That is not a "Very Low Voltage". For some alternators, it’s normal to see as low as 13 volts. For some, a constant 13.6 volts is an indication of a problem. For others, it’s normal to see as high as 16 volts for long stretches. Still, it’s perfectly normal for others to see the alternator not charge at all intermittently. What are the RPM's at the time you measure a 13.5 voltage output? How many amps were being produced? Where are you measuring these readings?
You already know that the alternator will not be giving your Lithium batteries the charge voltage they want. The question is can you keep the FLD Start battery charged enough to let it charge the Lithium batteries? Or will they suck the life out of your start battery, like a vampire.
Good to know. Good question on the rpm's. My boat never had an rpm gauge. I will have to check again this weekend and try and do a better set of tests once i rewire the alternator output to the start bank pos. bus. At least this will eliminate the poor wiring variable.
I was getting that reading from my Balmar SG-200, but to be honest at the time was not doing any deep diagnosis. I was just trying to confirm the diodes were not blown and the alternator was at least charging.
I suppose if the start battery is near full it wont take much of a charge so i guess it would make sense to see low charging voltages. I can drain the battery a little with some house loads i suppose to get the alternator to put out a higher charge once i get organized.
I need to figure out where this exciter wire is connected on my panel. I have been researching it and it looks like i have some options on how i can connect it better either using a light, a zener diode or maybe even my oil pressure gauge.
Good question, I dont know that answer yet. I need to think that one through. I never had the ability to monitor these things before, but now at least i have shunts and an SG-200 on the battery bank and an BMV-712 on the house bank and can see whats actually happening with the alternator output.
If the alternator can output lets say 14.6 ish volts peak and the lead bank is full and not accepting a charge, if i manually switched on a B2B charger, my thinking is that i could output 13.8 volts to the lithium bank without draining the start bank. I have never actually done this before though. All the instrument and house loads would be run from the lithium house bank so there would be no additional loads on the start bank once its fully charged. As long as the engine is running and the alternator putting out power is there any reason why this would not work? Am i missing something obvious?