Join Date: Apr 2008
Location: New Brunswick Canada
Thanked 3 Times in 3 Posts
Rep Power: 10
Re: m25 alternator question
1. A battery monitor is only accurate when it has been properly calibrated. Over time, they become less and less accurate unless re-calibrated.
2. Your new batteries may be nearly fully charged, so both the battery charger and the alternator are putting out about the same low amperage.
New batteries won't deliver their rated capacity until exercised (discharged and re-charged and, sometimes, equalized). I'd suggest you leave them on charge for a few days to make sure they're fully charged, then recalibrate your monitor.
After using the batteries, i.e., discharging them a few times to about 50% SOC and recharging them fully, re-calibrate the monitor again.
While they are 50% discharged or so, measure the voltage output of your alternator (should be 14.4 or above for flooded or AGM batteries) and measure the amperage output as well. That should give you a much better estimate of how well your alternator and regulator are working.
You reminded me and pointed out the problem. I set up the battery monitor and celebrated it with the battery's at 80% and the manual tells me I have to celebrate at 100%. So I assume that is why my BM-1 is off I think.