What do do about battery charger

[dencaw]

Hi guys,

I have a 1991 25' Sailfish that I bought at an auction last fall and am still exploring trying to figure out what switches go to what, etc. I discovered behind the wall in the aft cabin that there is a 15 amp battery charger, a Newmar RM-15 model. The only meter it has on it is for amps. When I plug in shore power, the meter moves just a bit, but remains below "0" and there is a hum on the unit, so I know power is getting to it. From doing a little research I have discovered it is an older unit, probably came stock with the boat. I am guessing it is not a "smart" charger, but don't know much else. Not sure what to do about it. Is it worth trying to fix and get it working it being so old or should I just replace it. And if I replace it, should I be reasonably confident that the wires I will just switch over to the new unit are all wired correctly on the other ends and how can I be sure my batteries are actually charging? As you can probably tell, I don't know much about this stuff. Any help would be appreciated. Thanks.

 

[Daman858]

If your batteries are charged, it will not read much above zero.

 

[ocnslr]

If your batteries are charged, it will not read much above zero.

Concur.

Turn on some DC loads and see if the needle moves to indicate a higher output rate.

 

[freddy063]

The easiest way is get a volt meter, check your battery volts, turn on charger see if the volts went up.

 

[dencaw]

Ok gentlemen,

I took your advice and put a volt meter on my batteries both before and after plugging in my shore power, which automatically turns on my battery charger. The reading on the port battery is 15 volts without being plugged in, 16 volts when I plug in the shore power. The starboard battery doesn't move the meter at all, no matter what settings I have my twin battery switches on. Is the 1 volt jump about right when the charger is on? I can see that the cable does run from the battery charger to the port engine. I guess it is designed to only charge one battery. One question I have is whether it is safe to leave the charger on all the time, assuming you guys think it is working properly. Thanks in advance.

 

[freddy063]

I would expect to see around 13 volts on the batterys alone, and around 14 to 15 with the charger. But any increase proves that it is chargeing. is there only one set of wires running to only one battery from the charger?

 

[dencaw]

Yup, there is only one wire (looks like romex) that runs form the charger to the port side battery.

 

[Curmudgeon]

The reading on the port battery is 15 volts without being plugged in,

:uhm I thought something on the order of 12.8v indicated full charge of a static battery. Something may be amiss if you're showing 15 volts ...