I'm assuming you are referring to the HF charge controller, although it is a bit unclear as to exactly where you are placing the probes from your meter. Most likely this is the panel voltage output leading to the controller (14-19v), or you are only seeing the voltage with the batteries disconnected. With the batteries connected, the display should be the battery voltage itself (your 11.3v)
The big question is have your 35ah thunderbolt agm batteries ever received a decent charge? The very first thing I'd do is charge each one individually to make sure. Remove the extra battery from the circuit leaving only one connected. Make sure that at some point, your voltage reads 12.9v or higher and let it be like that for many hours. Remove that fully charged one, and replace it with the other and repeat the charging process - with NO loads like a fan attached. All you are doing here is making sure that you can get a decent charge on an individual battery. It might take days, so be prepared. Doing it individually even if you plan to parallel them later can help point out a dud that won't take a charge, but will be a drag on the other one when they are eventually attached together.
You can move forward from there, but 11.3 volts is a very discharged battery, OR the load on it is so big, that it drags the voltage down badly - basically and undersized system right from the get-go.
The big question is have your 35ah thunderbolt agm batteries ever received a decent charge? The very first thing I'd do is charge each one individually to make sure. Remove the extra battery from the circuit leaving only one connected. Make sure that at some point, your voltage reads 12.9v or higher and let it be like that for many hours. Remove that fully charged one, and replace it with the other and repeat the charging process - with NO loads like a fan attached. All you are doing here is making sure that you can get a decent charge on an individual battery. It might take days, so be prepared. Doing it individually even if you plan to parallel them later can help point out a dud that won't take a charge, but will be a drag on the other one when they are eventually attached together.
You can move forward from there, but 11.3 volts is a very discharged battery, OR the load on it is so big, that it drags the voltage down badly - basically and undersized system right from the get-go.
Comment