I am certainly not the best person to help you, but I hate to see you left hanging with no answers. Trying to preserve the batteries and making sure the system is safe is the first step. From what you described about the Trimetric, the batteries are not charged and are in a dangerous state of discharge if they do not get charged soon. For now the best thing to do is to try to figure out if the charging system is working, and to make sure any loads that would use the batteries are disconnected. Hopefully there are no critical loads attached to the system that must remain powered, things like freeze protection or something that would cause great harm if disconnected. Ideally there should be a flow chart or drawings of the whole system showing what components are used and how they are wired. Was an installer involved, or did the owners DIY the system? It will be tough to help you with out that info, but is certainly still doable. Baisically everything starts with the solar panels. I am assuming they have solar panels, but perhaps not. Do they use a generator, a wind turbine, small hydro generator, or solar panels? The batteries may be beyond help but maybe not. 50% is about as far as you want to discharge most types of batteries with out recharging. So getting them charged soon is very important. See if you can get any more info about what specific components are used in the system and how they are wired. Also try to find out what type, brand and size batteries are being used, and what voltage the battery bank is designed for. If it is an Outback charge controller hooked to solar panels there are many folks here who can help you.