Alternator issues

[bud37]

Just be careful to NOT deadhead the alternators when testing or you may damage the diodes....they should always have some sort of load.

[g36]

If your house bank was 11.7 your batteries definitely won't last long if your dragging them down like that very often. Should only discharge them around 50%. If you take care of them and they are good quality you should get 5-6 or more years easily with them

[Helmsman]

Ok. Here was the solution. The electrician who helped me put in the isolator crossed the port engine wire and the house battery bank wire to the isolator. I found it after cleaning and re-tightening the battery connections, using the multimeter on every piece of equipment that I could, and establishing that it had to be the isolator.

I traced the wires to the engines and the two battery banks. The Proiso 2-4 Manual is specific that the two engines have to be connected at the Eng1 and Eng2 posts. The battery banks must be connected to the Bat1 and Bat2 posts. I found the Bat1 and Eng1 were mis-wired. The isolator attempts to charge the engine batteries until they are receiving 13.5 volts. Since the battery was reporting back through the engine that it wasn’t receiving the 13.5 volts (the house battery bank was) the isolator never started to charge the “bank” which was actually the engine battery.

After changing the wires, the all four battery banks were charging at 14.5 to 14.7. I unnecessarily complicated things by not getting the port alternator reading correct at the alternator until this morning. Anywho, that is the answer to the alternator issue. The gauge reading of 11 to 12 volts while underway was a result of the engine battery not receiving the intended charge.

Modern technology, huh? Thanks for all of the suggestions and help!

[Helmsman]

Source of the post If your house bank was 11.7 your batteries definitely won't last long if your dragging them down like that very often. Should only discharge them around 50%. If you take care of them and they are good quality you should get 5-6 or more years easily with them

Thanks. I didn’t realize they were down that far. There would normally be no reason to be down that far with the alternators charging the bank. We weren’t really using the inverter much, though it was on. The refrigerator is tied to it and that outlet was energized. We cruised for about 12 hours, stopped, ate lunch (microwave was used and tied to the inverter), and i found it discharged when we docked.

This was the longest cruise we have taken since installing the inverter and therefore was when the issue surfaced. Don’t expect to see that again, though I will watch the battery monitor in the future more closely.

[km1125]

Source of the post Ok. Here was the solution. The electrician who helped me put in the isolator crossed the port engine wire and the house battery bank wire to the isolator. I found it after cleaning and re-tightening the battery connections, using the multimeter on every piece of equipment that I could, and establishing that it had to be the isolator.

I traced the wires to the engines and the two battery banks. The Proiso 2-4 Manual is specific that the two engines have to be connected at the Eng1 and Eng2 posts. The battery banks must be connected to the Bat1 and Bat2 posts. I found the Bat1 and Eng1 were mis-wired. The isolator attempts to charge the engine batteries until they are receiving 13.5 volts. Since the battery was reporting back through the engine that it wasn’t receiving the 13.5 volts (the house battery bank was) the isolator never started to charge the “bank” which was actually the engine battery.

After changing the wires, the all four battery banks were charging at 14.5 to 14.7. I unnecessarily complicated things by not getting the port alternator reading correct at the alternator until this morning. Anywho, that is the answer to the alternator issue. The gauge reading of 11 to 12 volts while underway was a result of the engine battery not receiving the intended charge.

Modern technology, huh? Thanks for all of the suggestions and help!

Well, that makes sense.

The isolators are just diodes, which operate as one-way switches. Current can only flow from the alternator terminals to the battery terminals, so if those are reversed then it's as good as not even being connected. The alternator has a set voltage output (13.6 to 14.7) and if there's a difference from that voltage to the battery voltage (which, at rest, is about 12.6) then current will flow towards the battery. However, if the isolator is installed backwards, that "shuts the door" on current flow.