Battery or Charger? or nothing?

Dream_Inn

ok, over the weekend while we were anchored out for 3 days, I noticed that when I ran my generator and battery charger, the analog meter in the cabin would only jump up to 12.5V at initial turn on.  I know it didn't do that in the past, so I became more than curious.  I thought maybe one of my two house batteries was causing the problem.  So I connected each house battery separately (with and without load) and also read it on digital meter (Dig volt meter) right at the battery.  The cabin meter was maybe .2V lower than what I read directly at the DVM.  The analog meter on the charger would jump to 40 amps, but real fast go to 30, then down to 20.  The DVM I had on the battery would jump from 12.2 to 12.7...then in time climbed to about 13V total.  That was, well, maybe ok.  But when I'd turn the charger off, it'd drop to 12.3V ish.  OK, in time I'd think maybe it would be higher.

I think my charger is not going to that boost stage of 14.4 volts, and also not hitting the 90% charge stage of 13.3V.  It is just going to the maintain stage. 

Now, after sitting back at my dock for 5 hours or so, the meter was showing 13V (on the analog in the cabin).  I didn't mess with removing the load again and checking with the DVM.

Just thought I'd see what others thought.  I swear that thing should go right up over 14V initially all the time.  how bout you guys?  do you see your meter jump over 14V after you apply the battery charger?

Oh, batteries aren't quite two years old, and never taken down below 12V (probably stay over 12.2V).  I've always gotten 5 years out of my house batteries.

Dream_Inn

ok, I thought I'd at least fill in where I'm at in case someone is following. A couple weeks ago a dock buddy ordered a new charger, so I took advantage and installed it first on my boat. The meter jumped up to about 13.8V. Now, that said, we just got done on a 10-day trip and only 2 nights were on anchor, but those 2 nights it only dropped to 12v (which actually should be higher). It looks like what I'm seeing is the boost is not working. It will charge it up to about 13V, but takes time (like overnight). I went ahead and ordered a new charger, I hate messing around with battery issues and wouldn't want to lose valuable anchoring time.

Dream_Inn

RY, if you are getting 12V with a meter at your batteries, with charger on and fully charged, then something is not right. You could start with one battery at a time, to verify it isn't the batteries. My guess would be the charger. You probably would not notice with starter batteries because they would charge when you take the boat out. House batteries would also charge then as well, but you'd only notice with them if you anchored over night.

Dream_Inn

Oh, the new charger is now installed. Immediately when I turned it on, it jumped to 14V (actually 14.2ish). There was definitely an issue. I'm real curious when I get back down to the boat after being on the charger this week, first where is it while plugged in, second, when I unplug and put a draw on the battery initially, where is it then. I'm figuring it should be around 13.4 when I first look at it (that is the float stage), then removing shore power, it shouldn't drop more than initially around 12.6ish. Let's see if my guesses are close. Anyone care to take a guess?

Dream_Inn

When you say voltage never went over 11.8, where is that measure? Was that the entire time while the radio was on?  After 3 hours did it shut down?  What was the voltage when you shut it off after 3 hours?

12.8 is good charge and 13.8 is good with charger on.  That all sounds good.  Could be your batteries, but hard to tell with the info thus far.

Dream_Inn

I'm trying to figure out your steps. You were reading 12.8V. You then unplugged, ran the radio for 3 hours, stopped working, it was then 11.8? then plugged charger back in? or was charger on the entire time?

Dream_Inn

battery should never get to 11.8 when charger is plugged in. Definitely an issue with the charger.

Michael T

Steve, the fuse for my MB Quart was 70 amps so a 50 amp draw would certainly be a reasonable conclusion. MT

midweste

That sounds about right. If you have a significant battery draw whilst charging, it won't be a able to keep up. +1 on AC/DC at the proper volume 

Michael T

Rhetorical question Steve! :-) MT

Dream_Inn

Wow, that does not make a whole lot of sense!  Glad you figured out the issue though!

MarkB

Good you figured it out. So when you getting a new charger? 

MarkB

Very nice!