My sailboat has a Westerbeke W30 diesel with a 51-amp alternator with built-in single stage regulator (read "car alternator"). My house batteries are a pair of Trojan T105's. Not a good combo, I know, but due to limited finances right now it will have to do. I have a fridge that draws 3.5A all day long. Couple that with a little music and a little light and I figure my average draw is around 4A tops, so ~100Ah per day. Based on a 5A draw I should get just about 24 hours taking my battery from 100% to 50%.
My problem is that I'm getting nowhere near 51A out of my alternator. The alternator output is connected directly to the load side of the starting battery switch. When I start the engine it settles down to showing a few amps charge as the starting battery never discharges. When I combine the batteries, it jumps up to ~15A, never higher. After an hour or so it'll drop down to about 12A. If I'm drawing 4A and only putting 15A back in during charge, that means I need to run the engine for an hour for every 4 hours of discharge... not really a workable solution. The only thing I can see that looks substandard is the ground wiring on the alternator... I've read that it should be full-size wiring to handle the full alternator output, but it's not, it's rather thin-guage (14ga max) that runs back to a bolt on the engine. Could this affect my alternator output?
When the engine is on and revved up, the starting battery voltage at the panel shows ~13.8VDC. When I combine the house and starting batteries, the voltage drops to ~12.8VDC when the batteries are discharged. It takes literally an entire day of motoring to get the combined battery voltage up to 13.8VDC. I'll measure the voltage at the alternator itself, but I wouldn't expect a 0.6V drop between the alternator and the battery / panel guage... the wiring is hefty, maybe 8ga or 6ga. Maybe my regulator is toast?
Any help greatly appreciated.
Dave
dolce fa niente - CS36T
My problem is that I'm getting nowhere near 51A out of my alternator. The alternator output is connected directly to the load side of the starting battery switch. When I start the engine it settles down to showing a few amps charge as the starting battery never discharges. When I combine the batteries, it jumps up to ~15A, never higher. After an hour or so it'll drop down to about 12A. If I'm drawing 4A and only putting 15A back in during charge, that means I need to run the engine for an hour for every 4 hours of discharge... not really a workable solution. The only thing I can see that looks substandard is the ground wiring on the alternator... I've read that it should be full-size wiring to handle the full alternator output, but it's not, it's rather thin-guage (14ga max) that runs back to a bolt on the engine. Could this affect my alternator output?
When the engine is on and revved up, the starting battery voltage at the panel shows ~13.8VDC. When I combine the house and starting batteries, the voltage drops to ~12.8VDC when the batteries are discharged. It takes literally an entire day of motoring to get the combined battery voltage up to 13.8VDC. I'll measure the voltage at the alternator itself, but I wouldn't expect a 0.6V drop between the alternator and the battery / panel guage... the wiring is hefty, maybe 8ga or 6ga. Maybe my regulator is toast?
Any help greatly appreciated.
Dave
dolce fa niente - CS36T