Hi,
In your earlier posts I think you pointed out that the battery was at about 11.4 volts. If none of the llights (led's) on the detectors are dimmed, that is if they are glowing nicely when you walk in front of them, that's a good sign. When you do a system test (a walk test) and the external sounder is fairly loud and healthy that's another good sign. If you can set and unset the system without any problems, another good sign. But, as any installer worth his salt will tell you, even a battery showing 12 volts may not be in good health and there are specific load tests which the industy carries out, or should carry out, to determine the exact condition of the battery during a service call. A bit too much at this stage.
Since you established earlier, that the battery voltage was 11.4 volts at that time, then I should imagine that you are able to carry out a voltage check across the terminals of the removed, or disconnected battery. This voltage check is not totally accurate since the internal resistance of the multimeter should be taken into consideration, but having said that, if your meter reads somewhere in the region of 12.5 or higher after a few hours of carrying out the 'link test' and soak, then it should point to the fact that the panel was overloaded before the test was carried out.
Alarm systems do strange things, I have often stood baffled in front of a panel which showed a fault in the system, only for the fault to clear itself sometime later. So, we are effectively looking for a voltage which is a great deal higher than 11.4.
Is the battery receiving a charge. Well here we go with the multimeter again. Some are trickled at about 350 milliamps whilst others are at 500 milliamps. Place your meter on DC current, remove the positive lead from the battery and connect one lead to the now vacant pole and the other to the positive lead, you should be getting a reading in the regions mentioned, but check your manual because some are charged at an even lower current.
Is the battery receiving a voltage. Well, disconnect both leads from the battery terminals and with your meter on DC volts at about 20Vdc and touch them to the ends of the battery leads. It should read 12 volts since the regulator in the power supply end of the printed circuit board will only give you 12 volts. If it's anything less, then suspect it. When we say anything less, we must account for the tolerance of the meter which could be + or - 10% so a reading of say ll.9volts should be acceptable according to meter tolerance. However, carry out the same voltage check at the auxiliary supply terminals, if the voltages differ to a marked degree then it's possible that something is suspect.
There is a current limiting resistor in series with the battery. If this goes high value for any degree of time, then there should be a sort of scorch or burn mark on the pcb near the battery lead terminals. You won't always see this, but it's worth looking out for. The resistor value is about 470 ohms, but nowadays it tends to vary from panel to panel.
It is impossible in this short space to cover every check which the experts do on a daily basis, so we'll go on those tests first and see what the results are.
A simple check of the system is also worthwhile. How many internal and external sounders are there. How many detectors and how far away from the control panel are they. It's unusual in domestic's but long cable runs can cause voltage drop, hence the need for the panel to draw some power from the battery.
Another common feature found in the panel instructions is " ... this panel is rated at 1 amp with a fully charged battery .... " so it is not always the case that the panel is dishing out a total of 1 amp, this is where your device calculations should not really exceed 750 milliamps.