[eugenebrooks]

These are Absorbed Glass Mat (AGM) Valve Regulated Lead Acid (VLRA) batteries. The electrolyte is in a saturated glass mat sandwiched between the plates, there is supposed to no (or at least minimal) liquid electrolyte that is loose in the cell. Any hydrogen and oxygen produced in the cell during operation of the battery is supposed to recombine, returning the water to the mat so that it does not dry out. If the gas production rate gets out of the hand the valve releases it when the pressure in the cell gets to high. This can happen with high charge rates, charging a battery that is too warm, or excessive discharge rates that heats the battery. If you put a battery that is too hot (from high current loading) on a charger, it might go into thermal runaway and this can ruin the battery.

If your batteries measured 10.25 volts without load they were more than fully discharged, this limit being 10.5 volts. You should avoid fully discharging the batteries, it shortens their life.

The battery can be operated in any orientation, but upside down is not advised in case the valves release some gas and there is a little loose liquid at the valve. The battery should be vertical when charging.

If you run these batteries too hard, or charge them too fast, they can dry out and die prematurely. A sign of this is excessive heat during use or charging.

We had some minor leaking from the top of one of our batteries a couple of years ago, cleaned it up and load tested it, and it has remained one of our better performers for several years now without any further issues. Clean them up, give them a proper charge, and load test them. If they pass the load test and don't show any further leaking, they will be fine.

We load test at 20 amps load, recording the time they take to reach 11 volts (under the 20 amp load, and note that we don't go all the way to 10.5 volts). Any battery that gets too close to below 1000 seconds, or so, on this test gets pulled from competition service. A typical battery will last 1500 seconds, while a really good one will last close to 2000. We charge overnight using a three stage charger before testing a battery.

Lastly, you might have done everything right and the batteries might have just given out.
That little 18 amp-hour battery has a really hard life in a FIRST robot.

Have fun,
Eugene