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1) I have done much research over the years on deep cycle batteries since I have a small 120 watt solar panel system installed at my home. Based on the research that I have performed, many experts state that having batteries which are not 100% compatible, may have the potential to cause battery problems down the road, ie, not proper charging.
They state that only "like batteries" with the identical amount of amp-hours (AH) should be used when installed as either a series or a parallel bank. The reasoning behind this is that "un-like batteries" will have contention with each other since they are not equal or balanced in terms of the AH. I have also read where using multiple battery manufacturers within a string or an array can contribute to similar problems.
2) Since you have one battery that has corrosion around one terminal and it is partially bulging, this presents a safety hazard. A bulging battery is typically caused by over-charging and this presents a very serious safety hazard, since a bulging battery can explode and shoot acid everywhere. For your safety, you need to immediately remove the bulging battery from the array before it causes major problems and replace this battery. You do not want to be anywhere near an exploding battery.
I would recommend to contact your local fire department and ask them where you can safely take the bulging battery. Some fire departments will accept batteries for proper disposal or recycling. DO NOT throw the bulging battery into the garbage as this can also create a potential safety hazard for the local waste hauler driver.
3) You did not state the application of your battery arrays, but I'm assuming you are using these for a solar PV application since you mention that you have an Inverter. If using these batteries in a PV application, I would recommend to check the Charge Controller (CC) unit to make sure the amperage of the PV panels are sized accordingly to the CC. You can use a clamp-on amp meter to determine the maximum PV panel amperage output on a full sunshine day if your application is PV panels. Compare the actual PV amp output to the Charge Controller. Perhaps, the reason why one of the batteries is bulging is that the Charge Controller is over-charging the battery array?
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