remind members of FIRST that "wet" cell batteries of the type in you cars are nominally 13.8 volts when fully charged or 2.3 volts per cell. The manufacturers spec on our sealed, lead acid, battery or SLA, is 13 volts or 2.16 volts per cell. Different battery types all have different cell voltage, 1.25 volts for NiCad and nickle metal hydride, 3.6 volts for lithium, 1.5 volts for alkaline, etc. Now should you use a voltmeter to measure the terminal voltage of your car battery while it was charging in your car you may find the voltage regulator is putting out 14.2-14.5 volts which is a little high for our battery but fine for the "wet cell". Therefore any battery charger which puts out 18 volts with a battery connected would, in my opinion, be ready for the circular file. One that puts out both 18 volts and damages batteries has crossed over to junk status and should be treated as such.
I would like to remind everyone that the chargers supplied by FIRST or equivalent are the only ones that are legal for use in competition.
C20 When recharging Kit batteries, you may use the charger provided by FIRST or one
with equivalent charging characteristics.
(I like the new 6 amp smart charger but still use the 4 amp charger First had supplied for years.) Using other chargers, auto battery chargers included, runs the risk of battery leaks, battery damage, and injury. They put team members at risk as well as others that might be close by. If detected in the pits, I would expect a DQ on such use. Don't take safety lightly, especially in the pits.
Here is the official spec sheet on the battery...
http://www2.usfirst.org/2003comp/Specs/Exide.pdf