Join Date: Feb 2011
Location: San Francisco Bay area
Thanked 77 Times in 77 Posts
Rep Power: 6
Re: m25 alternator question
The general rule of thumb is that an alternator won't take the batteries much over 85% capacity. A shore charger will take them to 100%.
This is because the alternator's output voltage is designed such that you can motor for long periods without fear of overheating the batteries, which is good, but the downside is they only reach 85%.
So that's why your charge rate with the alternator was so low - you were already at capacity, as far as the alternator is concerned.
The shore charger is rather smarter, and switches between various modes.
Bristol 31.1, San Francisco Bay