E-28 Universal 12 charging question

[joe-fran]

I just bought my E28 this July and have a charging question. WHen I first start the engine, the ammeter would only show a slight charge. Not putting too much faith in the meter, I took my analog multimeter and tested the batteries with and without the enging rumming and there seeed to be no difference - just about 12 volts.
Since the batteries never wend dead I knew something was strange so next time out I brought my digital multimeter and got the following readings. Batteries with engine off 12.2 volts, with engine running 12.8 volts. I assumed that I should see 14-15 volts with the engine running and the ammeter should jump up when first starting and slowing go to neutral within a few minutes.

My current plan is to pull the alternator this winter and have it tested.

However, before doing anything I figured I should 'ask the experts'.



Any comments/suggestions are greatly appreciated.

Thanks in advance.

Joe

 

[newgringo]

Joe,
I have been all thru charging on a couple of boats and airplanes, and cars. First off you should see about 14.3 volts at the output terminal of the alternator with the engine running above idle. These things usually are only regulated to provide this voltage at their output. From there on the voltage will decrease in the wiring until it gets to the battery. If you are not getting the 14.3 then you probably have a alternator problem. If you are, then you have a voltage drop problem in the wiring between the alternator and the battery. My Universal M25 originally routed the alternator output to the engine panel alternator, thru a battery switch and finially to a battery. I could never get full charge into either of 2 batteries. I redesigned the wiring a couple of years ago. Problem solved.

 

[Tom Metzger]

If you have only 12.2 volts without the engine running your batteries are quite low. You should let the engine run for a while at a fairly high rpm (above 1500). Depending on the size of the batteries, their condition, alternator size, and wire size & length it may take a while for the voltage to come up. It should come up slowly, so take measurements every ten minutes or so with your digital meter and see if the voltage is coming up.

If you have more than one battery try charging only one at a time; the voltage may come up faster.